cc/resources/raster_source_helper.cc

   1 // Copyright 2014 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 "cc/resources/raster_source_helper.h"
   6
   7 #include "base/trace_event/trace_event.h"
   8 #include "cc/debug/debug_colors.h"
   9 #include "third_party/skia/include/core/SkCanvas.h"
  10 #include "ui/gfx/geometry/rect_conversions.h"
  11 #include "ui/gfx/skia_util.h"
  12
  13 namespace cc {
  14
  15 void RasterSourceHelper::PrepareForPlaybackToCanvas(
  16     SkCanvas* canvas,
  17     const gfx::Rect& canvas_rect,
  18     const gfx::Rect& source_rect,
  19     float contents_scale,
  20     SkColor background_color,
  21     bool clear_canvas_with_debug_color,
  22     bool requires_clear) {
  23   canvas->discard();
  24   if (clear_canvas_with_debug_color) {
  25     // Any non-painted areas in the content bounds will be left in this color.
  26     canvas->clear(DebugColors::NonPaintedFillColor());
  27   }
  28
  29   // If this raster source has opaque contents, it is guaranteeing that it will
  30   // draw an opaque rect the size of the layer.  If it is not, then we must
  31   // clear this canvas ourselves.
  32   if (requires_clear) {
  33     TRACE_EVENT_INSTANT0("cc", "SkCanvas::clear", TRACE_EVENT_SCOPE_THREAD);
  34     // Clearing is about ~4x faster than drawing a rect even if the content
  35     // isn't covering a majority of the canvas.
  36     canvas->clear(SK_ColorTRANSPARENT);
  37   } else {
  38     // Even if completely covered, for rasterizations that touch the edge of the
  39     // layer, we also need to raster the background color underneath the last
  40     // texel (since the recording won't cover it) and outside the last texel
  41     // (due to linear filtering when using this texture).
  42     gfx::Rect content_rect =
  43         gfx::ToEnclosingRect(gfx::ScaleRect(source_rect, contents_scale));
  44
  45     // The final texel of content may only be partially covered by a
  46     // rasterization; this rect represents the content rect that is fully
  47     // covered by content.
  48     gfx::Rect deflated_content_rect = content_rect;
  49     deflated_content_rect.Inset(0, 0, 1, 1);
  50     if (!deflated_content_rect.Contains(canvas_rect)) {
  51       if (clear_canvas_with_debug_color) {
  52         // Any non-painted areas outside of the content bounds are left in
  53         // this color.  If this is seen then it means that cc neglected to
  54         // rerasterize a tile that used to intersect with the content rect
  55         // after the content bounds grew.
  56         canvas->save();
  57         canvas->translate(-canvas_rect.x(), -canvas_rect.y());
  58         canvas->clipRect(gfx::RectToSkRect(content_rect),
  59                          SkRegion::kDifference_Op);
  60         canvas->drawColor(DebugColors::MissingResizeInvalidations(),
  61                           SkXfermode::kSrc_Mode);
  62         canvas->restore();
  63       }
  64
  65       // Drawing at most 2 x 2 x (canvas width + canvas height) texels is 2-3X
  66       // faster than clearing, so special case this.
  67       canvas->save();
  68       canvas->translate(-canvas_rect.x(), -canvas_rect.y());
  69       gfx::Rect inflated_content_rect = content_rect;
  70       inflated_content_rect.Inset(0, 0, -1, -1);
  71       canvas->clipRect(gfx::RectToSkRect(inflated_content_rect),
  72                        SkRegion::kReplace_Op);
  73       canvas->clipRect(gfx::RectToSkRect(deflated_content_rect),
  74                        SkRegion::kDifference_Op);
  75       canvas->drawColor(background_color, SkXfermode::kSrc_Mode);
  76       canvas->restore();
  77     }
  78   }
  79 }
  80
  81 }  // namespace cc