Up to this point, every font I've experienced with ligatures has
replaced the codepoints that were replaced for combining with a space.
For example, if a font has a ligature for "!=" to turn it into a glyph,
it'd shape to `[not equal glyph, space]`, so it'd still take up two
cells, allowing us to style both.
Monaspace, however, does not do this. It turns "!=" into `[not equal
glyph]` so styles like backgrounds, underlines, etc. were not extending.
This commit detects multi-cell glyphs and inserts synthetic blank cells
so that styling returns. I decided to do this via synthetic blank cells
instead of introducing a `cell_width` to the shaper result because this
simplifies the renderers to assume each shaper cell is one cell. We can
change this later if we need to.
Annoyingly, this does make the shaper slightly slower for EVERYONE to
accomodate one known font that behaves this way. I haven't benchmarked
it but my belief is that the performance impact will be negligible
because to figure out cell width we're only accessing subsequent cells
so they're likely to be in the CPU cache and also 99% of cells are going
to be width 1.
Rather than immediately converting a color palette index into an RGB
value for a cell color, when a palette color is used track the palette
color directly in the cell state and convert to an RGB value in the
renderer.
This causes palette color changes to take effect immediately instead of
only for newly drawn cells.
When font shaping grapheme clusters, we erroneously used the font index
of a font that only matches the first codepoint in the cell. This led to the
combining characters being [usually] unknown and rendering as boxes.
For a grapheme, we must find a font face that has a glyph for _all codepoints_
in the grapheme.
This also fixes an issue where we now properly render the unicode replacement
character if we can't find a font satisfying a codepoint.
* font: disable default font features for Menlo and Monaco
Both of these fonts have a default ligature on "fi" which makes terminal
rendering super ugly. The easiest thing to do is special-case these
fonts and disable ligatures. It appears other terminals do the same
thing.
