mus: Allow the WM to specify the windows that can have active children.

components/mus/ws/window_tree_host_impl.cc

Index: components/mus/ws/window_tree_host_impl.cc
diff --git a/components/mus/ws/window_tree_host_impl.cc b/components/mus/ws/window_tree_host_impl.cc
index 6f84e0e7ce9a551682956f3cc26a1a966f61c071..023d04cabb9c39baded081b7a7dfe1c9c5bb1c43 100644
--- a/components/mus/ws/window_tree_host_impl.cc
+++ b/components/mus/ws/window_tree_host_impl.cc
@@ -90,6 +90,11 @@ void WindowTreeHostImpl::SetFocusedWindow(ServerWindow* new_focused_window) {
   DCHECK(root_window()->Contains(new_focused_window));
   focus_controller_->SetFocusedWindow(new_focused_window);
   // TODO(beng): have the FocusController notify us via FocusControllerDelegate.
+  // It is possible that FocusController set the focus to a different window. So
+  // take that into account before calling into OnFocusChanged().
+  new_focused_window = focus_controller_->GetFocusedWindow();
+  if (new_focused_window == old_focused_window)
+    return;
   OnFocusChanged(old_focused_window, new_focused_window);
 }
 
@@ -133,6 +138,30 @@ void WindowTreeHostImpl::RemoveAccelerator(uint32_t id) {
   event_dispatcher_.RemoveAccelerator(id);
 }
 
+void WindowTreeHostImpl::SetActivationParent(uint32_t window_id, bool enable) {
+  ServerWindow* window =
+      connection_manager_->GetWindow(WindowIdFromTransportId(window_id));
+  bool wm_misbehaving = false;

[Ben Goodger (Google), 2015/11/19 07:26:24]

what's this for?

[sadrul, 2015/11/19 19:33:34]

I would normally do a DCHECK(window) here, but a misbehaving WM could then bring
down mus. I was contemplating having some mechanism to signal a misbehaving WM,
or shut it down + restart it if it is misbehaving too often. But we can look at
that in the future. Removed the relevant code.

+  if (window) {
+    if (enable) {
+      auto it = activation_parents_.insert(window->id());
+      if (!it.second)
+        wm_misbehaving = true;
+    } else {
+      size_t count = activation_parents_.erase(window->id());
+      if (!count)
+        wm_misbehaving = true;
+    }
+  } else {
+    wm_misbehaving = true;
+  }
+
+  if (wm_misbehaving) {
+    // TODO: kill the WM?
+    NOTREACHED();
+  }
+}
+
 void WindowTreeHostImpl::OnClientClosed() {
   // |display_manager_.reset()| destroys the display-manager first, and then
   // sets |display_manager_| to nullptr. However, destroying |display_manager_|
@@ -185,6 +214,20 @@ void WindowTreeHostImpl::OnCompositorFrameDrawn() {
   }
 }
 
+bool WindowTreeHostImpl::CanHaveActiveChildren(ServerWindow* window) const {
+  return window && activation_parents_.count(window->id()) > 0;
+}
+
+void WindowTreeHostImpl::OnActivationChanged(ServerWindow* old_active_window,
+                                             ServerWindow* new_active_window) {
+  DCHECK_NE(new_active_window, old_active_window);
+  if (new_active_window && new_active_window->parent()) {
+    // Raise the new active window.
+    // TODO(sad): Let the WM dictate whether to raise the window or not?
+    new_active_window->parent()->StackChildAtTop(new_active_window);

[Ben Goodger (Google), 2015/11/19 07:26:25]

does this account for transients?

[sadrul, 2015/11/19 19:33:34]

StackChildAtTop() etc. account for transients, yep. (turns out transiency isn't
quite set-up correctly yet from views. Fix up in
https://codereview.chromium.org/1462123002/)

+  }
+}
+
 void WindowTreeHostImpl::OnFocusChanged(ServerWindow* old_focused_window,
                                         ServerWindow* new_focused_window) {
   // There are up to four connections that need to be notified: