Factor code to rotate a canvas about a point.

samplecode/SampleApp.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SampleApp.h"
 
 #include "OverView.h"
@@ skipping 1354 matching lines @@
         orig->flush();
         fTimer.end();
         fMeasureFPS_Time += fTimer.fWall;
     }
 }
 
 void SampleWindow::beforeChild(SkView* child, SkCanvas* canvas) {
     if (fRotate) {
         SkScalar cx = this->width() / 2;
         SkScalar cy = this->height() / 2;
-        canvas->translate(cx, cy);
-        canvas->rotate(gAnimTimer.scaled(10));
-        canvas->translate(-cx, -cy);
+        canvas->rotate(gAnimTimer.scaled(10), cx, cy);
     }
 
     if (fPerspAnim) {
         SkScalar secs = gAnimTimer.scaled(1);
 
         static const SkScalar gAnimPeriod = 10 * SK_Scalar1;
         static const SkScalar gAnimMag = SK_Scalar1 / 1000;
         SkScalar t = SkScalarMod(secs, gAnimPeriod);
         if (SkScalarFloorToInt(secs / gAnimPeriod) & 0x1) {
             t = gAnimPeriod - t;
@@ skipping 865 matching lines @@
 #ifdef SK_BUILD_FOR_MAC
     setenv("ANDROID_ROOT", "/android/device/data", 0);
 #endif
     SkGraphics::Init();
     SkEvent::Init();
 }
 
 void application_term() {
     SkEvent::Term();
 }