Expose and use constants for DrawLooperLayerInfo.setPaintBits to dart.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1175403002.

engine/core/core.gni

@@ -1169,6 +1169,7 @@ core_idl_files = get_path_info([
 core_dart_files = get_path_info([
                                   "painting/Color.dart",
                                   "painting/ColorFilter.dart",
+                                  "painting/DrawLooperLayerInfo.dart",
                                   "painting/Gradient.dart",
                                   "painting/MaskFilter.dart",
                                   "painting/PaintingStyle.dart",

engine/core/painting/DrawLooperLayerInfo.dart

+// Copyright 2015 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.
+
+part of dart.sky;
+
+/// Paint masks for DrawLooperLayerInfo.setPaintBits. These specify which
+/// aspects of the layer's paint should replace the corresponding aspects on
+/// the draw's paint.
+///
+/// PaintBits.all means use the layer's paint completely.
+/// 0 means ignore the layer's paint... except for colorMode, which is
+/// always applied.
+class PaintBits {
+  static const int style       = 0x1;
+  static const int testSkewx   = 0x2;
+  static const int pathEffect  = 0x4;
+  static const int maskFilter  = 0x8;
+  static const int shader      = 0x10;
+  static const int colorFilter = 0x20;
+  static const int xfermode    = 0x40;
+  static const int all         = 0xFFFFFFFF;
+}

engine/core/painting/DrawLooperLayerInfo.idl

@@ -5,23 +5,9 @@
 [
   Constructor(),
 ] interface DrawLooperLayerInfo {
-  // Bits specifies which aspects of the layer's paint should replace the
-  // corresponding aspects on the draw's paint.
-  // ENTIRE_PAINT_BITS means use the layer's paint completely.
-  // 0 means ignore the layer's paint... except for colorMode, which is
-  // always applied.
-  // TODO(mpcomplete): maybe these should each be functions (e.g. useStyle()).
-  // TODO(mpcomplete): the IDL compiler doesn't use these for anything?
-  // TODO(mpcomplete): dart style says to name these like 'styleBit'.
-  const unsigned long STYLE_BIT        = 0x1;
-  const unsigned long TEXT_SKEWX_BIT   = 0x2;
-  const unsigned long PATH_EFFECT_BIT  = 0x4;
-  const unsigned long MASK_FILTER_BIT  = 0x8;
-  const unsigned long SHADER_BIT       = 0x10;
-  const unsigned long COLOR_FILTER_BIT = 0x20;
-  const unsigned long XFERMODE_BIT     = 0x40;
-  const unsigned long ENTIRE_PAINT_BITS = -1;
-
+  // Specifies which aspects of the layer's paint should replace the
+  // corresponding aspects on the draw's paint. Use PaintBits, defined in
+  // DrawLooperLayerInfo.dart.
   void setPaintBits(unsigned long bits);
   void setColorMode(TransferMode mode);
   // TODO(eseidel): Offset should be a Size not a Point.

examples/raw/painting.sky

@@ -51,7 +51,7 @@ void main() {
             new DrawLooperLayerInfo()
               ..setOffset(const Point(150.0, 0.0))
               ..setColorMode(TransferMode.srcMode)
-              ..setPaintBits(-1),
+              ..setPaintBits(PaintBits.all),
             (Paint layerPaint) {
           layerPaint.color = const Color.fromARGB(128, 255, 255, 0);
           layerPaint.setColorFilter(
@@ -64,13 +64,16 @@ void main() {
             new DrawLooperLayerInfo()
               ..setOffset(const Point(75.0, 75.0))
               ..setColorMode(TransferMode.srcMode)
-              ..setPaintBits(-1),
+              ..setPaintBits(PaintBits.shader),
             (Paint layerPaint) {
           Gradient redYellow = new Gradient.radial(
               new Point(0.0, 0.0), radius/3.0,
               [const Color(0xFFFFFF00), const Color(0xFFFF0000)],
               null, TileMode.mirror);
           layerPaint.setShader(redYellow);
+          // Since we're don't set PaintBits.maskFilter, this has no effect.
+          layerPaint.setMaskFilter(
+              new MaskFilter.blur(BlurStyle.normal, 50.0, highQuality: true));
         })
         ..addLayerOnTop(
             new DrawLooperLayerInfo()..setOffset(const Point(225.0, 75.0)),

examples/raw/shadow.dart

@@ -15,7 +15,7 @@ void beginFrame(double timeStamp) {
     // Shadow layer.
     ..addLayerOnTop(
         new DrawLooperLayerInfo()
-          ..setPaintBits(-1)
+          ..setPaintBits(PaintBits.all)
           ..setOffset(const Point(5.0, 5.0))
           ..setColorMode(TransferMode.srcInMode),
         (Paint layerPaint) {

sdk/lib/framework/painting/shadows.dart

@@ -12,7 +12,7 @@ class ShadowDrawLooperBuilder {
   void addShadow(sky.Size offset, sky.Color color, double blur) {
     builder_.addLayerOnTop(
           new sky.DrawLooperLayerInfo()
-            ..setPaintBits(-1)
+            ..setPaintBits(PaintBits.all)
             ..setOffset(offset.toPoint())
             ..setColorMode(sky.TransferMode.srcMode),
           (sky.Paint layerPaint) {