skia::AnalysisCanvas: implementation for IsCheapInRect().

cc/picture.cc

Index: cc/picture.cc
diff --git a/cc/picture.cc b/cc/picture.cc
index 1407f55dc4a1eb5ee470f302f155666abbec5b37..7ad3b4ff2a3497a1f6fe479dd3735cdde3b38d16 100644
--- a/cc/picture.cc
+++ b/cc/picture.cc
@@ -6,6 +6,7 @@
 #include "cc/content_layer_client.h"
 #include "cc/picture.h"
 #include "cc/rendering_stats.h"
+#include "skia/ext/analysis_canvas.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkData.h"
 #include "third_party/skia/include/core/SkTileGridPicture.h"
@@ -96,8 +97,21 @@ void Picture::Raster(
     SkCanvas* canvas,
     gfx::Rect content_rect,
     float contents_scale) {
-  TRACE_EVENT2("cc", "Picture::Raster",
-               "width", layer_rect_.width(), "height", layer_rect_.height());
+char strbuf[256];
+if (IsCheapInRect(content_rect)) {
+sprintf(strbuf, "CHEAP Picture::Raster");
+} else {
+sprintf(strbuf, "EXPENSIVE Picture::Raster");
+}
+SkBitmap emptyBitmap;
+emptyBitmap.setConfig(SkBitmap::kARGB_8888_Config, picture_->width(),

[Justin Novosad, 2013/02/04 20:23:55]

Config should be SkBitmap::kNo_Config

[Tom Hudson, 2013/02/05 10:23:24]

Done.

I'd cribbed this from GatherPixelRefDevice, which is also using kARGB_8888.

+                      picture_->height());
+skia::AnalysisDevice device(emptyBitmap);
+skia::AnalysisCanvas aCanvas(&device, gfx::RectToSkRect(content_rect));
+aCanvas.drawPicture(*picture_);
+TRACE_EVENT1("cc", strdup(strbuf), "cost", aCanvas.getEstimatedCost());
+  //TRACE_EVENT2("cc", strdup(strbuf),
+               //"width", layer_rect_.width(), "height", layer_rect_.height());
   DCHECK(picture_);
 
   canvas->save();
@@ -109,6 +123,24 @@ void Picture::Raster(
 }
 
 bool Picture::IsCheapInRect(const gfx::Rect& layer_rect) {
+TRACE_EVENT0("cc", "Picture::IsCheapInRect");
+  SkBitmap emptyBitmap;
+  emptyBitmap.setConfig(SkBitmap::kARGB_8888_Config, picture_->width(),
+                        picture_->height());
+  skia::AnalysisDevice device(emptyBitmap);
+  skia::AnalysisCanvas canvas(&device, gfx::RectToSkRect(layer_rect));
+  // If a picture has estimatd cost below this threshold, go ahead and
+  // wait until we have more pictures to draw (to amortize startup costs).
+  // If cost exceeds this threshold, start it now so we aren't blocked
+  // waiting for it.
+  // FIXME: Arbitrary number. Requires tuning & experimentation.
+  // Probably requires per-platform tuning; N10 average draw call takes
+  // 25x as long as Z620.
+  int pictureCostThreshold = 100;
+  canvas.drawPicture(*picture_);
+  if (canvas.getEstimatedCost() <= pictureCostThreshold) {
+    return true;
+  }
   return false;
 }