Vulkan: Handle changes to viewport when clip origin is modified

src/libANGLE/Caps.cpp

@@ -1035,6 +1035,7 @@ const ExtensionInfoMap &GetExtensionInfoMap()
         map["GL_EXT_draw_elements_base_vertex"] = enableableExtension(&Extensions::drawElementsBaseVertexEXT);
         map["GL_EXT_gpu_shader5"] = enableableExtension(&Extensions::gpuShader5EXT);
         map["GL_APPLE_clip_distance"] = enableableExtension(&Extensions::clipDistanceAPPLE);
+        map["GL_EXT_clip_control"] = enableableExtension(&Extensions::clipControlEXT);
         map["GL_EXT_EGL_image_array"] = enableableExtension(&Extensions::eglImageArray);
         map["GL_EXT_buffer_storage"] = enableableExtension(&Extensions::bufferStorageEXT);
         map["GL_EXT_external_buffer"] = enableableExtension(&Extensions::externalBufferEXT);

src/libANGLE/Caps.h

@@ -655,6 +655,9 @@ struct Extensions
     // GL_APPLE_clip_distance
     bool clipDistanceAPPLE = false;
 
+    // GL_EXT_clip_control
+    bool clipControlEXT = false;
+
     // GL_OES_texture_cube_map_array
     bool textureCubeMapArrayOES = false;
     // GL_EXT_texture_cube_map_array

src/libANGLE/Context.cpp

@@ -2020,6 +2020,14 @@ void Context::getIntegervImpl(GLenum pname, GLint *params) const
             *params = mState.mCaps.textureBufferOffsetAlignment;
             break;
 
+        // GL_EXT_clip_control
+        case GL_CLIP_ORIGIN_EXT:
+            *params = mState.mClipControlOrigin;
+            break;
+        case GL_CLIP_DEPTH_MODE_EXT:
+            *params = mState.mClipControlDepth;
+            break;
+
         default:
             ANGLE_CONTEXT_TRY(mState.getIntegerv(this, pname, params));
             break;
@@ -5287,6 +5295,11 @@ void Context::depthRangef(GLfloat zNear, GLfloat zFar)
     mState.setDepthRange(clamp01(zNear), clamp01(zFar));
 }
 
+void Context::clipControl(GLenum origin, GLenum depth)
+{
+    mState.setClipControl(origin, depth);
+}
+
 void Context::disable(GLenum cap)
 {
     mState.setEnableFeature(cap, false);

src/libANGLE/Context_gl.cpp

@@ -2935,11 +2935,6 @@ void Context::clearNamedFramebufferuiv(FramebufferID framebuffer,
     UNIMPLEMENTED();
 }
 
-void Context::clipControl(GLenum origin, GLenum depth)
-{
-    UNIMPLEMENTED();
-}
-
 void Context::compressedTextureSubImage1D(TextureID texture,
                                           GLint level,
                                           GLint xoffset,

src/libANGLE/State.cpp

@@ -416,6 +416,9 @@ void State::initialize(Context *context)
     mNearZ           = 0.0f;
     mFarZ            = 1.0f;
 
+    mClipControlOrigin = GL_LOWER_LEFT_EXT;
+    mClipControlDepth  = GL_NEGATIVE_ONE_TO_ONE_EXT;
+
     mActiveSampler = 0;
 
     mVertexAttribCurrentValues.resize(caps.maxVertexAttributes);
@@ -817,6 +820,21 @@ void State::setDepthRange(float zNear, float zFar)
     }
 }
 
+void State::setClipControl(GLenum origin, GLenum depth)
+{
+    if (mClipControlOrigin != origin)
+    {
+        mClipControlOrigin = origin;
+        mDirtyBits.set(DIRTY_BIT_EXTENDED);
+    }
+
+    if (mClipControlDepth != depth)
+    {
+        mClipControlDepth = depth;
+        mDirtyBits.set(DIRTY_BIT_EXTENDED);
+    }
+}
+
 void State::setBlend(bool enabled)
 {
     mBlendState.blend = enabled;
@@ -2366,6 +2384,16 @@ void State::getBooleanv(GLenum pname, GLboolean *params) const
         case GL_PRIMITIVE_RESTART_FOR_PATCHES_SUPPORTED:
             *params = isPrimitiveRestartEnabled() && getExtensions().tessellationShaderEXT;
             break;
+        // 2.2.2 Data Conversions For State Query Commands, in GLES 3.2 spec.
+        // If a command returning boolean data is called, such as GetBooleanv, a floating-point or
+        // integer value converts to FALSE if and only if it is zero. Otherwise it converts to TRUE.
+        // GL_EXT_clip_control
+        case GL_CLIP_ORIGIN_EXT:
+            *params = GL_TRUE;
+            break;
+        case GL_CLIP_DEPTH_MODE_EXT:
+            *params = GL_TRUE;
+            break;
         default:
             UNREACHABLE();
             break;
@@ -2482,6 +2510,15 @@ void State::getFloatv(GLenum pname, GLfloat *params) const
         case GL_MIN_SAMPLE_SHADING_VALUE:
             *params = mMinSampleShading;
             break;
+        // 2.2.2 Data Conversions For State Query Commands, in GLES 3.2 spec.
+        // If a command returning floating-point data is called, such as GetFloatv, ... An integer
+        // value is coerced to floating-point.
+        case GL_CLIP_ORIGIN_EXT:
+            *params = static_cast<float>(mClipControlOrigin);
+            break;
+        case GL_CLIP_DEPTH_MODE_EXT:
+            *params = static_cast<float>(mClipControlDepth);
+            break;
         default:
             UNREACHABLE();
             break;
@@ -2948,6 +2985,13 @@ angle::Result State::getIntegerv(const Context *context, GLenum pname, GLint *pa
             *params = mPatchVertices;
             break;
 
+        // GL_EXT_clip_control
+        case GL_CLIP_ORIGIN_EXT:
+            *params = mClipControlOrigin;
+            break;
+        case GL_CLIP_DEPTH_MODE_EXT:
+            *params = mClipControlDepth;
+            break;
         default:
             UNREACHABLE();
             break;

src/libANGLE/State.h

@@ -173,6 +173,15 @@ class State : angle::NonCopyable
     float getNearPlane() const { return mNearZ; }
     float getFarPlane() const { return mFarZ; }
 
+    // Clip control extension
+    void setClipControl(GLenum origin, GLenum depth);
+    bool isClipControlDepthZeroToOne() const { return mClipControlDepth == GL_ZERO_TO_ONE_EXT; }
+    gl::ClipSpaceOrigin getClipSpaceOrigin() const
+    {
+        return mClipControlOrigin == GL_UPPER_LEFT_EXT ? ClipSpaceOrigin::UpperLeft
+                                                       : ClipSpaceOrigin::LowerLeft;
+    }
+
     // Blend state manipulation
     bool isBlendEnabled() const { return mBlendStateExt.mEnabledMask.test(0); }
     bool isBlendEnabledIndexed(GLuint index) const
@@ -651,7 +660,8 @@ class State : angle::NonCopyable
         DIRTY_BIT_PROVOKING_VERTEX,
         DIRTY_BIT_SAMPLE_SHADING,
         DIRTY_BIT_PATCH_VERTICES,
-        DIRTY_BIT_EXTENDED,  // clip distances, mipmap generation hint, derivative hint.
+        DIRTY_BIT_EXTENDED,  // clip distances, mipmap generation hint, derivative hint,
+                             // EXT_clip_control
         DIRTY_BIT_INVALID,
         DIRTY_BIT_MAX = DIRTY_BIT_INVALID,
     };
@@ -989,6 +999,9 @@ class State : angle::NonCopyable
     float mNearZ;
     float mFarZ;
 
+    GLenum mClipControlOrigin;
+    GLenum mClipControlDepth;
+
     Framebuffer *mReadFramebuffer;
     Framebuffer *mDrawFramebuffer;
     BindingPointer<Renderbuffer> mRenderbuffer;

src/libANGLE/angletypes.h

@@ -83,6 +83,12 @@ struct Rectangle
 bool operator==(const Rectangle &a, const Rectangle &b);
 bool operator!=(const Rectangle &a, const Rectangle &b);
 
+enum class ClipSpaceOrigin
+{
+    LowerLeft = 0,
+    UpperLeft = 1
+};
+
 // Calculate the intersection of two rectangles.  Returns false if the intersection is empty.
 bool ClipRectangle(const Rectangle &source, const Rectangle &clip, Rectangle *intersection);
 // Calculate the smallest rectangle that covers both rectangles.  This rectangle may cover areas

src/libANGLE/queryutils.cpp

@@ -3270,6 +3270,7 @@ bool GetQueryParameterInfo(const State &glState,
             *numParams = 1;
             return true;
         case GL_MAX_CULL_DISTANCES_EXT:
+        case GL_MAX_COMBINED_CLIP_AND_CULL_DISTANCES_EXT:
             if (!extensions.clipCullDistanceEXT)
             {
                 return false;
@@ -3277,8 +3278,9 @@ bool GetQueryParameterInfo(const State &glState,
             *type      = GL_INT;
             *numParams = 1;
             return true;
-        case GL_MAX_COMBINED_CLIP_AND_CULL_DISTANCES_EXT:
-            if (!extensions.clipCullDistanceEXT)
+        case GL_CLIP_ORIGIN_EXT:
+        case GL_CLIP_DEPTH_MODE_EXT:
+            if (!extensions.clipControlEXT)
             {
                 return false;
             }

src/libANGLE/renderer/gl/StateManagerGL.cpp

@@ -2071,6 +2071,7 @@ angle::Result StateManagerGL::syncState(const gl::Context *context,
                 setClipDistancesEnable(state.getEnabledClipDistances());
                 // TODO(jmadill): handle mipmap generation hint
                 // TODO(jmadill): handle shader derivative hint
+                // Nothing to do until EXT_clip_contorl is implemented.
                 break;
             case gl::State::DIRTY_BIT_SAMPLE_SHADING:
                 // Nothing to do until OES_sample_shading is implemented.

src/libANGLE/renderer/metal/ContextMtl.mm

@@ -1044,6 +1044,7 @@ angle::Result ContextMtl::syncState(const gl::Context *context,
                 break;
             case gl::State::DIRTY_BIT_EXTENDED:
                 updateExtendedState(glState);
+                // Nothing to do until EXT_clip_control is implemented.
                 break;
             case gl::State::DIRTY_BIT_SAMPLE_SHADING:
                 // Nothing to do until OES_sample_shading is implemented.

src/libANGLE/renderer/vulkan/ContextVk.cpp

@@ -368,6 +368,7 @@ ContextVk::ContextVk(const gl::State &state, gl::ErrorSet *errorSet, RendererVk
       mXfbVertexCountPerInstance(0),
       mClearColorMasks(0),
       mFlipYForCurrentSurface(false),
+      mClipSpaceOrigin(gl::ClipSpaceOrigin::LowerLeft),
       mIsAnyHostVisibleBufferWritten(false),
       mEmulateSeamfulCubeMapSampling(false),
       mOutsideRenderPassCommands(nullptr),
@@ -2642,11 +2643,15 @@ void ContextVk::updateViewport(FramebufferVk *framebufferVk,
                     correctedRect, &rotatedRect);
 
     VkViewport vkViewport;
-    gl_vk::GetViewport(rotatedRect, nearPlane, farPlane, invertViewport,
-                       // If the surface is rotated 90/270 degrees, use the framebuffer's width
-                       // instead of the height for calculating the final viewport.
-                       isRotatedAspectRatioForDrawFBO() ? fbDimensions.width : fbDimensions.height,
-                       &vkViewport);
+    gl_vk::GetViewport(
+        rotatedRect, nearPlane, farPlane, invertViewport,
+        // If clip space origin is upper left, viewport origin's y value will be offset by the
+        // height of the viewport when clip space is mapped into screen space.
+        mClipSpaceOrigin == gl::ClipSpaceOrigin::UpperLeft,
+        // If the surface is rotated 90/270 degrees, use the framebuffer's width instead of the
+        // height for calculating the final viewport.
+        isRotatedAspectRatioForDrawFBO() ? fbDimensions.width : fbDimensions.height, &vkViewport);
+
     mGraphicsPipelineDesc->updateViewport(&mGraphicsPipelineTransition, vkViewport);
     invalidateGraphicsDriverUniforms();
 }
@@ -2904,7 +2909,7 @@ angle::Result ContextVk::syncState(const gl::Context *context,
             case gl::State::DIRTY_BIT_FRONT_FACE:
                 mGraphicsPipelineDesc->updateFrontFace(&mGraphicsPipelineTransition,
                                                        glState.getRasterizerState(),
-                                                       isViewportFlipEnabledForDrawFBO());
+                                                       isYFlipEnabledForDrawFBO());
                 break;
             case gl::State::DIRTY_BIT_POLYGON_OFFSET_FILL_ENABLED:
                 mGraphicsPipelineDesc->updatePolygonOffsetFillEnabled(
@@ -2980,9 +2985,10 @@ angle::Result ContextVk::syncState(const gl::Context *context,
                                glState.getFarPlane(), isViewportFlipEnabledForDrawFBO());
                 updateColorMasks(glState.getBlendStateExt());
                 updateRasterizationSamples(mDrawFramebuffer->getSamples());
+
                 mGraphicsPipelineDesc->updateFrontFace(&mGraphicsPipelineTransition,
                                                        glState.getRasterizerState(),
-                                                       isViewportFlipEnabledForDrawFBO());
+                                                       isYFlipEnabledForDrawFBO());
                 updateScissor(glState);
                 const gl::DepthStencilState depthStencilState = glState.getDepthStencilState();
                 mGraphicsPipelineDesc->updateDepthTestEnabled(&mGraphicsPipelineTransition,
@@ -3079,10 +3085,30 @@ angle::Result ContextVk::syncState(const gl::Context *context,
             case gl::State::DIRTY_BIT_PROVOKING_VERTEX:
                 break;
             case gl::State::DIRTY_BIT_EXTENDED:
+            {
                 // Handling clip distance enabled flags, mipmap generation hint & shader derivative
                 // hint.
                 invalidateGraphicsDriverUniforms();
+
+                // Handling clip space origin for EXT_clip_control.
+                if (glState.getClipSpaceOrigin() != getClipSpaceOrigin())
+                {
+                    updateClipSpaceOrigin(glState);
+                    updateViewport(vk::GetImpl(glState.getDrawFramebuffer()), glState.getViewport(),
+                                   glState.getNearPlane(), glState.getFarPlane(),
+                                   isViewportFlipEnabledForDrawFBO());
+                    // Since we are flipping the y coordinate, update front face state
+                    mGraphicsPipelineDesc->updateFrontFace(&mGraphicsPipelineTransition,
+                                                           glState.getRasterizerState(),
+                                                           isYFlipEnabledForDrawFBO());
+                    updateScissor(glState);
+
+                    // Nothing is needed for depth correction for EXT_clip_control.
+                    // glState will be used to toggle control path of depth correction code in
+                    // SPIR-V tranform options.
+                }
                 break;
+            }
             case gl::State::DIRTY_BIT_PATCH_VERTICES:
                 mGraphicsPipelineDesc->updatePatchVertices(&mGraphicsPipelineTransition,
                                                            glState.getPatchVertices());
@@ -3281,6 +3307,16 @@ void ContextVk::updateSurfaceRotationReadFramebuffer(const gl::State &glState)
         DetermineSurfaceRotation(readFramebuffer, mCurrentWindowSurface);
 }
 
+gl::ClipSpaceOrigin ContextVk::getClipSpaceOrigin() const
+{
+    return mClipSpaceOrigin;
+}
+
+void ContextVk::updateClipSpaceOrigin(const gl::State &glState)
+{
+    mClipSpaceOrigin = glState.getClipSpaceOrigin();
+}
+
 gl::Caps ContextVk::getNativeCaps() const
 {
     return mRenderer->getNativeCaps();

src/libANGLE/renderer/vulkan/ContextVk.h

@@ -208,6 +208,20 @@ class ContextVk : public ContextImpl, public vk::Context, public MultisampleText
     SurfaceRotation getRotationDrawFramebuffer() const;
     SurfaceRotation getRotationReadFramebuffer() const;
 
+    // View port (x, y, w, h) will be determined by a combination of -
+    // 1. clip space origin
+    // 2. isViewportFlipEnabledForDrawFBO
+    // For userdefined FBOs it will be based on the value of isViewportFlipEnabledForDrawFBO.
+    // For default FBOs it will be XOR of ClipOrigin and isViewportFlipEnabledForDrawFBO.
+    // isYFlipEnabledForDrawFBO indicates the rendered image is upside-down.
+    ANGLE_INLINE bool isYFlipEnabledForDrawFBO() const
+    {
+        return mClipSpaceOrigin == gl::ClipSpaceOrigin::UpperLeft
+                   ? !isViewportFlipEnabledForDrawFBO()
+                   : isViewportFlipEnabledForDrawFBO();
+    }
+    gl::ClipSpaceOrigin getClipSpaceOrigin() const;
+
     void invalidateProgramBindingHelper(const gl::State &glState);
     angle::Result invalidateProgramExecutableHelper(const gl::Context *context);
 
@@ -735,6 +749,8 @@ class ContextVk : public ContextImpl, public vk::Context, public MultisampleText
     void updateSurfaceRotationDrawFramebuffer(const gl::State &glState);
     void updateSurfaceRotationReadFramebuffer(const gl::State &glState);
 
+    void updateClipSpaceOrigin(const gl::State &glState);
+
     angle::Result updateActiveTextures(const gl::Context *context);
     angle::Result updateActiveImages(const gl::Context *context,
                                      vk::CommandBufferHelper *commandBufferHelper);
@@ -941,6 +957,9 @@ class ContextVk : public ContextImpl, public vk::Context, public MultisampleText
     bool mFlipViewportForDrawFramebuffer;
     bool mFlipViewportForReadFramebuffer;
 
+    // Cache clip origin state, needed for viewport calculation.
+    gl::ClipSpaceOrigin mClipSpaceOrigin;
+
     // If any host-visible buffer is written by the GPU since last submission, a barrier is inserted
     // at the end of the command buffer to make that write available to the host.
     bool mIsAnyHostVisibleBufferWritten;

src/libANGLE/renderer/vulkan/UtilsVk.cpp

@@ -1571,11 +1571,13 @@ angle::Result UtilsVk::clearFramebuffer(ContextVk *contextVk,
     VkViewport viewport;
     gl::Rectangle completeRenderArea = framebuffer->getRotatedCompleteRenderArea(contextVk);
     bool invertViewport              = contextVk->isViewportFlipEnabledForDrawFBO();
+    bool clipSpaceOriginUpperLeft =
+        contextVk->getClipSpaceOrigin() == gl::ClipSpaceOrigin::UpperLeft;
     // Set depth range to clear value.  If clearing depth, the vertex shader depth output is clamped
     // to this value, thus clearing the depth buffer to the desired clear value.
     const float clearDepthValue = params.depthStencilClearValue.depth;
     gl_vk::GetViewport(completeRenderArea, clearDepthValue, clearDepthValue, invertViewport,
-                       completeRenderArea.height, &viewport);
+                       clipSpaceOriginUpperLeft, completeRenderArea.height, &viewport);
     pipelineDesc.setViewport(viewport);
 
     // Scissored clears can create a large number of pipelines in some tests.  Use dynamic state for
@@ -1801,7 +1803,8 @@ angle::Result UtilsVk::blitResolveImpl(ContextVk *contextVk,
 
     VkViewport viewport;
     gl::Rectangle completeRenderArea = framebuffer->getRotatedCompleteRenderArea(contextVk);
-    gl_vk::GetViewport(completeRenderArea, 0.0f, 1.0f, false, completeRenderArea.height, &viewport);
+    gl_vk::GetViewport(completeRenderArea, 0.0f, 1.0f, false, false, completeRenderArea.height,
+                       &viewport);
     pipelineDesc.setViewport(viewport);
 
     pipelineDesc.setScissor(gl_vk::GetRect(params.blitArea));
@@ -2235,7 +2238,7 @@ angle::Result UtilsVk::copyImage(ContextVk *contextVk,
     }
 
     VkViewport viewport;
-    gl_vk::GetViewport(renderArea, 0.0f, 1.0f, false, dest->getExtents().height, &viewport);
+    gl_vk::GetViewport(renderArea, 0.0f, 1.0f, false, false, dest->getExtents().height, &viewport);
     pipelineDesc.setViewport(viewport);
 
     VkRect2D scissor = gl_vk::GetRect(renderArea);
@@ -2690,8 +2693,10 @@ angle::Result UtilsVk::unresolve(ContextVk *contextVk,
     VkViewport viewport;
     gl::Rectangle completeRenderArea = framebuffer->getRotatedCompleteRenderArea(contextVk);
     bool invertViewport              = contextVk->isViewportFlipEnabledForDrawFBO();
-    gl_vk::GetViewport(completeRenderArea, 0.0f, 1.0f, invertViewport, completeRenderArea.height,
-                       &viewport);
+    bool clipSpaceOriginUpperLeft =
+        contextVk->getClipSpaceOrigin() == gl::ClipSpaceOrigin::UpperLeft;
+    gl_vk::GetViewport(completeRenderArea, 0.0f, 1.0f, invertViewport, clipSpaceOriginUpperLeft,
+                       completeRenderArea.height, &viewport);
     pipelineDesc.setViewport(viewport);
 
     pipelineDesc.setScissor(gl_vk::GetRect(completeRenderArea));

src/libANGLE/renderer/vulkan/vk_utils.cpp

@@ -1310,6 +1310,7 @@ void GetViewport(const gl::Rectangle &viewport,
                  float nearPlane,
                  float farPlane,
                  bool invertViewport,
+                 bool clipSpaceOriginUpperLeft,
                  GLint renderAreaHeight,
                  VkViewport *viewportOut)
 {
@@ -1320,10 +1321,60 @@ void GetViewport(const gl::Rectangle &viewport,
     viewportOut->minDepth = gl::clamp01(nearPlane);
     viewportOut->maxDepth = gl::clamp01(farPlane);
 
-    if (invertViewport)
+    // Say an application intends to draw a primitive (shown as 'o' below), it can choose to use
+    // different clip space origin. When clip space origin (shown as 'C' below) is switched from
+    // lower-left to upper-left, primitives will be rendered with its y-coordinate flipped.
+
+    // Rendered content will differ based on whether it is a default framebuffer or a user defined
+    // framebuffer. We modify the viewport's 'y' and 'h' accordingly.
+
+    // clip space origin is lower-left
+    // Expected draw in GLES        default framebuffer    user defined framebuffer
+    // (0,H)                        (0,0)                  (0,0)
+    // +                            +-----------+  (W,0)   +-----------+ (W,0)
+    // |                            |                      |  C----+
+    // |                            |                      |  |    | (h)
+    // |  +----+                    |  +----+              |  | O  |
+    // |  | O  |                    |  | O  | (-h)         |  +----+
+    // |  |    |                    |  |    |              |
+    // |  C----+                    |  C----+              |
+    // +-----------+ (W,0)          +                      +
+    // (0,0)                        (0,H)                  (0,H)
+    //                              y' = H - h             y' = y
+
+    // clip space origin is upper-left
+    // Expected draw in GLES        default framebuffer     user defined framebuffer
+    // (0,H)                        (0,0)                  (0,0)
+    // +                            +-----------+  (W,0)   +-----------+ (W,0)
+    // |                            |                      |  +----+
+    // |                            |                      |  | O  | (-h)
+    // |  C----+                    |  C----+              |  |    |
+    // |  |    |                    |  |    | (h)          |  C----+
+    // |  | O  |                    |  | O  |              |
+    // |  +----+                    |  +----+              |
+    // +-----------+  (W,0)         +                      +
+    // (0,0)                        (0,H)                  (0,H)
+    //                              y' = H - (y + h)       y' = y + H
+
+    if (clipSpaceOriginUpperLeft)
     {
-        viewportOut->y      = static_cast<float>(renderAreaHeight - viewport.y);
-        viewportOut->height = -viewportOut->height;
+        if (invertViewport)
+        {
+            viewportOut->y = static_cast<float>(renderAreaHeight - (viewport.height + viewport.y));
+        }
+        else
+        {
+            viewportOut->y      = static_cast<float>(viewport.height + viewport.y);
+            viewportOut->height = -viewportOut->height;
+        }
+    }
+    else
+    {
+        if (invertViewport)
+        {
+            viewportOut->y      = static_cast<float>(renderAreaHeight - viewport.y);
+            viewportOut->height = -viewportOut->height;
+        }
     }
 }
 

src/libANGLE/renderer/vulkan/vk_utils.h

@@ -960,6 +960,7 @@ void GetViewport(const gl::Rectangle &viewport,
                  float nearPlane,
                  float farPlane,
                  bool invertViewport,
+                 bool upperLeftOrigin,
                  GLint renderAreaHeight,
                  VkViewport *viewportOut);
 

src/libANGLE/validationESEXT.cpp

@@ -1338,7 +1338,19 @@ bool ValidateBufferStorageEXT(const Context *context,
 // GL_EXT_clip_control
 bool ValidateClipControlEXT(const Context *context, GLenum origin, GLenum depth)
 {
-    return false;
+    if ((origin != GL_LOWER_LEFT_EXT) && (origin != GL_UPPER_LEFT_EXT))
+    {
+        context->validationError(GL_INVALID_ENUM, kInvalidOriginEnum);
+        return false;
+    }
+
+    if ((depth != GL_NEGATIVE_ONE_TO_ONE_EXT) && (depth != GL_ZERO_TO_ONE_EXT))
+    {
+        context->validationError(GL_INVALID_ENUM, kInvalidDepthEnum);
+        return false;
+    }
+
+    return true;
 }
 
 // GL_EXT_external_buffer