Rename text alignment settings

[rfuest]

This PR changes the names of the HorizontalAlignment and VerticalAlignment enums to Alignment and Baseline. The reason for this change is that VerticalAlignment might be misleading, because the vertical alignment does only apply to the first line of multiline text:

The text on the left is the actual result for Baseline::Middle and the right is an example of what users might expect for VerticalAlignment::Center. This also matches the names used in the HTML5 canvas API: https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/textBaseline, https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/textAlign

The PR also included some tweaks to the TextRenderer trait. I've removed the vertical_offset method, which was intended as a performance optimization. The potential grain of saving a few additions and subtractions per text object isn't worth having an more error prone API.

[rfuest]

Ignored because of #562

[jamwaffles]

LGTM, and the reasoning makes sense.

I haven't been following the text changes too closely, but does this need a breaking changelog entry for any behavioural changes since the last alpha?

[rfuest]

I haven't been following the text changes too closely, but does this need a breaking changelog entry for any behavioural changes since the last alpha?

The behavior shouldn't have changes, but I've added changelog entries for the naming changes and the changed text renderer API.

[bugadani]

Just a few nits. Otherwise, looks good.

[bugadani]

I think these could/should be explained better than just echoing the variant names.

For example I'm not entirely sure what Alphabetic refers to, although I have a guess. Also, does Top refer to the topmost pixel of the character, or something else? Perhaps we could adapt the text from the linked canvas docs.

[rfuest]

The docs need some work in general, I'll add a note to the tracking issue to revisit this later.

For example I'm not entirely sure what Alphabetic refers to, although I have a guess.

The main reason I changed it from Baseline to Alphabetic is that Baseline::Baseline would look weird. But it also matches the canvas API. I don't think we will ever support ideographic or hanging baselines in the internal text renderer.

Also, does Top refer to the topmost pixel of the character, or something else?

It refers to the top of the glyph bounding box. This can include additional blank pixels above the caps if the font includes them.

[bugadani]

I mean, I know what these are (although I had to think about alphabetic for a moment), but it's not obvious from the docs :)

[rfuest]

I know what these are, ... ,but it's not obvious from the docs :)

The docs for the font/text stuff really need some work. Contributions to the docs are always welcome 😉