Transparent apps support

chrome/browser/ui/views/extensions/shell_window_views.cc

 // Copyright (c) 2012 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/ui/views/extensions/shell_window_views.h"
 
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/extensions/extension_host.h"
 #include "chrome/browser/favicon/favicon_tab_helper.h"
 #include "chrome/browser/ui/tab_contents/tab_contents.h"
@@ skipping 301 matching lines @@
   DCHECK(!window_->frameless());
   if (sender == close_button_)
     frame_->Close();
 }
 
 ShellWindowViews::ShellWindowViews(ShellWindow* shell_window,
                                    const ShellWindow::CreateParams& win_params)
     : shell_window_(shell_window),
       web_view_(NULL),
       is_fullscreen_(false),
-      frameless_(win_params.frame == ShellWindow::CreateParams::FRAME_NONE) {
+      frameless_(win_params.frame == ShellWindow::CreateParams::FRAME_NONE),
+      transparent_background_(win_params.transparent_background) {
+  Observe(shell_window_->web_contents());
   window_ = new views::Widget;
   views::Widget::InitParams params(views::Widget::InitParams::TYPE_WINDOW);
   params.delegate = this;
   params.remove_standard_frame = true;

[sky, 2012/09/28 22:29:13]

Don't you need to set params.transparent here?

WebView creates a WebContentsViewAura. You may need to mark its window as not
transparent too. Although I'm not sure since its' not drawn. Antoine could tell
you if that matters.

Does this work on windows?

[reveman, 2012/09/28 22:50:38]

It works with Ash independent of the platform. I'm pretty sure this doesn't work
on any platforms unless using Ash. Could be made to work without Ash on
platforms with support for top-level windows with alpha channel but not sure
that's a good idea.

We should check what happens when using this without Ash so we don't end up
drawing garbage..

[Bernie, 2012/10/10 21:05:01]

I tried on Linux: setting the transparent background has no effect.

   params.use_system_default_icon = true;
   minimum_size_ = win_params.minimum_size;
   maximum_size_ = win_params.maximum_size;
   window_->Init(params);
   gfx::Rect window_bounds =
       window_->non_client_view()->GetWindowBoundsForClientBounds(
           win_params.bounds);
   window_->SetBounds(window_bounds);
   // Center window if no position was specified.
   if (win_params.bounds.x() < 0 || win_params.bounds.y() < 0)
@@ skipping 261 matching lines @@
     if (!app_icon.IsEmpty())
       return *app_icon.ToImageSkia();
   }
   return gfx::ImageSkia();
 }
 
 bool ShellWindowViews::ShouldShowWindowTitle() const {
   return false;
 }
 
+void ShellWindowViews::RenderViewCreated(
+    content::RenderViewHost* render_view_host) {
+  if (transparent_background_) {

[sky, 2012/09/28 22:29:13]

Does this result in flicker? Might it be possible for the page to attempt to
paint before this is applied?

[Bernie, 2012/10/10 21:05:01]

The window opens with a white background, then it becomes transparent, and the
content is rendered last.

I'm not sure where we could hook to make the background transparent earlier than
this.

[reveman, 2012/10/11 17:25:58]

We'll need to fix this. But I think it's OK to address it in a follow up patch
if you just file a bug for it and reference that bug in a TODO comment here.

+    // Use a background with transparency to trigger transparency in Webkit.
+    SkBitmap background;
+    background.setConfig(SkBitmap::kARGB_8888_Config, 1, 1);
+    background.allocPixels();
+    background.eraseARGB(0x00, 0x00, 0x00, 0x00);
+
+    content::RenderWidgetHostView* view = render_view_host->GetView();
+    DCHECK(view);
+    view->SetBackground(background);
+  }
+}
+
 void ShellWindowViews::Layout() {
   DCHECK(web_view_);
   web_view_->SetBounds(0, 0, width(), height());
   OnViewWasResized();
 }
 
 void ShellWindowViews::UpdateWindowIcon() {
   window_->UpdateWindowIcon();
 }
 
@@ skipping 66 matching lines @@
                                            ui::WindowShowState show_state) {
   views::WidgetDelegate::SaveWindowPlacement(bounds, show_state);
   shell_window_->SaveWindowPosition();
 }
 
 // static
 NativeShellWindow* NativeShellWindow::Create(
     ShellWindow* shell_window, const ShellWindow::CreateParams& params) {
   return new ShellWindowViews(shell_window, params);
 }