WebGL: Validate texture copying feedback loops.

src/libANGLE/Framebuffer.cpp

@@ -1018,4 +1018,26 @@ bool Framebuffer::formsRenderingFeedbackLoopWith(const State &state) const
     return false;
 }
 
+bool Framebuffer::formsCopyingFeedbackLoopWith(GLuint copyTextureID, GLint copyTextureLevel) const
+{
+    if (mId == 0)
+    {
+        // It seems impossible to form a texture copying feedback loop with the default FBO.
+        return false;
+    }
+
+    const FramebufferAttachment *readAttachment = getReadColorbuffer();
+    ASSERT(readAttachment);
+
+    if (readAttachment->isTextureWithId(copyTextureID))
+    {
+        // TODO(jmadill): 3D/Array texture layers.
+        if (readAttachment->getTextureImageIndex().mipIndex == copyTextureLevel)
+        {
+            return true;
+        }
+    }
+    return false;
+}
+
 }  // namespace gl

src/libANGLE/Framebuffer.h

@@ -214,6 +214,7 @@ class Framebuffer final : public LabeledObject, public angle::SignalReceiver
     void signal(angle::SignalToken token) override;
 
     bool formsRenderingFeedbackLoopWith(const State &state) const;
+    bool formsCopyingFeedbackLoopWith(GLuint copyTextureID, GLint copyTextureLevel) const;
 
   private:
     void detachResourceById(GLenum resourceType, GLuint resourceId);

src/libANGLE/validationES.cpp

@@ -3124,6 +3124,19 @@ bool ValidateCopyTexImageParametersBase(ValidationContext *context,
     {
         *textureFormatOut = texture->getFormat(target, level);
     }
+
+    // Detect texture copying feedback loops for WebGL.
+    if (context->getExtensions().webglCompatibility)
+    {
+        if (readFramebuffer->formsCopyingFeedbackLoopWith(texture->id(), level))
+        {
+            context->handleError(Error(GL_INVALID_OPERATION,
+                                       "Texture copying feedback loop formed between Framebuffer "
+                                       "and specified Texture level."));
+            return false;
+        }
+    }
+
     return true;
 }
 

src/tests/gl_tests/WebGLCompatibilityTest.cpp

@@ -528,6 +528,67 @@ TEST_P(WebGLCompatibilityTest, RenderingFeedbackLoop)
     EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::red);
 }
 
+// Test tests that texture copying feedback loops are properly rejected in WebGL.
+// Based on the WebGL test conformance/textures/misc/texture-copying-feedback-loops.html
+TEST_P(WebGLCompatibilityTest, TextureCopyingFeedbackLoops)
+{
+    GLTexture texture;
+    glBindTexture(GL_TEXTURE_2D, texture.get());
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 2, 2, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+
+    GLTexture texture2;
+    glBindTexture(GL_TEXTURE_2D, texture2.get());
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 2, 2, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+
+    GLFramebuffer framebuffer;
+    glBindFramebuffer(GL_FRAMEBUFFER, framebuffer.get());
+    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture.get(), 0);
+
+    // framebuffer should be FRAMEBUFFER_COMPLETE.
+    ASSERT_GLENUM_EQ(GL_FRAMEBUFFER_COMPLETE, glCheckFramebufferStatus(GL_FRAMEBUFFER));
+    ASSERT_GL_NO_ERROR();
+
+    // testing copyTexImage2D
+
+    // copyTexImage2D to same texture but different level
+    glBindTexture(GL_TEXTURE_2D, texture.get());
+    glCopyTexImage2D(GL_TEXTURE_2D, 1, GL_RGBA, 0, 0, 2, 2, 0);
+    EXPECT_GL_NO_ERROR();
+
+    // copyTexImage2D to same texture same level, invalid feedback loop
+    glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 0, 0, 2, 2, 0);
+    EXPECT_GL_ERROR(GL_INVALID_OPERATION);
+
+    // copyTexImage2D to different texture
+    glBindTexture(GL_TEXTURE_2D, texture2.get());
+    glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 0, 0, 2, 2, 0);
+    EXPECT_GL_NO_ERROR();
+
+    // testing copyTexSubImage2D
+
+    // copyTexSubImage2D to same texture but different level
+    glBindTexture(GL_TEXTURE_2D, texture.get());
+    glCopyTexSubImage2D(GL_TEXTURE_2D, 1, 0, 0, 0, 0, 1, 1);
+    EXPECT_GL_NO_ERROR();
+
+    // copyTexSubImage2D to same texture same level, invalid feedback loop
+    glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, 1, 1);
+    EXPECT_GL_ERROR(GL_INVALID_OPERATION);
+
+    // copyTexSubImage2D to different texture
+    glBindTexture(GL_TEXTURE_2D, texture2.get());
+    glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, 1, 1);
+    EXPECT_GL_NO_ERROR();
+}
+
 // Use this to select which configurations (e.g. which renderer, which GLES major version) these
 // tests should be run against.
 ANGLE_INSTANTIATE_TEST(WebGLCompatibilityTest,