third_party/WebKit/Source/platform/graphics/ExpensiveCanvasHeuristicParameters.h

   1 // Copyright 2015 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef ExpensiveCanvasHeuristicParameters_h
   6 #define ExpensiveCanvasHeuristicParameters_h
   7
   8 namespace blink {
   9
  10 namespace ExpensiveCanvasHeuristicParameters {
  11
  12 enum {
  13     // Layer promotion heuristic parameters
  14     //======================================
  15
  16     // FIXME (crbug.com/463239):
  17     // The Layer promotion heuristics should go away after slimming paint
  18     // is completely phased in and display list canvases are modified to
  19     // use a lightweight layering primitive instead of the
  20     // SkCanvas::saveLayer.
  21
  22     // Heuristic: Canvases that are overdrawn beyond this factor in a
  23     // single frame are promoted to a direct composited layer so that
  24     // their contents not be re-rasterized by the compositor when the
  25     // containing layer is the object of a paint invalidation.
  26     ExpensiveOverdrawThreshold = 3,
  27
  28     ExpensivePathPointCount = 50,
  29
  30     SVGImageSourcesAreExpensive = 1,
  31
  32     ConcavePathsAreExpensive = 1,
  33
  34     ComplexClipsAreExpensive = 1,
  35
  36     BlurredShadowsAreExpensive = 1,
  37
  38     // Heuristic: When drawing a source image that has more pixels than
  39     // the destination canvas by the following factor or more, the draw
  40     // is considered expensive.
  41     ExpensiveImageSizeRatio = 4,
  42
  43     // Display list fallback heuristic parameters
  44     //============================================
  45
  46     // Frames ending with more than this number of levels remaining
  47     // on the state stack at the end of a frame are too expensive to
  48     // remain in display list mode. This criterion is motivated by an
  49     // O(N) cost in carying over state from one frame to the next when
  50     // in display list mode. The value of this parameter should be high
  51     // enough to almost never kick in other than for cases with unmatched
  52     // save()/restore() calls are low enough to kick in before state
  53     // management becomes measurably expensive.
  54     ExpensiveRecordingStackDepth = 50,
  55
  56     // GPU vs. display list heuristic parameters
  57     //===========================================
  58
  59     // Pixel count beyond which we should always prefer to use display
  60     // lists. Rationale: The allocation of large textures for canvas
  61     // tends to starve the compositor, and increase the probability of
  62     // failure of subsequent allocations required for double buffering.
  63     PreferDisplayListOverGpuSizeThreshold = 4096 * 4096,
  64
  65 }; // enum
  66
  67 } // ExpensiveCanvasHeuristicParameters
  68
  69 } // blink
  70
  71 #endif