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Infinite loop when drawing large ligatures to char atlas #4362

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LabhanshAgrawal opened this issue Jan 2, 2023 · 0 comments · May be fixed by #4386
Open

Infinite loop when drawing large ligatures to char atlas #4362

LabhanshAgrawal opened this issue Jan 2, 2023 · 0 comments · May be fixed by #4386
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area/addon/canvas area/addon/ligatures area/addon/webgl help wanted type/bug Something is misbehaving

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@LabhanshAgrawal
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some fonts provide extremely long ligatures, e.g. Fira Code for ===================================================
The char atlas code tries to find a row to fit it but fails and gets stuck in an infinite loop

xterm.js/src/browser/renderer/shared/TextureAtlas.ts

Lines 792 to 799 in fe89817

// If there is not enough room in the current row, finish it and try again
if (activeRow === activePage.currentRow) {
activeRow.x = 0;
activeRow.y += activeRow.height;
activeRow.height = 0;
} else {
activePage.fixedRows.splice(activePage.fixedRows.indexOf(activeRow), 1);
}

^Here we're checking if there's room on the current row and creating a new one if not.

Details

  • Browser and browser version: chrome 108
  • OS version: macOS 12
  • xterm.js version: 5.1.0 (also on latest master branch)

Steps to reproduce

  1. Install Fira Code font, Run the xterm demo and enable ligatures
  2. start typing =
  3. Keep looking at the char atlas drawn below, once the glyph is almost the same width as char atlas, typing the next = will freeze everything.

Screenshot 2023-01-02 at 13 32 47
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area/addon/canvas area/addon/ligatures area/addon/webgl help wanted type/bug Something is misbehaving
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split extremely wide ligature glyphs to fit atlas LabhanshAgrawal/xterm.js
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@Tyriar @LabhanshAgrawal