Fix read size validation for RGBX formats.

GL_RGBX8_ANGLE is the only format where the upload format is 3-channel
RGB, whilethe download format is 4-channel RGBX.  As such, the internal
format corresponding to format+type expects 3-byte input/output.  The
format is fixed here for readPixels to output 4 bytes per pixel.

Bug: chromium:1458046
Change-Id: Iec737ed64bade003cfab50dc5f595eb4875e81e4
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4706957
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>

src/libANGLE/formatutils.cpp

@@ -1702,7 +1702,15 @@ const InternalFormat &GetInternalFormatInfo(GLenum internalFormat, GLenum type)
 GLuint InternalFormat::computePixelBytes(GLenum formatType) const
 {
     const auto &typeInfo = GetTypeInfo(formatType);
-    GLuint components    = typeInfo.specialInterpretation ? 1u : componentCount;
+    GLuint components    = componentCount;
+    if (sizedInternalFormat == GL_RGBX8_ANGLE)
+    {
+        components = 4;
+    }
+    else if (typeInfo.specialInterpretation)
+    {
+        components = 1;
+    }
     return components * typeInfo.bytes;
 }
 

src/libANGLE/renderer/vulkan/FramebufferVk.cpp

@@ -813,15 +813,6 @@ angle::Result FramebufferVk::readPixels(const gl::Context *context,
                                         gl::Buffer *packBuffer,
                                         void *pixels)
 {
-    // Note that GL_RGBX8_ANGLE is the only format where the upload format is 3-channel RGB, while
-    // the download format is 4-channel RGBX.  As such, the internal format corresponding to
-    // format+type expects 3-byte input/output.  The format is fixed here for readPixels to output
-    // 4 bytes per pixel.
-    if (format == GL_RGBX8_ANGLE)
-    {
-        format = GL_RGBA8;
-    }
-
     // Clip read area to framebuffer.
     const gl::Extents &fbSize = getState().getReadPixelsAttachment(format)->getSize();
     const gl::Rectangle fbRect(0, 0, fbSize.width, fbSize.height);