canvas renderer double underline is a single underline

[jerch]

Not sure if this is linked to the other canvas underline issues, but the curly underline does not look very curly to me:

(Get the same output in Chrome && Firefox...)

Edit: Oh well, double is also not doubled 🙈

[Tyriar]

Curly is a general problem tracked here: #4064

The double underline is canvas-specific as no row can draw in another row by design, so the only way we could handle that is to draw the underline upwards instead of downwards.

[Tyriar]

Suggested fix is to configure the texture atlas to avoid drawing below or above bounds of the cell which would then tweak the values of yTop and yBot here:

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

Lines 543 to 549 in 22a4dc4

	switch (this._workAttributeData.extended.underlineStyle) {
	case UnderlineStyle.DOUBLE:
	this._tmpCtx.moveTo(xChLeft, yTop);
	this._tmpCtx.lineTo(xChRight, yTop);
	this._tmpCtx.moveTo(xChLeft, yBot);
	this._tmpCtx.lineTo(xChRight, yBot);
	break;

[tisilent]

try try

[Tyriar]

Actually the muted curly is different to being cut off on canvas, created #4653