Validating draw buffers now also considers color mask settings

src/libANGLE/Context.cpp

@@ -4512,6 +4512,7 @@ void Context::colorMask(GLboolean red, GLboolean green, GLboolean blue, GLboolea
 {
     mState.setColorMask(ConvertToBool(red), ConvertToBool(green), ConvertToBool(blue),
                         ConvertToBool(alpha));
+    mStateCache.onColorMaskChange(this);
 }
 
 void Context::cullFace(CullFaceMode mode)
@@ -8525,6 +8526,11 @@ void StateCache::onUniformBufferStateChange(Context *context)
     updateBasicDrawStatesError();
 }
 
+void StateCache::onColorMaskChange(Context *context)
+{
+    updateBasicDrawStatesError();
+}
+
 void StateCache::setValidDrawModes(bool pointsOK,
                                    bool linesOK,
                                    bool trisOK,

src/libANGLE/Context.h

@@ -141,7 +141,8 @@ class StateCache final : angle::NonCopyable
     // 11. onQueryChange.
     // 12. onActiveTransformFeedbackChange.
     // 13. onUniformBufferStateChange.
-    // 14. onBufferBindingChange.
+    // 14. onColorMaskChange.
+    // 15. onBufferBindingChange.
     bool hasBasicDrawStatesError(Context *context) const
     {
         if (mCachedBasicDrawStatesError == 0)
@@ -233,6 +234,7 @@ class StateCache final : angle::NonCopyable
     void onQueryChange(Context *context);
     void onActiveTransformFeedbackChange(Context *context);
     void onUniformBufferStateChange(Context *context);
+    void onColorMaskChange(Context *context);
     void onBufferBindingChange(Context *context);
 
   private:

src/libANGLE/State.cpp

@@ -580,11 +580,6 @@ const RasterizerState &State::getRasterizerState() const
     return mRasterizer;
 }
 
-const BlendState &State::getBlendState() const
-{
-    return mBlend;
-}
-
 const DepthStencilState &State::getDepthStencilState() const
 {
     return mDepthStencil;

src/libANGLE/State.h

@@ -89,7 +89,7 @@ class State : angle::NonCopyable
 
     // State chunk getters
     const RasterizerState &getRasterizerState() const;
-    const BlendState &getBlendState() const;
+    const BlendState &getBlendState() const { return mBlend; }
     const DepthStencilState &getDepthStencilState() const;
 
     // Clear behavior setters & state parameter block generation function

src/libANGLE/validationES.cpp

@@ -2778,16 +2778,19 @@ const char *ValidateDrawStates(Context *context)
                 return kVertexShaderTypeMismatch;
             }
 
-            // Detect that if there's active color buffer without fragment shader output
-            if (!ValidateFragmentShaderColorBufferMaskMatch(context))
+            if (!context->getState().getBlendState().allChannelsMasked())
             {
-                return kDrawBufferMaskMismatch;
-            }
+                // Detect that if there's active color buffer without fragment shader output
+                if (!ValidateFragmentShaderColorBufferMaskMatch(context))
+                {
+                    return kDrawBufferMaskMismatch;
+                }
 
-            // Detect that the color buffer types match the fragment shader output types
-            if (!ValidateFragmentShaderColorBufferTypeMatch(context))
-            {
-                return kDrawBufferTypeMismatch;
+                // Detect that the color buffer types match the fragment shader output types
+                if (!ValidateFragmentShaderColorBufferTypeMatch(context))
+                {
+                    return kDrawBufferTypeMismatch;
+                }
             }
 
             const VertexArray *vao = context->getState().getVertexArray();

src/tests/gl_tests/DrawBuffersTest.cpp

@@ -444,6 +444,16 @@ TEST_P(DrawBuffersWebGL2Test, TwoProgramsWithDifferentOutputsAndClear)
     setDrawBuffers(kMaxBuffers, allBufs);
     drawQuad(program, positionAttrib(), 0.5, 1.0f, true);
     ASSERT_GL_ERROR(GL_INVALID_OPERATION);
+    // Exception: when all 4 channels of color mask are set to false.
+    glColorMask(false, false, false, false);
+    drawQuad(program, positionAttrib(), 0.5, 1.0f, true);
+    ASSERT_GL_NO_ERROR();
+    glColorMask(false, true, false, false);
+    drawQuad(program, positionAttrib(), 0.5, 1.0f, true);
+    ASSERT_GL_ERROR(GL_INVALID_OPERATION);
+    glColorMask(true, true, true, true);
+    drawQuad(program, positionAttrib(), 0.5, 1.0f, true);
+    ASSERT_GL_ERROR(GL_INVALID_OPERATION);
 
     // Clear again. All attachments should be cleared.
     glClear(GL_COLOR_BUFFER_BIT);

src/tests/gl_tests/StateChangeTest.cpp

@@ -3027,6 +3027,16 @@ void main()
     ASSERT_GL_NO_ERROR() << "Draw to float texture with invalid mask";
     glDrawArrays(GL_TRIANGLES, 0, 6);
     EXPECT_GL_ERROR(GL_INVALID_OPERATION);
+    // Set all 4 channels of color mask to false. Validate success.
+    glColorMask(false, false, false, false);
+    glDrawArrays(GL_TRIANGLES, 0, 6);
+    EXPECT_GL_NO_ERROR();
+    glColorMask(false, true, false, false);
+    glDrawArrays(GL_TRIANGLES, 0, 6);
+    EXPECT_GL_ERROR(GL_INVALID_OPERATION);
+    glColorMask(true, true, true, true);
+    glDrawArrays(GL_TRIANGLES, 0, 6);
+    EXPECT_GL_ERROR(GL_INVALID_OPERATION);
 
     // Restore state.
     glDrawBuffers(2, kColor0Enabled);