x11_common: handle window dragging in ButtonPress event

Begin the _NET_WM_MOVERESIZE window dragging in ButtonPress event
to match the behavior of win32 and wayland, simplify logic by dropping
the win_drag_button1_down hack required by the old method, and fix a race
condition described in commit 19f101db680f966a6e56035a16784541be390982,
which happens when moving the mouse and releasing the button at the same time.

The race condition can be easily triggered when using a touch screen
(tested with libinput driver), where a tap is translated to MotionNotify,
ButtonPress, MotionNotify, and ButtonRelease in sequence, with the last 2
events having the same timestamp. This has caused some window managers to
not stop dragging after the ButtonRelease, resulting in window being stuck
in dragging state after a single tap.

1 files changed, 17 insertions, 25 deletions

diff --git a/video/out/x11_common.c b/video/out/x11_common.c
index 83584795fb..3437336619 100644
--- a/video/out/x11_common.c
+++ b/video/out/x11_common.c
@@ -1219,7 +1219,6 @@ static void release_all_keys(struct vo *vo)
 
     if (x11->no_autorepeat)
         mp_input_put_key(x11->input_ctx, MP_INPUT_RELEASE_ALL);
-    x11->win_drag_button1_down = false;
 }
 
 void vo_x11_check_events(struct vo *vo)
@@ -1290,30 +1289,12 @@ void vo_x11_check_events(struct vo *vo)
             release_all_keys(vo);
             break;
         case MotionNotify:
-            if (x11->win_drag_button1_down && !x11->fs &&
-                !mp_input_test_dragging(x11->input_ctx, Event.xmotion.x,
-                                                        Event.xmotion.y))
-            {
-                mp_input_put_key(x11->input_ctx, MP_INPUT_RELEASE_ALL);
-                XUngrabPointer(x11->display, CurrentTime);
-
-                long params[5] = {
-                    Event.xmotion.x_root, Event.xmotion.y_root,
-                    8, // _NET_WM_MOVERESIZE_MOVE
-                    1, // button 1
-                    1, // source indication: normal
-                };
-                x11_send_ewmh_msg(x11, "_NET_WM_MOVERESIZE", params);
-            } else {
-                mp_input_set_mouse_pos(x11->input_ctx, Event.xmotion.x,
-                                                       Event.xmotion.y);
-            }
-            x11->win_drag_button1_down = false;
+            mp_input_set_mouse_pos(x11->input_ctx, Event.xmotion.x,
+                                                   Event.xmotion.y);
             break;
         case LeaveNotify:
             if (Event.xcrossing.mode != NotifyNormal)
                 break;
-            x11->win_drag_button1_down = false;
             mp_input_put_key(x11->input_ctx, MP_KEY_MOUSE_LEAVE);
             break;
         case EnterNotify:
@@ -1324,19 +1305,30 @@ void vo_x11_check_events(struct vo *vo)
         case ButtonPress:
             if (Event.xbutton.button - 1 >= MP_KEY_MOUSE_BTN_COUNT)
                 break;
-            if (Event.xbutton.button == 1)
-                x11->win_drag_button1_down = true;
             mp_input_put_key(x11->input_ctx,
                              (MP_MBTN_BASE + Event.xbutton.button - 1) |
                              get_mods(Event.xbutton.state) | MP_KEY_STATE_DOWN);
             long msg[4] = {XEMBED_REQUEST_FOCUS};
             vo_x11_xembed_send_message(x11, msg);
+            if (Event.xbutton.button == 1 && !x11->fs &&
+                !mp_input_test_dragging(x11->input_ctx, Event.xmotion.x,
+                                                        Event.xmotion.y))
+            {
+                mp_input_put_key(x11->input_ctx, MP_INPUT_RELEASE_ALL);
+                XUngrabPointer(x11->display, CurrentTime);
+
+                long params[5] = {
+                    Event.xmotion.x_root, Event.xmotion.y_root,
+                    8, // _NET_WM_MOVERESIZE_MOVE
+                    1, // button 1
+                    1, // source indication: normal
+                };
+                x11_send_ewmh_msg(x11, "_NET_WM_MOVERESIZE", params);
+            }
             break;
         case ButtonRelease:
             if (Event.xbutton.button - 1 >= MP_KEY_MOUSE_BTN_COUNT)
                 break;
-            if (Event.xbutton.button == 1)
-                x11->win_drag_button1_down = false;
             mp_input_put_key(x11->input_ctx,
                              (MP_MBTN_BASE + Event.xbutton.button - 1) |
                              get_mods(Event.xbutton.state) | MP_KEY_STATE_UP);