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.