Unify grid metrics calculations by relying on shared logic mostly based
on values directly from the font tables, this deduplicates a lot of code
and gives us more control over how we interpret various metrics.
Also separate metrics for underlined, strikethrough, and overline
thickness and position, and box drawing thickness, so that they can
individually be adjusted as the user desires.
addresses #2561 - adds support for most Git branch drawing characters as
specified in 
except for fading vertical and horizontal lines.
Adds git_draw_node function and a new Git node type.
Add this range (0xf5d0...0xf60d) for Git branch characters, to tests.
adds vline_middle_xy and hline_middle_xy for node connections.
add git characters to Face.zig.
More complete coverage of the Symbols For Legacy Computing block,
including characters from Unicode 16.0.
Pixman and the web canvas impl for Canvas have been removed in favor of
z2d for drawing, since it has a nicer API with more powerful methods,
and is in Zig with no specific platform optimizations so should compile
to wasm no problem.
This adds Powerline rendering for the trapezoid characters (E0D2 and
E0D4).
This is the last of the Powerline additions for now. These are the
shapes that 1) render the most egregiously with stock fonts (off-center,
bleeding background, visible gaps), and 2) are simple enough to be
rendered without resorting to more complex measures like embedding SVG.
Some box codepoints (the cursor) want to use the original font metrics
height but others (corners) want to use the full grid height. I can't
see a better way to do this than manually maintaining a switch here. We
can add codepoints as needed.
This adds in-terminal rendering for the powerline glyphs E0B4 and E0B6,
similar to how we are rendering the triangle shapes currently.
The circle glyphs use a much more complex rendering due to the nuances
of drawing them: we use a midpoint algorithm for drawing on a 4x
supersampled matrix, fill, and then downsample. We use the same
downsampling approach as is done in the arc box drawing code.
The midpoint variant we're using here is described by Dennis Yurichev:
https://yurichev.com/news/20220322_circle/, although there are similar
variants elsewhere (some cited at the bottom of his article).
This adds the Powerline face to our set of built-in faces, which
represents glyphs that are used to draw Powerline-style shell prompts
and status lines.
Since these are used similar to box-drawing characters, alignment is
important, and this gives us the most control in preventing related
artifacts.
This initial commit is scaffolding and support for the various solid
triangles - additional glyphs will come in other commits.
Fixes#675.
