Bug 917703 - Mark gfxSubimageSurface as opaque if it is within the opaque rect of the parent surface. r=roc

gfx/thebes/gfxImageSurface.cpp

@@ -299,21 +299,30 @@ gfxImageSurface::GetSubimage(const gfxRect& aRect)
     r.Round();
     MOZ_ASSERT(gfxRect(0, 0, mSize.width, mSize.height).Contains(r));
 
+    gfxImageFormat format = Format();
+
     unsigned char* subData = Data() +
         (Stride() * (int)r.Y()) +
         (int)r.X() * gfxASurface::BytePerPixelFromFormat(Format());
 
+    if (format == ImageFormatARGB32 &&
+        GetOpaqueRect().Contains(aRect)) {
+        format = ImageFormatRGB24;
+    }
+
     nsRefPtr<gfxSubimageSurface> image =
         new gfxSubimageSurface(this, subData,
-                               gfxIntSize((int)r.Width(), (int)r.Height()));
+                               gfxIntSize((int)r.Width(), (int)r.Height()),
+                               format);
 
     return image.forget();
 }
 
 gfxSubimageSurface::gfxSubimageSurface(gfxImageSurface* aParent,
                                        unsigned char* aData,
-                                       const gfxIntSize& aSize)
-  : gfxImageSurface(aData, aSize, aParent->Stride(), aParent->Format())
+                                       const gfxIntSize& aSize,
+                                       gfxImageFormat aFormat)
+  : gfxImageSurface(aData, aSize, aParent->Stride(), aFormat)
   , mParent(aParent)
 {
 }

gfx/thebes/gfxImageSurface.h

@@ -149,7 +149,8 @@ protected:
     friend class gfxImageSurface;
     gfxSubimageSurface(gfxImageSurface* aParent,
                        unsigned char* aData,
-                       const gfxIntSize& aSize);
+                       const gfxIntSize& aSize,
+                       gfxImageFormat aFormat);
 private:
     nsRefPtr<gfxImageSurface> mParent;
 };

gfx/thebes/gfxQPainterSurface.cpp

@@ -72,6 +72,7 @@ gfxQPainterSurface::GetAsImageSurface()
     assert(cairo_surface_get_type(isurf) == CAIRO_SURFACE_TYPE_IMAGE);
 
     nsRefPtr<gfxImageSurface> asurf = new gfxImageSurface(isurf);
+    asurf->SetOpaqueRect(GetOpaqueRect());
     return asurf.forget();
 }
 #endif

gfx/thebes/gfxQuartzImageSurface.cpp

@@ -67,5 +67,8 @@ gfxQuartzImageSurface::GetAsImageSurface()
         return nullptr;
     }
 
-    return gfxASurface::Wrap(isurf).downcast<gfxImageSurface>();
+    nsRefPtr<gfxImageSurface> result = gfxASurface::Wrap(isurf).downcast<gfxImageSurface>();
+    result->SetOpaqueRect(GetOpaqueRect());
+
+    return result.forget();
 }

gfx/thebes/gfxQuartzSurface.cpp

@@ -194,6 +194,8 @@ already_AddRefed<gfxImageSurface> gfxQuartzSurface::GetAsImageSurface()
     // explicitly so we don't leak.
     img->Release();
 
+    img->SetOpaqueRect(GetOpaqueRect());
+
     return img.forget().downcast<gfxImageSurface>();
 }
 

gfx/thebes/gfxWindowsSurface.cpp

@@ -193,7 +193,10 @@ gfxWindowsSurface::GetAsImageSurface()
     if (!isurf)
         return nullptr;
 
-	return gfxASurface::Wrap(isurf).downcast<gfxImageSurface>();
+    nsRefPtr<gfxImageSurface> result = gfxASurface::Wrap(isurf).downcast<gfxImageSurface>();
+    result->SetOpaqueRect(GetOpaqueRect());
+
+    return result.forget();
 }
 
 already_AddRefed<gfxWindowsSurface>

image/src/imgFrame.cpp

@@ -814,6 +814,7 @@ void imgFrame::SetHasNoAlpha()
   if (mFormat == gfxASurface::ImageFormatARGB32) {
       mFormat = gfxASurface::ImageFormatRGB24;
       mFormatChanged = true;
+      ThebesSurface()->SetOpaqueRect(gfxRect(0, 0, mSize.width, mSize.height));
   }
 }