Add app.window.alphaEnabled() and onAlphaEnabledChanged.

This allows an app to determine whether a window created with
"transparent_background" will work as expected.

This also allows the app to detect when "transparent_background" might
stop working, e.g. when Windows changes from Aero to Classic.

This also fixes the bug where "transparent_background" windows
created in Classic render as black rectangles.

BUG=260810

Review URL: https://codereview.chromium.org/375183002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284026 0039d316-1c4b-4281-b951-d872f2087c98

5 files changed, 33 insertions, 5 deletions

diff --git a/apps/app_window.cc b/apps/app_window.cc
index db1f543..340d54c 100644
--- a/apps/app_window.cc
+++ b/apps/app_window.cc
@@ -245,7 +245,8 @@ AppWindow::AppWindow(BrowserContext* context,
       has_been_shown_(false),
       can_send_events_(false),
       is_hidden_(false),
-      cached_always_on_top_(false) {
+      cached_always_on_top_(false),
+      requested_transparent_background_(false) {
   extensions::ExtensionsBrowserClient* client =
       extensions::ExtensionsBrowserClient::Get();
   CHECK(!client->IsGuestSession(context) || context->IsOffTheRecord())
@@ -285,6 +286,8 @@ void AppWindow::Init(const GURL& url,
   if (new_params.state == ui::SHOW_STATE_FULLSCREEN)
     new_params.always_on_top = false;
 
+  requested_transparent_background_ = new_params.transparent_background;
+
   native_app_window_.reset(delegate_->CreateNativeAppWindow(this, new_params));
 
   popup_manager_.reset(
@@ -756,6 +759,9 @@ void AppWindow::GetSerializedState(base::DictionaryValue* properties) const {
   properties->SetBoolean("maximized", native_app_window_->IsMaximized());
   properties->SetBoolean("alwaysOnTop", IsAlwaysOnTop());
   properties->SetBoolean("hasFrameColor", native_app_window_->HasFrameColor());
+  properties->SetBoolean("alphaEnabled",
+                         requested_transparent_background_ &&
+                             native_app_window_->CanHaveAlphaEnabled());
 
   // These properties are undocumented and are to enable testing. Alpha is
   // removed to
diff --git a/apps/app_window.h b/apps/app_window.h
index 9873eed..4e9403b 100644
--- a/apps/app_window.h
+++ b/apps/app_window.h
@@ -363,6 +363,11 @@ class AppWindow : public content::NotificationObserver,
   // app.
   void WindowEventsReady();
 
+  // Whether the app window wants a transparent background.
+  bool requested_transparent_background() const {
+    return requested_transparent_background_;
+  }
+
  protected:
   virtual ~AppWindow();
 
@@ -563,6 +568,9 @@ class AppWindow : public content::NotificationObserver,
   // taskbar.
   bool cached_always_on_top_;
 
+  // Whether |transparent_background| was set in the CreateParams.
+  bool requested_transparent_background_;
+
   DISALLOW_COPY_AND_ASSIGN(AppWindow);
 };
 
diff --git a/apps/ui/native_app_window.h b/apps/ui/native_app_window.h
index cde4c1d..fd0cc26 100644
--- a/apps/ui/native_app_window.h
+++ b/apps/ui/native_app_window.h
@@ -87,6 +87,10 @@ class NativeAppWindow : public ui::BaseWindow,
   virtual void SetContentSizeConstraints(const gfx::Size& min_size,
                                          const gfx::Size& max_size) = 0;
 
+  // Returns false if the underlying native window ignores alpha transparency
+  // when compositing.
+  virtual bool CanHaveAlphaEnabled() const = 0;
+
   virtual ~NativeAppWindow() {}
 };
 
diff --git a/apps/ui/views/native_app_window_views.cc b/apps/ui/views/native_app_window_views.cc
index 62b941d..da84d8a 100644
--- a/apps/ui/views/native_app_window_views.cc
+++ b/apps/ui/views/native_app_window_views.cc
@@ -27,14 +27,12 @@ NativeAppWindowViews::NativeAppWindowViews()
       web_view_(NULL),
       widget_(NULL),
       frameless_(false),
-      transparent_background_(false),
       resizable_(false) {}
 
 void NativeAppWindowViews::Init(AppWindow* app_window,
                                 const AppWindow::CreateParams& create_params) {
   app_window_ = app_window;
   frameless_ = create_params.frame == AppWindow::FRAME_NONE;
-  transparent_background_ = create_params.transparent_background;
   resizable_ = create_params.resizable;
   size_constraints_.set_minimum_size(
       create_params.GetContentMinimumSize(gfx::Insets()));
@@ -53,6 +51,10 @@ NativeAppWindowViews::~NativeAppWindowViews() {
   web_view_->SetWebContents(NULL);
 }
 
+void NativeAppWindowViews::OnCanHaveAlphaEnabledChanged() {
+  app_window_->OnNativeWindowChanged();
+}
+
 void NativeAppWindowViews::InitializeWindow(
     AppWindow* app_window,
     const AppWindow::CreateParams& create_params) {
@@ -260,7 +262,8 @@ void NativeAppWindowViews::OnWidgetActivationChanged(views::Widget* widget,
 
 void NativeAppWindowViews::RenderViewCreated(
     content::RenderViewHost* render_view_host) {
-  if (transparent_background_) {
+  if (app_window_->requested_transparent_background() &&
+      CanHaveAlphaEnabled()) {
     content::RenderWidgetHostView* view = render_view_host->GetView();
     DCHECK(view);
     view->SetBackgroundOpaque(false);
@@ -398,4 +401,8 @@ void NativeAppWindowViews::SetContentSizeConstraints(
   size_constraints_.set_maximum_size(max_size);
 }
 
+bool NativeAppWindowViews::CanHaveAlphaEnabled() const {
+  return widget_->IsTranslucentWindowOpacitySupported();
+}
+
 }  // namespace apps
diff --git a/apps/ui/views/native_app_window_views.h b/apps/ui/views/native_app_window_views.h
index bdebfde..917feca 100644
--- a/apps/ui/views/native_app_window_views.h
+++ b/apps/ui/views/native_app_window_views.h
@@ -52,6 +52,9 @@ class NativeAppWindowViews : public NativeAppWindow,
   void Init(AppWindow* app_window,
             const AppWindow::CreateParams& create_params);
 
+  // Signal that CanHaveTransparentBackground has changed.
+  void OnCanHaveAlphaEnabledChanged();
+
   views::Widget* widget() { return widget_; }
 
   void set_window_for_testing(views::Widget* window) { widget_ = window; }
@@ -156,6 +159,7 @@ class NativeAppWindowViews : public NativeAppWindow,
   virtual gfx::Size GetContentMaximumSize() const OVERRIDE;
   virtual void SetContentSizeConstraints(const gfx::Size& min_size,
                                          const gfx::Size& max_size) OVERRIDE;
+  virtual bool CanHaveAlphaEnabled() const OVERRIDE;
 
   // web_modal::WebContentsModalDialogHost implementation.
   virtual gfx::NativeView GetHostView() const OVERRIDE;
@@ -177,7 +181,6 @@ class NativeAppWindowViews : public NativeAppWindow,
   scoped_ptr<SkRegion> draggable_region_;
 
   bool frameless_;
-  bool transparent_background_;
   bool resizable_;
   apps::SizeConstraints size_constraints_;