Exit full screen mode if changing window

with alt-tab etc. unintended way.

src/win/win_ui.c

@@ -961,6 +961,9 @@ MainWindowProcedure(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
 		break;
 
 	case WM_WINDOWPOSCHANGED:
+		if (video_fullscreen & 1)
+			PostMessage(hwndMain, WM_LEAVEFULLSCREEN, 0, 0);
+
 		pos = (WINDOWPOS*)lParam;
 		GetClientRect(hwndMain, &rect);
 
@@ -1160,6 +1163,13 @@ MainWindowProcedure(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
 		}
 		break;
 
+	case WM_ACTIVATEAPP:
+		/* Leave full screen on switching application except
+		   for OpenGL Core and VNC renderers. */
+		if (video_fullscreen & 1 && wParam == FALSE && vid_api < 3)
+			PostMessage(hwndMain, WM_LEAVEFULLSCREEN, 0, 0);
+		break;
+
 	case WM_ENTERSIZEMOVE:
 		user_resize = 1;
 		break;