cc/priority_calculator.cc

   1 // Copyright 2012 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 #include "config.h"
   6
   7 #include "CCPriorityCalculator.h"
   8
   9 using namespace std;
  10
  11 namespace cc {
  12
  13 static const int uiDrawsToRootSurfacePriority = -1;
  14 static const int visibleDrawsToRootSurfacePriority = 0;
  15 static const int renderSurfacesPriority = 1;
  16 static const int uiDoesNotDrawToRootSurfacePriority = 2;
  17 static const int visibleDoesNotDrawToRootSurfacePriority = 3;
  18
  19 // The lower digits are how far from being visible the texture is,
  20 // in pixels.
  21 static const int notVisibleBasePriority = 1000000;
  22 static const int notVisibleLimitPriority = 1900000;
  23
  24 // Small animated layers are treated as though they are 512 pixels
  25 // from being visible.
  26 static const int smallAnimatedLayerPriority = notVisibleBasePriority + 512;
  27
  28 static const int lingeringBasePriority = 2000000;
  29 static const int lingeringLimitPriority = 2900000;
  30
  31 // static
  32 int CCPriorityCalculator::uiPriority(bool drawsToRootSurface)
  33 {
  34     return drawsToRootSurface ? uiDrawsToRootSurfacePriority : uiDoesNotDrawToRootSurfacePriority;
  35 }
  36
  37 // static
  38 int CCPriorityCalculator::visiblePriority(bool drawsToRootSurface)
  39 {
  40     return drawsToRootSurface ? visibleDrawsToRootSurfacePriority : visibleDoesNotDrawToRootSurfacePriority;
  41 }
  42
  43 // static
  44 int CCPriorityCalculator::renderSurfacePriority()
  45 {
  46     return renderSurfacesPriority;
  47 }
  48
  49 // static
  50 int CCPriorityCalculator::lingeringPriority(int previousPriority)
  51 {
  52     // FIXME: We should remove this once we have priorities for all
  53     //        textures (we can't currently calculate distances for
  54     //        off-screen textures).
  55     return min(lingeringLimitPriority,
  56                max(lingeringBasePriority, previousPriority + 1));
  57 }
  58
  59 namespace {
  60 int manhattanDistance(const IntRect& a, const IntRect& b)
  61 {
  62     IntRect c = unionRect(a, b);
  63     int x = max(0, c.width() - a.width() - b.width() + 1);
  64     int y = max(0, c.height() - a.height() - b.height() + 1);
  65     return (x + y);
  66 }
  67 }
  68
  69 // static
  70 int CCPriorityCalculator::priorityFromDistance(const IntRect& visibleRect, const IntRect& textureRect, bool drawsToRootSurface)
  71 {
  72     int distance = manhattanDistance(visibleRect, textureRect);
  73     if (!distance)
  74         return visiblePriority(drawsToRootSurface);
  75     return min(notVisibleLimitPriority, notVisibleBasePriority + distance);
  76 }
  77
  78 // static
  79 int CCPriorityCalculator::smallAnimatedLayerMinPriority()
  80 {
  81     return smallAnimatedLayerPriority;
  82 }
  83
  84 } // cc