Qt4: remove custom X11 display with --x11-display

In older VLC versions, we had to use the same X11 display for the
window provider (the UI) and the video outputs to avoid Xlib aborts.
We do not need this anymore. Morever, the XCB outputs can detect the
error and fail safe.

To change the UI display, the DISPLAY environment variable is used.
The only real use case for --x11-display is output to a different
display than that of the UI. This change restores this use case,
and simplifies the Qt4 interface.

modules/gui/qt4/qt4.cpp

@@ -309,9 +309,6 @@ vlc_module_end ()
 
 /* Ugly, but the Qt4 interface assumes single instance anyway */
 static vlc_sem_t ready;
-#ifdef Q_WS_X11
-static char *x11_display = NULL;
-#endif
 static QMutex lock;
 static bool busy = false;
 static bool active = false;
@@ -347,24 +344,19 @@ static int Open( vlc_object_t *p_this, bool isDialogProvider )
     if( !vlc_xlib_init( p_this ) )
         return VLC_EGENERIC;
 
-    char *display = var_CreateGetNonEmptyString( p_intf, "x11-display" );
-    Display *p_display = XOpenDisplay( x11_display );
+    Display *p_display = XOpenDisplay( NULL );
     if( !p_display )
     {
         msg_Err( p_intf, "Could not connect to X server" );
-        free (display);
         return VLC_EGENERIC;
     }
     XCloseDisplay( p_display );
-#else
-    char *display = NULL;
 #endif
 
     QMutexLocker locker (&lock);
     if (busy)
     {
         msg_Err (p_this, "cannot start Qt4 multiple times");
-        free (display);
         return VLC_EGENERIC;
     }
 
@@ -374,9 +366,6 @@ static int Open( vlc_object_t *p_this, bool isDialogProvider )
     p_sys->p_mi = NULL;
 
     /* */
-#ifdef Q_WS_X11
-    x11_display = display;
-#endif
     vlc_sem_init (&ready, 0);
 #ifdef Q_WS_MAC
     /* Run mainloop on the main thread as Cocoa requires */
@@ -386,7 +375,6 @@ static int Open( vlc_object_t *p_this, bool isDialogProvider )
     if( vlc_clone( &p_sys->thread, Thread, p_intf, VLC_THREAD_PRIORITY_LOW ) )
     {
         delete p_sys;
-        free (display);
         return VLC_ENOMEM;
     }
 #endif
@@ -438,10 +426,6 @@ static void Close( vlc_object_t *p_this )
     msg_Dbg( p_this, "waiting for UI thread..." );
 #ifndef Q_WS_MAC
     vlc_join (p_sys->thread, NULL);
-#endif
-#ifdef Q_WS_X11
-    free (x11_display);
-    x11_display = NULL;
 #endif
     delete p_sys;
 
@@ -455,21 +439,12 @@ static void *Thread( void *obj )
     intf_thread_t *p_intf = (intf_thread_t *)obj;
     MainInterface *p_mi;
     char dummy[] = "vlc"; /* for WM_CLASS */
-    char *argv[4] = { dummy, NULL, };
+    char *argv[2] = { dummy, NULL, };
     int argc = 1;
 
     Q_INIT_RESOURCE( vlc );
 
     /* Start the QApplication here */
-#ifdef Q_WS_X11
-    if( x11_display != NULL )
-    {
-        argv[argc++] = const_cast<char *>("-display");
-        argv[argc++] = x11_display;
-        argv[argc] = NULL;
-    }
-#endif
-
     QVLCApp app( argc, argv );
 
     p_intf->p_sys->p_app = &app;
@@ -644,7 +619,7 @@ static int WindowOpen( vout_window_t *p_wnd, const vout_window_cfg_t *cfg )
     p_wnd->handle.xid = p_mi->getVideo( &i_x, &i_y, &i_width, &i_height );
     if( !p_wnd->handle.xid )
         return VLC_EGENERIC;
-    p_wnd->display.x11 = x11_display;
+    p_wnd->display.x11 = NULL;
 
 #elif defined (Q_WS_WIN)
     p_wnd->handle.hwnd = p_mi->getVideo( &i_x, &i_y, &i_width, &i_height );