Fix robust resource initialization with clipped CopyTexSubImage2D.

src/libANGLE/Texture.cpp

@@ -1192,7 +1192,27 @@ angle::Result Texture::copySubImage(Context *context,
 {
     ASSERT(TextureTargetToType(index.getTarget()) == mState.mType);
 
-    Box destBox(destOffset.x, destOffset.y, destOffset.z, sourceArea.width, sourceArea.height, 1);
+    // Most if not all renderers clip these copies to the size of the source framebuffer, leaving
+    // other pixels untouched. For safety in robust resource initialization, assume that that
+    // clipping is going to occur when computing the region for which to ensure initialization. If
+    // the copy lies entirely off the source framebuffer, initialize as though a zero-size box is
+    // going to be set during the copy operation. Note that this assumes that
+    // ensureSubImageInitialized ensures initialization of the entire destination texture, and not
+    // just a sub-region.
+    Box destBox;
+    if (context->isRobustResourceInitEnabled())
+    {
+        Extents fbSize = source->getReadColorAttachment()->getSize();
+        Rectangle clippedArea;
+        if (ClipRectangle(sourceArea, Rectangle(0, 0, fbSize.width, fbSize.height), &clippedArea))
+        {
+            const Offset clippedOffset(destOffset.x + clippedArea.x - sourceArea.x,
+                                       destOffset.y + clippedArea.y - sourceArea.y, 0);
+            destBox = Box(clippedOffset.x, clippedOffset.y, clippedOffset.z, clippedArea.width,
+                          clippedArea.height, 1);
+        }
+    }
+
     ANGLE_TRY(
         ensureSubImageInitialized(context, index.getTarget(), index.getLevelIndex(), destBox));
 
@@ -1859,6 +1879,8 @@ angle::Result Texture::ensureSubImageInitialized(const Context *context,
                                 area.depth == desc.size.depth;
         if (!coversWholeImage)
         {
+            // NOTE: do not optimize this to only initialize the passed area of the texture, or the
+            // initialization logic in copySubImage will be incorrect.
             ANGLE_TRY(initializeContents(context, imageIndex));
         }
         setInitState(imageIndex, InitState::Initialized);

src/libANGLE/renderer/gl/TextureGL.cpp

@@ -749,8 +749,8 @@ angle::Result TextureGL::copySubImage(const gl::Context *context,
                                       const gl::Rectangle &sourceArea,
                                       gl::Framebuffer *source)
 {
-    const FunctionsGL *functions = GetFunctionsGL(context);
-    StateManagerGL *stateManager = GetStateManagerGL(context);
+    const FunctionsGL *functions      = GetFunctionsGL(context);
+    StateManagerGL *stateManager      = GetStateManagerGL(context);
     const angle::FeaturesGL &features = GetFeaturesGL(context);
 
     gl::TextureTarget target                 = index.getTarget();

src/tests/gl_tests/RobustResourceInitTest.cpp

@@ -291,6 +291,8 @@ class RobustResourceInitTest : public ANGLETest
 
     template <typename ClearFunc>
     void maskedStencilClear(ClearFunc clearFunc);
+
+    void copyTexSubImage2DCustomFBOTest(int offsetX, int offsetY);
 };
 
 class RobustResourceInitTestES3 : public RobustResourceInitTest
@@ -1531,6 +1533,60 @@ TEST_P(RobustResourceInitTest, CopyTexSubImage2D)
     VerifyRGBA8PixelRect<kDestSize>(destInitTest);
 }
 
+void RobustResourceInitTest::copyTexSubImage2DCustomFBOTest(int offsetX, int offsetY)
+{
+    const int texSize = 512;
+    const int fboSize = 16;
+
+    GLTexture texture;
+    glBindTexture(GL_TEXTURE_2D, texture.get());
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, texSize, texSize, 0, GL_RGBA, GL_UNSIGNED_BYTE,
+                 nullptr);
+    ASSERT_GL_NO_ERROR();
+
+    GLRenderbuffer renderbuffer;
+    glBindRenderbuffer(GL_RENDERBUFFER, renderbuffer.get());
+    glRenderbufferStorage(GL_RENDERBUFFER, GL_RGBA4, fboSize, fboSize);
+    ASSERT_GL_NO_ERROR();
+
+    GLFramebuffer framebuffer;
+    glBindFramebuffer(GL_FRAMEBUFFER, framebuffer.get());
+    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER,
+                              renderbuffer.get());
+    ASSERT_GL_NO_ERROR();
+    ASSERT_GL_FRAMEBUFFER_COMPLETE(GL_FRAMEBUFFER);
+
+    glClearColor(1.0, 0.0, 0.0, 1.0);
+    glClear(GL_COLOR_BUFFER_BIT);
+    ASSERT_GL_NO_ERROR();
+
+    glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, offsetX, offsetY, texSize, texSize);
+    ASSERT_GL_NO_ERROR();
+
+    GLFramebuffer readbackFBO;
+    glBindFramebuffer(GL_FRAMEBUFFER, readbackFBO.get());
+    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture.get(), 0);
+    ASSERT_GL_FRAMEBUFFER_COMPLETE(GL_FRAMEBUFFER);
+    checkCustomFramebufferNonZeroPixels(texSize, texSize, -offsetX, -offsetY, fboSize, fboSize,
+                                        GLColor::red);
+}
+
+// Test CopyTexSubImage2D clipped to size of custom FBO, zero x/y source offset.
+TEST_P(RobustResourceInitTest, CopyTexSubImage2DCustomFBOZeroOffsets)
+{
+    // TODO(anglebug.com/4507): pass this test on the Metal backend.
+    ANGLE_SKIP_TEST_IF(IsMetal());
+    copyTexSubImage2DCustomFBOTest(0, 0);
+}
+
+// Test CopyTexSubImage2D clipped to size of custom FBO, negative x/y source offset.
+TEST_P(RobustResourceInitTest, CopyTexSubImage2DCustomFBONegativeOffsets)
+{
+    // TODO(anglebug.com/4507): pass this test on the Metal backend.
+    ANGLE_SKIP_TEST_IF(IsMetal());
+    copyTexSubImage2DCustomFBOTest(-8, -8);
+}
+
 // Tests that calling CopyTexSubImage3D will initialize the source & destination.
 TEST_P(RobustResourceInitTestES3, CopyTexSubImage3D)
 {