Add drawBitmapLattice() API

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 894 matching lines @@
      */
     void drawBitmapRect(const SkBitmap& bitmap, const SkRect& src, const SkRect& dst,
                         const SkPaint* paint, SrcRectConstraint = kStrict_SrcRectConstraint);
     // variant where src is SkIRect
     void drawBitmapRect(const SkBitmap& bitmap, const SkIRect& isrc, const SkRect& dst,
                         const SkPaint* paint, SrcRectConstraint = kStrict_SrcRectConstraint);
     void drawBitmapRect(const SkBitmap& bitmap, const SkRect& dst, const SkPaint* paint,
                         SrcRectConstraint = kStrict_SrcRectConstraint);
 
     /**
-     *  Draw the bitmap stretched differentially to fit into dst.
+     *  Draw the bitmap stretched or shrunk differentially to fit into dst.
      *  center is a rect within the bitmap, and logically divides the bitmap
      *  into 9 sections (3x3). For example, if the middle pixel of a [5x5]
      *  bitmap is the "center", then the center-rect should be [2, 2, 3, 3].
      *
      *  If the dst is >= the bitmap size, then...
      *  - The 4 corners are not stretched at all.
      *  - The sides are stretched in only one axis.
      *  - The center is stretched in both axes.
      * Else, for each axis where dst < bitmap,
      *  - 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) patches.
+     */
+    struct NinePatchDivs {
+        // An array of x-coordinates that divide the bitmap vertically.
+        // These must be unique, increasing, and in the set [0, width].
+        // Does not have ownership.
+        uint32_t* fXDivs;

[reed1, 2016/05/19 18:21:01]

I would make all of these int instead of uint32_t, mostly just to make the
general skia style.

+
+        // The number of fXDivs.
+        uint32_t  fXCount;
+
+        // An array of y-coordinates that divide the bitmap horiztonally.
+        // These must be unique, increasing, and in the set [0, height].
+        // Does not have ownership.
+        uint32_t* fYDivs;
+
+        // The number of fYDivs.
+        uint32_t  fYCount;
+    };
+
+    /**
+     *  Draw the bitmap stretched or shrunk differentially to fit into dst.
+     *
+     *  Moving horizontally across the bitmap alternating patches will be "scalable"
+     *  (in the x-dimension) to fit into dst or must be left "fixed".  The first patch

[f(malita), 2016/05/19 19:24:20]

The last patch is also fixed, right?

[msarett, 2016/05/19 19:30:58]

In the Android implementation, it really depends on the number of patches, since
they just alternate between "fixed" and "scalable".

In practical use cases, I think it is almost always:
First and last patch are both fixed
OR
First non-empty patch is scalable and last patch is also scalable

[f(malita), 2016/05/19 19:36:11]

Ah, that makes sense (I didn't parse the "alternating" bit off the bat).

+     *  is treated as "fixed", but it's possible to specify an empty first patch by
+     *  making divs.fXDivs[0] = 0.
+     *
+     *  The scale factor for all "scalable" patches will be the same, and may be greater
+     *  than or less than 1 (meaning we can stretch or shrink).  If the number of
+     *  "fixed" pixels is greater than the width of the dst, we will collapse all of
+     *  the "scalable" regions and appropriately downscale the "fixed" regions.
+     *
+     *  The same interpretation also applies the y-dimension.
+     */
+    void drawBitmapNine(const SkBitmap& bitmap, const NinePatchDivs& divs, const SkRect& dst,
+                        const SkPaint* paint = nullptr);
+
     /** Draw the text, with origin at (x,y), using the specified paint.
         The origin is interpreted based on the Align setting in the paint.
         @param text The text to be drawn
         @param byteLength   The number of bytes to read from the text parameter
         @param x        The x-coordinate of the origin of the text being drawn
         @param y        The y-coordinate of the origin of the text being drawn
         @param paint    The paint used for the text (e.g. color, size, style)
     */
     void drawText(const void* text, size_t byteLength, SkScalar x, SkScalar y,
                   const SkPaint& paint);
@@ skipping 638 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