Cache auxiliary bitmap across draw frames

android_webview/java/src/org/chromium/android_webview/JavaBrowserViewRendererHelper.java

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.android_webview;
 
 import android.graphics.Bitmap;
 import android.graphics.Canvas;
 import android.graphics.Color;
 import android.graphics.Picture;
 
 import org.chromium.base.CalledByNative;
 import org.chromium.base.JNINamespace;
 
+import java.lang.ref.SoftReference;
+
 /**
  * Provides auxiliary methods related to Picture objects and native SkPictures.
  */
 @JNINamespace("android_webview")
 public class JavaBrowserViewRendererHelper {
 
+    private static SoftReference<Bitmap> sCachedBitmap;
+
     /**
      * Provides a Bitmap object with a given width and height used for auxiliary rasterization.
      */
     @CalledByNative
-    private static Bitmap createBitmap(int width, int height) {
-        return Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
+    private static Bitmap createBitmap(int width, int height, boolean cacheResult) {
+        if (cacheResult && sCachedBitmap != null) {
+            Bitmap result = sCachedBitmap.get();
+            if (result != null && result.getWidth() == width && result.getHeight() == height) {
+                return result;
+            }
+        }
+        Bitmap result = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
+        if (cacheResult) sCachedBitmap = new SoftReference<Bitmap>(result);

[kaanb, 2013/05/23 16:56:11]

nit: it would be more readable if you break this statement into two lines.

[joth, 2013/05/23 20:23:14]

Done.

+        return result;
     }
 
     /**
      * Draws a provided bitmap into a canvas.
      * Used for convenience from the native side and other static helper methods.
      */
     @CalledByNative
     private static void drawBitmapIntoCanvas(Bitmap bitmap, Canvas canvas) {
         canvas.drawBitmap(bitmap, 0, 0, null);
     }
@@ skipping 10 matching lines @@
             drawBitmapIntoCanvas(bitmap, recordingCanvas);
             picture.endRecording();
         }
         return picture;
     }
 
     // Should never be instantiated.
     private JavaBrowserViewRendererHelper() {
     }
 }