[Android WebView] Migrate the rendering code to a separate set of classes.

android_webview/java/src/org/chromium/android_webview/RenderHelper.java

+
+// Copyright (c) 2012 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 abstract class RenderHelper {

[mkosiba (inactive), 2013/01/22 02:13:34]

nit1: like in my other comment - you should probably call this the same as the
C++ class (maybe JavaViewRendererHelper (or JavaViewRendererDelegate?)

ni2: rather than marking it abstract (which means "inherit me to make me
useful", make the constructor private).

[Leandro Graciá Gil, 2013/01/22 08:18:46]

Done.

+
+    // Cached bitmap used for auxiliary rasterization in rendering fallback modes.
+    private static SoftReference<Bitmap> sBitmapCache;
+
+    /**
+     * Provides a Bitmap object with a given width and height used for auxiliary rasterization.
+     * Might reuse cached bitmaps.
+     */
+    @CalledByNative
+    private static Bitmap createBitmap(int width, int height) {

[joth, 2013/01/21 22:54:24]

maybe  createTemporaryBitmap? to reflect fact the returned bitmap shouldn't be
held onto beyond the current callstack.

[Leandro Graciá Gil, 2013/01/22 08:18:46]

Leaving as it is since we're removing the soft reference code.

+        Bitmap bitmap = sBitmapCache != null ? sBitmapCache.get() : null;
+        if (bitmap == null || bitmap.getWidth() != width || bitmap.getHeight() != height) {
+            bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);

[benm (inactive), 2013/01/21 20:34:49]

in the case that bitmap != null, would bitmap.recycle be helpful?

[joth, 2013/01/21 22:54:24]

In general this could be dangerous, as the caller maybe still holding a
reference to that old bitmap (see my comment in
https://codereview.chromium.org/12041009/diff/1/android_webview/browser/view_...)
and recycle actually destroys the bitmap.

The complication is this one until method can be used for 2 different purposes,
(both only as fallbacks for dev purposes...) and only one is truly 'temporary'
bitmap (as the capture-picture could theoretically hold onto the bitmap
indefinitely).

Hmm. as this is all fallback mode only, how about we just remove the
SoftReference altogether. Spend the effort on making the real supported modes
efficient instead :)

[Leandro Graciá Gil, 2013/01/22 08:18:46]

Removing SoftReference as suggested.

+            bitmap.eraseColor(Color.BLACK);
+            sBitmapCache = new SoftReference<Bitmap>(bitmap);
+        }
+        return bitmap;
+    }
+
+    /**
+     * 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);
+    }
+
+    /**
+     * Creates a new Picture that records drawing a provided bitmap.
+     */
+    @CalledByNative
+    private static Picture recordRasterizedBitmap(Bitmap bitmap) {

[joth, 2013/01/21 22:54:24]

maybe clearer as createPictureFromBitmap or convertBitmapToPicture or
recordBitmapIntoPicture.

The fact that this is a "rasterized" bitmap isn't very interesting (what other
sort of bitmap is there?) and 'record' was ambiguous to me without the word
"Picture' in the name too.

[Leandro Graciá Gil, 2013/01/22 08:18:46]

Using recordBitmapIntoPicture to make it consistent with
https://codereview.chromium.org/11823027/.

+        Picture picture = new Picture();
+        Canvas recordingCanvas = picture.beginRecording(bitmap.getWidth(), bitmap.getHeight());
+        drawBitmapIntoCanvas(bitmap, recordingCanvas);
+        picture.endRecording();
+        return picture;
+    }
+}