Factor out checkerboard function in gm and sampleapp into tools.

gm/xfermodeimagefilter.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "gm.h"
+#include "Checkerboard.h"
 #include "SkArithmeticMode.h"
 #include "SkOffsetImageFilter.h"
 #include "SkXfermodeImageFilter.h"
 #include "SkBitmapSource.h"
 
 #define WIDTH 600
 #define HEIGHT 600
 #define MARGIN 12
 
 namespace skiagm {
@@ skipping 15 matching lines @@
         canvas.clear(0x00000000);
         SkPaint paint;
         paint.setAntiAlias(true);
         sk_tool_utils::set_portable_typeface(&paint);
         paint.setColor(0xD000D000);
         paint.setTextSize(SkIntToScalar(96));
         const char* str = "e";
         canvas.drawText(str, strlen(str), SkIntToScalar(15), SkIntToScalar(65), paint);
     }
 
-    void make_checkerboard() {
-        fCheckerboard.allocN32Pixels(80, 80);
-        SkCanvas canvas(fCheckerboard);
-        canvas.clear(0x00000000);
-        SkPaint darkPaint;
-        darkPaint.setColor(0xFF404040);
-        SkPaint lightPaint;
-        lightPaint.setColor(0xFFA0A0A0);
-        for (int y = 0; y < 80; y += 16) {
-          for (int x = 0; x < 80; x += 16) {
-            canvas.save();
-            canvas.translate(SkIntToScalar(x), SkIntToScalar(y));
-            canvas.drawRect(SkRect::MakeXYWH(0, 0, 8, 8), darkPaint);
-            canvas.drawRect(SkRect::MakeXYWH(8, 0, 8, 8), lightPaint);
-            canvas.drawRect(SkRect::MakeXYWH(0, 8, 8, 8), lightPaint);
-            canvas.drawRect(SkRect::MakeXYWH(8, 8, 8, 8), darkPaint);
-            canvas.restore();
-          }
-        }
-    }
-
     SkISize onISize() SK_OVERRIDE {
         return SkISize::Make(WIDTH, HEIGHT);
     }
 
     static void drawClippedBitmap(SkCanvas* canvas, const SkBitmap& bitmap, const SkPaint& paint,
                            int x, int y) {
         canvas->save();
         canvas->translate(SkIntToScalar(x), SkIntToScalar(y));
         canvas->clipRect(SkRect::MakeWH(
             SkIntToScalar(bitmap.width()), SkIntToScalar(bitmap.height())));
         canvas->drawBitmap(bitmap, 0, 0, &paint);
         canvas->restore();
     }
 
     static void drawClippedPaint(SkCanvas* canvas, const SkRect& rect, const SkPaint& paint,
                           int x, int y) {
         canvas->save();
         canvas->translate(SkIntToScalar(x), SkIntToScalar(y));
         canvas->clipRect(rect);
         canvas->drawPaint(paint);
         canvas->restore();
     }
 
     void onOnceBeforeDraw() SK_OVERRIDE {
         make_bitmap();
-        make_checkerboard();
+
+        fCheckerboard.allocN32Pixels(80, 80);
+        SkCanvas checkerboardCanvas(fCheckerboard);
+        sk_tools::DrawCheckerboard(&checkerboardCanvas, 0xFFA0A0A0, 0xFF404040, 8);
     }
 
     void onDraw(SkCanvas* canvas) SK_OVERRIDE {
         canvas->clear(0x00000000);
         SkPaint paint;
 
         const struct {
             SkXfermode::Mode  fMode;
             const char*         fLabel;
         } gModes[] = {
@@ skipping 117 matching lines @@
 private:
     SkBitmap fBitmap, fCheckerboard;
     typedef GM INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 DEF_GM( return new XfermodeImageFilterGM; );
 
 }