More genericity: overload isPaintOpaque(SkPaint, SkBitmap)

src/core/SkPaintPriv.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPaintPriv_DEFINED
 #define SkPaintPriv_DEFINED
 
 class SkBitmap;
 class SkPaint;
 
 #include "SkTypes.h"
+
+enum SkPaintBitmapOpacity {

[reed1, 2014/10/21 19:44:05]

The comments here seem to focus in on "color", but the predicate is really about
what "drawing with the paint" will do, yes?

another bikeshed: why PaintBitmapOpacity? Why not just PaintOpacity?

[Rémi Piotaix, 2014/10/21 20:01:32]

Yes. We need to have this parameter because, is some cases, the opacity of the
thing that will be drawn does not depends on the alpha value of the paint but on
the alpha of the thing that is drawn with the paint.
The enum is not really about the opacity of the paint itself, so PaintOpacity is
maybe not the good choice.
PaintBitmapOpacity is not really better because i am doing this change to be
able to call isPaintOpaque() without a bitmap (a SkImage in this case)

+    // No content replaces the paint's color

[reed1, 2014/10/21 19:44:05]

why are these explicitly numbered? In general we don't do that for skia's enums.

[Rémi Piotaix, 2014/10/21 20:01:32]

Yes, i forgot to clean it :s

Ack

+    kNoBitmap_SkPaintBitmapOpacity = 0,

[reed1, 2014/10/21 19:44:05]

Hmmm, kNoBitmap? I definitely find kTransparent_ very clear (esp. when it is
along side kOpaque). 

[Rémi Piotaix, 2014/10/21 20:01:32]

The kNoBitmap is because it happens that the isPaintOpaque is called with
bitmap=NULL.

For the 2 other values, the thing is that the isOpaque() method returns true
only if we are 100% sure that the image(or bitmap) is opaque. So, having
isOpaque()==false does not means that the bitmap is transparent.

+    // The color replacement is known to be opaque
+    kOpaque_SkPaintBitmapOpacity = 1,
+    // We have no information about the color or it is transparent
+    kUnknown_SkPaintBitmapOpacity = 2
+};
+
 /** Returns true if draw calls that use the paint will completely occlude
     canvas contents that are covered by the draw.
     @param paint The paint to be analyzed, NULL is equivalent to
+        the default paint.
+    @param contentType The type of the content that will be drawn,
+        kNoBitmap_SkPaintBitmapOpacity if there is no content in adition to the paint.
+    @return true if paint is opaque
+*/
+bool isPaintOpaque(const SkPaint* paint, SkPaintBitmapOpacity contentType);
+
+/** Returns true if draw calls that use the paint will completely occlude
+    canvas contents that are covered by the draw.
+    @param paint The paint to be analyzed, NULL is equivalent to
         the default paint.
     @param bmpReplacesShader a bitmap to be used in place of the paint's
         shader.
     @return true if paint is opaque
 */
 bool isPaintOpaque(const SkPaint* paint,
                    const SkBitmap* bmpReplacesShader = NULL);
 #endif