Add ligature support to terminal take 3

[Tyriar]

Fixes #34103

Supersedes #139537

This adds an experimental ligatures setting, this will get us self hosting on the ligatures addon without any additional work and we can then stabilize it over time. It mostly works currently, known issues are:

• Rendering issues with webgl and ligatures xtermjs/xterm.js#3303 / WebGL ligatures are storing wrong color for cells, causing bad rendering sometimes when type ahead is used in VS Code xtermjs/xterm.js#3288
• Some ligatures seem to overlap xtermjs/xterm.js#3998
• Selection doesn't render correctly for ligatures (webgl only) xtermjs/xterm.js#4000

This adds some node modules so we'll need to make sure that's all good as well.

[Tyriar]

Might be overlapping ranges here?

xtermjs/xterm.js#3998

[Tyriar]

Also (xtermjs/xterm.js#3303) still happens when toggling off and on:

[Tyriar]

@deepak1556 can you please review the permissions related parts in src/main.js, vs/codeandvs/platform/protocol`?

[meganrogge]

just two questions

[Tyriar]

The long ===== is actually expected:

Here it is in Windows Terminal:

The width is correct there though.

[Tyriar]

We ceil the cell width, that's my guess of why the width thing doesn't happen. In order to workaround that we would need sub-pixel offset rendering and then we would hit more glyph overlap problems.

[Tyriar]

Still more bundling problems, these are only an issue because until now all modules outside the main bundle are stand alone, whereas xterm-addon-ligatures has several dependencies like opentype.js

[Tyriar]

Unfortunately this is getting put on hold again this iteration due to the packaging issues I've been having. They're related to the font-ligatures package using node APIs and the way webpack is bundling it doesn't work inside sandboxed electron renderers. Here's the webpack config if anyone want to investigate https://github.com/xtermjs/xterm.js/blob/master/addons/xterm-addon-ligatures/webpack.config.js

[lhecker]

We ceil the cell width, that's my guess of why the width thing doesn't happen. In order to workaround that we would need sub-pixel offset rendering and then we would hit more glyph overlap problems.

@Tyriar Hey I just came across this PR and saw your long-ligature problem (long ==== ligatures seemingly shrink shorter and shorter). I'm not sure whether you already solved it in this PR, but I just so happen to have worked on this exact problem just a few weeks ago when I added ligature support for the new Windows Terminal text renderer. If you have any questions or would like to collaborate on this in any way, please let me know. 🙂
This is the PR that fixes it: microsoft/terminal#13549 and this part is the relevant addition (for Direct2D however): https://github.com/microsoft/terminal/blob/dfa92559611f5c982f78cba73d123638a5e54227/src/renderer/atlas/AtlasEngine.r.cpp#L352-L365
advanceScale is simply ceil(glyphAdvance) / glyphAdvance - it's basically the approach that you already thought of and it seems to work pretty great so far.

[Tyriar]

@lhecker thanks for the info! Good to know you hit the same problem and upscale

[andrewgazelka]

Any updates?

[junaga]

oh my god it's happening

[canopus1io]

what's the current status on this?

[Why-not-now]

I hope it passes asap

[junaga]

We got ChatGPT, and NVIDIA moved the Nasdaq by 2% on it's own, while this PR was open.

[Why-not-now]

Let's hope it goes through this time 🙏

[andrewgazelka]

Let's hope it goes through this time 🙏

It won't. There are still conflicts.

[Why-not-now]

Let's hope it goes through this time 🙏

It won't. There are still conflicts.

Rip, glad it is getting attention again though.

[Tyriar]

Sorry, but closing to clean up PRs as this is stale and would need a new PR when we retry this.