selectionHighlight still slow and blocking for long non-wrapped lines

[myfonj]

• VSCode Version: Code 1.15.1 (41abd21, 2017-08-16T18:07:25.676Z)
• OS Version: Windows_NT x64 10.0.15063

---

Steps to Reproduce:

1. Save https://upload.wikimedia.org/wikipedia/commons/f/fd/Ghostscript_Tiger.svg and open in VSC.
2. Ensure settings "editor.selectionHighlight": true and "editor.fontLigatures": true
3. Select entire document.
4. Invoke >Join Lines.
5. If lines are wrapped, invoke >Toggle word wrap .
6. Select 0 (zero, or any other digit).

Actual behavior:

Editor completely frozen (i.e. does not react for any kind of input) for circa 15 seconds.
After highlights appear editor works normally again.

Expected behavior:

No freeze.
Would not mind missing or delayed highlights.

Notes:

Quite OK with wrapped lines.
Older (closed) issues relevant to this "long lines" topic: #31425 #6885 #13515

Reproduces without extensions: Yes

[alexdima]

@myfonj I am thinking we are running into #33525 which is similar, when we don't end up doing our monospace optimizations and end up relying on Chromium to give us the positions of the highlights.

I am thinking this issue reproduces when:

• not using a monospace font
• (or) enabling ligatures
• having a long line with may decorations

Can you please confirm that is the case ?

[myfonj]

Ah, ligatures! Yes, confirming: setting "editor.fontLigatures": false prevents described lag from happening.

[alexdima]

Thank you. Let's continue tracking in #33525