Draggable peeking/fullscreen launcher with transparent background.

ash/app_list/app_list_delegate_impl.cc

Index: ash/app_list/app_list_delegate_impl.cc
diff --git a/ash/app_list/app_list_delegate_impl.cc b/ash/app_list/app_list_delegate_impl.cc
index ef2f8c9b579a4da651b5222e1ce36f44e52c55d6..6df6dd849722dabb57d1dc6939cdb0a2aaf2af26 100644
--- a/ash/app_list/app_list_delegate_impl.cc
+++ b/ash/app_list/app_list_delegate_impl.cc
@@ -10,6 +10,7 @@
 #include "ash/shelf/shelf_widget.h"
 #include "ash/shell.h"
 #include "ash/shell_port.h"
+#include "ui/app_list/app_list_features.h"
 #include "ui/app_list/presenter/app_list.h"
 
 namespace ash {
@@ -35,6 +36,9 @@ void AppListDelegateImpl::OnAppListVisibilityChanged(bool visible,
     app_list_button->OnAppListShown();
   else
     app_list_button->OnAppListDismissed();
+
+  if (app_list::features::IsFullscreenAppListEnabled())
+    Shelf::ForWindow(root_window)->OnAppListIsActive();

[msw, 2017/06/01 20:03:45]

Why does this call OnAppListIsActive without arguments regardless of whether the
app list is shown or hidden? There are several changes I'd like to see here:
(1) At the minimum, combine Shelf::OnAppListIsActive and
Shelf::OnAppListShownOrDismissed into a single method, called regardless of the
fullscreen flag, it should be called something like
OnAppListVisibilityChanged(bool visible) (presuming it's only called for the
Shelf instance on the corresponding display). That function should update the
AppListButton, that should not be done here.
(2) If you're more ambitious, skip a bunch of indirection, by removing this
AppListDelegateImpl class, rename the AppListDelegate interface to
AppListObserver, implemented by Shelf, and let Shelf just do
Shell::Get()->app_list()->AddObserver(this).

[newcomer, 2017/06/05 22:01:44]

The function has no arguments because its purpose is to force ShelfLayoutManager
to run MaybeUpdateShelfBackground(), which does not require a Bool because
MaybeUpdateShelfBackground() checks to see if the app list is active.

(1)&(2) sky@ just recommended we get rid of AppListDelegateImpl and implement
AppListDelegate in Shell. This would mean that the mash implementation would
call the same OnAppListVisibilityChanged(bool visible) as Ash. I have it
implemented, I'm planning on submitting it after this CL (BUG ->
https://bugs.chromium.org/p/chromium/issues/detail?id=729715) 

 }
 
 }  // namespace ash