Fix isotropic spacing when working on a mirrored canvas
Summary: BUG:372545
Test Plan:
This patch touches rotation and mirroring capabilities of the brushes. These
parameters depend on both, brush and canvas rotation/mirroring capabilities,
so they should be tested in complex.
- Test with rotated (or drawing angle) brushes
- Test with mirrored (including using sensor) brushes
- Test with rotated canvas
- Test with mirrored canvas
- Test with all combinations of the above :)
The general idea of canvas rotation/mirroring is:
Whenever you rotate or mirror the canvas, brush shape *doesn't* change
its shape from your point of view. That is if you paint with a
vertical rectangular brush, the brush should still stay vertical
whenever you rotate/miror the canvas. In other words, the brush shape
is linked to your stylus tip, not to the canvas.
Reviewers: Krita, woltherav, timotheegiet
Differential Revision: https://phabricator.kde.org/D3420