//
// Copyright (c) 2013-2014 The ANGLE Project Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//

// validationES.h: Validation functions for generic OpenGL ES entry point parameters

#include "libANGLE/validationES.h"
#include "libANGLE/validationES2.h"
#include "libANGLE/validationES3.h"
#include "libANGLE/Context.h"
#include "libANGLE/Display.h"
#include "libANGLE/Texture.h"
#include "libANGLE/Framebuffer.h"
#include "libANGLE/FramebufferAttachment.h"
#include "libANGLE/formatutils.h"
#include "libANGLE/Image.h"
#include "libANGLE/Query.h"
#include "libANGLE/Program.h"
#include "libANGLE/Uniform.h"
#include "libANGLE/TransformFeedback.h"
#include "libANGLE/VertexArray.h"

#include "common/mathutil.h"
#include "common/utilities.h"

namespace gl
{
const char *g_ExceedsMaxElementErrorMessage = "Element value exceeds maximum element index.";

namespace
{
bool ValidateDrawAttribs(ValidationContext *context, GLint primcount, GLint maxVertex)
{
    const gl::State &state     = context->getState();
    const gl::Program *program = state.getProgram();

    const VertexArray *vao     = state.getVertexArray();
    const auto &vertexAttribs  = vao->getVertexAttributes();
    size_t maxEnabledAttrib = vao->getMaxEnabledAttribute();
    for (size_t attributeIndex = 0; attributeIndex < maxEnabledAttrib; ++attributeIndex)
    {
        const VertexAttribute &attrib = vertexAttribs[attributeIndex];
        if (program->isAttribLocationActive(attributeIndex) && attrib.enabled)
        {
            gl::Buffer *buffer = attrib.buffer.get();

            if (buffer)
            {
                GLint64 attribStride     = static_cast<GLint64>(ComputeVertexAttributeStride(attrib));
                GLint64 maxVertexElement = 0;

                if (attrib.divisor > 0)
                {
                    maxVertexElement =
                        static_cast<GLint64>(primcount) / static_cast<GLint64>(attrib.divisor);
                }
                else
                {
                    maxVertexElement = static_cast<GLint64>(maxVertex);
                }

                // If we're drawing zero vertices, we have enough data.
                if (maxVertexElement > 0)
                {
                    // Note: Last vertex element does not take the full stride!
                    GLint64 attribSize =
                        static_cast<GLint64>(ComputeVertexAttributeTypeSize(attrib));
                    GLint64 attribDataSize = (maxVertexElement - 1) * attribStride + attribSize;
                    GLint64 attribOffset   = static_cast<GLint64>(attrib.offset);

                    // [OpenGL ES 3.0.2] section 2.9.4 page 40:
                    // We can return INVALID_OPERATION if our vertex attribute does not have
                    // enough backing data.
                    if (attribDataSize + attribOffset > buffer->getSize())
                    {
                        context->handleError(
                            Error(GL_INVALID_OPERATION,
                                  "Vertex buffer is not big enough for the draw call"));
                        return false;
                    }
                }
            }
            else if (attrib.pointer == NULL)
            {
                // This is an application error that would normally result in a crash,
                // but we catch it and return an error
                context->handleError(Error(
                    GL_INVALID_OPERATION, "An enabled vertex array has no buffer and no pointer."));
                return false;
            }
        }
    }

    return true;
}

}  // anonymous namespace

bool ValidCap(const Context *context, GLenum cap)
{
    switch (cap)
    {
      // EXT_multisample_compatibility
      case GL_MULTISAMPLE_EXT:
      case GL_SAMPLE_ALPHA_TO_ONE_EXT:
          return context->getExtensions().multisampleCompatibility;

      case GL_CULL_FACE:
      case GL_POLYGON_OFFSET_FILL:
      case GL_SAMPLE_ALPHA_TO_COVERAGE:
      case GL_SAMPLE_COVERAGE:
      case GL_SCISSOR_TEST:
      case GL_STENCIL_TEST:
      case GL_DEPTH_TEST:
      case GL_BLEND:
      case GL_DITHER:
        return true;

      case GL_PRIMITIVE_RESTART_FIXED_INDEX:
      case GL_RASTERIZER_DISCARD:
        return (context->getClientVersion() >= 3);

      case GL_DEBUG_OUTPUT_SYNCHRONOUS:
      case GL_DEBUG_OUTPUT:
          return context->getExtensions().debug;

      default:
        return false;
    }
}

bool ValidTextureTarget(const ValidationContext *context, GLenum target)
{
    switch (target)
    {
      case GL_TEXTURE_2D:
      case GL_TEXTURE_CUBE_MAP:
        return true;

      case GL_TEXTURE_3D:
      case GL_TEXTURE_2D_ARRAY:
        return (context->getClientVersion() >= 3);

      default:
        return false;
    }
}

bool ValidTexture2DTarget(const ValidationContext *context, GLenum target)
{
    switch (target)
    {
        case GL_TEXTURE_2D:
        case GL_TEXTURE_CUBE_MAP:
            return true;

        default:
            return false;
    }
}

bool ValidTexture3DTarget(const ValidationContext *context, GLenum target)
{
    switch (target)
    {
        case GL_TEXTURE_3D:
        case GL_TEXTURE_2D_ARRAY:
            return (context->getClientVersion() >= 3);

        default:
            return false;
    }
}

// Most texture GL calls are not compatible with external textures, so we have a separate validation
// function for use in the GL calls that do
bool ValidTextureExternalTarget(const ValidationContext *context, GLenum target)
{
    return (target == GL_TEXTURE_EXTERNAL_OES) &&
           (context->getExtensions().eglImageExternal ||
            context->getExtensions().eglStreamConsumerExternal);
}

// This function differs from ValidTextureTarget in that the target must be
// usable as the destination of a 2D operation-- so a cube face is valid, but
// GL_TEXTURE_CUBE_MAP is not.
// Note: duplicate of IsInternalTextureTarget
bool ValidTexture2DDestinationTarget(const ValidationContext *context, GLenum target)
{
    switch (target)
    {
      case GL_TEXTURE_2D:
      case GL_TEXTURE_CUBE_MAP_POSITIVE_X:
      case GL_TEXTURE_CUBE_MAP_NEGATIVE_X:
      case GL_TEXTURE_CUBE_MAP_POSITIVE_Y:
      case GL_TEXTURE_CUBE_MAP_NEGATIVE_Y:
      case GL_TEXTURE_CUBE_MAP_POSITIVE_Z:
      case GL_TEXTURE_CUBE_MAP_NEGATIVE_Z:
        return true;
      default:
          return false;
    }
}

bool ValidTexture3DDestinationTarget(const ValidationContext *context, GLenum target)
{
    switch (target)
    {
      case GL_TEXTURE_3D:
      case GL_TEXTURE_2D_ARRAY:
          return true;
      default:
        return false;
    }
}

bool ValidFramebufferTarget(GLenum target)
{
    static_assert(GL_DRAW_FRAMEBUFFER_ANGLE == GL_DRAW_FRAMEBUFFER && GL_READ_FRAMEBUFFER_ANGLE == GL_READ_FRAMEBUFFER,
                  "ANGLE framebuffer enums must equal the ES3 framebuffer enums.");

    switch (target)
    {
      case GL_FRAMEBUFFER:      return true;
      case GL_READ_FRAMEBUFFER: return true;
      case GL_DRAW_FRAMEBUFFER: return true;
      default:                  return false;
    }
}

bool ValidBufferTarget(const Context *context, GLenum target)
{
    switch (target)
    {
      case GL_ARRAY_BUFFER:
      case GL_ELEMENT_ARRAY_BUFFER:
        return true;

      case GL_PIXEL_PACK_BUFFER:
      case GL_PIXEL_UNPACK_BUFFER:
          return (context->getExtensions().pixelBufferObject || context->getClientVersion() >= 3);

      case GL_COPY_READ_BUFFER:
      case GL_COPY_WRITE_BUFFER:
      case GL_TRANSFORM_FEEDBACK_BUFFER:
      case GL_UNIFORM_BUFFER:
        return (context->getClientVersion() >= 3);

      default:
        return false;
    }
}

bool ValidBufferParameter(const Context *context, GLenum pname)
{
    const Extensions &extensions = context->getExtensions();

    switch (pname)
    {
      case GL_BUFFER_USAGE:
      case GL_BUFFER_SIZE:
        return true;

      case GL_BUFFER_ACCESS_OES:
        return extensions.mapBuffer;

      case GL_BUFFER_MAPPED:
        static_assert(GL_BUFFER_MAPPED == GL_BUFFER_MAPPED_OES, "GL enums should be equal.");
        return (context->getClientVersion() >= 3) || extensions.mapBuffer || extensions.mapBufferRange;

      // GL_BUFFER_MAP_POINTER is a special case, and may only be
      // queried with GetBufferPointerv
      case GL_BUFFER_ACCESS_FLAGS:
      case GL_BUFFER_MAP_OFFSET:
      case GL_BUFFER_MAP_LENGTH:
        return (context->getClientVersion() >= 3) || extensions.mapBufferRange;

      default:
        return false;
    }
}

bool ValidMipLevel(const ValidationContext *context, GLenum target, GLint level)
{
    const auto &caps    = context->getCaps();
    size_t maxDimension = 0;
    switch (target)
    {
        case GL_TEXTURE_2D:
            maxDimension = caps.max2DTextureSize;
            break;
      case GL_TEXTURE_CUBE_MAP:
      case GL_TEXTURE_CUBE_MAP_POSITIVE_X:
      case GL_TEXTURE_CUBE_MAP_NEGATIVE_X:
      case GL_TEXTURE_CUBE_MAP_POSITIVE_Y:
      case GL_TEXTURE_CUBE_MAP_NEGATIVE_Y:
      case GL_TEXTURE_CUBE_MAP_POSITIVE_Z:
      case GL_TEXTURE_CUBE_MAP_NEGATIVE_Z:
          maxDimension = caps.maxCubeMapTextureSize;
          break;
      case GL_TEXTURE_3D:
          maxDimension = caps.max3DTextureSize;
          break;
      case GL_TEXTURE_2D_ARRAY:
          maxDimension = caps.max2DTextureSize;
          break;
      default: UNREACHABLE();
    }

    return level <= gl::log2(static_cast<int>(maxDimension));
}

bool ValidImageSizeParameters(const Context *context,
                              GLenum target,
                              GLint level,
                              GLsizei width,
                              GLsizei height,
                              GLsizei depth,
                              bool isSubImage)
{
    if (level < 0 || width < 0 || height < 0 || depth < 0)
    {
        return false;
    }

    // TexSubImage parameters can be NPOT without textureNPOT extension,
    // as long as the destination texture is POT.
    if (!isSubImage && !context->getExtensions().textureNPOT &&
        (level != 0 && (!gl::isPow2(width) || !gl::isPow2(height) || !gl::isPow2(depth))))
    {
        return false;
    }

    if (!ValidMipLevel(context, target, level))
    {
        return false;
    }

    return true;
}

bool CompressedTextureFormatRequiresExactSize(GLenum internalFormat)
{
    // List of compressed format that require that the texture size is smaller than or a multiple of
    // the compressed block size.
    switch (internalFormat)
    {
        case GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
        case GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
        case GL_COMPRESSED_RGBA_S3TC_DXT3_ANGLE:
        case GL_COMPRESSED_RGBA_S3TC_DXT5_ANGLE:
        case GL_ETC1_RGB8_LOSSY_DECODE_ANGLE:
            return true;

        default:
            return false;
    }
}

bool ValidCompressedImageSize(const ValidationContext *context,
                              GLenum internalFormat,
                              GLsizei width,
                              GLsizei height)
{
    const gl::InternalFormat &formatInfo = gl::GetInternalFormatInfo(internalFormat);
    if (!formatInfo.compressed)
    {
        return false;
    }

    if (width < 0 || height < 0)
    {
        return false;
    }

    if (CompressedTextureFormatRequiresExactSize(internalFormat))
    {
        if ((static_cast<GLuint>(width) > formatInfo.compressedBlockWidth &&
             width % formatInfo.compressedBlockWidth != 0) ||
            (static_cast<GLuint>(height) > formatInfo.compressedBlockHeight &&
             height % formatInfo.compressedBlockHeight != 0))
        {
            return false;
        }
    }

    return true;
}

bool ValidQueryType(const Context *context, GLenum queryType)
{
    static_assert(GL_ANY_SAMPLES_PASSED == GL_ANY_SAMPLES_PASSED_EXT, "GL extension enums not equal.");
    static_assert(GL_ANY_SAMPLES_PASSED_CONSERVATIVE == GL_ANY_SAMPLES_PASSED_CONSERVATIVE_EXT, "GL extension enums not equal.");

    switch (queryType)
    {
      case GL_ANY_SAMPLES_PASSED:
      case GL_ANY_SAMPLES_PASSED_CONSERVATIVE:
        return true;
      case GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN:
        return (context->getClientVersion() >= 3);
      case GL_TIME_ELAPSED_EXT:
          return context->getExtensions().disjointTimerQuery;
      case GL_COMMANDS_COMPLETED_CHROMIUM:
          return context->getExtensions().syncQuery;
      default:
        return false;
    }
}

Program *GetValidProgram(Context *context, GLuint id)
{
    // ES3 spec (section 2.11.1) -- "Commands that accept shader or program object names will generate the
    // error INVALID_VALUE if the provided name is not the name of either a shader or program object and
    // INVALID_OPERATION if the provided name identifies an object that is not the expected type."

    Program *validProgram = context->getProgram(id);

    if (!validProgram)
    {
        if (context->getShader(id))
        {
            context->handleError(
                Error(GL_INVALID_OPERATION, "Expected a program name, but found a shader name"));
        }
        else
        {
            context->handleError(Error(GL_INVALID_VALUE, "Program name is not valid"));
        }
    }

    return validProgram;
}

Shader *GetValidShader(Context *context, GLuint id)
{
    // See ValidProgram for spec details.

    Shader *validShader = context->getShader(id);

    if (!validShader)
    {
        if (context->getProgram(id))
        {
            context->handleError(
                Error(GL_INVALID_OPERATION, "Expected a shader name, but found a program name"));
        }
        else
        {
            context->handleError(Error(GL_INVALID_VALUE, "Shader name is invalid"));
        }
    }

    return validShader;
}

bool ValidateAttachmentTarget(gl::Context *context, GLenum attachment)
{
    if (attachment >= GL_COLOR_ATTACHMENT0_EXT && attachment <= GL_COLOR_ATTACHMENT15_EXT)
    {
        const unsigned int colorAttachment = (attachment - GL_COLOR_ATTACHMENT0_EXT);

        if (colorAttachment >= context->getCaps().maxColorAttachments)
        {
            context->handleError(Error(GL_INVALID_VALUE));
            return false;
        }
    }
    else
    {
        switch (attachment)
        {
          case GL_DEPTH_ATTACHMENT:
          case GL_STENCIL_ATTACHMENT:
            break;

          case GL_DEPTH_STENCIL_ATTACHMENT:
            if (context->getClientVersion() < 3)
            {
                context->handleError(Error(GL_INVALID_ENUM));
                return false;
            }
            break;

          default:
              context->handleError(Error(GL_INVALID_ENUM));
            return false;
        }
    }

    return true;
}

bool ValidateRenderbufferStorageParametersBase(gl::Context *context, GLenum target, GLsizei samples,
                                               GLenum internalformat, GLsizei width, GLsizei height)
{
    switch (target)
    {
      case GL_RENDERBUFFER:
        break;
      default:
          context->handleError(Error(GL_INVALID_ENUM));
        return false;
    }

    if (width < 0 || height < 0 || samples < 0)
    {
        context->handleError(Error(GL_INVALID_VALUE));
        return false;
    }

    const TextureCaps &formatCaps = context->getTextureCaps().get(internalformat);
    if (!formatCaps.renderable)
    {
        context->handleError(Error(GL_INVALID_ENUM));
        return false;
    }

    // ANGLE_framebuffer_multisample does not explicitly state that the internal format must be
    // sized but it does state that the format must be in the ES2.0 spec table 4.5 which contains
    // only sized internal formats.
    const gl::InternalFormat &formatInfo = gl::GetInternalFormatInfo(internalformat);
    if (formatInfo.pixelBytes == 0)
    {
        context->handleError(Error(GL_INVALID_ENUM));
        return false;
    }

    if (static_cast<GLuint>(std::max(width, height)) > context->getCaps().maxRenderbufferSize)
    {
        context->handleError(Error(GL_INVALID_VALUE));
        return false;
    }

    GLuint handle = context->getState().getRenderbufferId();
    if (handle == 0)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    return true;
}

bool ValidateRenderbufferStorageParametersANGLE(gl::Context *context, GLenum target, GLsizei samples,
                                                GLenum internalformat, GLsizei width, GLsizei height)
{
    ASSERT(samples == 0 || context->getExtensions().framebufferMultisample);

    // ANGLE_framebuffer_multisample states that the value of samples must be less than or equal
    // to MAX_SAMPLES_ANGLE (Context::getCaps().maxSamples) otherwise GL_INVALID_VALUE is
    // generated.
    if (static_cast<GLuint>(samples) > context->getCaps().maxSamples)
    {
        context->handleError(Error(GL_INVALID_VALUE));
        return false;
    }

    // ANGLE_framebuffer_multisample states GL_OUT_OF_MEMORY is generated on a failure to create
    // the specified storage. This is different than ES 3.0 in which a sample number higher
    // than the maximum sample number supported  by this format generates a GL_INVALID_VALUE.
    // The TextureCaps::getMaxSamples method is only guarenteed to be valid when the context is ES3.
    if (context->getClientVersion() >= 3)
    {
        const TextureCaps &formatCaps = context->getTextureCaps().get(internalformat);
        if (static_cast<GLuint>(samples) > formatCaps.getMaxSamples())
        {
            context->handleError(Error(GL_OUT_OF_MEMORY));
            return false;
        }
    }

    return ValidateRenderbufferStorageParametersBase(context, target, samples, internalformat, width, height);
}

bool ValidateFramebufferRenderbufferParameters(gl::Context *context, GLenum target, GLenum attachment,
                                               GLenum renderbuffertarget, GLuint renderbuffer)
{
    if (!ValidFramebufferTarget(target))
    {
        context->handleError(Error(GL_INVALID_ENUM));
        return false;
    }

    gl::Framebuffer *framebuffer = context->getState().getTargetFramebuffer(target);

    ASSERT(framebuffer);
    if (framebuffer->id() == 0)
    {
        context->handleError(
            Error(GL_INVALID_OPERATION, "Cannot change default FBO's attachments"));
        return false;
    }

    if (!ValidateAttachmentTarget(context, attachment))
    {
        return false;
    }

    // [OpenGL ES 2.0.25] Section 4.4.3 page 112
    // [OpenGL ES 3.0.2] Section 4.4.2 page 201
    // 'renderbuffer' must be either zero or the name of an existing renderbuffer object of
    // type 'renderbuffertarget', otherwise an INVALID_OPERATION error is generated.
    if (renderbuffer != 0)
    {
        if (!context->getRenderbuffer(renderbuffer))
        {
            context->handleError(Error(GL_INVALID_OPERATION));
            return false;
        }
    }

    return true;
}

bool ValidateBlitFramebufferParameters(gl::Context *context,
                                       GLint srcX0,
                                       GLint srcY0,
                                       GLint srcX1,
                                       GLint srcY1,
                                       GLint dstX0,
                                       GLint dstY0,
                                       GLint dstX1,
                                       GLint dstY1,
                                       GLbitfield mask,
                                       GLenum filter)
{
    switch (filter)
    {
      case GL_NEAREST:
        break;
      case GL_LINEAR:
        break;
      default:
          context->handleError(Error(GL_INVALID_ENUM));
        return false;
    }

    if ((mask & ~(GL_COLOR_BUFFER_BIT | GL_STENCIL_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)) != 0)
    {
        context->handleError(Error(GL_INVALID_VALUE));
        return false;
    }

    if (mask == 0)
    {
        // ES3.0 spec, section 4.3.2 specifies that a mask of zero is valid and no
        // buffers are copied.
        return false;
    }

    // ES3.0 spec, section 4.3.2 states that linear filtering is only available for the
    // color buffer, leaving only nearest being unfiltered from above
    if ((mask & ~GL_COLOR_BUFFER_BIT) != 0 && filter != GL_NEAREST)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    if (context->getState().getReadFramebuffer()->id() == context->getState().getDrawFramebuffer()->id())
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    const gl::Framebuffer *readFramebuffer = context->getState().getReadFramebuffer();
    const gl::Framebuffer *drawFramebuffer = context->getState().getDrawFramebuffer();

    if (!readFramebuffer || !drawFramebuffer)
    {
        context->handleError(Error(GL_INVALID_FRAMEBUFFER_OPERATION));
        return false;
    }

    if (!readFramebuffer->checkStatus(context->getData()))
    {
        context->handleError(Error(GL_INVALID_FRAMEBUFFER_OPERATION));
        return false;
    }

    if (!drawFramebuffer->checkStatus(context->getData()))
    {
        context->handleError(Error(GL_INVALID_FRAMEBUFFER_OPERATION));
        return false;
    }

    if (drawFramebuffer->getSamples(context->getData()) != 0)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    bool sameBounds = srcX0 == dstX0 && srcY0 == dstY0 && srcX1 == dstX1 && srcY1 == dstY1;

    if (mask & GL_COLOR_BUFFER_BIT)
    {
        const gl::FramebufferAttachment *readColorBuffer = readFramebuffer->getReadColorbuffer();
        const gl::FramebufferAttachment *drawColorBuffer = drawFramebuffer->getFirstColorbuffer();
        const Extensions &extensions                     = context->getExtensions();

        if (readColorBuffer && drawColorBuffer)
        {
            GLenum readInternalFormat = readColorBuffer->getInternalFormat();
            const InternalFormat &readFormatInfo = GetInternalFormatInfo(readInternalFormat);

            for (size_t drawbufferIdx = 0;
                 drawbufferIdx < drawFramebuffer->getDrawbufferStateCount(); ++drawbufferIdx)
            {
                const FramebufferAttachment *attachment =
                    drawFramebuffer->getDrawBuffer(drawbufferIdx);
                if (attachment)
                {
                    GLenum drawInternalFormat            = attachment->getInternalFormat();
                    const InternalFormat &drawFormatInfo = GetInternalFormatInfo(drawInternalFormat);

                    // The GL ES 3.0.2 spec (pg 193) states that:
                    // 1) If the read buffer is fixed point format, the draw buffer must be as well
                    // 2) If the read buffer is an unsigned integer format, the draw buffer must be as well
                    // 3) If the read buffer is a signed integer format, the draw buffer must be as well
                    // Changes with EXT_color_buffer_float:
                    // Case 1) is changed to fixed point OR floating point
                    GLenum readComponentType = readFormatInfo.componentType;
                    GLenum drawComponentType = drawFormatInfo.componentType;
                    bool readFixedPoint = (readComponentType == GL_UNSIGNED_NORMALIZED ||
                                           readComponentType == GL_SIGNED_NORMALIZED);
                    bool drawFixedPoint = (drawComponentType == GL_UNSIGNED_NORMALIZED ||
                                           drawComponentType == GL_SIGNED_NORMALIZED);

                    if (extensions.colorBufferFloat)
                    {
                        bool readFixedOrFloat = (readFixedPoint || readComponentType == GL_FLOAT);
                        bool drawFixedOrFloat = (drawFixedPoint || drawComponentType == GL_FLOAT);

                        if (readFixedOrFloat != drawFixedOrFloat)
                        {
                            context->handleError(Error(GL_INVALID_OPERATION,
                                                       "If the read buffer contains fixed-point or "
                                                       "floating-point values, the draw buffer "
                                                       "must as well."));
                            return false;
                        }
                    }
                    else if (readFixedPoint != drawFixedPoint)
                    {
                        context->handleError(Error(GL_INVALID_OPERATION,
                                                   "If the read buffer contains fixed-point "
                                                   "values, the draw buffer must as well."));
                        return false;
                    }

                    if (readComponentType == GL_UNSIGNED_INT &&
                        drawComponentType != GL_UNSIGNED_INT)
                    {
                        context->handleError(Error(GL_INVALID_OPERATION));
                        return false;
                    }

                    if (readComponentType == GL_INT && drawComponentType != GL_INT)
                    {
                        context->handleError(Error(GL_INVALID_OPERATION));
                        return false;
                    }

                    if (readColorBuffer->getSamples() > 0 && (readInternalFormat != drawInternalFormat || !sameBounds))
                    {
                        context->handleError(Error(GL_INVALID_OPERATION));
                        return false;
                    }
                }
            }

            if ((readFormatInfo.componentType == GL_INT || readFormatInfo.componentType == GL_UNSIGNED_INT) && filter == GL_LINEAR)
            {
                context->handleError(Error(GL_INVALID_OPERATION));
                return false;
            }
        }
    }

    GLenum masks[] = {GL_DEPTH_BUFFER_BIT, GL_STENCIL_BUFFER_BIT};
    GLenum attachments[] = {GL_DEPTH_ATTACHMENT, GL_STENCIL_ATTACHMENT};
    for (size_t i = 0; i < 2; i++)
    {
        if (mask & masks[i])
        {
            const gl::FramebufferAttachment *readBuffer = readFramebuffer->getAttachment(attachments[i]);
            const gl::FramebufferAttachment *drawBuffer = drawFramebuffer->getAttachment(attachments[i]);

            if (readBuffer && drawBuffer)
            {
                if (readBuffer->getInternalFormat() != drawBuffer->getInternalFormat())
                {
                    context->handleError(Error(GL_INVALID_OPERATION));
                    return false;
                }

                if (readBuffer->getSamples() > 0 && !sameBounds)
                {
                    context->handleError(Error(GL_INVALID_OPERATION));
                    return false;
                }
            }
        }
    }

    return true;
}

bool ValidateGetVertexAttribParameters(Context *context, GLenum pname)
{
    switch (pname)
    {
      case GL_VERTEX_ATTRIB_ARRAY_ENABLED:
      case GL_VERTEX_ATTRIB_ARRAY_SIZE:
      case GL_VERTEX_ATTRIB_ARRAY_STRIDE:
      case GL_VERTEX_ATTRIB_ARRAY_TYPE:
      case GL_VERTEX_ATTRIB_ARRAY_NORMALIZED:
      case GL_VERTEX_ATTRIB_ARRAY_BUFFER_BINDING:
      case GL_CURRENT_VERTEX_ATTRIB:
        return true;

      case GL_VERTEX_ATTRIB_ARRAY_DIVISOR:
        // Don't verify ES3 context because GL_VERTEX_ATTRIB_ARRAY_DIVISOR_ANGLE uses
        // the same constant.
        static_assert(GL_VERTEX_ATTRIB_ARRAY_DIVISOR == GL_VERTEX_ATTRIB_ARRAY_DIVISOR_ANGLE,
                      "ANGLE extension enums not equal to GL enums.");
        return true;

      case GL_VERTEX_ATTRIB_ARRAY_INTEGER:
        if (context->getClientVersion() < 3)
        {
            context->handleError(Error(GL_INVALID_ENUM));
            return false;
        }
        return true;

      default:
          context->handleError(Error(GL_INVALID_ENUM));
        return false;
    }
}

bool ValidateTexParamParameters(gl::Context *context, GLenum target, GLenum pname, GLint param)
{
    switch (pname)
    {
      case GL_TEXTURE_WRAP_R:
      case GL_TEXTURE_SWIZZLE_R:
      case GL_TEXTURE_SWIZZLE_G:
      case GL_TEXTURE_SWIZZLE_B:
      case GL_TEXTURE_SWIZZLE_A:
      case GL_TEXTURE_BASE_LEVEL:
      case GL_TEXTURE_MAX_LEVEL:
      case GL_TEXTURE_COMPARE_MODE:
      case GL_TEXTURE_COMPARE_FUNC:
      case GL_TEXTURE_MIN_LOD:
      case GL_TEXTURE_MAX_LOD:
          if (context->getClientVersion() < 3)
        {
            context->handleError(Error(GL_INVALID_ENUM));
            return false;
        }
        if (target == GL_TEXTURE_EXTERNAL_OES && !context->getExtensions().eglImageExternalEssl3)
        {
            context->handleError(Error(GL_INVALID_ENUM,
                                       "ES3 texture parameters are not available without "
                                       "GL_OES_EGL_image_external_essl3."));
            return false;
        }
        break;

      default: break;
    }

    switch (pname)
    {
      case GL_TEXTURE_WRAP_S:
      case GL_TEXTURE_WRAP_T:
      case GL_TEXTURE_WRAP_R:
        switch (param)
        {
          case GL_CLAMP_TO_EDGE:
              return true;
          case GL_REPEAT:
          case GL_MIRRORED_REPEAT:
              if (target == GL_TEXTURE_EXTERNAL_OES)
              {
                  // OES_EGL_image_external specifies this error.
                  context->handleError(Error(
                      GL_INVALID_ENUM, "external textures only support CLAMP_TO_EDGE wrap mode"));
                  return false;
              }
              return true;
          default:
              context->handleError(Error(GL_INVALID_ENUM));
            return false;
        }

      case GL_TEXTURE_MIN_FILTER:
        switch (param)
        {
          case GL_NEAREST:
          case GL_LINEAR:
              return true;
          case GL_NEAREST_MIPMAP_NEAREST:
          case GL_LINEAR_MIPMAP_NEAREST:
          case GL_NEAREST_MIPMAP_LINEAR:
          case GL_LINEAR_MIPMAP_LINEAR:
              if (target == GL_TEXTURE_EXTERNAL_OES)
              {
                  // OES_EGL_image_external specifies this error.
                  context->handleError(
                      Error(GL_INVALID_ENUM,
                            "external textures only support NEAREST and LINEAR filtering"));
                  return false;
              }
              return true;
          default:
              context->handleError(Error(GL_INVALID_ENUM));
            return false;
        }
        break;

      case GL_TEXTURE_MAG_FILTER:
        switch (param)
        {
          case GL_NEAREST:
          case GL_LINEAR:
            return true;
          default:
              context->handleError(Error(GL_INVALID_ENUM));
            return false;
        }
        break;

      case GL_TEXTURE_USAGE_ANGLE:
        switch (param)
        {
          case GL_NONE:
          case GL_FRAMEBUFFER_ATTACHMENT_ANGLE:
            return true;
          default:
              context->handleError(Error(GL_INVALID_ENUM));
            return false;
        }
        break;

      case GL_TEXTURE_MAX_ANISOTROPY_EXT:
        if (!context->getExtensions().textureFilterAnisotropic)
        {
            context->handleError(Error(GL_INVALID_ENUM));
            return false;
        }

        // we assume the parameter passed to this validation method is truncated, not rounded
        if (param < 1)
        {
            context->handleError(Error(GL_INVALID_VALUE));
            return false;
        }
        return true;

      case GL_TEXTURE_MIN_LOD:
      case GL_TEXTURE_MAX_LOD:
        // any value is permissible
        return true;

      case GL_TEXTURE_COMPARE_MODE:
        // Acceptable mode parameters from GLES 3.0.2 spec, table 3.17
        switch (param)
        {
          case GL_NONE:
          case GL_COMPARE_REF_TO_TEXTURE:
            return true;
          default:
              context->handleError(Error(GL_INVALID_ENUM));
            return false;
        }
        break;

      case GL_TEXTURE_COMPARE_FUNC:
        // Acceptable function parameters from GLES 3.0.2 spec, table 3.17
        switch (param)
        {
          case GL_LEQUAL:
          case GL_GEQUAL:
          case GL_LESS:
          case GL_GREATER:
          case GL_EQUAL:
          case GL_NOTEQUAL:
          case GL_ALWAYS:
          case GL_NEVER:
            return true;
          default:
              context->handleError(Error(GL_INVALID_ENUM));
            return false;
        }
        break;

      case GL_TEXTURE_SWIZZLE_R:
      case GL_TEXTURE_SWIZZLE_G:
      case GL_TEXTURE_SWIZZLE_B:
      case GL_TEXTURE_SWIZZLE_A:
        switch (param)
        {
          case GL_RED:
          case GL_GREEN:
          case GL_BLUE:
          case GL_ALPHA:
          case GL_ZERO:
          case GL_ONE:
            return true;
          default:
              context->handleError(Error(GL_INVALID_ENUM));
            return false;
        }
        break;

      case GL_TEXTURE_BASE_LEVEL:
          if (param < 0)
          {
              context->handleError(Error(GL_INVALID_VALUE));
              return false;
          }
          if (target == GL_TEXTURE_EXTERNAL_OES && param != 0)
          {
              context->handleError(
                  Error(GL_INVALID_OPERATION, "Base level must be 0 for external textures."));
              return false;
          }
          return true;

      case GL_TEXTURE_MAX_LEVEL:
          if (param < 0)
          {
              context->handleError(Error(GL_INVALID_VALUE));
              return false;
          }
          return true;
      default:
          context->handleError(Error(GL_INVALID_ENUM));
          return false;
    }
}

bool ValidateSamplerObjectParameter(gl::Context *context, GLenum pname)
{
    switch (pname)
    {
      case GL_TEXTURE_MIN_FILTER:
      case GL_TEXTURE_MAG_FILTER:
      case GL_TEXTURE_WRAP_S:
      case GL_TEXTURE_WRAP_T:
      case GL_TEXTURE_WRAP_R:
      case GL_TEXTURE_MIN_LOD:
      case GL_TEXTURE_MAX_LOD:
      case GL_TEXTURE_COMPARE_MODE:
      case GL_TEXTURE_COMPARE_FUNC:
        return true;

      default:
          context->handleError(Error(GL_INVALID_ENUM));
        return false;
    }
}

bool ValidateReadPixels(Context *context,
                        GLint x,
                        GLint y,
                        GLsizei width,
                        GLsizei height,
                        GLenum format,
                        GLenum type,
                        GLvoid *pixels)
{
    if (width < 0 || height < 0)
    {
        context->handleError(Error(GL_INVALID_VALUE, "width and height must be positive"));
        return false;
    }

    Framebuffer *framebuffer = context->getState().getReadFramebuffer();
    ASSERT(framebuffer);

    if (framebuffer->checkStatus(context->getData()) != GL_FRAMEBUFFER_COMPLETE)
    {
        context->handleError(Error(GL_INVALID_FRAMEBUFFER_OPERATION));
        return false;
    }

    if (context->getState().getReadFramebuffer()->id() != 0 &&
        framebuffer->getSamples(context->getData()) != 0)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    const FramebufferAttachment *readBuffer = framebuffer->getReadColorbuffer();
    if (!readBuffer)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    GLenum currentFormat = framebuffer->getImplementationColorReadFormat();
    GLenum currentType = framebuffer->getImplementationColorReadType();
    GLenum currentInternalFormat = readBuffer->getInternalFormat();
    GLuint clientVersion = context->getClientVersion();

    bool validReadFormat = (clientVersion < 3) ? ValidES2ReadFormatType(context, format, type) :
                                                 ValidES3ReadFormatType(context, currentInternalFormat, format, type);

    if (!(currentFormat == format && currentType == type) && !validReadFormat)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    return true;
}

bool ValidateReadnPixelsEXT(Context *context,
                            GLint x,
                            GLint y,
                            GLsizei width,
                            GLsizei height,
                            GLenum format,
                            GLenum type,
                            GLsizei bufSize,
                            GLvoid *pixels)
{
    if (bufSize < 0)
    {
        context->handleError(Error(GL_INVALID_VALUE, "bufSize must be a positive number"));
        return false;
    }

    GLenum sizedInternalFormat = GetSizedInternalFormat(format, type);
    const InternalFormat &sizedFormatInfo = GetInternalFormatInfo(sizedInternalFormat);

    GLsizei outputPitch =
        sizedFormatInfo.computeRowPitch(type, width, context->getState().getPackAlignment(),
                                        context->getState().getPackRowLength());
    // sized query sanity check
    int requiredSize = outputPitch * height;
    if (requiredSize > bufSize)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    return ValidateReadPixels(context, x, y, width, height, format, type, pixels);
}

bool ValidateGenQueriesEXT(gl::Context *context, GLsizei n)
{
    if (!context->getExtensions().occlusionQueryBoolean &&
        !context->getExtensions().disjointTimerQuery)
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Query extension not enabled"));
        return false;
    }

    return ValidateGenOrDelete(context, n);
}

bool ValidateDeleteQueriesEXT(gl::Context *context, GLsizei n)
{
    if (!context->getExtensions().occlusionQueryBoolean &&
        !context->getExtensions().disjointTimerQuery)
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Query extension not enabled"));
        return false;
    }

    return ValidateGenOrDelete(context, n);
}

bool ValidateBeginQueryBase(gl::Context *context, GLenum target, GLuint id)
{
    if (!ValidQueryType(context, target))
    {
        context->handleError(Error(GL_INVALID_ENUM, "Invalid query target"));
        return false;
    }

    if (id == 0)
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Query id is 0"));
        return false;
    }

    // From EXT_occlusion_query_boolean: If BeginQueryEXT is called with an <id>
    // of zero, if the active query object name for <target> is non-zero (for the
    // targets ANY_SAMPLES_PASSED_EXT and ANY_SAMPLES_PASSED_CONSERVATIVE_EXT, if
    // the active query for either target is non-zero), if <id> is the name of an
    // existing query object whose type does not match <target>, or if <id> is the
    // active query object name for any query type, the error INVALID_OPERATION is
    // generated.

    // Ensure no other queries are active
    // NOTE: If other queries than occlusion are supported, we will need to check
    // separately that:
    //    a) The query ID passed is not the current active query for any target/type
    //    b) There are no active queries for the requested target (and in the case
    //       of GL_ANY_SAMPLES_PASSED_EXT and GL_ANY_SAMPLES_PASSED_CONSERVATIVE_EXT,
    //       no query may be active for either if glBeginQuery targets either.

    if (context->getState().isQueryActive(target))
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Other query is active"));
        return false;
    }

    Query *queryObject = context->getQuery(id, true, target);

    // check that name was obtained with glGenQueries
    if (!queryObject)
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Invalid query id"));
        return false;
    }

    // check for type mismatch
    if (queryObject->getType() != target)
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Query type does not match target"));
        return false;
    }

    return true;
}

bool ValidateBeginQueryEXT(gl::Context *context, GLenum target, GLuint id)
{
    if (!context->getExtensions().occlusionQueryBoolean &&
        !context->getExtensions().disjointTimerQuery && !context->getExtensions().syncQuery)
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Query extension not enabled"));
        return false;
    }

    return ValidateBeginQueryBase(context, target, id);
}

bool ValidateEndQueryBase(gl::Context *context, GLenum target)
{
    if (!ValidQueryType(context, target))
    {
        context->handleError(Error(GL_INVALID_ENUM, "Invalid query target"));
        return false;
    }

    const Query *queryObject = context->getState().getActiveQuery(target);

    if (queryObject == nullptr)
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Query target not active"));
        return false;
    }

    return true;
}

bool ValidateEndQueryEXT(gl::Context *context, GLenum target)
{
    if (!context->getExtensions().occlusionQueryBoolean &&
        !context->getExtensions().disjointTimerQuery && !context->getExtensions().syncQuery)
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Query extension not enabled"));
        return false;
    }

    return ValidateEndQueryBase(context, target);
}

bool ValidateQueryCounterEXT(Context *context, GLuint id, GLenum target)
{
    if (!context->getExtensions().disjointTimerQuery)
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Disjoint timer query not enabled"));
        return false;
    }

    if (target != GL_TIMESTAMP_EXT)
    {
        context->handleError(Error(GL_INVALID_ENUM, "Invalid query target"));
        return false;
    }

    Query *queryObject = context->getQuery(id, true, target);
    if (queryObject == nullptr)
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Invalid query id"));
        return false;
    }

    if (context->getState().isQueryActive(queryObject))
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Query is active"));
        return false;
    }

    return true;
}

bool ValidateGetQueryivBase(Context *context, GLenum target, GLenum pname)
{
    if (!ValidQueryType(context, target) && target != GL_TIMESTAMP_EXT)
    {
        context->handleError(Error(GL_INVALID_ENUM, "Invalid query type"));
        return false;
    }

    switch (pname)
    {
        case GL_CURRENT_QUERY_EXT:
            if (target == GL_TIMESTAMP_EXT)
            {
                context->handleError(
                    Error(GL_INVALID_ENUM, "Cannot use current query for timestamp"));
                return false;
            }
            break;
        case GL_QUERY_COUNTER_BITS_EXT:
            if (!context->getExtensions().disjointTimerQuery ||
                (target != GL_TIMESTAMP_EXT && target != GL_TIME_ELAPSED_EXT))
            {
                context->handleError(Error(GL_INVALID_ENUM, "Invalid pname"));
                return false;
            }
            break;
        default:
            context->handleError(Error(GL_INVALID_ENUM, "Invalid pname"));
            return false;
    }

    return true;
}

bool ValidateGetQueryivEXT(Context *context, GLenum target, GLenum pname, GLint *params)
{
    if (!context->getExtensions().occlusionQueryBoolean &&
        !context->getExtensions().disjointTimerQuery && !context->getExtensions().syncQuery)
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Query extension not enabled"));
        return false;
    }

    return ValidateGetQueryivBase(context, target, pname);
}

bool ValidateGetQueryObjectValueBase(Context *context, GLuint id, GLenum pname)
{
    Query *queryObject = context->getQuery(id, false, GL_NONE);

    if (!queryObject)
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Query does not exist"));
        return false;
    }

    if (context->getState().isQueryActive(queryObject))
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Query currently active"));
        return false;
    }

    switch (pname)
    {
        case GL_QUERY_RESULT_EXT:
        case GL_QUERY_RESULT_AVAILABLE_EXT:
            break;

        default:
            context->handleError(Error(GL_INVALID_ENUM, "Invalid pname enum"));
            return false;
    }

    return true;
}

bool ValidateGetQueryObjectivEXT(Context *context, GLuint id, GLenum pname, GLint *params)
{
    if (!context->getExtensions().disjointTimerQuery)
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Timer query extension not enabled"));
        return false;
    }
    return ValidateGetQueryObjectValueBase(context, id, pname);
}

bool ValidateGetQueryObjectuivEXT(Context *context, GLuint id, GLenum pname, GLuint *params)
{
    if (!context->getExtensions().disjointTimerQuery &&
        !context->getExtensions().occlusionQueryBoolean && !context->getExtensions().syncQuery)
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Query extension not enabled"));
        return false;
    }
    return ValidateGetQueryObjectValueBase(context, id, pname);
}

bool ValidateGetQueryObjecti64vEXT(Context *context, GLuint id, GLenum pname, GLint64 *params)
{
    if (!context->getExtensions().disjointTimerQuery)
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Timer query extension not enabled"));
        return false;
    }
    return ValidateGetQueryObjectValueBase(context, id, pname);
}

bool ValidateGetQueryObjectui64vEXT(Context *context, GLuint id, GLenum pname, GLuint64 *params)
{
    if (!context->getExtensions().disjointTimerQuery)
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Timer query extension not enabled"));
        return false;
    }
    return ValidateGetQueryObjectValueBase(context, id, pname);
}

static bool ValidateUniformCommonBase(gl::Context *context,
                                      GLenum targetUniformType,
                                      GLint location,
                                      GLsizei count,
                                      const LinkedUniform **uniformOut)
{
    if (count < 0)
    {
        context->handleError(Error(GL_INVALID_VALUE));
        return false;
    }

    gl::Program *program = context->getState().getProgram();
    if (!program)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    if (program->isIgnoredUniformLocation(location))
    {
        // Silently ignore the uniform command
        return false;
    }

    if (!program->isValidUniformLocation(location))
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    const LinkedUniform &uniform = program->getUniformByLocation(location);

    // attempting to write an array to a non-array uniform is an INVALID_OPERATION
    if (!uniform.isArray() && count > 1)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    *uniformOut = &uniform;
    return true;
}

bool ValidateUniform(gl::Context *context, GLenum uniformType, GLint location, GLsizei count)
{
    // Check for ES3 uniform entry points
    if (VariableComponentType(uniformType) == GL_UNSIGNED_INT && context->getClientVersion() < 3)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    const LinkedUniform *uniform = nullptr;
    if (!ValidateUniformCommonBase(context, uniformType, location, count, &uniform))
    {
        return false;
    }

    GLenum targetBoolType = VariableBoolVectorType(uniformType);
    bool samplerUniformCheck = (IsSamplerType(uniform->type) && uniformType == GL_INT);
    if (!samplerUniformCheck && uniformType != uniform->type && targetBoolType != uniform->type)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    return true;
}

bool ValidateUniformMatrix(gl::Context *context, GLenum matrixType, GLint location, GLsizei count,
                           GLboolean transpose)
{
    // Check for ES3 uniform entry points
    int rows = VariableRowCount(matrixType);
    int cols = VariableColumnCount(matrixType);
    if (rows != cols && context->getClientVersion() < 3)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    if (transpose != GL_FALSE && context->getClientVersion() < 3)
    {
        context->handleError(Error(GL_INVALID_VALUE));
        return false;
    }

    const LinkedUniform *uniform = nullptr;
    if (!ValidateUniformCommonBase(context, matrixType, location, count, &uniform))
    {
        return false;
    }

    if (uniform->type != matrixType)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    return true;
}

bool ValidateStateQuery(gl::Context *context, GLenum pname, GLenum *nativeType, unsigned int *numParams)
{
    if (!context->getQueryParameterInfo(pname, nativeType, numParams))
    {
        context->handleError(Error(GL_INVALID_ENUM));
        return false;
    }

    const Caps &caps = context->getCaps();

    if (pname >= GL_DRAW_BUFFER0 && pname <= GL_DRAW_BUFFER15)
    {
        unsigned int colorAttachment = (pname - GL_DRAW_BUFFER0);

        if (colorAttachment >= caps.maxDrawBuffers)
        {
            context->handleError(Error(GL_INVALID_OPERATION));
            return false;
        }
    }

    switch (pname)
    {
      case GL_TEXTURE_BINDING_2D:
      case GL_TEXTURE_BINDING_CUBE_MAP:
      case GL_TEXTURE_BINDING_3D:
      case GL_TEXTURE_BINDING_2D_ARRAY:
        break;
      case GL_TEXTURE_BINDING_EXTERNAL_OES:
          if (!context->getExtensions().eglStreamConsumerExternal)
          {
              context->handleError(
                  Error(GL_INVALID_ENUM, "NV_EGL_stream_consumer_external extension not enabled"));
              return false;
          }
          break;

      case GL_IMPLEMENTATION_COLOR_READ_TYPE:
      case GL_IMPLEMENTATION_COLOR_READ_FORMAT:
        {
            Framebuffer *framebuffer = context->getState().getReadFramebuffer();
            ASSERT(framebuffer);
            if (framebuffer->checkStatus(context->getData()) != GL_FRAMEBUFFER_COMPLETE)
            {
                context->handleError(Error(GL_INVALID_OPERATION));
                return false;
            }

            const FramebufferAttachment *attachment = framebuffer->getReadColorbuffer();
            if (!attachment)
            {
                context->handleError(Error(GL_INVALID_OPERATION));
                return false;
            }
        }
        break;

      default:
        break;
    }

    // pname is valid, but there are no parameters to return
    if (numParams == 0)
    {
        return false;
    }

    return true;
}

bool ValidateCopyTexImageParametersBase(ValidationContext *context,
                                        GLenum target,
                                        GLint level,
                                        GLenum internalformat,
                                        bool isSubImage,
                                        GLint xoffset,
                                        GLint yoffset,
                                        GLint zoffset,
                                        GLint x,
                                        GLint y,
                                        GLsizei width,
                                        GLsizei height,
                                        GLint border,
                                        GLenum *textureFormatOut)
{
    if (level < 0 || xoffset < 0 || yoffset < 0 || zoffset < 0 || width < 0 || height < 0)
    {
        context->handleError(Error(GL_INVALID_VALUE));
        return false;
    }

    if (std::numeric_limits<GLsizei>::max() - xoffset < width || std::numeric_limits<GLsizei>::max() - yoffset < height)
    {
        context->handleError(Error(GL_INVALID_VALUE));
        return false;
    }

    if (border != 0)
    {
        context->handleError(Error(GL_INVALID_VALUE));
        return false;
    }

    if (!ValidMipLevel(context, target, level))
    {
        context->handleError(Error(GL_INVALID_VALUE));
        return false;
    }

    const gl::Framebuffer *framebuffer = context->getState().getReadFramebuffer();
    if (framebuffer->checkStatus(context->getData()) != GL_FRAMEBUFFER_COMPLETE)
    {
        context->handleError(Error(GL_INVALID_FRAMEBUFFER_OPERATION));
        return false;
    }

    const auto &state = context->getState();
    if (state.getReadFramebuffer()->id() != 0 && framebuffer->getSamples(context->getData()) != 0)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    const gl::Caps &caps = context->getCaps();

    GLuint maxDimension = 0;
    switch (target)
    {
      case GL_TEXTURE_2D:
        maxDimension = caps.max2DTextureSize;
        break;

      case GL_TEXTURE_CUBE_MAP_POSITIVE_X:
      case GL_TEXTURE_CUBE_MAP_NEGATIVE_X:
      case GL_TEXTURE_CUBE_MAP_POSITIVE_Y:
      case GL_TEXTURE_CUBE_MAP_NEGATIVE_Y:
      case GL_TEXTURE_CUBE_MAP_POSITIVE_Z:
      case GL_TEXTURE_CUBE_MAP_NEGATIVE_Z:
        maxDimension = caps.maxCubeMapTextureSize;
        break;

      case GL_TEXTURE_2D_ARRAY:
        maxDimension = caps.max2DTextureSize;
        break;

      case GL_TEXTURE_3D:
        maxDimension = caps.max3DTextureSize;
        break;

      default:
          context->handleError(Error(GL_INVALID_ENUM));
        return false;
    }

    gl::Texture *texture =
        state.getTargetTexture(IsCubeMapTextureTarget(target) ? GL_TEXTURE_CUBE_MAP : target);
    if (!texture)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    if (texture->getImmutableFormat() && !isSubImage)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    const gl::InternalFormat &formatInfo = gl::GetInternalFormatInfo(internalformat);

    if (formatInfo.depthBits > 0)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    if (formatInfo.compressed && !ValidCompressedImageSize(context, internalformat, width, height))
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    if (isSubImage)
    {
        if (static_cast<size_t>(xoffset + width) > texture->getWidth(target, level) ||
            static_cast<size_t>(yoffset + height) > texture->getHeight(target, level) ||
            static_cast<size_t>(zoffset) >= texture->getDepth(target, level))
        {
            context->handleError(Error(GL_INVALID_VALUE));
            return false;
        }
    }
    else
    {
        if (IsCubeMapTextureTarget(target) && width != height)
        {
            context->handleError(Error(GL_INVALID_VALUE));
            return false;
        }

        if (!formatInfo.textureSupport(context->getClientVersion(), context->getExtensions()))
        {
            context->handleError(Error(GL_INVALID_ENUM));
            return false;
        }

        int maxLevelDimension = (maxDimension >> level);
        if (static_cast<int>(width) > maxLevelDimension || static_cast<int>(height) > maxLevelDimension)
        {
            context->handleError(Error(GL_INVALID_VALUE));
            return false;
        }
    }

    *textureFormatOut = texture->getInternalFormat(target, level);
    return true;
}

static bool ValidateDrawBase(ValidationContext *context,
                             GLenum mode,
                             GLsizei count,
                             GLsizei primcount)
{
    switch (mode)
    {
      case GL_POINTS:
      case GL_LINES:
      case GL_LINE_LOOP:
      case GL_LINE_STRIP:
      case GL_TRIANGLES:
      case GL_TRIANGLE_STRIP:
      case GL_TRIANGLE_FAN:
        break;
      default:
          context->handleError(Error(GL_INVALID_ENUM));
        return false;
    }

    if (count < 0)
    {
        context->handleError(Error(GL_INVALID_VALUE));
        return false;
    }

    const State &state = context->getState();

    // Check for mapped buffers
    if (state.hasMappedBuffer(GL_ARRAY_BUFFER))
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    if (context->getLimitations().noSeparateStencilRefsAndMasks)
    {
        const Framebuffer *framebuffer             = context->getState().getDrawFramebuffer();
        const FramebufferAttachment *stencilBuffer = framebuffer->getStencilbuffer();
        GLuint stencilBits                         = stencilBuffer ? stencilBuffer->getStencilSize() : 0;
        GLuint minimumRequiredStencilMask          = (1 << stencilBits) - 1;
        const DepthStencilState &depthStencilState = state.getDepthStencilState();
        if ((depthStencilState.stencilWritemask & minimumRequiredStencilMask) !=
                (depthStencilState.stencilBackWritemask & minimumRequiredStencilMask) ||
            state.getStencilRef() != state.getStencilBackRef() ||
            (depthStencilState.stencilMask & minimumRequiredStencilMask) !=
                (depthStencilState.stencilBackMask & minimumRequiredStencilMask))
        {
            // Note: these separate values are not supported in WebGL, due to D3D's limitations. See
            // Section 6.10 of the WebGL 1.0 spec
            ERR(
                "This ANGLE implementation does not support separate front/back stencil "
                "writemasks, reference values, or stencil mask values.");
            context->handleError(Error(GL_INVALID_OPERATION));
            return false;
        }
    }

    const gl::Framebuffer *fbo = state.getDrawFramebuffer();
    if (!fbo || fbo->checkStatus(context->getData()) != GL_FRAMEBUFFER_COMPLETE)
    {
        context->handleError(Error(GL_INVALID_FRAMEBUFFER_OPERATION));
        return false;
    }

    gl::Program *program = state.getProgram();
    if (!program)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    if (!program->validateSamplers(NULL, context->getCaps()))
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    // Uniform buffer validation
    for (unsigned int uniformBlockIndex = 0; uniformBlockIndex < program->getActiveUniformBlockCount(); uniformBlockIndex++)
    {
        const gl::UniformBlock &uniformBlock = program->getUniformBlockByIndex(uniformBlockIndex);
        GLuint blockBinding = program->getUniformBlockBinding(uniformBlockIndex);
        const OffsetBindingPointer<Buffer> &uniformBuffer =
            state.getIndexedUniformBuffer(blockBinding);

        if (uniformBuffer.get() == nullptr)
        {
            // undefined behaviour
            context->handleError(
                Error(GL_INVALID_OPERATION,
                      "It is undefined behaviour to have a used but unbound uniform buffer."));
            return false;
        }

        size_t uniformBufferSize = uniformBuffer.getSize();
        if (uniformBufferSize == 0)
        {
            // Bind the whole buffer.
            uniformBufferSize = static_cast<size_t>(uniformBuffer->getSize());
        }

        if (uniformBufferSize < uniformBlock.dataSize)
        {
            // undefined behaviour
            context->handleError(
                Error(GL_INVALID_OPERATION,
                      "It is undefined behaviour to use a uniform buffer that is too small."));
            return false;
        }
    }

    // No-op if zero count
    return (count > 0);
}

bool ValidateDrawArrays(Context *context, GLenum mode, GLint first, GLsizei count, GLsizei primcount)
{
    if (first < 0)
    {
        context->handleError(Error(GL_INVALID_VALUE));
        return false;
    }

    const State &state = context->getState();
    gl::TransformFeedback *curTransformFeedback = state.getCurrentTransformFeedback();
    if (curTransformFeedback && curTransformFeedback->isActive() && !curTransformFeedback->isPaused() &&
        curTransformFeedback->getPrimitiveMode() != mode)
    {
        // It is an invalid operation to call DrawArrays or DrawArraysInstanced with a draw mode
        // that does not match the current transform feedback object's draw mode (if transform feedback
        // is active), (3.0.2, section 2.14, pg 86)
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    if (!ValidateDrawBase(context, mode, count, primcount))
    {
        return false;
    }

    if (!ValidateDrawAttribs(context, primcount, count))
    {
        return false;
    }

    return true;
}

bool ValidateDrawArraysInstanced(Context *context, GLenum mode, GLint first, GLsizei count, GLsizei primcount)
{
    if (primcount < 0)
    {
        context->handleError(Error(GL_INVALID_VALUE));
        return false;
    }

    if (!ValidateDrawArrays(context, mode, first, count, primcount))
    {
        return false;
    }

    // No-op if zero primitive count
    return (primcount > 0);
}

static bool ValidateDrawInstancedANGLE(Context *context)
{
    // Verify there is at least one active attribute with a divisor of zero
    const gl::State& state = context->getState();

    gl::Program *program = state.getProgram();

    const VertexArray *vao = state.getVertexArray();
    for (size_t attributeIndex = 0; attributeIndex < MAX_VERTEX_ATTRIBS; attributeIndex++)
    {
        const VertexAttribute &attrib = vao->getVertexAttribute(attributeIndex);
        if (program->isAttribLocationActive(attributeIndex) && attrib.divisor == 0)
        {
            return true;
        }
    }

    context->handleError(Error(GL_INVALID_OPERATION,
                               "ANGLE_instanced_arrays requires that at least one active attribute"
                               "has a divisor of zero."));
    return false;
}

bool ValidateDrawArraysInstancedANGLE(Context *context, GLenum mode, GLint first, GLsizei count, GLsizei primcount)
{
    if (!ValidateDrawInstancedANGLE(context))
    {
        return false;
    }

    return ValidateDrawArraysInstanced(context, mode, first, count, primcount);
}

bool ValidateDrawElements(ValidationContext *context,
                          GLenum mode,
                          GLsizei count,
                          GLenum type,
                          const GLvoid *indices,
                          GLsizei primcount,
                          IndexRange *indexRangeOut)
{
    switch (type)
    {
      case GL_UNSIGNED_BYTE:
      case GL_UNSIGNED_SHORT:
        break;
      case GL_UNSIGNED_INT:
          if (context->getClientVersion() < 3 && !context->getExtensions().elementIndexUint)
        {
            context->handleError(Error(GL_INVALID_ENUM));
            return false;
        }
        break;
      default:
          context->handleError(Error(GL_INVALID_ENUM));
        return false;
    }

    const State &state = context->getState();

    gl::TransformFeedback *curTransformFeedback = state.getCurrentTransformFeedback();
    if (curTransformFeedback && curTransformFeedback->isActive() && !curTransformFeedback->isPaused())
    {
        // It is an invalid operation to call DrawElements, DrawRangeElements or DrawElementsInstanced
        // while transform feedback is active, (3.0.2, section 2.14, pg 86)
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    // Check for mapped buffers
    if (state.hasMappedBuffer(GL_ELEMENT_ARRAY_BUFFER))
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    const gl::VertexArray *vao = state.getVertexArray();
    gl::Buffer *elementArrayBuffer = vao->getElementArrayBuffer().get();
    if (!indices && !elementArrayBuffer)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    if (elementArrayBuffer)
    {
        const gl::Type &typeInfo = gl::GetTypeInfo(type);

        GLint64 offset = reinterpret_cast<GLint64>(indices);
        GLint64 byteCount = static_cast<GLint64>(typeInfo.bytes) * static_cast<GLint64>(count)+offset;

        // check for integer overflows
        if (static_cast<GLuint>(count) > (std::numeric_limits<GLuint>::max() / typeInfo.bytes) ||
            byteCount > static_cast<GLint64>(std::numeric_limits<GLuint>::max()))
        {
            context->handleError(Error(GL_OUT_OF_MEMORY));
            return false;
        }

        // Check for reading past the end of the bound buffer object
        if (byteCount > elementArrayBuffer->getSize())
        {
            context->handleError(Error(GL_INVALID_OPERATION));
            return false;
        }
    }
    else if (!indices)
    {
        // Catch this programming error here
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    if (!ValidateDrawBase(context, mode, count, primcount))
    {
        return false;
    }

    // Use max index to validate if our vertex buffers are large enough for the pull.
    // TODO: offer fast path, with disabled index validation.
    // TODO: also disable index checking on back-ends that are robust to out-of-range accesses.
    if (elementArrayBuffer)
    {
        uintptr_t offset = reinterpret_cast<uintptr_t>(indices);
        Error error =
            elementArrayBuffer->getIndexRange(type, static_cast<size_t>(offset), count,
                                              state.isPrimitiveRestartEnabled(), indexRangeOut);
        if (error.isError())
        {
            context->handleError(error);
            return false;
        }
    }
    else
    {
        *indexRangeOut = ComputeIndexRange(type, indices, count, state.isPrimitiveRestartEnabled());
    }

    // If we use an index greater than our maximum supported index range, return an error.
    // The ES3 spec does not specify behaviour here, it is undefined, but ANGLE should always
    // return an error if possible here.
    if (static_cast<GLuint64>(indexRangeOut->end) >= context->getCaps().maxElementIndex)
    {
        context->handleError(Error(GL_INVALID_OPERATION, g_ExceedsMaxElementErrorMessage));
        return false;
    }

    if (!ValidateDrawAttribs(context, primcount, static_cast<GLint>(indexRangeOut->vertexCount())))
    {
        return false;
    }

    // No op if there are no real indices in the index data (all are primitive restart).
    return (indexRangeOut->vertexIndexCount > 0);
}

bool ValidateDrawElementsInstanced(Context *context,
                                   GLenum mode,
                                   GLsizei count,
                                   GLenum type,
                                   const GLvoid *indices,
                                   GLsizei primcount,
                                   IndexRange *indexRangeOut)
{
    if (primcount < 0)
    {
        context->handleError(Error(GL_INVALID_VALUE));
        return false;
    }

    if (!ValidateDrawElements(context, mode, count, type, indices, primcount, indexRangeOut))
    {
        return false;
    }

    // No-op zero primitive count
    return (primcount > 0);
}

bool ValidateDrawElementsInstancedANGLE(Context *context,
                                        GLenum mode,
                                        GLsizei count,
                                        GLenum type,
                                        const GLvoid *indices,
                                        GLsizei primcount,
                                        IndexRange *indexRangeOut)
{
    if (!ValidateDrawInstancedANGLE(context))
    {
        return false;
    }

    return ValidateDrawElementsInstanced(context, mode, count, type, indices, primcount, indexRangeOut);
}

bool ValidateFramebufferTextureBase(Context *context, GLenum target, GLenum attachment,
                                    GLuint texture, GLint level)
{
    if (!ValidFramebufferTarget(target))
    {
        context->handleError(Error(GL_INVALID_ENUM));
        return false;
    }

    if (!ValidateAttachmentTarget(context, attachment))
    {
        return false;
    }

    if (texture != 0)
    {
        gl::Texture *tex = context->getTexture(texture);

        if (tex == NULL)
        {
            context->handleError(Error(GL_INVALID_OPERATION));
            return false;
        }

        if (level < 0)
        {
            context->handleError(Error(GL_INVALID_VALUE));
            return false;
        }
    }

    const gl::Framebuffer *framebuffer = context->getState().getTargetFramebuffer(target);
    ASSERT(framebuffer);

    if (framebuffer->id() == 0)
    {
        context->handleError(
            Error(GL_INVALID_OPERATION, "Cannot change default FBO's attachments"));
        return false;
    }

    return true;
}

bool ValidateFramebufferTexture2D(Context *context, GLenum target, GLenum attachment,
                                  GLenum textarget, GLuint texture, GLint level)
{
    // Attachments are required to be bound to level 0 without ES3 or the GL_OES_fbo_render_mipmap extension
    if (context->getClientVersion() < 3 && !context->getExtensions().fboRenderMipmap && level != 0)
    {
        context->handleError(Error(GL_INVALID_VALUE));
        return false;
    }

    if (!ValidateFramebufferTextureBase(context, target, attachment, texture, level))
    {
        return false;
    }

    if (texture != 0)
    {
        gl::Texture *tex = context->getTexture(texture);
        ASSERT(tex);

        const gl::Caps &caps = context->getCaps();

        switch (textarget)
        {
          case GL_TEXTURE_2D:
            {
                if (level > gl::log2(caps.max2DTextureSize))
                {
                    context->handleError(Error(GL_INVALID_VALUE));
                    return false;
                }
                if (tex->getTarget() != GL_TEXTURE_2D)
                {
                    context->handleError(Error(GL_INVALID_OPERATION));
                    return false;
                }
            }
            break;

          case GL_TEXTURE_CUBE_MAP_POSITIVE_X:
          case GL_TEXTURE_CUBE_MAP_NEGATIVE_X:
          case GL_TEXTURE_CUBE_MAP_POSITIVE_Y:
          case GL_TEXTURE_CUBE_MAP_NEGATIVE_Y:
          case GL_TEXTURE_CUBE_MAP_POSITIVE_Z:
          case GL_TEXTURE_CUBE_MAP_NEGATIVE_Z:
            {
                if (level > gl::log2(caps.maxCubeMapTextureSize))
                {
                    context->handleError(Error(GL_INVALID_VALUE));
                    return false;
                }
                if (tex->getTarget() != GL_TEXTURE_CUBE_MAP)
                {
                    context->handleError(Error(GL_INVALID_OPERATION));
                    return false;
                }
            }
            break;

          default:
              context->handleError(Error(GL_INVALID_ENUM));
            return false;
        }

        const gl::InternalFormat &internalFormatInfo = gl::GetInternalFormatInfo(tex->getInternalFormat(textarget, level));
        if (internalFormatInfo.compressed)
        {
            context->handleError(Error(GL_INVALID_OPERATION));
            return false;
        }
    }

    return true;
}

bool ValidateGetUniformBase(Context *context, GLuint program, GLint location)
{
    if (program == 0)
    {
        context->handleError(Error(GL_INVALID_VALUE));
        return false;
    }

    gl::Program *programObject = GetValidProgram(context, program);
    if (!programObject)
    {
        return false;
    }

    if (!programObject || !programObject->isLinked())
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    if (!programObject->isValidUniformLocation(location))
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    return true;
}

bool ValidateGetUniformfv(Context *context, GLuint program, GLint location, GLfloat* params)
{
    return ValidateGetUniformBase(context, program, location);
}

bool ValidateGetUniformiv(Context *context, GLuint program, GLint location, GLint* params)
{
    return ValidateGetUniformBase(context, program, location);
}

static bool ValidateSizedGetUniform(Context *context, GLuint program, GLint location, GLsizei bufSize)
{
    if (!ValidateGetUniformBase(context, program, location))
    {
        return false;
    }

    gl::Program *programObject = context->getProgram(program);
    ASSERT(programObject);

    // sized queries -- ensure the provided buffer is large enough
    const LinkedUniform &uniform = programObject->getUniformByLocation(location);
    size_t requiredBytes = VariableExternalSize(uniform.type);
    if (static_cast<size_t>(bufSize) < requiredBytes)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    return true;
}

bool ValidateGetnUniformfvEXT(Context *context, GLuint program, GLint location, GLsizei bufSize, GLfloat* params)
{
    return ValidateSizedGetUniform(context, program, location, bufSize);
}

bool ValidateGetnUniformivEXT(Context *context, GLuint program, GLint location, GLsizei bufSize, GLint* params)
{
    return ValidateSizedGetUniform(context, program, location, bufSize);
}

bool ValidateDiscardFramebufferBase(Context *context, GLenum target, GLsizei numAttachments,
                                    const GLenum *attachments, bool defaultFramebuffer)
{
    if (numAttachments < 0)
    {
        context->handleError(Error(GL_INVALID_VALUE, "numAttachments must not be less than zero"));
        return false;
    }

    for (GLsizei i = 0; i < numAttachments; ++i)
    {
        if (attachments[i] >= GL_COLOR_ATTACHMENT0 && attachments[i] <= GL_COLOR_ATTACHMENT31)
        {
            if (defaultFramebuffer)
            {
                context->handleError(Error(
                    GL_INVALID_ENUM, "Invalid attachment when the default framebuffer is bound"));
                return false;
            }

            if (attachments[i] >= GL_COLOR_ATTACHMENT0 + context->getCaps().maxColorAttachments)
            {
                context->handleError(Error(GL_INVALID_OPERATION,
                                           "Requested color attachment is greater than the maximum "
                                           "supported color attachments"));
                return false;
            }
        }
        else
        {
            switch (attachments[i])
            {
              case GL_DEPTH_ATTACHMENT:
              case GL_STENCIL_ATTACHMENT:
              case GL_DEPTH_STENCIL_ATTACHMENT:
                if (defaultFramebuffer)
                {
                    context->handleError(
                        Error(GL_INVALID_ENUM,
                              "Invalid attachment when the default framebuffer is bound"));
                    return false;
                }
                break;
              case GL_COLOR:
              case GL_DEPTH:
              case GL_STENCIL:
                if (!defaultFramebuffer)
                {
                    context->handleError(
                        Error(GL_INVALID_ENUM,
                              "Invalid attachment when the default framebuffer is not bound"));
                    return false;
                }
                break;
              default:
                  context->handleError(Error(GL_INVALID_ENUM, "Invalid attachment"));
                return false;
            }
        }
    }

    return true;
}

bool ValidateInsertEventMarkerEXT(Context *context, GLsizei length, const char *marker)
{
    // Note that debug marker calls must not set error state

    if (length < 0)
    {
        return false;
    }

    if (marker == nullptr)
    {
        return false;
    }

    return true;
}

bool ValidatePushGroupMarkerEXT(Context *context, GLsizei length, const char *marker)
{
    // Note that debug marker calls must not set error state

    if (length < 0)
    {
        return false;
    }

    if (length > 0 && marker == nullptr)
    {
        return false;
    }

    return true;
}

bool ValidateEGLImageTargetTexture2DOES(Context *context,
                                        egl::Display *display,
                                        GLenum target,
                                        egl::Image *image)
{
    if (!context->getExtensions().eglImage && !context->getExtensions().eglImageExternal)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    switch (target)
    {
        case GL_TEXTURE_2D:
            if (!context->getExtensions().eglImage)
            {
                context->handleError(Error(
                    GL_INVALID_ENUM, "GL_TEXTURE_2D texture target requires GL_OES_EGL_image."));
            }
            break;

        case GL_TEXTURE_EXTERNAL_OES:
            if (!context->getExtensions().eglImageExternal)
            {
                context->handleError(Error(
                    GL_INVALID_ENUM,
                    "GL_TEXTURE_EXTERNAL_OES texture target requires GL_OES_EGL_image_external."));
            }
            break;

        default:
            context->handleError(Error(GL_INVALID_ENUM, "invalid texture target."));
            return false;
    }

    if (!display->isValidImage(image))
    {
        context->handleError(Error(GL_INVALID_VALUE, "EGL image is not valid."));
        return false;
    }

    if (image->getSamples() > 0)
    {
        context->handleError(Error(GL_INVALID_OPERATION,
                                   "cannot create a 2D texture from a multisampled EGL image."));
        return false;
    }

    const TextureCaps &textureCaps = context->getTextureCaps().get(image->getInternalFormat());
    if (!textureCaps.texturable)
    {
        context->handleError(Error(GL_INVALID_OPERATION,
                                   "EGL image internal format is not supported as a texture."));
        return false;
    }

    return true;
}

bool ValidateEGLImageTargetRenderbufferStorageOES(Context *context,
                                                  egl::Display *display,
                                                  GLenum target,
                                                  egl::Image *image)
{
    if (!context->getExtensions().eglImage)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    switch (target)
    {
        case GL_RENDERBUFFER:
            break;

        default:
            context->handleError(Error(GL_INVALID_ENUM, "invalid renderbuffer target."));
            return false;
    }

    if (!display->isValidImage(image))
    {
        context->handleError(Error(GL_INVALID_VALUE, "EGL image is not valid."));
        return false;
    }

    const TextureCaps &textureCaps = context->getTextureCaps().get(image->getInternalFormat());
    if (!textureCaps.renderable)
    {
        context->handleError(Error(
            GL_INVALID_OPERATION, "EGL image internal format is not supported as a renderbuffer."));
        return false;
    }

    return true;
}

bool ValidateBindVertexArrayBase(Context *context, GLuint array)
{
    if (!context->isVertexArrayGenerated(array))
    {
        // The default VAO should always exist
        ASSERT(array != 0);
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    return true;
}

bool ValidateLinkProgram(Context *context, GLuint program)
{
    if (context->hasActiveTransformFeedback(program))
    {
        // ES 3.0.4 section 2.15 page 91
        context->handleError(Error(GL_INVALID_OPERATION,
                                   "Cannot link program while program is associated with an active "
                                   "transform feedback object."));
        return false;
    }
    return true;
}

bool ValidateProgramBinaryBase(Context *context,
                               GLuint program,
                               GLenum binaryFormat,
                               const void *binary,
                               GLint length)
{
    Program *programObject = GetValidProgram(context, program);
    if (programObject == nullptr)
    {
        return false;
    }

    const std::vector<GLenum> &programBinaryFormats = context->getCaps().programBinaryFormats;
    if (std::find(programBinaryFormats.begin(), programBinaryFormats.end(), binaryFormat) ==
        programBinaryFormats.end())
    {
        context->handleError(Error(GL_INVALID_ENUM, "Program binary format is not valid."));
        return false;
    }

    if (context->hasActiveTransformFeedback(program))
    {
        // ES 3.0.4 section 2.15 page 91
        context->handleError(Error(GL_INVALID_OPERATION,
                                   "Cannot change program binary while program is associated with "
                                   "an active transform feedback object."));
        return false;
    }

    return true;
}

bool ValidateGetProgramBinaryBase(Context *context,
                                  GLuint program,
                                  GLsizei bufSize,
                                  GLsizei *length,
                                  GLenum *binaryFormat,
                                  void *binary)
{
    Program *programObject = GetValidProgram(context, program);
    if (programObject == nullptr)
    {
        return false;
    }

    if (!programObject->isLinked())
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Program is not linked."));
        return false;
    }

    return true;
}

bool ValidateUseProgram(Context *context, GLuint program)
{
    if (program != 0)
    {
        Program *programObject = context->getProgram(program);
        if (!programObject)
        {
            // ES 3.1.0 section 7.3 page 72
            if (context->getShader(program))
            {
                context->handleError(
                    Error(GL_INVALID_OPERATION,
                          "Attempted to use a single shader instead of a shader program."));
                return false;
            }
            else
            {
                context->handleError(Error(GL_INVALID_VALUE, "Program invalid."));
                return false;
            }
        }
        if (!programObject->isLinked())
        {
            context->handleError(Error(GL_INVALID_OPERATION, "Program not linked."));
            return false;
        }
    }
    if (context->getState().isTransformFeedbackActiveUnpaused())
    {
        // ES 3.0.4 section 2.15 page 91
        context->handleError(
            Error(GL_INVALID_OPERATION,
                  "Cannot change active program while transform feedback is unpaused."));
        return false;
    }

    return true;
}

bool ValidateCopyTexImage2D(ValidationContext *context,
                            GLenum target,
                            GLint level,
                            GLenum internalformat,
                            GLint x,
                            GLint y,
                            GLsizei width,
                            GLsizei height,
                            GLint border)
{
    if (context->getClientVersion() < 3)
    {
        return ValidateES2CopyTexImageParameters(context, target, level, internalformat, false, 0,
                                                 0, x, y, width, height, border);
    }

    ASSERT(context->getClientVersion() == 3);
    return ValidateES3CopyTexImage2DParameters(context, target, level, internalformat, false, 0, 0,
                                               0, x, y, width, height, border);
}

bool ValidateFramebufferRenderbuffer(Context *context,
                                     GLenum target,
                                     GLenum attachment,
                                     GLenum renderbuffertarget,
                                     GLuint renderbuffer)
{
    if (!ValidFramebufferTarget(target) ||
        (renderbuffertarget != GL_RENDERBUFFER && renderbuffer != 0))
    {
        context->handleError(Error(GL_INVALID_ENUM));
        return false;
    }

    return ValidateFramebufferRenderbufferParameters(context, target, attachment,
                                                     renderbuffertarget, renderbuffer);
}

bool ValidateDrawBuffersBase(ValidationContext *context, GLsizei n, const GLenum *bufs)
{
    // INVALID_VALUE is generated if n is negative or greater than value of MAX_DRAW_BUFFERS
    if (n < 0 || static_cast<GLuint>(n) > context->getCaps().maxDrawBuffers)
    {
        context->handleError(
            Error(GL_INVALID_VALUE, "n must be non-negative and no greater than MAX_DRAW_BUFFERS"));
        return false;
    }

    ASSERT(context->getState().getDrawFramebuffer());
    GLuint frameBufferId      = context->getState().getDrawFramebuffer()->id();
    GLuint maxColorAttachment = GL_COLOR_ATTACHMENT0_EXT + context->getCaps().maxColorAttachments;

    // This should come first before the check for the default frame buffer
    // because when we switch to ES3.1+, invalid enums will return INVALID_ENUM
    // rather than INVALID_OPERATION
    for (int colorAttachment = 0; colorAttachment < n; colorAttachment++)
    {
        const GLenum attachment = GL_COLOR_ATTACHMENT0_EXT + colorAttachment;

        if (bufs[colorAttachment] != GL_NONE && bufs[colorAttachment] != GL_BACK &&
            (bufs[colorAttachment] < GL_COLOR_ATTACHMENT0 ||
             bufs[colorAttachment] > GL_COLOR_ATTACHMENT31))
        {
            // Value in bufs is not NONE, BACK, or GL_COLOR_ATTACHMENTi
            // The 3.0.4 spec says to generate GL_INVALID_OPERATION here, but this
            // was changed to GL_INVALID_ENUM in 3.1, which dEQP also expects.
            // 3.1 is still a bit ambiguous about the error, but future specs are
            // expected to clarify that GL_INVALID_ENUM is the correct error.
            context->handleError(Error(GL_INVALID_ENUM, "Invalid buffer value"));
            return false;
        }
        else if (bufs[colorAttachment] >= maxColorAttachment)
        {
            context->handleError(
                Error(GL_INVALID_OPERATION, "Buffer value is greater than MAX_DRAW_BUFFERS"));
            return false;
        }
        else if (bufs[colorAttachment] != GL_NONE && bufs[colorAttachment] != attachment &&
                 frameBufferId != 0)
        {
            // INVALID_OPERATION-GL is bound to buffer and ith argument
            // is not COLOR_ATTACHMENTi or NONE
            context->handleError(
                Error(GL_INVALID_OPERATION, "Ith value does not match COLOR_ATTACHMENTi or NONE"));
            return false;
        }
    }

    // INVALID_OPERATION is generated if GL is bound to the default framebuffer
    // and n is not 1 or bufs is bound to value other than BACK and NONE
    if (frameBufferId == 0)
    {
        if (n != 1)
        {
            context->handleError(Error(GL_INVALID_OPERATION,
                                       "n must be 1 when GL is bound to the default framebuffer"));
            return false;
        }

        if (bufs[0] != GL_NONE && bufs[0] != GL_BACK)
        {
            context->handleError(Error(
                GL_INVALID_OPERATION,
                "Only NONE or BACK are valid values when drawing to the default framebuffer"));
            return false;
        }
    }

    return true;
}

bool ValidateCopyTexSubImage2D(Context *context,
                               GLenum target,
                               GLint level,
                               GLint xoffset,
                               GLint yoffset,
                               GLint x,
                               GLint y,
                               GLsizei width,
                               GLsizei height)
{
    if (context->getClientVersion() < 3)
    {
        return ValidateES2CopyTexImageParameters(context, target, level, GL_NONE, true, xoffset,
                                                 yoffset, x, y, width, height, 0);
    }

    return ValidateES3CopyTexImage2DParameters(context, target, level, GL_NONE, true, xoffset,
                                               yoffset, 0, x, y, width, height, 0);
}

bool ValidateGetBufferPointervBase(Context *context, GLenum target, GLenum pname, void **params)
{
    if (!ValidBufferTarget(context, target))
    {
        context->handleError(Error(GL_INVALID_ENUM, "Buffer target not valid: 0x%X", target));
        return false;
    }

    if (pname != GL_BUFFER_MAP_POINTER)
    {
        context->handleError(Error(GL_INVALID_ENUM, "pname not valid: 0x%X", pname));
        return false;
    }

    Buffer *buffer = context->getState().getTargetBuffer(target);

    // GLES 3.0 section 2.10.1: "Attempts to attempts to modify or query buffer object state for a
    // target bound to zero generate an INVALID_OPERATION error."
    // GLES 3.1 section 6.6 explicitly specifies this error.
    if (!buffer)
    {
        context->handleError(
            Error(GL_INVALID_OPERATION, "Can not get pointer for reserved buffer name zero."));
        return false;
    }

    return true;
}

bool ValidateUnmapBufferBase(Context *context, GLenum target)
{
    if (!ValidBufferTarget(context, target))
    {
        context->handleError(Error(GL_INVALID_ENUM, "Invalid buffer target."));
        return false;
    }

    Buffer *buffer = context->getState().getTargetBuffer(target);

    if (buffer == nullptr || !buffer->isMapped())
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Buffer not mapped."));
        return false;
    }

    return true;
}

bool ValidateMapBufferRangeBase(Context *context,
                                GLenum target,
                                GLintptr offset,
                                GLsizeiptr length,
                                GLbitfield access)
{
    if (!ValidBufferTarget(context, target))
    {
        context->handleError(Error(GL_INVALID_ENUM, "Invalid buffer target."));
        return false;
    }

    if (offset < 0 || length < 0)
    {
        context->handleError(Error(GL_INVALID_VALUE, "Invalid offset or length."));
        return false;
    }

    Buffer *buffer = context->getState().getTargetBuffer(target);

    if (!buffer)
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Attempted to map buffer object zero."));
        return false;
    }

    // Check for buffer overflow
    size_t offsetSize = static_cast<size_t>(offset);
    size_t lengthSize = static_cast<size_t>(length);

    if (!rx::IsUnsignedAdditionSafe(offsetSize, lengthSize) ||
        offsetSize + lengthSize > static_cast<size_t>(buffer->getSize()))
    {
        context->handleError(
            Error(GL_INVALID_VALUE, "Mapped range does not fit into buffer dimensions."));
        return false;
    }

    // Check for invalid bits in the mask
    GLbitfield allAccessBits = GL_MAP_READ_BIT | GL_MAP_WRITE_BIT | GL_MAP_INVALIDATE_RANGE_BIT |
                               GL_MAP_INVALIDATE_BUFFER_BIT | GL_MAP_FLUSH_EXPLICIT_BIT |
                               GL_MAP_UNSYNCHRONIZED_BIT;

    if (access & ~(allAccessBits))
    {
        context->handleError(Error(GL_INVALID_VALUE, "Invalid access bits: 0x%X.", access));
        return false;
    }

    if (length == 0)
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Buffer mapping length is zero."));
        return false;
    }

    if (buffer->isMapped())
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Buffer is already mapped."));
        return false;
    }

    // Check for invalid bit combinations
    if ((access & (GL_MAP_READ_BIT | GL_MAP_WRITE_BIT)) == 0)
    {
        context->handleError(
            Error(GL_INVALID_OPERATION, "Need to map buffer for either reading or writing."));
        return false;
    }

    GLbitfield writeOnlyBits =
        GL_MAP_INVALIDATE_RANGE_BIT | GL_MAP_INVALIDATE_BUFFER_BIT | GL_MAP_UNSYNCHRONIZED_BIT;

    if ((access & GL_MAP_READ_BIT) != 0 && (access & writeOnlyBits) != 0)
    {
        context->handleError(Error(GL_INVALID_OPERATION,
                                   "Invalid access bits when mapping buffer for reading: 0x%X.",
                                   access));
        return false;
    }

    if ((access & GL_MAP_WRITE_BIT) == 0 && (access & GL_MAP_FLUSH_EXPLICIT_BIT) != 0)
    {
        context->handleError(Error(
            GL_INVALID_OPERATION,
            "The explicit flushing bit may only be set if the buffer is mapped for writing."));
        return false;
    }
    return true;
}

bool ValidateFlushMappedBufferRangeBase(Context *context,
                                        GLenum target,
                                        GLintptr offset,
                                        GLsizeiptr length)
{
    if (offset < 0 || length < 0)
    {
        context->handleError(Error(GL_INVALID_VALUE, "Invalid offset/length parameters."));
        return false;
    }

    if (!ValidBufferTarget(context, target))
    {
        context->handleError(Error(GL_INVALID_ENUM, "Invalid buffer target."));
        return false;
    }

    Buffer *buffer = context->getState().getTargetBuffer(target);

    if (buffer == nullptr)
    {
        context->handleError(Error(GL_INVALID_OPERATION, "Attempted to flush buffer object zero."));
        return false;
    }

    if (!buffer->isMapped() || (buffer->getAccessFlags() & GL_MAP_FLUSH_EXPLICIT_BIT) == 0)
    {
        context->handleError(Error(
            GL_INVALID_OPERATION, "Attempted to flush a buffer not mapped for explicit flushing."));
        return false;
    }

    // Check for buffer overflow
    size_t offsetSize = static_cast<size_t>(offset);
    size_t lengthSize = static_cast<size_t>(length);

    if (!rx::IsUnsignedAdditionSafe(offsetSize, lengthSize) ||
        offsetSize + lengthSize > static_cast<size_t>(buffer->getMapLength()))
    {
        context->handleError(
            Error(GL_INVALID_VALUE, "Flushed range does not fit into buffer mapping dimensions."));
        return false;
    }

    return true;
}

bool ValidateGenerateMipmap(Context *context, GLenum target)
{
    if (!ValidTextureTarget(context, target))
    {
        context->handleError(Error(GL_INVALID_ENUM));
        return false;
    }

    Texture *texture = context->getTargetTexture(target);

    if (texture == nullptr)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    const GLuint effectiveBaseLevel = texture->getTextureState().getEffectiveBaseLevel();

    // This error isn't spelled out in the spec in a very explicit way, but we interpret the spec so
    // that out-of-range base level has a non-color-renderable / non-texture-filterable format.
    if (effectiveBaseLevel >= gl::IMPLEMENTATION_MAX_TEXTURE_LEVELS)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    GLenum baseTarget                = (target == GL_TEXTURE_CUBE_MAP) ? GL_TEXTURE_CUBE_MAP_POSITIVE_X : target;
    GLenum internalFormat            = texture->getInternalFormat(baseTarget, effectiveBaseLevel);
    const TextureCaps &formatCaps    = context->getTextureCaps().get(internalFormat);
    const InternalFormat &formatInfo = GetInternalFormatInfo(internalFormat);

    // GenerateMipmap should not generate an INVALID_OPERATION for textures created with
    // unsized formats or that are color renderable and filterable.  Since we do not track if
    // the texture was created with sized or unsized format (only sized formats are stored),
    // it is not possible to make sure the the LUMA formats can generate mipmaps (they should
    // be able to) because they aren't color renderable.  Simply do a special case for LUMA
    // textures since they're the only texture format that can be created with unsized formats
    // that is not color renderable.  New unsized formats are unlikely to be added, since ES2
    // was the last version to use add them.
    bool isLUMA = internalFormat == GL_LUMINANCE8_EXT ||
                  internalFormat == GL_LUMINANCE8_ALPHA8_EXT || internalFormat == GL_ALPHA8_EXT;

    if (formatInfo.depthBits > 0 || formatInfo.stencilBits > 0 || !formatCaps.filterable ||
        (!formatCaps.renderable && !isLUMA) || formatInfo.compressed)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    // GL_EXT_sRGB does not support mipmap generation on sRGB textures
    if (context->getClientVersion() == 2 && formatInfo.colorEncoding == GL_SRGB)
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    // Non-power of 2 ES2 check
    if (!context->getExtensions().textureNPOT &&
        (!isPow2(static_cast<int>(texture->getWidth(baseTarget, 0))) ||
         !isPow2(static_cast<int>(texture->getHeight(baseTarget, 0)))))
    {
        ASSERT(context->getClientVersion() <= 2 &&
               (target == GL_TEXTURE_2D || target == GL_TEXTURE_CUBE_MAP));
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    // Cube completeness check
    if (target == GL_TEXTURE_CUBE_MAP && !texture->getTextureState().isCubeComplete())
    {
        context->handleError(Error(GL_INVALID_OPERATION));
        return false;
    }

    return true;
}

bool ValidateGenBuffers(Context *context, GLint n, GLuint *)
{
    return ValidateGenOrDelete(context, n);
}

bool ValidateDeleteBuffers(Context *context, GLint n, const GLuint *)
{
    return ValidateGenOrDelete(context, n);
}

bool ValidateGenFramebuffers(Context *context, GLint n, GLuint *)
{
    return ValidateGenOrDelete(context, n);
}

bool ValidateDeleteFramebuffers(Context *context, GLint n, const GLuint *)
{
    return ValidateGenOrDelete(context, n);
}

bool ValidateGenRenderbuffers(Context *context, GLint n, GLuint *)
{
    return ValidateGenOrDelete(context, n);
}

bool ValidateDeleteRenderbuffers(Context *context, GLint n, const GLuint *)
{
    return ValidateGenOrDelete(context, n);
}

bool ValidateGenTextures(Context *context, GLint n, GLuint *)
{
    return ValidateGenOrDelete(context, n);
}

bool ValidateDeleteTextures(Context *context, GLint n, const GLuint *)
{
    return ValidateGenOrDelete(context, n);
}

bool ValidateGenOrDelete(Context *context, GLint n)
{
    if (n < 0)
    {
        context->handleError(Error(GL_INVALID_VALUE, "n < 0"));
        return false;
    }
    return true;
}

}  // namespace gl
