`ScrollByPage` can accept non-integer values in the configuration.
This allows fractional page scrolling, such as by half a page.
The default remains the same, at 1 page.
Define a way to compute a client ID and pass that through to the
mux server when verifying version compatibility.
Once associated, the session handler will keep some metadata
updated in the mux.
A new cli subcommand exposes the info:
```
; ./target/debug/wezterm cli list-clients
USER HOST PID CONNECTED IDLE WORKSPACE
wez mba.localdomain 52979 30.009225s 1.009225s
```
refs: #1531
Using the new publish/discovery stuff from the past couple of commits,
if we can find a matching socket path for a running gui, and the
configuration is likely a match, then use the mux protocol to talk
to the already running gui and ask it to spawn the equivalent program
into the same process.
refs: https://github.com/wez/wezterm/discussions/1486
ConPTY emits a sequence that sets the title to the name of the
program that is initially launched into it.
This commit tries to ignore that sequence in that circumstance,
so that the logic in b5d156c282
can more dynamically set the tab title.
Add `get_foreground_process_name` to both Pane and the lua wrapper.
Add `foreground_process_name` and `current_working_dir` fields to
`PaneInformation`. In order for those to be dynamically fetched,
switch the lua conversion for `PaneInformation` to be a UserData
with field access methods. It's a little more verbose but allows
us to lazily compute these two new fields.
refs: https://github.com/wez/wezterm/discussions/1421
refs: https://github.com/wez/wezterm/issues/915
refs: https://github.com/wez/wezterm/issues/876
This commit expands quick select mode so that you can trigger it
with distinct sets of patterns (eg: urls on one key assignment,
hashes on a different key assignment), different alphabets,
and lastly, the option to perform a different action from
the default copy action.
You can pair this with `action_callback` to run lua code to
do something with the selected text.
This commit also adds `wezterm.open_with`, a helper function
for opening documents/URLs.
refs: #846
refs: #1362
Adds some plumbing to allow the GUI to implement a download handler
and connect that up for iterm2 image/file transfers that have their
inline property set to false.
Previously we'd just log an error.
Now we will by default download the file to the user's download
directory.
This behavior can be turned off via the new `allow_download_protocols`
configuration setting.
File transfers can be initiated on a remote host via the
https://iterm2.com/utilities/it2dl script.
When the download completes, a toast notification is shown that will
open the file when clicked.
refs: https://github.com/wez/wezterm/discussions/1450
This commit adds plumbing to support mapping the process tree to
lua objects which in turn allows a new `mux-is-process-stateful`
event to be defined by the user for finer control over closing
prompt behavior.
refs: #1412
It looks like the debian 9 test failures with libssh are the
same underlying issue as https://github.com/wez/wezterm/issues/1262
Poking around in the debug output, and then spelunking through the code,
we can use the `pubkeyacceptedtypes` ssh config option to add the key
type to the list of keys. This doesn't appear to be a documented
option in the current versions of openssh.
I'm not 100% sure that this is right, but it's worth a shot.
Route logging via the `log` crate because on Windows there is
no stderr visible to libssh.
libssh will override any explicitly set options when it parses
the config file, so we need to apply those after we've loaded it.
A recent cargo update caused openssl-sys to do a minor semver update
from 0.9.71 -> 0.9.72, but that release downgraded from openssl 3
to openssl 1 to resolve a performance regression:
<https://github.com/sfackler/rust-openssl/pull/1578>
That in turn caused libssh to fail to build because the ENGINE
feature required by libssh isn't compiled in in openssl-src 1
crate when vendoring on windows.
For now, my libssh git repo is constrained to openssl-sys 0.9.71,
and we're pointing to that from the wezterm repo.
In the mux layer, we have some code that takes a `Child` and then
does a bit of naughty reaching through the abstraction to get at
the pid/handle of the child so that we can send it signals even
if the child is itself mutably (and thus exclusively) borrowed
for the purposes of waiting.
That worked fine for local processes spawned in the mux, but we also
use LocalPane to wrap around arbitrary `Child`ren, such as Ssh,
that are not local and that don't have a local process id, which
meant that this hack wouldn't work for them.
To make things a bit worse, those ssh ptys were used to ssh2 days
where we didn't have a way to signal the remote process and just
did nothing, leading to confusing situations such as
https://github.com/wez/wezterm/issues/1197
This commit graduates the hack mentioned in the first paragraph
to its own ChildKiller trait. This makes the concept of waiting
for the Child distinct from signalling it and explicitly allows
getting a separate object that can be used for signalling.
With that in place, we're forced to implement something appropriate
for the ssh pty implementations; one in the pty crate itself,
one in wezterm-ssh and the wrapper that we use in the mux crate.
The upshot of this is that the `CloseCurrentPane` action now operates
correctly on panes that were the result of split operations.
This is a fairly far-reaching commit. The idea is:
* Introduce a unicode_version config that specifies the default level
of unicode conformance for each newly created Terminal (each Pane)
* The unicode_version is passed down to the `grapheme_column_width`
function which interprets the width based on the version
* `Cell` records the width so that later calculations don't need to
know the unicode version
In a subsequent diff, I will introduce an escape sequence that allows
setting/pushing/popping the unicode version so that it can be overridden
via eg: a shell alias prior to launching an application that uses a
different version of unicode from the default.
This approach allows output from multiple applications with differing
understanding of unicode to coexist on the same screen a little more
sanely.
Note that the default `unicode_version` is set to 9, which means that
emoji presentation selectors are now by-default ignored. This was
selected to better match the level of support in widely deployed
applications.
I expect to raise that default version in the future.
Also worth noting: there are a number of callers of
`unicode_column_width` in things like overlays and lua helper functions
that pass `None` for the unicode version: these will assume the latest
known-to-wezterm/termwiz version of unicode to be desired. If those
overlays do things with emoji presentation selectors, then there may be
some alignment artifacts. That can be tackled in a follow up commit.
refs: #1231
refs: #997
We rely on using freetype in order to support more fonts in more
situations, and we have a deeper existing integration with harfbuzz.
I'm unlikely to come back to allsorts to complete our integration,
and in the meantime, it just adds overhead to build/test and those
builds are taking longer and longer.
I loved the idea of using pure rust for all the font stuff, but
its time is not now.
closes: #587closes: #66
This works, but on macOS, there is a segfault in openssl when the
session is closed... I'm going to try this on Linux to see if it
is consistent behavior and ponder next steps.
The port number is guaranteed to be set in the config parser,
just like for the host and user, so the unwrap is "OK", but it's
less brittle to handle the error consistent with the others here.
* WIP: IME support for X11
* Handle text generated by IME.
* Set IME position according to the cursor position.
* Improve IME position handling.
Geometry as well as window focus changes are now handled.
* Dispatch IME strings like it's done on windows.
* Make sure not to silently drop IME errors.
* Respect `use_ime` configuration.
* Add xcb-util as dependency.
* Only update IME position if necessary.
* Formatting.
* Update xcb-imdkit-rs.
* Set IME position under the start of the cursor.
This seems to be the way it is commonly done among gui frameworks.
(Tested with Firefox for GTK and Konsole for QT).
* Update xcb-imdkit-rs.
* Handle systems only providing libxcb-util0-dev.
* Add libxcb to freebsd dependencies.
Required by xcb-imdkit-rs.
* Update xcb-imdkit-rs.
* Try to use more recent gcc on centos7.
* More recent C++ compiler on centos7 as well.
* Also setup correct env on centos7 for tests.
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
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
Adds a use_image feature to termwiz that enables an optional
dep on the image crate. This in turn allows decoding of animation
formats (gif, apng) from file data, but more crucially, allows
modeling animation frames at the termwiz layer, which is a pre-req
for enabling kitty img protocol animation support.
refs: #986
Adding an edge from wezterm-ssh -> async_ossl causes the
openssl vendoring feature selection logic to trigger, which
in turn allows `cargo build -p window --examples` to succeed
again on macos.
0.8 doesn't seem to build with rusttls, but I don't think
we need that any more: we've been using vendored openssl on windows
and mac for some time.
closes: #924
refs: https://github.com/jayjamesjay/http_req/issues/48
The main culprit was the calloop feature that is used by default
in the underlying SCTK crate.
This commit:
* Routes keyboard processing via the same keyboard mapping code
that we use for X11
* Implements key repeats directly, and with awareness of elapsed
time in case the repeat rate is quicker than the event dispatching
quantum
* Disables the calloop feature of SCTK and let us do our own polling
of the wayland connection.
Critically, key repeat is sticky and unpredictable while calloop is
enabled.
closes: #669
This changes the fill_rect function over to use the zeno crate.
zeno allows describing a path and filling or stroking.
This commit doesn't strictly need that, but it sets things
up for more interesting custom glyphs in later commits.
refs: #584
refs: #588
Since removing the regular periodic background tasks, we're now
prone to not noticing child processes exiting.
This commit explicictly schedules a thread to do that on Windows
so that we can close a tab as soon as it exits.
Removes the callbacks type and replaces event dispatch with
an async capable channel.
This makes it a bit simpler to model some of the window internals,
and to prepare for a wgpu enabled future.
This changes have been tested only on linux so far.
Adds a `ShowDebugOverlay` key assignment that will create a tab
overlay that shows a limited number of recently logged events.
refs: https://github.com/wez/wezterm/issues/641
The intent is to reveal more context on what's happening in
https://github.com/wez/wezterm/issues/671
As a nice side benefit, this avoids the potential inability
to open paths that are not utf8 or representable as c-strings
on Windows.
And on top of that: this enables memory mapped file IO as well,
which wasn't enabled previously. This should help to reduce
extraneous copies of the font in memory, have fewer open files
and minimize the chances of racing with O_CLOEXEC.
Replaces the last usage of ttf-parser with calling into freetype.
This removes a source of inconsistency, as ttf-parser doesn't support
all of the things that freetype does.
Notably, this prevents a weird error from blowing up codepoint coverage
calculations on a system where I have helvetica.bdf in my font dir for
long-forgotten reasons.
There are a few notable changes as a result:
* A number of `.ssh/config` options are now respected; host matching
and aliasing and identity file are the main things
* The authentication prompt is inline in the window, rather than
popping up a separate authentication window
Refs: https://github.com/wez/wezterm/issues/457
I can't get this to succeed though; I suspect there may be a lingering
bug from libssh2 and/or trailing support for newer openssh features.
refs: https://github.com/wez/wezterm/issues/457
The wincng based build doesn't recognize newer keys which makes it
impossible to connect to a reasonably up to date Fedora installation.
This commit points to my branch of ssh2-rs that has some changes to
build ssh2 against the vendored openssl that is already part of
the dependency graph for wezterm.
refs: https://github.com/wez/wezterm/issues/507
Rust 1.51 allows addressesing a long-standing TODO which was that we
shouldn't need to build a vendored copy of openssl on most sensible unix
systems.
We do require a vendored copy on macOS and Windows, but due to the way
that Cargo's feature resolver worked, it wasn't possible for this
requirement to be respected.
Rust 1.51 introduces `resolver="2"` which can deal with this feature
resolution!
https://doc.rust-lang.org/nightly/cargo/reference/features.html#feature-resolver-version-2
The upshot of this is that building wezterm on real unix systems that
are not macos will now link against the system libssl, resulting in both
a shorter compile time and less headaches arising from having a slightly
different openssl used by wezterm than the rest of the system.
cc: @jsgf
There's something fishy with colorspaces and blending.
This commit removes the `window::Color` type and replaces
it and the confusing array of color types exposed by the
`palette` crate with a pair of much simpler types:
`LinearRgb` - a tuple of f32 linear color components
`SrgbaPixel` - the u32 sRGBA pixel representation
This doesn't change anything about rendering, it just
makes it a bit simpler and makes the SrgbaPixel -> LinearRgb
conversion happen slightly earlier which shaves off some
ad-hoc conversions.
Refs: https://github.com/wez/wezterm/issues/544
CI got broken by the termwiz release. This commit teaches the
various `git describe --tags` calls to filter to the wezterm
tags which all start with the year. We're match `20*` which should
be good for the next 79 years.
I've removed the vergen dependency as there was no way to teach it
to do the equivalent matching, and it wasn't a terrible burden
to just inline the git describe call anyway.
Using a boxed slice means that we hold exactly the memory required
for the file data, rather than the next-power-of-two, which can
be wasteful when a large number of images are being sent to
the terminal.
This is a API breaking change for termwiz, so bump its version.
refs: #534
Queries the system battery information and returns an array of
battery information.
Each element is a lua table with the following entries:
* state_of_charge: expressed as percents
* vendor: the battery manufacturer
* model: the battery model
* serial: the battery serial number
* time_to_full: how long until the battery is full
* time_to_empty: how long until the battery is empty
* state: "Charging", "Discharging", "Empty", "Full", "Unknown"
I haven't run this on a system with a battery yet, so I'm holding
off from showing an example until I've got a work one.
refs: https://github.com/wez/wezterm/issues/500
This commit expands on the prior commits to introduce the concept
of per-window configuration overrides.
Each TermWindow maintains json compatible object value holding
a map of config key -> config value overrides.
When the window notices that the config has changed, the config
file is loaded, the CLI overrides (if any) are applied, and then
finally the per-window overrides, before attempting to coerce
the resultant lua value into a Config object.
This mechanism has some important constraints:
* Only data can be assigned to the overrides. Closures or special
lua userdata object handles are not permitted. This is because
the lifetime of those objects is tied to the lua context in which
they were parsed, which doesn't really exist in the context of
the window.
* Only simple keys are supported for the per-window overrides.
That means that trying to override a very specific field of
a deeply structured value (eg: something like `font_rules[1].italic = false`
isn't able to be expressed in this scheme. Instead, you would
need to assign the entire `font_rules` key. I don't anticipate
this being a common desire at this time; if more advance manipulations
are required, then I have some thoughts on an event where arbitrary
lua modifications can be applied.
The implementation details are fairly straight-forward, but in testing
the two examplary use cases I noticed that some hangovers from
supporting overrides for a couple of font related options meant that the
window-specific config wasn't being honored. I've removed the code that
handled those overrides in favor of the newer more general CLI option
override support, and threaded the config through to the font code.
closes: #469closes: #329
`wezterm`, `wezterm-gui` and `wezterm-mux-server` now all support
a new `--config name=value` CLI option that can be specified
multiple times to supply config overrides.
Since there isn't a simple, direct way to update arbitrary fields
of a struct in Rust (there's no runtime reflection), we do this
work in lua.
The config file returns a config table. Before that is mapped
to the Rust Config type, we have a new phase that takes each
of the `--config` values and applies it to the config table.
For example, you can think of configuration as working like this
if wezterm is started as `wezterm --config foo="bar"`:
```lua
config = load_config_file();
config.foo = "bar";
return config;
```
The `--config name=value` option is split into `name` and `value`
parts. The name part is literally concatenated with `config` in
the generated lua code, so the name MUST be valid in that context.
The `value` portion is literally inserted verbatim as the rvalue in the
assignment. Not quoting or other processing is done, which means
that you can (and must!) use the same form that you would use in
the config file for the RHS. Strings must be quoted. This allows
you to use more complicated expressions on the right hand side,
such as:
```
wezterm --config 'font=wezterm.font("Fira Code")'
```
The overrides stick for the lifetime of the process; even if
you change the config file and reload, then the value specified
by the override will take precedence.
refs: https://github.com/wez/wezterm/issues/469
refs: https://github.com/wez/wezterm/issues/499
This function is intended to deal with certain kinds of ligatures
and certain combining sequences that don't have corresponding glyphs.
It isn't hooked up to the gui yet, but does have unit tests that
are probably mostly correct.
refs: https://github.com/wez/wezterm/issues/478
In the earlier times wezterm supported different font rasterizers,
and the configuration was a bit vague and generic to accomodate
differences in how the rasterizers worked.
Since then, we've standardized on freetype.
One of the things that's been bothering me for a while is that
we have some fiddly logic to transform from the config to the freetype
flags.
This commit does away with the transformation and simply exposes
the two sets of freetype options.
The main thing that I expect people to play with is
`freetype_load_target` which can have one of the following values:
```
pub enum FreeTypeLoadTarget {
/// This corresponds to the default hinting algorithm, optimized
for standard gray-level rendering.
Normal,
/// A lighter hinting algorithm for non-monochrome modes. Many
generated glyphs are more fuzzy but better resemble its original
shape. A bit like rendering on Mac OS X. This target implies
FT_LOAD_FORCE_AUTOHINT.
Light,
/// Strong hinting algorithm that should only be used for
monochrome output. The result is probably unpleasant if the glyph
is rendered in non-monochrome modes.
Mono,
/// A variant of Normal optimized for horizontally decimated LCD displays.
HorizontalLcd,
/// A variant of Normal optimized for vertically decimated LCD displays.
VerticalLcd,
}
```
I expect most people will want to set this to one of `Normal`, `Light`
or `HorizontalLcd`. `HorizontalLcd` is what `font_antialias=Subpixel`
used to select.
refs: #491
Replaces notify-rust with directly calling into the zbus crate.
This provides a pure rust interface to DBUS and provides more
flexible control over notification handling.
closes: #485
However, I'm not able to create wayland windows any more on my nvidia
system (either with or without this change).
I don't know if this is specific to my nvidia drivers or something else
:-/
refs: https://github.com/wez/wezterm/issues/476
This commit implements the deprecated NSUserNotification bits needed
to be able to handle clicking on a notification and open our choice
of URL.
Ideally we'd use the newer UserNotifications framework, but that
requires code signing.
This persuades the CI to install both the arm and intel flavors
of the rust toolchain on macOS, and the deploy script to generate
a universal binary.
* need big sur to build for M1
* Use cross-compilation compatible mlua from my fork for now
It's been replaced with an opaque termwiz error type instead.
This is a bit of a more conservative approach than that in (refs: #407)
and has less of an impact on the surrounding code, which appeals to
me from a maintenance perspective.
refs: #406
refs: #407
wezterm sets a more restrictive umask (`0o077`) by default so that any files
that it creates (eg: unix domain socket, log files) are more secure
by default.
However, some environments rely on the more general default of (`0o022`)
without checking that it is set.
This matters because programs spawned by wezterm inherit its more
restricted umask.
I hadn't noticed this because I've had `umask 022` in my shell RC files
since sometime in the 1990's.
This commit adds some plumbing to the pty layer to specify an optional
umask for the child process, and some more to our umask saver helper
so that any thread can determine the saved umask without needing a
reference to the saver itself, which may be in a different crate.
The logic in the config crate has been adjusted to connect the saved
value to the default command builder arguments.
The net result of this is that running `wezterm -n start bash -- --norc`
and typing `umask` in the resultant window now prints `0022`.
refs: #416
This allows us to support the kitty style underline sequence,
or the : separated form of the true color escape sequences.
refs: https://github.com/wez/wezterm/issues/415
When running the GUI, we generate a unix domain socket path for
the current process and start up a mux server for that path.
This allows `wezterm cli list` and `wezterm cli split-pane` to
work implicitly inside the GUI session.
When started in this way, the mux server is not persistent;
when the GUI process is terminated, all of its windows, tabs
and panes are terminated.
refs: https://github.com/wez/wezterm/issues/230
* Allow injecting some initial output to new panes
* Have the update checker set this new-pane-banner to a short
upsell to let the user know there is an update.
* Refactor toast notifications into their own crate
* Have the update checker call a new stub function that triggers
a toast notification with an URL... but it does nothing because
the rust ecosystem doesn't support this on macos yet and I'm
writing this code there
Tidies up the plumbing around pixel dimensions so that ImageData
can be rendered via the termwiztermtab bits.
I put this together to play with sticking the wezterm logo in
the close confirmation dialogs. I didn't end up using that though,
but have preserved the commented code for use in future hacking.
80214319ae broke the use of RUST_LOG to
turn up trace logging.
This commit refactors logger initialization into the env-bootstrap crate
so that it is centralized, and adopts the use of `WEZTERM_LOG` to
override the default logging filters, rather than `RUST_LOG`.
My original goal was to update to allsorts 0.5 but the API
changes are significant and not clearly described.
To make that transition easier, the prior commit moved the shaping
logic into our allsorts shaper module, leaving the name parsing
here in parser.rs.
This commit now replaces that logic with ttf_parser, which is
potentially faster (there's more emphasis on optimal code in that
crate than in allsorts) but definitely simpler.
It's not a slam-dunk transition: ttf_parser doesn't know how to
decode MacRoman encoded text, so there's a bit of logic borrowed
from allsorts here to handle that.
I'm gradually improving snapshot testing macro devx in k9 and preparing
to ship v1. Before i do this i'm changing the inline snapshot macro to be
just `snapshot!()` that takes `Debug` trait an an arg and figures out
serialization of it.
This commit adjusts the default color palette to use the same color
cube calculation as xterm; it isn't the ideal color cube calculation
and results in slightly brighter colors.
This commit also memoizes the default palette calculation so that
it isn't recomputed each time a palette is created.
refs: https://github.com/wez/wezterm/issues/348
This commit is a bit noisy because it also meant flipping the key map
code from using the termwiz input types to the window input types, which
I thought I'd done some time ago, but clearly didn't.
This commit allows defining key assignments in terms of the underlying
operating system raw codes, if provided by the relevant layer in the
window crate (currently, only X11/Wayland).
The raw codes are inherently OS/Machine/Hardware dependent; they are the
rawest value that we have available and there is no meaningful
understanding that we can perform in code to understand what that key
is.
One useful property of the raw code is that, because it hasn't gone
through any OS level keymapping processing, its value reflects its
physical position on the keyboard, allowing you to map keys by position
rather than by value. That's useful if you use software to implement
eg: DVORAK or COLEMAK but want your muscle memory to kick in for some of
your key bindings.
New config option:
`debug_key_events = true` will cause wezterm to log an "error" to stderr
each time you press a key and show the details in the key event:
```
2020-12-06T21:23:10.313Z ERROR wezterm_gui::gui::termwindow > key_event KeyEvent { key: Char('@'), modifiers: SHIFT | CTRL, raw_key: None, raw_modifiers: SHIFT | CTRL, raw_code: Some(11), repeat_count: 1, key_is_down: true }
```
This is useful if you want to figure out the `raw_code` for a key in your
setup.
In your config, you can use this information to setup new key bindings.
The motivating example for me is that because `raw_key` (the unmodified
equivalent of `key`) is `None`, the built-in `CTRL-SHIFT-1` key
assignment doesn't function for me on Linux, but I can now "fix" this in
my local configuration, taking care to make it linux specific:
```lua
local wezterm = require 'wezterm';
local keys = {}
if wezterm.target_triple == "x86_64-unknown-linux-gnu" then
local tab_no = 0
-- raw codes 10 through 19 correspond to the number key 1-9 positions
-- on my keyboard on my linux system. They may be different on
-- your system!
for i = 10, 20 do
table.insert(keys, {
key="raw:"..tostring(i),
mods="CTRL|SHIFT",
action=wezterm.action{ActivateTab=tab_no},
})
tab_no = tab_no + 1
end
end
return {
keys = keys,
}
```
Notice that the key assignment accepts encoding a raw key code using
a value like `key="raw:11"` to indicate that you want a `raw_code` of
`11` to match your key assignment. The `raw_modifiers` portion of
the `KeyEvent` is used together with the `raw_code` when deciding
the key assignment.
cc: @bew
This tidies up the font-dir and built-in font management a little
bit and paves the way for codepoint -> font resolution for fonts
discovered in font-dirs.
This commit uses a bit of DirectWrite to discover which font(s)
can be used to render a set of codepoints.
While hooking this up, I found that the method we were using
to extract the font data didn't handle TTC data so this commit
improves some parser diagnostics and handling for that.
refs: https://github.com/wez/wezterm/issues/299
98f289f511 causes more metrics retrieval
than in earlier versions; each unchached glyph render would trigger
a metrics recompute for the relevant font.
Add a simple cache for this.
refs: #353
This is one of those massive time sinks that I almost regret...
As part of recent changes to dust-off the allsorts shaper, I noticed
that the harfbuzz shaper wasn't shaping as well as the allsorts one.
This commit:
* Adds emoji-test.txt, a text file you can `cat` to see how well
the emoji are shaped and rendered.
* Fixes (or at least, improves) the column width calculation for
combining sequences such as "deaf man" which was previously calculated
at 3 cells in width when it should have just been 2 cells wide, which
resulted in a weird "prismatic" effect during rendering where the
glyph would be rendered with an extra RHS portion of the glyph across
3 cells.
* Improved/simplified the clustering logic used to compute fallbacks.
Previously we could end up with some wonky/disjoint sequence of
undefined glyphs which wouldn't be successfully resolved from a
fallback font. We now make a better effort to consolidate runs of
undefined glyphs for fallback.
* For sequences such as "woman with veil: dark skin tone" that occupy a
single cell, the shaper may return 3 clusters with 3 glyphs in the
case that the font doesn't fully support this grapheme. At render
time we'd just take the last glyph from that sequence and render it,
resulting in eg: a female symbol in this particular case. It is
generally a bit more useful to show the first glyph in the sequence
(eg: person with veil) rather than the gender or skin tone, so the
renderer now checks for this kind of overlapping sequence and renders
only the first glyph from the sequence.
