More sensible rotation when using the drag-from-corner mode
(rotates around center of the shape, as you'd expect, rather than
around one of the corners of the shape's bounding box, as it has
been doing all this time).
Stretching a shape from bottom to top causes an upside-down shape
(e.g., before, a triangle would always start out up-pointing
regardless as to whether you clicked and drag downwards or upwards;
now, it will start out down-pointing if you drag upwards when
initially placing & stretching the shape).
...deactivate all code for this within color mixer, since it's
not actually implemented yet (going to be tricky! -- probably
holding off to a future version).
Also, sound effect for cross-color grabbing within rainbow palette
dialog.
Locking to 0-degrees when mouse is within a UI-button-sized
square centered around the stamp's center (h/t Pere for the idea).
Change mouse pointer to 'hand' when in the center (so at the start
of the rotation step), and to the 'circle arrow' rotation symbol
when actually rotating.
WIP (disabled for now) Drawing a XOR'd line out of the stamp's
center to the mouse, to show the angle you're rotating at.
(Needs more work to avoid leaving residuals on the screen.)
Rotation off of zero (0) degrees only occurs when dragging outside
the bounding box (rectangle around the width/height) of the stamp.
No longer warping mouse to the right of the stamp, to cause it to
default to zero degrees. (The mouse being at the center of the
stamp now causes this, per the above change.)
Motivation - Placing stamps on mobile (touchscreen) was difficult
and non-intuitive. Now, you can at least double-tap the same
spot on the screen to position, and then place (without rotation)
the stamp. It's still not perfect, and I think a UI option to
enable/disable stamp rotation (leaving it off by default) is needed.
