Display density changes lead to corrupted characters

[Eugeny]

When switching between a built-in Retina display and an external normal-density display, some characters will be drawn with incorrect size by the canvas renderer.

Now, I can't confirm whether it's possibly Electron's fault, but I suspect that Chrome would behave the same.

xterm 3.13.2

[Tyriar]

Might be rel;ated to ligature problems in #2135?

[Eugeny]

Might be, but I don't think so. Looks like some chars might be cached in the renderer atlas with a smaller resolution?

[Tyriar]

@Eugeny seems to me like the cached parts are -r, -x and --.

[Eugeny]

Good point - these are the ones that are incorrectly rendered in #2135

[Eugeny]

Weirdly enough, switching to a higher density makes these characters larger, and switching to a smaller density display makes them smaller.

[Tyriar]

The APIs that https://github.com/xtermjs/xterm-addon-ligatures use probably just need some updating for the recent updates to renderers.

[jerch]

Cannot repro this and the other issue #2135 (on Ubuntu though, with Fira Mono and ligatures enabled).
Kinda sounds as the dpr change gets not applied? @Eugeny Could you test, if the demo shows the same wrongly scaled glyphs when you switch the screens?

[Eugeny]

Still reliably reproducible in master with the webgl renderer:

The font doesn't get corrupted immediately after the DPI switch, but rather after font-family and font-size are updated (re-set to the same values) in xterm.