Re: [drew.adams@oracle.com: RE: moving overlay loses its priority?]

[Chong Yidong <cyd@stupidchicken.com>]

> The basic problem (as noted by Kim Storm) is that inside a
> `track-mouse' form, `read-event' is not returning mouse motion
> events if there is a `help-echo' text property present (NOT
> `mouse-face' as mistakenly stated in a previous thread).

I found the problem.  show_help_echo calls mouse-fixup-help-message,
which calls mouse-pixel-position, which calls XTmouse_position, whose
side-effect is to clear the mouse_moved flags of every frame.  The
documentation of XTmouse_position says that this is "so we can wait
for the next mouse movement", but it causes a bug if we are in the
middle of tracking the mouse.

I've checked in a fix into show_help_echo.  Now, when we are tracking
the mouse, we save the mouse_moved flag and restore it after the call
to mouse-fixup-help-message.