Use translucent style with fullscreen window

wingpanel-interface/BackgroundManager.vala

@@ -121,6 +121,10 @@ public class WingpanelInterface.BackgroundManager : Object {
             check_for_state_change (MINIMIZE_DURATION);
         });
 
+        window.notify["fullscreen"].connect (() => {
+            check_for_state_change (SNAP_DURATION);
+        });
+
         window.workspace_changed.connect (() => {
             check_for_state_change (WORKSPACE_SWITCH_DURATION);
         });
@@ -156,27 +160,33 @@ public class WingpanelInterface.BackgroundManager : Object {
      * Check if Wingpanel's background state should change.
      *
      * The state is defined as follows:
-     *  - If there's a maximized window, the state should be MAXIMIZED;
+     *  - If there's a maximized or fullscreen window, the state should be MAXIMIZED;
      *  - If no information about the background could be gathered, it should be TRANSLUCENT;
      *  - If there's too much contrast or sharpness, it should be TRANSLUCENT;
      *  - If the background is too bright, it should be DARK;
      *  - Else it should be LIGHT.
      */
     private void check_for_state_change (uint animation_duration) {
+        bool has_fullscreen_window = false;
         bool has_maximized_window = false;
 
-        foreach (unowned Meta.Window window in current_workspace.list_windows ()) {
-            if (window.is_on_primary_monitor ()) {
-                if (!window.minimized && window.maximized_vertically) {
-                    has_maximized_window = true;
-                    break;
-                }
+        foreach (unowned var window in current_workspace.list_windows ()) {
+            if (!window.is_on_primary_monitor () || window.minimized) {
+                continue;
+            }
+
+            if (window.fullscreen) {
+                has_fullscreen_window = true;
+            } else if (window.maximized_vertically) {
+                has_maximized_window = true;
             }
         }
 
         BackgroundState new_state;
 
-        if (has_maximized_window) {
+        if (has_fullscreen_window) {
+            new_state = BackgroundState.TRANSLUCENT_LIGHT;
+        } else if (has_maximized_window) {
             new_state = BackgroundState.MAXIMIZED;
         } else if (bk_color_info == null) {
             new_state = BackgroundState.TRANSLUCENT_LIGHT;