The Problem
-----------

Qt cannot use Space (or any non-modifier) key as a modifier. When
we assign "Space+R" shortcut to "Reset rotation" in Krita settings,
Qt actually assigns it not to "Space+R", but to "Space, R". That is,
the user is expected to press the two keys sequentially, not
simultaneously (though the latter option also works).

It means that after the user presses "Space" key, Qt transits into a
special state of an incomplete match and starts waiting for the following
key. While in this state, Qt (without this patch) eats all the shortcut
events.

Solution
--------

There is no proper solution for the problem, because Qt will still wait
for the second key to be pressed. That is, there is no way to instruct
Qt that Space and R keys should be pressed simultaneously (it is not
possible by design of QKeySequence.

This patch adds a workaround for the problem. It makes sure that all the
shortcut events are delivered to Krita, whatever the state Qt has
internally.

Test Plan
---------

Configuration:

1) Assign W as a primary shortcut for Zoom-In in **Canvas Input Settings**
2) Assign Space,R as a primary shortcut for Zoom-Out in **Keyboard Shortcuts**
3) Assign Space,W as a primary shortcut Rotate Canvas Left in **Keyboard Shortcuts**

Testcase 1:

1) Press Space, Release Space
2) Press W, Release W

Expected: canvas is zoomed in and not rotated, space+drag gesture still works fine

Testcase 2:

1) Press Space, Release Space
2) Press W, Release W
2) Press R, Release R

Expected: no zoom-out action happens (because Space modifier has already been consumed by the former action)

Testcase 3:

1) Press Space, Release Space
2) Press R, Release R

Expected: zoom-out action happens, space+drag gesture still works fine


Testcase 4:

Press Space, W and R randomly, it should still behave "in a sane way" :)

BUG:409613