Add option to skip rects to drawImageLattice()

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 916 matching lines @@
      *  - The corners shrink proportionally
      *  - The sides (along the shrink axis) and center are not drawn
      */
     void drawBitmapNine(const SkBitmap& bitmap, const SkIRect& center, const SkRect& dst,
                         const SkPaint* paint = NULL);
 
     /**
      *  Specifies coordinates to divide a bitmap into (xCount*yCount) rects.
      */
     struct Lattice {
+        enum Flags : uint8_t {
+            // If set, indicates that we should not draw corresponding rect.
+            kTransparent_Flags = 1 << 0,
+        };
+
         // An array of x-coordinates that divide the bitmap vertically.
-        // These must be unique, increasing, and in the set [0, width].
+        // These must be unique, increasing, and in the set [0, width).

[msarett, 2016/09/01 16:27:24]

Notice subtle change here.  Width and height are no longer valid divs.

         // Does not have ownership.
-        const int* fXDivs;
+        const int*   fXDivs;
+
+        // An array of y-coordinates that divide the bitmap horizontally.
+        // These must be unique, increasing, and in the set [0, height).
+        // Does not have ownership.
+        const int*   fYDivs;
+
+        // If non-null, the length of this array must be equal to
+        // (fXCount + 1) * (fYCount + 1).  Note that we allow the first rect
+        // in each direction to empty (divs[0] = 0).  In this case, the
+        // caller still must specify a flag (as a placeholder) for these
+        // empty rects.
+        // The flags correspond to the rects in the lattice, first moving
+        // left to right and then top to bottom.
+        const Flags* fFlags;
 
         // The number of fXDivs.
-        int        fXCount;
-
-        // An array of y-coordinates that divide the bitmap horizontally.
-        // These must be unique, increasing, and in the set [0, height].
-        // Does not have ownership.
-        const int* fYDivs;
+        int          fXCount;
 
         // The number of fYDivs.
-        int        fYCount;
+        int          fYCount;
     };
 
     /**
      *  Draw the bitmap stretched or shrunk differentially to fit into dst.
      *
      *  Moving horizontally across the bitmap, alternating rects will be "scalable"
      *  (in the x-dimension) to fit into dst or must be left "fixed".  The first rect
      *  is treated as "fixed", but it's possible to specify an empty first rect by
      *  making lattice.fXDivs[0] = 0.
      *
@@ skipping 755 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