This commit reimplements the (normally) 45 degree (depends on
the widths) connection between to adjacent borders. Which is
needed to paint the 'caret' icon seen in a few buttons on GitHub.
The issue of overlapping pixels while painting this has also
been solved for the 45 degree case (the the most likely case,
the other cases only occur of mixed-with borders).
This commit adds some much nicer border painting, which now supports:
- Elliptical corners
- Blending between different border thicknesses, with rounded corners
- Anti-aliasing
There are some little TODOs left to tackle:
- Painting the corners with line styles other than solid
- Blending between colors on the corners (see comments)
The painting requires allocating a small bitmap, that only fits the
corners (so in most cases this is very small).
This bitmap is then cached so for all paints but the first there will
be no further allocations.
The logic here is needed by InlineNode too. Moving it into a
`paint_all_borders()` function makes it available to them both, as well
as anyone else who wants it. :^)
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
