Aura: Switch window mode when screen resolution changes

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index 1b065669974cd22ada29c2081cfeb05916ee7a6b..59582e9e199c76cc11610ad79ab0a9465706a938 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -57,6 +57,7 @@ namespace ash {
 
 namespace {
 
+using aura::Window;
 using views::Widget;
 
 // Screen width at or below which we automatically start in compact window mode,
@@ -186,9 +187,11 @@ Shell::Shell(ShellDelegate* delegate)
       status_widget_(NULL) {
   aura::RootWindow::GetInstance()->SetEventFilter(
       new internal::RootWindowEventFilter);
+  aura::RootWindow::GetInstance()->AddRootWindowObserver(this);
 }
 
 Shell::~Shell() {
+  aura::RootWindow::GetInstance()->RemoveRootWindowObserver(this);
   RemoveRootWindowEventFilter(input_method_filter_.get());
   RemoveRootWindowEventFilter(window_modality_controller_.get());
   RemoveRootWindowEventFilter(accelerator_filter_.get());
@@ -252,6 +255,21 @@ void Shell::DeleteInstance() {
   instance_ = NULL;
 }
 
+void Shell::OnRootWindowResized(const gfx::Size& new_size) {
+  // Developers often run the Aura shell in small windows on their desktop.
+  // Don't switch window modes for them.
+  if (!aura::RootWindow::use_fullscreen_host_window())
+    return;
+
+  // If we're running on a device, a resize event means the user plugged in or
+  // unplugged an external monitor. Change window mode to be appropriate for
+  // the new screen resolution.
+  gfx::Size monitor_size = gfx::Screen::GetPrimaryMonitorSize();
+  CommandLine* command_line = CommandLine::ForCurrentProcess();
+  WindowMode new_mode = ComputeWindowMode(monitor_size, command_line);
+  ChangeWindowMode(new_mode);
+}
+
 void Shell::Init() {
   // InputMethodEventFilter must be added first since it has the highest
   // priority.
@@ -401,8 +419,15 @@ void Shell::ChangeWindowMode(WindowMode mode) {
     SetupCompactWindowMode();
   else
     SetupNonCompactWindowMode();
-  // Force a layout.
-  aura::RootWindow::GetInstance()->layout_manager()->OnWindowResized();
+  // Force a layout of all containers.
+  aura::RootWindow* root_window = aura::RootWindow::GetInstance();
+  root_window->layout_manager()->OnWindowResized();
+  for (Window::Windows::const_iterator it = root_window->children().begin();

[sky, 2012/02/03 21:47:42]

Don't the children handle this themselves?

[James Cook, 2012/02/03 22:02:44]

They do, but too early for it to be useful for me.  By the time I get the
OnRootWindowResized() call in Shell the children have already had their bounds
set and OnWindowResized called.  Do you think the window-mode-selection code
should be triggered by RootWindowLayoutManager::OnWindowResized() so it can
happen before child bounds are set?

+       it != root_window->children().end();
+       ++it) {
+    if ((*it)->layout_manager())
+      (*it)->layout_manager()->OnWindowResized();
+  }
 }
 
 bool Shell::IsScreenLocked() const {