This bug is an intermittent annoyance and does not seem likely to be
fixed soon. It means that every so often my acme becomes unusable
because it behaves as if a mouse button is permanently set.
Avoid that issue by keeping track of mouse button state directly.
While we're about it, fix another annoying issue: under Linux the
FocusOut event reset the kstate field but not the kbuttons field,
meaning that the buttons state could inappropriately persist. This
happened occasionally by accident, but was easy to reproduce: with the
mouse button held down, drag outside the window and click Alt-Tab to
switch away from the window. We see a KeyDown event followed by FocusOut
but no KeyUp event.
Change-Id: I3708316478c80c41806d7157ae9929c6cd84b662
Certain XkbOptions in X11 would change keysyms for modifier keys
between the key press and key release.
For example, under the XkbOptions "grp:shifts_toggle", though shift
keys remain Shift_L/R when pressed, they become ISO_Group_Next/Prev
when released.
This behavior makes devdraw unable to detect the release event
correctly and as a result mouse button 1 click always interpreted
as button 3 event after a shift key is used.
