Version info : 4.13.5git-44d2d6 (Xfce 4.13) Manjaro Linux 18.0.4 pacman branch testing. Panel hung . Major. How to reproduce? - Window Buttons Preferences -> Window grouping = Always - Open multiple window with the same app. - Left click to show windows title list - Right click on one of the title - Leftclick on any other apps (including wallpaper background) - Panel will hang and is restartable by using xkill
I can confirm this bug, easily reproducible. Running git bisect, I was able to determine which commit introduce the regression for sure, but it's most likely caused by one of these: https://git.xfce.org/xfce/xfce4-panel/commit/?id=43dfa79 https://git.xfce.org/xfce/xfce4-panel/commit/?id=bffe11c I manually revert the changes from the first commit made to tasklist-widget.c, now the panel doesn't crash but I get the following error message at xfce_tasklist_button_button_press_event: Gtk-CRITICAL **: 22:23:03.218: gtk_toggle_button_set_active: assertion 'GTK_IS_TOGGLE_BUTTON (toggle_button)' failed
Not sure yet where the problem is, but if you cancel the popup menu with the "Esc" key it exits correctly. So the problem seems to be happening when destroying the menu...
My current suggestion would be to deactivate this particular right-click submenu. It's not very useful (you can get to it more easily and obviously through the left-click menu) and I can't seem to figure out why it causes that crash. It may also take quite a bit longer to get to the bottom of it, including reading the source of libwnck (wnck_action_menu_new). My findings so far are that the right-click menu doesn't seem to get any signal when losing its focus (so it can't destroy itself) and the toplevel menu (which contains the application windows) doesn't seem to be able to destroy the attached submenu when losing focus.
Simon Steinbeiss referenced this bugreport in commit 0ad33088dc56673a652ea0b5919ba0e3b3b560d5 tasklist: Don't show actionsmenu in grouped windows (Bug #15622) https://git.xfce.org/xfce/xfce4-panel/commit?id=0ad33088dc56673a652ea0b5919ba0e3b3b560d5
I went for handling right-click like left-click, i.e. it doesn't show yet-another-menu stacked on top of a menu, but instead simply activates the window the user clicked. All other window actions are available in the regular right-click menu anyway and that's the consistent way to find those actions (as it's consistent with ungrouped window buttons).