bug#36779: 25.1; mouse click not recognized for frames with large left position

[martin rudalics]

> Additionally, I noticed that the *shape* of the mouse cursor changes
> correctly in accordance with the contents of the window frame at the
> mouse position; however, no click is recognized *except for* some
> "shallow" part of the menu.

Can you mark text with the mouse?  Does the bug happen only when the
entire frame is positioned to the right of 3840 or do you see it with
a frame starting before 3840 but extending to the right of the display
as well?

If you want to debug mouse clicks it should suffice to set a break
point with gdb at the top of the body below the lines

    case ButtonRelease:
    case ButtonPress:

of xterm.c (in Emacs 25 they are at line 8499 here) and look whether
it triggers.  If it triggers, then the call of x_window_to_frame in

        f = (x_mouse_grabbed (dpyinfo) ? dpyinfo->last_mouse_frame
             : x_window_to_frame (dpyinfo, event->xbutton.window));

should give us some preliminary information.

martin