Bug 1427668 - Assert that no-alpha backbuffers have 0xff alpha. - r=daoshengmu

MozReview-Commit-ID: 5UJdoud0f2C

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();

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;

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();

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");
 

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);