Inaccurate background-size with ch units

• Component: Layout and Rendering
• Status: NEW ---

[Gabor Vajda]

Created attachment 430966 [details]
Inaccurate background layout in Safari

The issue is demonstrated here: https://codepen.io/vajdagabor/pen/VwpBRQG

I'm trying to create a (monospace) code display with repeated background pattern, where background-image is positioned precisely to every character. Setting background-size with ch unit would be ideal, but the result is inaccurate on Safari. The example works well on Chrome and Firefox.

Also, the pattern in the example is not visible when the font is small.

This is the CSS:

pre {
  background-image: linear-gradient(to right, black 0%, black 1px, transparent 1px, transparent 100%);
  background-size: 1ch;
}

[Radar WebKit Bug Importer]

<rdar://problem/79398089>