Allows using up to date simde and newer compilers for small performance
improvements. Ubuntu 18 and 20 are EOL and Ubuntu 22 was released over four
years ago.
This will also hopefully allow us to build slang for the upcoming
transition to slang based shaders.
Change the graphics protocol N key from a boolean into a usage-hints
bitmask. Define the first bit as a transient hint, allowing the terminal
to treat the image data as short-lived and apply optimizations such as
skipping disk cache writes.
Propagate the transient hint through frame coalescing and composition, so
a composed frame is transient if any contributing frame is transient.
The coverage threshold (0.5 in fbd4e5ad1, lowered to 0.3 in d4106ef2d to
get CI green) is environment-dependent: a correctly sized emoji covers
~0.84 of its cell on one box but ~0.39 in CI, while the buggy render is
~0.28, so the margin is thin and font/cell dependent.
Render the same font two ways at one size instead: via its fontconfig
descriptor (which carries the size-fixup matrix) and via its file path
(which does not). They must come out the same size; the bug shrinks the
descriptor one. Only the matrix differs, so the check no longer depends
on the environment or the emoji artwork.
ee937bdd1b routed FC_MATRIX through the cairo font matrix so synthetic
slant reaches color glyphs. But FC_MATRIX is also how fontconfig encodes
the pixel-size fixup of fixed-size faces. Noto Color Emoji is a ~109px
bitmap strike and fontconfig hands consumers a matrix scaling it to the
requested size (factor = requested_px / strike_px). cairo_set_font_size()
already brings the strike to the requested size, so feeding that matrix
into cairo_set_font_matrix() in apply_cairo_font_size() scales it down
again by the fixup factor. At terminal cell sizes that is a large shrink,
up to ~9x for small cells (easing to 1x as the cell nears the strike), so
color emoji render as a dot; fit_cairo_glyph() only shrinks, so it never
grows them back.
Only the shear carries synthetic slant; the diagonal is the size, which
cairo_set_font_size() and fit_cairo_glyph() already handle. Apply only
the shear and fall through to cairo_set_font_size() when there is no
shear. Pure-slant matrices are unchanged. This carries only the shear to
color glyphs, so a non-uniform diagonal scale from a hand-built FC_MATRIX
is dropped on that path; the stock fixup is uniform, so dropping it is
the intended behaviour.
Add a regression test that renders a color emoji and checks it fills its
cells, skipped unless a fixed-size color font with a fontconfig fixup
matrix is present.
Fixes#10144
