Added the framework for having canvas/recorder/picture record depth_set's.

include/core/SkCanvas.h

Index: include/core/SkCanvas.h
diff --git a/include/core/SkCanvas.h b/include/core/SkCanvas.h
index ec14829ca85296d12d79d27a04073c6ee587c20e..ce9e52adef727414871f147c50e085c3b98c4f1e 100644
--- a/include/core/SkCanvas.h
+++ b/include/core/SkCanvas.h
@@ -444,6 +444,19 @@ public:
     */
     void resetMatrix();
 
+    /** Set the current draw depth of the canvas.
+        @param z    The integer depth, intended between 0 - 255 inclusive
+                    0 is lowest (into screen), 255 is highest (out of screen)
+    */

[robertphillips, 2016/07/07 20:43:08]

I don't think Z can be restricted to the index range. We want to treat the Z
values as if they were real and applied matrices to them and have the shadows
look right. I think we need to remap the Z values to the 0..255 range
internally.

[vjiaoblack, 2016/07/08 17:13:47]

Done.

+    void setZ(uint32_t z) {

[Brian Osman, 2016/07/07 20:06:37]

If this (and the member variable, getter, etc...) are uint8_t, the user can't
violate the contract in the comment.

[vjiaoblack, 2016/07/08 17:13:47]

Acknowledged.

+        this->fCurDrawDepth = z;
+        this->didSetZ(z);
+    }
+
+    /** Returns the current draw depth of the canvas.
+    */
+    uint32_t getZ() const { return this->fCurDrawDepth; }
+
     /**
      *  Modify the current clip with the specified rectangle.
      *  @param rect The rect to combine with the current clip
@@ -1307,6 +1320,7 @@ protected:
     virtual void didRestore() {}
     virtual void didConcat(const SkMatrix&) {}
     virtual void didSetMatrix(const SkMatrix&) {}
+    virtual void didSetZ(const uint32_t) {}
 
     virtual void onDrawAnnotation(const SkRect&, const char key[], SkData* value);
     virtual void onDrawDRRect(const SkRRect&, const SkRRect&, const SkPaint&);
@@ -1385,6 +1399,8 @@ protected:
                         const SkImageFilter* imageFilter = NULL);
 
 private:

[robertphillips, 2016/07/07 20:43:08]

I think we want the Z to be a member of the MCRec class and participate in the
save/restore system.

I will be up to the use to ensure that the painter's order matches the Z-order.

[vjiaoblack, 2016/07/08 17:13:47]

Done.

+    uint32_t fCurDrawDepth = 0;
+
     static bool BoundsAffectsClip(SaveLayerFlags);
     static SaveLayerFlags LegacySaveFlagsToSaveLayerFlags(uint32_t legacySaveFlags);