Draggable peeking/fullscreen launcher with transparent background.

ash/shelf/shelf_layout_manager.cc

Index: ash/shelf/shelf_layout_manager.cc
diff --git a/ash/shelf/shelf_layout_manager.cc b/ash/shelf/shelf_layout_manager.cc
index 3b2c1704ef60e16da604241b400ed1b09ec1865e..d5474587e1094ffe79c4f8b8d689435be23ec07a 100644
--- a/ash/shelf/shelf_layout_manager.cc
+++ b/ash/shelf/shelf_layout_manager.cc
@@ -28,6 +28,7 @@
 #include "base/auto_reset.h"
 #include "base/command_line.h"
 #include "base/i18n/rtl.h"
+#include "ui/app_list/app_list_features.h"
 #include "ui/base/ui_base_switches.h"
 #include "ui/compositor/layer.h"
 #include "ui/compositor/layer_animation_observer.h"
@@ -425,6 +426,16 @@ void ShelfLayoutManager::OnVirtualKeyboardStateChanged(
       &keyboard_observer_);
 }
 
+void ShelfLayoutManager::OnAppListVisibilityChanged(bool shown,
+                                                    aura::Window* root_window) {
+  if (shelf_ != Shelf::ForWindow(root_window))
+    return;
+
+  is_app_list_visible_ = shown;
+  if (app_list::features::IsFullscreenAppListEnabled())
+    MaybeUpdateShelfBackground(AnimationChangeType::IMMEDIATE);
+}
+
 void ShelfLayoutManager::OnWindowActivated(ActivationReason reason,
                                            aura::Window* gained_active,
                                            aura::Window* lost_active) {
@@ -468,6 +479,10 @@ ShelfBackgroundType ShelfLayoutManager::GetShelfBackgroundType() const {
   if (state_.session_state != session_manager::SessionState::ACTIVE)
     return SHELF_BACKGROUND_OVERLAP;
 
+  // If the app list is active, hide the shelf background to prevent overlap.
+  if (is_app_list_visible_ && app_list::features::IsFullscreenAppListEnabled())
+    return SHELF_BACKGROUND_DEFAULT;
+
   if (state_.visibility_state != SHELF_AUTO_HIDE &&
       state_.window_state == wm::WORKSPACE_WINDOW_STATE_MAXIMIZED) {
     return SHELF_BACKGROUND_MAXIMIZED;