If a cell contained a ligature, the math used to track where the
next quad was going to be placed could lose consistency with
the cluster/shaping information and result in offset glyphs.
This was most noticeable to me in tab titles in the tab bar;
my shell dotfiles append `-- something` to the title when a
command is launched, and the `--` is a ligature in my font.
I think I've also seen this mess up positioning in the notcurses
demo as well.
The solution is to take the cluster initial cell index rather
than trying to reverse engineer it from incomplete info.
A while back I made the line lengths lazily grown; the reduction
in memory was nice, and it helped with render performance for
really wide screens.
Unfortunately, it puts a bunch of reallocation into the hot path
of the parser and updating the terminal model when people run
the inevitable `cat giant-file.txt` benchmark.
This commit reinstates pre-allocating lines to match the physical
terminal width, and tweaks the code a bit to take advantage of
const Cell allocation and to avoid some clones (a really micro
optimization).
For simple graphemes, we can avoid subsequently calling
grapheme_column_width and cache that information in TeenyString.
Make blank TeenyString and Cell initializations const.
This size seems to be ~sweet spot for `time cat bigfile`, cutting the
time in half from the prior value. Making the buffer smaller doesn't
improve things, nor does making it bigger; this is balancing the latency
of applying the update to the model with the back-pressured parsing
latency.
The recent presentation logic needs to be tweaked to ensure that
we ignore presentation when we reach the fallback font, otherwise
we'll end up in a bad error stack and crash the program.
This commit annotates fonts with a boolean that indicates whether
we think it contains glyphs with emoji presentation, and then
passes the cluster.presentation field down to the shaper.
If the presentation doesn't match the current font in the fallback,
then it will be skipped until we exhaust its options.
`wezterm ls-fonts` also shows whether we think a font has emoji
presentation.
refs: #997
This replaces the slightly gnarly subpixel enabled blending in the
shader with Dual Source Blending, which is a technique where the
fragment shader can specify both the primary color (RGBA) as well
as an additional per-channel mask that can be used to alpha blend
with the destination.
This enables artifact-free alpha blending when used together
with a transparent window background.
refs: https://github.com/wez/wezterm/issues/932
Tag CursorPosition with the seqno of the cursor move instead.
This should avoid over-invalidating lines and the selection
if it was just the cursor that moved.
Without this check, something, presumably in the guts of rust itself,
generates `fatal runtime error: assertion failed:
output.write(&bytes).is_ok()` on the output stream of the spawned child
when attempting to spawn `wsl.exe` on linux.
refs: #1005
Terminal now maintains a sequence number that increments
for each Action that is applied to it.
Changes to lines are tagged with the current sequence number.
This makes it a bit easier to reason about when an individual
line has changed relative to some point in "time"; the consumer
of the terminal can sample the current sequence number and then
can later determine which lines have changed since that point
in time.
refs: https://github.com/wez/wezterm/issues/867
Use the newer logical line method in pane rather than going
via the hyperlink function, so that we can better reason
about physical vs. logical line breaks, and get the results
very slightly faster too.
refs: #874
We were previously only remembering the most recently pressed
button, but that's a lossy thing to do.
This commit remembers the button presses so that we can correctly
report all press/release events.
refs: #973
