New class to simplify rasterization.

skia::PaintSimplifier subclasses SkDrawFilter to reduce the quality of draws. The intent is to be able to place less of a burden on the rasterizer during Android flings or other situations where we need a lot of pixels but they won't spend long on screen.

This CL does not actually invoke the PaintSimplifier. The code is extracted from https://codereview.chromium.org/12210081/; deciding when to simplify will be a separate CL.

BUG=174945
TBR=reed

Review URL: https://chromiumcodereview.appspot.com/12207157

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@182475 0039d316-1c4b-4281-b951-d872f2087c98

skia/ext/paint_simplifier.cc

+// 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.
+
+#include "skia/ext/paint_simplifier.h"
+#include "third_party/skia/include/core/SkPaint.h"
+
+namespace skia {
+
+PaintSimplifier::PaintSimplifier()
+  : INHERITED() {
+
+}
+
+PaintSimplifier::~PaintSimplifier() {
+
+}
+
+bool PaintSimplifier::filter(SkPaint* paint, Type type) {
+
+  // Preserve a modicum of text quality; black & white text is
+  // just too blocky, even during a fling.
+  if (type != kText_Type) {
+    paint->setAntiAlias(false);
+  }
+  paint->setSubpixelText(false);
+  paint->setLCDRenderText(false);
+
+  paint->setFilterBitmap(false);
+  paint->setMaskFilter(NULL);
+
+  // Uncomment this line to shade simplified tiles pink during debugging.
+  //paint->setColor(SkColorSetRGB(255, 127, 127));
+
+  return true;
+}
+
+
+}  // namespace skia
+
+

skia/ext/paint_simplifier.h

+// 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.
+
+#ifndef SKIA_EXT_PAINT_SIMPLIFIER_H
+#define SKIA_EXT_PAINT_SIMPLIFIER_H
+
+#include "base/values.h"
+#include "third_party/skia/include/core/SkDrawFilter.h"
+
+class SkPaint;
+
+namespace skia {
+
+/*
+  When installed on a SkCanvas, reduces the quality of all draws
+  to that canvas. This improves rasterization speed during flings.
+  We turn off blurs, filters, and antialiasing *except for* text.
+*/
+class SK_API PaintSimplifier : public SkDrawFilter {
+ public:
+  PaintSimplifier();
+  virtual ~PaintSimplifier();
+  virtual bool filter(SkPaint*, Type) OVERRIDE;
+
+ private:
+  typedef SkDrawFilter INHERITED;
+};
+
+}  // namespace skia
+
+#endif  // SKIA_EXT_PAINT_SIMPLIFIER_H
+

skia/skia.gyp

@@ -168,6 +168,8 @@
         'ext/lazy_pixel_ref.cc',
         'ext/lazy_pixel_ref.h',
         'ext/SkThread_chrome.cc',
+        'ext/paint_simplifier.cc',
+        'ext/paint_simplifier.h',
         'ext/platform_canvas.cc',
         'ext/platform_canvas.h',
         'ext/platform_device.cc',