Support lineHeight in DOM renderer

[pelmers]

The line height configuration is only supported in the canvas renderer (as of 3.6.0).
pointer:

xterm.js/src/renderer/dom/DomRenderer.ts

Line 53 in e736f12

this._rowContainer.style.lineHeight = 'normal';

I thought I had seen an issue for this already but wasn't able to find it now.

[Tyriar]

I don't think there's an issue but there's a comment calling this out.

xterm.js/typings/xterm.d.ts

Line 152 in e736f12

* - Line height

Open to PRs.

[Tyriar]

You can see how this used to be handled by looking at the old DOM renderer in #938

[leomoty]

Hello @Tyriar, I would like to tackle this one, is it just a matter of using lineHeight from options inside DomRenderer.ts and defaulting to normal otherwise?

[Tyriar]

@leomoty great!

We want it to act like line height in the canvas renderer, which is used here:

xterm.js/src/renderer/Renderer.ts

Lines 222 to 230 in e7ae4be

	// Calculate the scaled cell height, if lineHeight is not 1 then the value
	// will be floored because since lineHeight can never be lower then 1, there
	// is a guarentee that the scaled line height will always be larger than
	// scaled char height.
	this.dimensions.scaledCellHeight = Math.floor(this.dimensions.scaledCharHeight * this._terminal.options.lineHeight);
	// Calculate the y coordinate within a cell that text should draw from in
	// order to draw in the center of a cell.
	this.dimensions.scaledCharTop = this._terminal.options.lineHeight === 1 ? 0 : Math.round((this.dimensions.scaledCellHeight - this.dimensions.scaledCharHeight) / 2);

Also the value is always set so you don't need to worry about using normal:

xterm.js/src/Terminal.ts

Line 94 in e7ae4be

lineHeight: 1.0,

You can see how we used to do it by looking at src/Renderer.ts in this PR:

#938

[leomoty]

@Tyriar this can be closed :)