Provide the custom thumbnail for live preview of stacked panels

chrome/browser/ui/views/panels/panel_stack_view.cc

Index: chrome/browser/ui/views/panels/panel_stack_view.cc
diff --git a/chrome/browser/ui/views/panels/panel_stack_view.cc b/chrome/browser/ui/views/panels/panel_stack_view.cc
index 96c19750835938facf0140d7a1241593a823291d..d7d4b9ed7e986fed32385d597d3222ac70cc6aa8 100644
--- a/chrome/browser/ui/views/panels/panel_stack_view.cc
+++ b/chrome/browser/ui/views/panels/panel_stack_view.cc
@@ -19,7 +19,6 @@
 #if defined(OS_WIN)
 #include "base/win/windows_version.h"
 #include "chrome/browser/shell_integration.h"
-#include "chrome/browser/ui/views/panels/taskbar_window_thumbnailer_win.h"
 #include "ui/base/win/shell.h"
 #include "ui/views/win/hwnd_util.h"
 #endif
@@ -46,6 +45,7 @@ PanelStackView::PanelStackView(NativePanelStackWindowDelegate* delegate)
       window_(NULL),
       is_closing_(false),
       is_drawing_attention_(false),
+      is_minimizing_(false),
       animate_bounds_updates_(false),
       bounds_updates_started_(false) {
   DCHECK(delegate);
@@ -74,6 +74,10 @@ void PanelStackView::AddPanel(Panel* panel) {
 
   window_->UpdateWindowTitle();
   window_->UpdateWindowIcon();
+
+#if defined(OS_WIN)
+  StartOrStopCustomThumbnailForMinimizePanel();
+#endif
 }
 
 void PanelStackView::RemovePanel(Panel* panel) {
@@ -81,6 +85,10 @@ void PanelStackView::RemovePanel(Panel* panel) {
 
   MakeStackWindowOwnPanelWindow(panel, NULL);
   UpdateStackWindowBounds();
+
+#if defined(OS_WIN)
+  StartOrStopCustomThumbnailForMinimizePanel();
+#endif
 }
 
 void PanelStackView::MergeWith(NativePanelStackWindow* another) {
@@ -172,10 +180,15 @@ void PanelStackView::Minimize() {
   // When the owner stack window is minimized by the system, its live preview
   // is lost. We need to set it explicitly. This has to be done before the
   // minimization.
-  CaptureThumbnailForLivePreview();
+  CaptureThumbnailForLivePreview(true);
 #endif
 
+  // On Windows, the system will activate the window before it is minimized.
+  // Set this flag such that the thumbnailer will not be stopped in
+  // OnWidgetActivationChanged.
+  is_minimizing_ = true;
   window_->Minimize();
+  is_minimizing_ = false;
 }
 
 bool PanelStackView::IsMinimized() const {
@@ -273,7 +286,7 @@ void PanelStackView::OnWidgetDestroying(views::Widget* widget) {
 void PanelStackView::OnWidgetActivationChanged(views::Widget* widget,
                                                bool active) {
 #if defined(OS_WIN)
-  if (active && thumbnailer_)
+  if (active && !is_minimizing_ && thumbnailer_)
     thumbnailer_->Stop();
 #endif
 }
@@ -296,6 +309,20 @@ void PanelStackView::OnNativeFocusChange(gfx::NativeView focused_before,
 #endif
 }
 
+#if defined(OS_WIN)
+std::vector<HWND> PanelStackView::GetSnapshotWindowHandles() const {
+  std::vector<HWND> native_panel_windows;
+  for (Panels::const_iterator iter = panels_.begin();
+       iter != panels_.end(); ++iter) {
+    Panel* panel = *iter;
+    native_panel_windows.push_back(
+        views::HWNDForWidget(
+            static_cast<PanelView*>(panel->native_panel())->window()));
+  }
+  return native_panel_windows;
+}
+#endif
+
 void PanelStackView::AnimationEnded(const ui::Animation* animation) {
   bounds_updates_started_ = false;
 
@@ -307,6 +334,10 @@ void PanelStackView::AnimationEnded(const ui::Animation* animation) {
   bounds_updates_.clear();
 
   delegate_->PanelBoundsBatchUpdateCompleted();
+
+#if defined(OS_WIN)
+  StartOrStopCustomThumbnailForMinimizePanel();
+#endif
 }
 
 void PanelStackView::AnimationProgressed(const ui::Animation* animation) {
@@ -455,7 +486,30 @@ void PanelStackView::EnsureWindowCreated() {
 }
 
 #if defined(OS_WIN)
-void PanelStackView::CaptureThumbnailForLivePreview() {
+void PanelStackView::StartOrStopCustomThumbnailForMinimizePanel() {

[Dmitry Titov, 2013/05/29 01:14:48]

Is it possible to have a StartThumbnailer() and StopThumbnailer() separately?
It could be more readable then create a single method that combines all
behaviors so it can be used from 3 places...

[jianli, 2013/05/29 18:31:52]

All 3 places need the same code because otherwise we will have the following
simplified duplicated code in all 3 places and we need to put comments too.
  StopThumbnailerForLivePreview();
  if (HasMinimizedPanels())
    StartThumbnailerForLivePreview(false);

+  bool has_minimized_panel = false;
+  for (Panels::const_iterator iter = panels_.begin();
+       iter != panels_.end(); ++iter) {
+    if ((*iter)->IsMinimized()) {
+      has_minimized_panel = true;
+      break;
+    }
+  }
+
+  // If custom thumbnail is still needed, stopping the thumbnailer and starting
+  // it again will make the system use the fresh snapshot.
+  if (thumbnailer_)
+    thumbnailer_->Stop();
+
+  // Start the thumbnailer to capture the snapshot only when the system requests
+  // it. When a panel has just been changed, its rendering might not be
+  // completed at this point. So we want to delay the snapshot until the system
+  // asks for it.
+  if (has_minimized_panel)
+    CaptureThumbnailForLivePreview(false);
+}
+
+void PanelStackView::CaptureThumbnailForLivePreview(bool should_capture_now) {
   // Live preview is only available since Windows 7.
   if (base::win::GetVersion() < base::win::VERSION_WIN7)
     return;
@@ -464,19 +518,11 @@ void PanelStackView::CaptureThumbnailForLivePreview() {
 
   if (!thumbnailer_.get()) {
     DCHECK(native_window);
-    thumbnailer_.reset(new TaskbarWindowThumbnailerWin(native_window));
+    thumbnailer_.reset(new TaskbarWindowThumbnailerWin(native_window, this));
     ui::HWNDSubclass::AddFilterToTarget(native_window, thumbnailer_.get());
   }
 
-  std::vector<HWND> native_panel_windows;
-  for (Panels::const_iterator iter = panels_.begin();
-       iter != panels_.end(); ++iter) {
-    Panel* panel = *iter;
-    native_panel_windows.push_back(
-        views::HWNDForWidget(
-            static_cast<PanelView*>(panel->native_panel())->window()));
-  }
-  thumbnailer_->Start(native_panel_windows);
+  thumbnailer_->Start(should_capture_now);
 }
 
 void PanelStackView::DeferUpdateNativeWindowBounds(HDWP defer_window_pos_info,