Implemented transparent gradients

src/pdf/SkPDFGraphicState.h

Index: src/pdf/SkPDFGraphicState.h
diff --git a/src/pdf/SkPDFGraphicState.h b/src/pdf/SkPDFGraphicState.h
index 64f34f8744ad65d3e8dd976ed13dc6745fc1785e..84c429105e7042a4f3675c1c0fba8780a5d36505 100644
--- a/src/pdf/SkPDFGraphicState.h
+++ b/src/pdf/SkPDFGraphicState.h
@@ -28,6 +28,11 @@ class SkPDFFormXObject;
 */
 class SkPDFGraphicState : public SkPDFDict {
 public:
+    enum SkPDFSMaskMode {
+        kAlpha_SMaskMode,
+        kLuminosity_SMaskMode
+    };
+
     virtual ~SkPDFGraphicState();
 
     virtual void getResources(const SkTSet<SkPDFObject*>& knownResourceObjects,
@@ -51,11 +56,13 @@ public:
     /** Make a graphic state that only sets the passed soft mask. The
      *  reference count of the object is incremented and it is the caller's
      *  responsibility to unreference it when done.
-     *  @param sMask  The form xobject to use as a soft mask.
-     *  @param invert Indicates if the alpha of the sMask should be inverted.
+     *  @param sMask     The form xobject to use as a soft mask.
+     *  @param invert    Indicates if the alpha of the sMask should be inverted.
+     *  @param sMaskMode Whether to use alpha or luminosity for the sMask.
      */
     static SkPDFGraphicState* GetSMaskGraphicState(SkPDFFormXObject* sMask,

[edisonn, 2013/07/17 17:52:24]

Nit: not your problem, since the code was like this, but Get_Foo() implies
getting something, not making something, especially with an extra parameter, it
is confusing.

I recommend to rename Get with Make, which would be better name for what the
function actually does 

[ducky, 2013/07/17 22:18:20]

Hm - I think get_* is often used in a way that's similar to return_*, rather
than literally get-a-stored-value.

As for changing this to make, I think that, while it would make what it's doing
clearer, it would make the class as a whole inelegant - you have similar
functions like GetNoSMaskGraphicState(...) and GetInvertFunction(), all of them
which also create (though also cache) objects. Renaming this one to Make...
could make it appear as there is something significantly different about this
one, even though it has the same refing semantics as the rest.

GetSMaskGraphicState could also be written in a way where it's cached, though
the current argument against that was it's unlikely you'd reuse a SMask. With
gradients, that may change.

On 2013/07/17 17:52:24, edisonn wrote:

-                                                   bool invert);
+                                                   bool invert,
+                                                   SkPDFSMaskMode sMaskMode);
 
     /** Get a graphic state that only unsets the soft mask. The reference
      *  count of the object is incremented and it is the caller's responsibility