BackingStoreSkia: Use skia for painting in RenderWidgetHostViewViews.

chrome/browser/renderer_host/backing_store_skia.cc

+// Copyright (c) 2011 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.
+
+#include "chrome/browser/renderer_host/backing_store_skia.h"
+
+#include "chrome/browser/renderer_host/render_process_host.h"
+#include "gfx/canvas.h"
+#include "gfx/canvas_skia.h"
+#include "gfx/rect.h"
+#include "skia/ext/platform_canvas.h"
+#include "third_party/skia/include/core/SkCanvas.h"
+
+// Assume that somewhere along the line, someone will do width * height * 4
+// with signed numbers. If the maximum value is 2**31, then 2**31 / 4 =
+// 2**29 and floor(sqrt(2**29)) = 23170.
+
+// Max height and width for layers
+static const int kMaxVideoLayerSize = 23170;
+
+BackingStoreSkia::BackingStoreSkia(RenderWidgetHost* widget,
+                                   const gfx::Size& size)
+    : BackingStore(widget, size) {
+  bitmap_.setConfig(SkBitmap::kARGB_8888_Config, size.width(), size.height());
+  bitmap_.allocPixels();
+  canvas_.reset(new SkCanvas(bitmap_));
+}
+
+BackingStoreSkia::~BackingStoreSkia() {
+}
+
+void BackingStoreSkia::SkiaShowRect(const gfx::Point& point,
+                                    gfx::Canvas* canvas) {
+  canvas->AsCanvasSkia()->drawBitmap(bitmap_, point.x(), point.y());
+}
+
+size_t BackingStoreSkia::MemorySize() {
+  return size().GetArea() * 4;

[rjkroege, 2011/02/07 19:36:40]

you are making a presumption about the way that bitmaps are stored that is not
necessarily valid. e.g.: if the SkCanvas is a sub-rectangle of a larger bitmap,
this will not be true.

[sadrul, 2011/02/07 20:55:39]

I wasn't exactly sure what to do where. The SkBitmap in the backing store is of
size size() and uses 32 bits per pixels. Both the X and the windows backing
store seem to do something similar. So I went with it as well.

+}
+
+void BackingStoreSkia::PaintToBackingStore(
+    RenderProcessHost* process,
+    TransportDIB::Id bitmap,
+    const gfx::Rect& bitmap_rect,
+    const std::vector<gfx::Rect>& copy_rects) {
+  if (bitmap_rect.IsEmpty())
+    return;
+
+  const int width = bitmap_rect.width();
+  const int height = bitmap_rect.height();
+
+  if (width <= 0 || width > kMaxVideoLayerSize ||
+      height <= 0 || height > kMaxVideoLayerSize)
+    return;
+
+  TransportDIB* dib = process->GetTransportDIB(bitmap);
+  if (!dib)
+    return;
+
+  scoped_ptr<skia::PlatformCanvas> p_canvas(
+      dib->GetPlatformCanvas(width, height));
+  for (size_t i = 0; i < copy_rects.size(); i++) {
+    const gfx::Rect& copy_rect = copy_rects[i];
+    int x = copy_rect.x() - bitmap_rect.x();
+    int y = copy_rect.y() - bitmap_rect.y();
+    int w = copy_rect.width();
+    int h = copy_rect.height();
+    SkIRect rect = SkIRect::MakeXYWH(x, y, w, h);
+    SkBitmap b;

[rjkroege, 2011/02/07 19:36:40]

This looks like a double copy of the bitmap. If so, it makes me sad. Is there a
way to eliminate the double copy? Yes, I know this is interim. But...

[sadrul, 2011/02/07 20:55:39]

I changed this to use drawBitmapRect instead of readPixels/writePixels. I think
this rids of double copy?

+    p_canvas->readPixels(rect, &b);
+    canvas_.get()->writePixels(b, copy_rect.x(), copy_rect.y());
+  }
+}
+
+void BackingStoreSkia::ScrollBackingStore(int dx, int dy,
+                                          const gfx::Rect& clip_rect,
+                                          const gfx::Size& view_size) {
+  int x = std::min(clip_rect.x(), clip_rect.x() - dx);
+  int y = std::min(clip_rect.y(), clip_rect.y() - dy);
+  int w = clip_rect.width() + abs(dx);
+  int h = clip_rect.height() + abs(dy);
+  SkIRect rect = SkIRect::MakeXYWH(x, y, w, h);
+  bitmap_.scrollRect(&rect, dx, dy);
+}
+
+bool BackingStoreSkia::CopyFromBackingStore(const gfx::Rect& rect,
+                                            skia::PlatformCanvas* output) {
+  const int width = std::min(size().width(), rect.width());
+  const int height = std::min(size().height(), rect.height());
+  if (!output->initialize(width, height, true))
+    return false;
+
+  SkBitmap bitmap = output->getTopPlatformDevice().accessBitmap(true);
+  SkIRect skrect = SkIRect::MakeXYWH(rect.x(), rect.y(), width, height);
+  SkBitmap b;
+  if (!canvas_->readPixels(skrect, &b))
+    return false;
+  output->writePixels(b, rect.x(), rect.y());
+  return true;
+}