Recenlty this thing was enabled, and I now have this issue:
1) stable Xfce,
2) Firefox 74.0.1 (also was broken in some 74.0 revisions), title bar disabled, drag space disabled, window is maximized,
Sometimes, but not always, when I move a cursor to the very top, I cannot click on the very top pixel. It breaks the following actions: close tab with middle button click, open new tab with middle click, activate tab with left mouse click. It happens like this: move cursor to the very top (often without looking at it), don't move the cursor, click on mouse button. Expected action should be performed immediately, but I have to click several times and move cursor.
I did check my mouse, and it works properly, by deliberately positioning cursor in the middle of the tab, everything works in this case.
I hope it can be fixed. Also I don't understand why such important changes were made to the stable ebuild. There are a lot of commits to the ebuild recently and they were all marked as stable immediately.
Start firefox with MOZ_USE_XINPUT2=0 set and see if it makes any difference.
*** This bug has been marked as a duplicate of bug 715604 ***