From 8ab9a9aa21904593dd3adf4c4a5e73afe75ed575 Mon Sep 17 00:00:00 2001
From: Jeff Gilbert <jgilbert@mozilla.com>
Date: Thu, 21 Dec 2017 17:42:52 -0800
Subject: [PATCH] Bug 1427668 - Assert that no-alpha backbuffers have 0xff
 alpha. - r=daoshengmu

MozReview-Commit-ID: 5UJdoud0f2C
---
 dom/canvas/WebGLContext.cpp           | 9 +++++++++
 dom/canvas/WebGLContext.h             | 2 +-
 gfx/gl/GLContext.h                    | 1 -
 gfx/gl/GLReadTexImageHelper.cpp       | 5 -----
 gfx/layers/CopyableCanvasRenderer.cpp | 4 ++--
 5 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/dom/canvas/WebGLContext.cpp b/dom/canvas/WebGLContext.cpp
index 2e8a132b4b27..a5aa7cc22268 100644
--- a/dom/canvas/WebGLContext.cpp
+++ b/dom/canvas/WebGLContext.cpp
@@ -1576,6 +1576,15 @@ WebGLContext::PresentScreenBuffer()
     gl->fBindFramebuffer(LOCAL_GL_FRAMEBUFFER, 0);
     BlitBackbufferToCurDriverFB();
 
+#ifdef DEBUG
+    if (!mOptions.alpha) {
+        gl->fBindFramebuffer(LOCAL_GL_FRAMEBUFFER, 0);
+        uint32_t pixel = 3;
+        gl->fReadPixels(0, 0, 1, 1, LOCAL_GL_RGBA, LOCAL_GL_UNSIGNED_BYTE, &pixel);
+        MOZ_ASSERT((pixel & 0xff000000) == 0xff000000);
+    }
+#endif
+
     if (!screen->PublishFrame(screen->Size())) {
         GenerateWarning("PublishFrame failed. Losing context.");
         ForceLoseContext();
diff --git a/dom/canvas/WebGLContext.h b/dom/canvas/WebGLContext.h
index 208d502c7de9..b2f6865cba28 100644
--- a/dom/canvas/WebGLContext.h
+++ b/dom/canvas/WebGLContext.h
@@ -366,7 +366,7 @@ public:
     GetSurfaceSnapshot(gfxAlphaType* out_alphaType) override;
 
     virtual void SetIsOpaque(bool) override {};
-    bool GetIsOpaque() override { return false; }
+    bool GetIsOpaque() override { return !mOptions.alpha; }
     NS_IMETHOD SetContextOptions(JSContext* cx,
                                  JS::Handle<JS::Value> options,
                                  ErrorResult& aRvForDictionaryInit) override;
diff --git a/gfx/gl/GLContext.h b/gfx/gl/GLContext.h
index 4f80fe2046be..7dc53835ff43 100644
--- a/gfx/gl/GLContext.h
+++ b/gfx/gl/GLContext.h
@@ -1543,7 +1543,6 @@ public:
     }
 
     void raw_fReadPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format, GLenum type, GLvoid* pixels) {
-        ASSERT_NOT_PASSING_STACK_BUFFER_TO_GL(pixels);
         BEFORE_GL_CALL;
         mSymbols.fReadPixels(x, y, width, height, format, type, pixels);
         OnSyncCall();
diff --git a/gfx/gl/GLReadTexImageHelper.cpp b/gfx/gl/GLReadTexImageHelper.cpp
index bc0d3b4f5ae1..92a8a59dcabf 100644
--- a/gfx/gl/GLReadTexImageHelper.cpp
+++ b/gfx/gl/GLReadTexImageHelper.cpp
@@ -632,11 +632,6 @@ GLReadTexImageHelper::ReadTexImage(DataSourceSurface* aDest,
             CLEANUP_IF_GLERROR_OCCURRED("when binding texture");
         }
 
-        /* Draw quad */
-        mGL->fClearColor(1.0f, 0.0f, 1.0f, 1.0f);
-        mGL->fClear(LOCAL_GL_COLOR_BUFFER_BIT);
-        CLEANUP_IF_GLERROR_OCCURRED("when clearing color buffer");
-
         mGL->fDrawArrays(LOCAL_GL_TRIANGLE_STRIP, 0, 4);
         CLEANUP_IF_GLERROR_OCCURRED("when drawing texture");
 
diff --git a/gfx/layers/CopyableCanvasRenderer.cpp b/gfx/layers/CopyableCanvasRenderer.cpp
index 1bfa07a15d1a..3c571c18edeb 100644
--- a/gfx/layers/CopyableCanvasRenderer.cpp
+++ b/gfx/layers/CopyableCanvasRenderer.cpp
@@ -155,8 +155,8 @@ CopyableCanvasRenderer::ReadbackSurface()
   }
 
   IntSize readSize(frontbuffer->mSize);
-  SurfaceFormat format = frontbuffer->mHasAlpha ? SurfaceFormat::B8G8R8X8
-                                                : SurfaceFormat::B8G8R8A8;
+  SurfaceFormat format = frontbuffer->mHasAlpha ? SurfaceFormat::B8G8R8A8
+                                                : SurfaceFormat::B8G8R8X8;
   bool needsPremult = frontbuffer->mHasAlpha && !mIsAlphaPremultiplied;
 
   RefPtr<DataSourceSurface> resultSurf = GetTempSurface(readSize, format);