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

include/core/SkCanvas.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkCanvas_DEFINED
 #define SkCanvas_DEFINED
 
@@ skipping 426 matching lines @@
 
     /** Replace the current matrix with a copy of the specified matrix.
         @param matrix The matrix that will be copied into the current matrix.
     */
     void setMatrix(const SkMatrix& matrix);
 
     /** Helper for setMatrix(identity). Sets the current matrix to identity.
     */
     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
      *  @param op The region op to apply to the current clip
      *  @param doAntiAlias true if the clip should be antialiased
      */
     void clipRect(const SkRect& rect,
                   SkRegion::Op op = SkRegion::kIntersect_Op,
                   bool doAntiAlias = false);
 
@@ skipping 843 matching lines @@
 
     virtual void willSave() {}
     // Overriders should call the corresponding INHERITED method up the inheritance chain.
     virtual SaveLayerStrategy getSaveLayerStrategy(const SaveLayerRec&) {
         return kFullLayer_SaveLayerStrategy;
     }
     virtual void willRestore() {}
     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&);
 
     virtual void onDrawText(const void* text, size_t byteLength, SkScalar x,
                             SkScalar y, const SkPaint& paint);
 
     virtual void onDrawPosText(const void* text, size_t byteLength,
                                const SkPoint pos[], const SkPaint& paint);
 
@@ skipping 57 matching lines @@
     // is not released or deleted by the caller.
     virtual SkCanvas* canvasForDrawIter();
 
     // Clip rectangle bounds. Called internally by saveLayer.
     // returns false if the entire rectangle is entirely clipped out
     // If non-NULL, The imageFilter parameter will be used to expand the clip
     // and offscreen bounds for any margin required by the filter DAG.
     bool clipRectBounds(const SkRect* bounds, SaveLayerFlags, SkIRect* intersection,
                         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);
 
     enum ShaderOverrideOpacity {
         kNone_ShaderOverrideOpacity,        //!< there is no overriding shader (bitmap or image)
         kOpaque_ShaderOverrideOpacity,      //!< the overriding shader is opaque
         kNotOpaque_ShaderOverrideOpacity,   //!< the overriding shader may not be opaque
     };
 
     // notify our surface (if we have one) that we are about to draw, so it
@@ skipping 187 matching lines @@
 
 class SkCanvasClipVisitor {
 public:
     virtual ~SkCanvasClipVisitor();
     virtual void clipRect(const SkRect&, SkRegion::Op, bool antialias) = 0;
     virtual void clipRRect(const SkRRect&, SkRegion::Op, bool antialias) = 0;
     virtual void clipPath(const SkPath&, SkRegion::Op, bool antialias) = 0;
 };
 
 #endif