Implement intra-frame cacheing in image filters.

src/core/SkCanvas.cpp

 
 /*
  * Copyright 2008 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.
  */
 
 
 #include "SkCanvas.h"
@@ skipping 1240 matching lines @@
         SkImageFilter* filter = paint->getImageFilter();
         SkIPoint pos = { x - iter.getX(), y - iter.getY() };
         if (filter && !dstDev->canHandleImageFilter(filter)) {
             SkDeviceImageFilterProxy proxy(dstDev);
             SkBitmap dst;
             SkIPoint offset = SkIPoint::Make(0, 0);
             const SkBitmap& src = srcDev->accessBitmap(false);
             SkMatrix matrix = *iter.fMatrix;
             matrix.postTranslate(SkIntToScalar(-pos.x()), SkIntToScalar(-pos.y()));
             SkIRect clipBounds = SkIRect::MakeWH(srcDev->width(), srcDev->height());
-            SkImageFilter::Context ctx(matrix, clipBounds);
+            SkImageFilter::Cache* cache = SkImageFilter::Cache::Create(2);

[reed1, 2014/04/10 21:23:26]

That '2' is mysterious to the new reviewer...

1. Why is 2 a good answer?

2. How about...

const int minChildren = 2; // answer to #1
cache = SkImageFilter::Cache::Create(minChildren);

[Stephen White, 2014/04/10 21:26:36]

2 means "cache only image filters with 2 or more children".

(In an upcoming change, I'm going to reuse this class externally with a value
other than 2.)
How about I make it the default param?

+            SkAutoUnref aur(cache);
+            SkImageFilter::Context ctx(matrix, clipBounds, cache);
             if (filter->filterImage(&proxy, src, ctx, &dst, &offset)) {
                 SkPaint tmpUnfiltered(*paint);
                 tmpUnfiltered.setImageFilter(NULL);
                 dstDev->drawSprite(iter, dst, pos.x() + offset.x(), pos.y() + offset.y(),
                                    tmpUnfiltered);
             }
         } else {
             dstDev->drawDevice(iter, srcDev, pos.x(), pos.y(), *paint);
         }
     }
@@ skipping 19 matching lines @@
         paint = &looper.paint();
         SkImageFilter* filter = paint->getImageFilter();
         SkIPoint pos = { x - iter.getX(), y - iter.getY() };
         if (filter && !iter.fDevice->canHandleImageFilter(filter)) {
             SkDeviceImageFilterProxy proxy(iter.fDevice);
             SkBitmap dst;
             SkIPoint offset = SkIPoint::Make(0, 0);
             SkMatrix matrix = *iter.fMatrix;
             matrix.postTranslate(SkIntToScalar(-pos.x()), SkIntToScalar(-pos.y()));
             SkIRect clipBounds = SkIRect::MakeWH(bitmap.width(), bitmap.height());
-            SkImageFilter::Context ctx(matrix, clipBounds);
+            SkImageFilter::Cache* cache = SkImageFilter::Cache::Create(2);
+            SkAutoUnref aur(cache);
+            SkImageFilter::Context ctx(matrix, clipBounds, cache);
             if (filter->filterImage(&proxy, bitmap, ctx, &dst, &offset)) {
                 SkPaint tmpUnfiltered(*paint);
                 tmpUnfiltered.setImageFilter(NULL);
                 iter.fDevice->drawSprite(iter, dst, pos.x() + offset.x(), pos.y() + offset.y(),
                                          tmpUnfiltered);
             }
         } else {
             iter.fDevice->drawSprite(iter, bitmap, pos.x(), pos.y(), *paint);
         }
     }
@@ skipping 1336 matching lines @@
     if (!bitmap.installPixels(info, pixels, rowBytes)) {
         return NULL;
     }
 
     // should this functionality be moved into allocPixels()?
     if (!bitmap.info().isOpaque()) {
         bitmap.eraseColor(0);
     }
     return SkNEW_ARGS(SkCanvas, (bitmap));
 }