Allow reads from a multiview framebuffer with one view

extensions/ANGLE_multiview.txt

@@ -24,7 +24,7 @@ Status
 
 Version
 
-    Last Modified Date: July 14, 2017
+    Last Modified Date: July 31, 2018
     Author Revision: 1
 
 Number
@@ -128,7 +128,9 @@ Additions to Chapter 3 of the OpenGL ES 3.0 Specification (Rasterization)
 
     "Calling CopyTexSubImage3D, CopyTexImage2D, or CopyTexSubImage2D will
     result in an INVALID_FRAMEBUFFER_OPERATION error if the multi-view
-    layout of the current read framebuffer is not NONE."
+    layout of the current read framebuffer is
+    FRAMEBUFFER_MULTIVIEW_SIDE_BY_SIDE_ANGLE or the number of views in the
+    current read framebuffer is more than one."
 
 Additions to Chapter 4 of the OpenGL ES 3.0 Specification
 (Per-Fragment Operations and the Framebuffer)
@@ -169,7 +171,9 @@ Additions to Chapter 4 of the OpenGL ES 3.0 Specification
     Add to the end of the section:
 
     "   ReadPixels generates an INVALID_FRAMEBUFFER_OPERATION error if
-    the multi-view layout of the current read framebuffer is not NONE."
+    the multi-view layout of the current read framebuffer is
+    FRAMEBUFFER_MULTIVIEW_SIDE_BY_SIDE_ANGLE or the number of views in the
+    current read framebuffer is more than one."
 
     Modify section 4.3.3 (Copying pixels), p. 198
 
@@ -181,8 +185,10 @@ Additions to Chapter 4 of the OpenGL ES 3.0 Specification
     add a new paragraph:
 
     "Calling BlitFramebuffer will result in an INVALID_FRAMEBUFFER_OPERATION
-    error if the multi-view layout of the current draw framebuffer or
-    read framebuffer is not NONE."
+    error if the multi-view layout of the current draw framebuffer is not NONE,
+    or the multi-view layout of the current read framebuffer is
+    FRAMEBUFFER_MULTIVIEW_SIDE_BY_SIDE_ANGLE, or the number of views in the
+    current read framebuffer is more than one."
 
 
     Modify section 4.4.2 (Attaching Images to Framebuffer Objects), p. 202

src/libANGLE/Framebuffer.cpp

@@ -2057,6 +2057,12 @@ GLenum Framebuffer::getMultiviewLayout() const
     return mState.getMultiviewLayout();
 }
 
+bool Framebuffer::readDisallowedByMultiview() const
+{
+    return (mState.getMultiviewLayout() != GL_NONE && mState.getNumViews() > 1) ||
+           mState.getMultiviewLayout() == GL_FRAMEBUFFER_MULTIVIEW_SIDE_BY_SIDE_ANGLE;
+}
+
 Error Framebuffer::ensureClearAttachmentsInitialized(const Context *context, GLbitfield mask)
 {
     const auto &glState = context->getGLState();

src/libANGLE/Framebuffer.h

@@ -195,6 +195,7 @@ class Framebuffer final : public angle::ObserverInterface, public LabeledObject
 
     const FramebufferAttachment *getAttachment(const Context *context, GLenum attachment) const;
     GLenum getMultiviewLayout() const;
+    bool readDisallowedByMultiview() const;
     GLsizei getNumViews() const;
     GLint getBaseViewIndex() const;
     const std::vector<Offset> *getViewportOffsets() const;

src/libANGLE/validationES.cpp

@@ -1506,8 +1506,10 @@ bool ValidateBlitFramebufferParameters(Context *context,
 
     // ANGLE_multiview, Revision 1:
     // Calling BlitFramebuffer will result in an INVALID_FRAMEBUFFER_OPERATION error if the
-    // multi-view layout of the current draw framebuffer or read framebuffer is not NONE.
-    if (readFramebuffer->getMultiviewLayout() != GL_NONE)
+    // multi-view layout of the current draw framebuffer is not NONE, or if the multi-view layout of
+    // the current read framebuffer is FRAMEBUFFER_MULTIVIEW_SIDE_BY_SIDE_ANGLE or the number of
+    // views in the current read framebuffer is more than one.
+    if (readFramebuffer->readDisallowedByMultiview())
     {
         context->handleError(InvalidFramebufferOperation()
                              << "Attempt to read from a multi-view framebuffer.");
@@ -2522,8 +2524,9 @@ bool ValidateCopyTexImageParametersBase(Context *context,
     // ANGLE_multiview spec, Revision 1:
     // Calling CopyTexSubImage3D, CopyTexImage2D, or CopyTexSubImage2D will result in an
     // INVALID_FRAMEBUFFER_OPERATION error if the multi-view layout of the current read framebuffer
-    // is not NONE.
-    if (source->getMultiviewLayout() != GL_NONE)
+    // is FRAMEBUFFER_MULTIVIEW_SIDE_BY_SIDE_ANGLE or the number of views in the current read
+    // framebuffer is more than one.
+    if (readFramebuffer->readDisallowedByMultiview())
     {
         context->handleError(InvalidFramebufferOperation()
                              << "The active read framebuffer object has multiview attachments.");
@@ -5707,8 +5710,9 @@ bool ValidateReadPixelsBase(Context *context,
 
     // ANGLE_multiview, Revision 1:
     // ReadPixels generates an INVALID_FRAMEBUFFER_OPERATION error if the multi-view layout of the
-    // current read framebuffer is not NONE.
-    if (readBuffer->getMultiviewLayout() != GL_NONE)
+    // current read framebuffer is FRAMEBUFFER_MULTIVIEW_SIDE_BY_SIDE_ANGLE or the number of views
+    // in the current read framebuffer is more than one.
+    if (framebuffer->readDisallowedByMultiview())
     {
         context->handleError(InvalidFramebufferOperation()
                              << "Attempting to read from a multi-view framebuffer.");

src/tests/test_utils/ANGLETest.cpp

@@ -231,6 +231,7 @@ ANGLETestBase::ANGLETestBase(const angle::PlatformParameters &params)
       mQuadVertexBuffer(0),
       mQuadIndexBuffer(0),
       m2DTexturedQuadProgram(0),
+      m3DTexturedQuadProgram(0),
       mDeferContextInit(false)
 {
     mEGLWindow = new EGLWindow(params.majorVersion, params.minorVersion, params.eglParameters);
@@ -269,6 +270,10 @@ ANGLETestBase::~ANGLETestBase()
     {
         glDeleteProgram(m2DTexturedQuadProgram);
     }
+    if (m3DTexturedQuadProgram)
+    {
+        glDeleteProgram(m3DTexturedQuadProgram);
+    }
     SafeDelete(mEGLWindow);
 }
 
@@ -639,13 +644,72 @@ GLuint ANGLETestBase::get2DTexturedQuadProgram()
     return m2DTexturedQuadProgram;
 }
 
+GLuint ANGLETestBase::get3DTexturedQuadProgram()
+{
+    if (m3DTexturedQuadProgram)
+    {
+        return m3DTexturedQuadProgram;
+    }
+
+    const std::string &vs =
+        R"(#version 300 es
+        in vec2 position;
+        out vec2 texCoord;
+        void main()
+        {
+            gl_Position = vec4(position, 0, 1);
+            texCoord = position * 0.5 + vec2(0.5);
+        })";
+
+    const std::string &fs =
+        R"(#version 300 es
+        precision highp float;
+
+        in vec2 texCoord;
+        out vec4 my_FragColor;
+
+        uniform highp sampler3D tex;
+        uniform float u_layer;
+
+        void main()
+        {
+            my_FragColor = texture(tex, vec3(texCoord, u_layer));
+        })";
+
+    m3DTexturedQuadProgram = CompileProgram(vs, fs);
+    return m3DTexturedQuadProgram;
+}
+
 void ANGLETestBase::draw2DTexturedQuad(GLfloat positionAttribZ,
                                        GLfloat positionAttribXYScale,
                                        bool useVertexBuffer)
 {
     ASSERT_NE(0u, get2DTexturedQuadProgram());
-    return drawQuad(get2DTexturedQuadProgram(), "position", positionAttribZ, positionAttribXYScale,
-                    useVertexBuffer);
+    drawQuad(get2DTexturedQuadProgram(), "position", positionAttribZ, positionAttribXYScale,
+             useVertexBuffer);
+}
+
+void ANGLETestBase::draw3DTexturedQuad(GLfloat positionAttribZ,
+                                       GLfloat positionAttribXYScale,
+                                       bool useVertexBuffer,
+                                       float layer)
+{
+    GLuint program = get3DTexturedQuadProgram();
+    ASSERT_NE(0u, program);
+    GLint activeProgram = 0;
+    glGetIntegerv(GL_CURRENT_PROGRAM, &activeProgram);
+    if (static_cast<GLuint>(activeProgram) != program)
+    {
+        glUseProgram(program);
+    }
+    glUniform1f(glGetUniformLocation(program, "u_layer"), layer);
+
+    drawQuad(program, "position", positionAttribZ, positionAttribXYScale, useVertexBuffer);
+
+    if (static_cast<GLuint>(activeProgram) != program)
+    {
+        glUseProgram(static_cast<GLuint>(activeProgram));
+    }
 }
 
 GLuint ANGLETestBase::compileShader(GLenum type, const std::string &source)

src/tests/test_utils/ANGLETest.h

@@ -314,6 +314,12 @@ class ANGLETestBase
                             GLfloat positionAttribXYScale,
                             bool useVertexBuffer);
 
+    // The layer parameter chooses the 3D texture layer to sample from.
+    void draw3DTexturedQuad(GLfloat positionAttribZ,
+                            GLfloat positionAttribXYScale,
+                            bool useVertexBuffer,
+                            float layer);
+
     static GLuint compileShader(GLenum type, const std::string &source);
     static bool extensionEnabled(const std::string &extName);
     static bool extensionRequestable(const std::string &extName);
@@ -362,6 +368,9 @@ class ANGLETestBase
 
     GLuint get2DTexturedQuadProgram();
 
+    // Has a float uniform "u_layer" to choose the 3D texture layer.
+    GLuint get3DTexturedQuadProgram();
+
     angle::PlatformMethods mPlatformMethods;
 
     class ScopedIgnorePlatformMessages : angle::NonCopyable
@@ -399,6 +408,7 @@ class ANGLETestBase
 
     // Used for texture rendering.
     GLuint m2DTexturedQuadProgram;
+    GLuint m3DTexturedQuadProgram;
 
     TestPlatformContext mPlatformContext;