Fix bug 105043: Panels [WIN]: For minimize panels, taskbar hover preview show the 4-pixel represent…

chrome/browser/ui/panels/panel_browser_view.cc

Index: chrome/browser/ui/panels/panel_browser_view.cc
diff --git a/chrome/browser/ui/panels/panel_browser_view.cc b/chrome/browser/ui/panels/panel_browser_view.cc
index 96f060e9e1e4a8b4f5a80493a3995376585fe937..911e0ee24a7f94aae612800a56355b872befac4b 100644
--- a/chrome/browser/ui/panels/panel_browser_view.cc
+++ b/chrome/browser/ui/panels/panel_browser_view.cc
@@ -13,16 +13,23 @@
 #include "chrome/browser/ui/panels/panel_browser_frame_view.h"
 #include "chrome/browser/ui/panels/panel_manager.h"
 #include "chrome/browser/ui/panels/panel_strip.h"
+#include "chrome/browser/ui/panels/taskbar_window_thumbnailer_win.h"
 #include "chrome/browser/ui/views/frame/browser_frame.h"
 #include "chrome/common/chrome_notification_types.h"
 #include "content/public/browser/notification_service.h"
 #include "grit/chromium_strings.h"
 #include "ui/base/l10n/l10n_util.h"
+#include "ui/gfx/canvas.h"
 #include "ui/views/controls/button/image_button.h"
 #include "ui/views/controls/label.h"
 #include "ui/views/widget/widget.h"
 
+#if defined(OS_WIN)
+#include "base/win/windows_version.h"
+#endif
+
 using content::NativeWebKeyboardEvent;
+
 using content::WebContents;
 
 NativePanel* Panel::CreateNativePanel(Browser* browser, Panel* panel,
@@ -42,6 +49,7 @@ PanelBrowserView::PanelBrowserView(Browser* browser, Panel* panel,
     mouse_pressed_(false),
     mouse_dragging_state_(NO_DRAGGING),
     is_drawing_attention_(false),
+    force_to_paint_as_inactive_(false),
     old_focused_view_(NULL) {
 }
 
@@ -519,7 +527,6 @@ void PanelBrowserView::UpdatePanelMinimizeRestoreButtonVisibility() {
   GetFrameView()->UpdateTitleBarMinimizeRestoreButtonVisibility();
 }
 
-
 #if defined(OS_WIN) && !defined(USE_AURA)
 void PanelBrowserView::UpdateWindowAttribute(int attribute_index,
                                              int attribute_value,
@@ -536,6 +543,46 @@ void PanelBrowserView::UpdateWindowAttribute(int attribute_index,
 }
 #endif
 
+void PanelBrowserView::PanelExpansionStateChanging(
+    Panel::ExpansionState old_state, Panel::ExpansionState new_state) {
+#if defined(OS_WIN) && !defined(USE_ASH)
+  // Live preview is only available since Windows 7.
+  if (base::win::GetVersion() < base::win::VERSION_WIN7)
+    return;
+
+  bool is_minimized = old_state != Panel::EXPANDED;
+  bool will_be_minimized = new_state != Panel::EXPANDED;
+  if (is_minimized == will_be_minimized)
+    return;
+
+  HWND native_window = GetNativeHandle();
+
+  if (!thumbnail_subclass_.get()) {
+    thumbnail_subclass_.reset(new ui::HWNDSubclass(native_window));
+    thumbnailer_ = new TaskbarWindowThumbnailerWin(native_window);

[Ben Goodger (Google), 2012/05/22 23:41:55]

keeping the thumbnailer as a member is dangerous, because it's actually owned by
the subclass. you don't need it for anything else so you can just do

thumbnail_subclass_->SetFilter(new TaskbarWindowThumbnailerWin(native_window));

[jianli, 2012/05/22 23:50:30]

Yes, I agree. However, I need to stop custom thumbnailing when the panel is
restored and restart custom thumbnailing  and capture a new snapshot when the
panel is minimized again.

I could move the logic to call DwmSetWindowAttribute and grab a window snapshot
to PanelBrowserView, but I need to expose the snapshot member to let
TaskbarWindowThumbnailerWin access it. This looks kind of ugly. How do you
think?

[Ben Goodger (Google), 2012/05/23 00:02:19]

Hrm. Seems like since this class owns the subclass though it can't be called
back after the subclass has deleted it, so I think your code is ok.

+    thumbnail_subclass_->SetFilter(thumbnailer_);

[Dmitry Titov, 2012/05/23 00:21:10]

Could you please add a short comment here explaining the thumbnailer_ is deleted
in the HWNDSubclass?

+  }
+
+  // Cache the image at this point.
+  if (will_be_minimized) {
+    // If the panel is still active (we will deactivate the minimizd panel at
+    // later time), we need to paint it immediately as inactive so that we can
+    // take a snapshot of inactive panel.
+    if (focused_) {
+      force_to_paint_as_inactive_ = true;
+      ::RedrawWindow(native_window, NULL, NULL,
+                     RDW_NOCHILDREN | RDW_INVALIDATE | RDW_UPDATENOW);
+    }
+
+    thumbnailer_->Start();
+  } else {
+    force_to_paint_as_inactive_ = false;
+    thumbnailer_->Stop();
+  }
+
+#endif
+}
+
 // NativePanelTesting implementation.
 class NativePanelTestingWin : public NativePanelTesting {
  public: