Add transparency support to RenderWidgetHostView.

This is used to make the background behind toolstrips 'shine
through' them. It isn't possible to make them really transparent
due to cleartype (cleartype must know the pixels behind the text
to work), so instead we paint the background we want behind the
transparent webview.

Review URL: http://codereview.chromium.org/88076

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@14378 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 48 insertions, 1 deletions

diff --git a/chrome/renderer/render_view.cc b/chrome/renderer/render_view.cc
index 1893e25..e3cbc9f 100644
--- a/chrome/renderer/render_view.cc
+++ b/chrome/renderer/render_view.cc
@@ -443,6 +443,7 @@ void RenderView::OnMessageReceived(const IPC::Message& message) {
     IPC_MESSAGE_HANDLER(ViewMsg_MoveOrResizeStarted, OnMoveOrResizeStarted)
     IPC_MESSAGE_HANDLER(ViewMsg_ExtensionResponse, OnExtensionResponse)
     IPC_MESSAGE_HANDLER(ViewMsg_ClearFocusedNode, OnClearFocusedNode)
+    IPC_MESSAGE_HANDLER(ViewMsg_SetBackground, OnSetBackground)
 
     // Have the super handle all other messages.
     IPC_MESSAGE_UNHANDLED(RenderWidget::OnMessageReceived(message))
@@ -2954,6 +2955,13 @@ void RenderView::OnClearFocusedNode() {
     webview()->ClearFocusedNode();
 }
 
+void RenderView::OnSetBackground(const SkBitmap& background) {
+  if (webview())
+    webview()->SetIsTransparent(!background.empty());
+
+  SetBackground(background);
+}
+
 void RenderView::SendExtensionRequest(const std::string& name,
                                       const std::string& args,
                                       int callback_id,
diff --git a/chrome/renderer/render_view.h b/chrome/renderer/render_view.h
index eb3aa55..505dca0 100644
--- a/chrome/renderer/render_view.h
+++ b/chrome/renderer/render_view.h
@@ -26,6 +26,7 @@
 #include "chrome/renderer/external_host_bindings.h"
 #include "chrome/renderer/external_js_object.h"
 #include "chrome/renderer/render_widget.h"
+#include "skia/include/SkBitmap.h"
 #include "testing/gtest/include/gtest/gtest_prod.h"
 #include "third_party/WebKit/WebKit/chromium/public/WebConsoleMessage.h"
 #include "webkit/glue/dom_serializer_delegate.h"
@@ -52,7 +53,6 @@ class FilePath;
 class GURL;
 class RenderThread;
 class ResourceDispatcher;
-class SkBitmap;
 class WebAccessibilityManager;
 class WebError;
 class WebFrame;
@@ -582,6 +582,10 @@ class RenderView : public RenderWidget,
   // Sends the selection text to the browser.
   void OnRequestSelectionText();
 
+  // Handle message to make the RenderView transparent and render it on top of
+  // a custom background.
+  void OnSetBackground(const SkBitmap& background);
+
   // Prints the page listed in |params|.
   void PrintPage(const ViewMsg_PrintPage_Params& params,
                  const gfx::Size& canvas_size,
diff --git a/chrome/renderer/render_widget.cc b/chrome/renderer/render_widget.cc
index 4cd54c1..23f27da 100644
--- a/chrome/renderer/render_widget.cc
+++ b/chrome/renderer/render_widget.cc
@@ -14,6 +14,7 @@
 #include "chrome/common/transport_dib.h"
 #include "chrome/renderer/render_process.h"
 #include "skia/ext/platform_canvas.h"
+#include "skia/include/SkShader.h"
 #include "third_party/WebKit/WebKit/chromium/public/WebRect.h"
 #include "third_party/WebKit/WebKit/chromium/public/WebScreenInfo.h"
 #include "third_party/WebKit/WebKit/chromium/public/WebSize.h"
@@ -308,6 +309,25 @@ void RenderWidget::ClearFocus() {
 
 void RenderWidget::PaintRect(const gfx::Rect& rect,
                              skia::PlatformCanvas* canvas) {
+
+  // If there is a custom background, tile it.
+  if (!background_.empty()) {
+    canvas->save();
+    
+    SkIRect clipRect = { rect.x(), rect.y(), rect.right(), rect.bottom() };
+    canvas->setClipRegion(SkRegion(clipRect));
+
+    SkPaint paint;
+    SkShader* shader = SkShader::CreateBitmapShader(background_,
+                                                    SkShader::kRepeat_TileMode,
+                                                    SkShader::kRepeat_TileMode);
+    paint.setShader(shader)->unref();
+    paint.setPorterDuffXfermode(SkPorterDuff::kSrcOver_Mode);
+    canvas->drawPaint(paint);
+
+    canvas->restore();
+  }
+
   // Bring the canvas into the coordinate system of the paint rect
   canvas->translate(static_cast<SkScalar>(-rect.x()),
                     static_cast<SkScalar>(-rect.y()));
@@ -675,6 +695,12 @@ void RenderWidget::OnSetTextDirection(int direction) {
   }
 }
 
+void RenderWidget::SetBackground(const SkBitmap& background) {
+  background_ = background;
+  // Generate a full repaint.
+  DidInvalidateRect(webwidget_, gfx::Rect(size_.width(), size_.height()));
+}
+
 bool RenderWidget::next_paint_is_resize_ack() const {
   return ViewHostMsg_PaintRect_Flags::is_resize_ack(next_paint_flags_);
 }
diff --git a/chrome/renderer/render_widget.h b/chrome/renderer/render_widget.h
index 668b4fd..62777e8 100644
--- a/chrome/renderer/render_widget.h
+++ b/chrome/renderer/render_widget.h
@@ -16,6 +16,7 @@
 #include "chrome/common/ipc_channel.h"
 #include "chrome/renderer/render_process.h"
 #include "skia/ext/platform_canvas.h"
+#include "skia/include/SkBitmap.h"
 
 #include "webkit/glue/webwidget_delegate.h"
 #include "webkit/glue/webcursor.h"
@@ -123,6 +124,11 @@ class RenderWidget : public IPC::Channel::Listener,
   // corresponding paint or scroll message is send to the widget host.
   virtual void DidPaint() {}
 
+  // Set the background of the render widget to a bitmap. The bitmap will be
+  // tiled in both directions if it isn't big enough to fill the area. This is
+  // mainly intended to be used in conjuction with WebView::SetIsTransparent().
+  virtual void SetBackground(const SkBitmap& bitmap);
+
   // RenderWidget IPC message handlers
   void OnClose();
   void OnCreatingNewAck(gfx::NativeViewId parent);
@@ -271,6 +277,9 @@ class RenderWidget : public IPC::Channel::Listener,
   // Holds all the needed plugin window moves for a scroll.
   std::vector<WebPluginGeometry> plugin_window_moves_;
 
+  // A custom background for the widget.
+  SkBitmap background_;
+
   DISALLOW_COPY_AND_ASSIGN(RenderWidget);
 };