`text_layout.krk`

[klange]

Think of this ticket more like a wiki page than an issue report.

What is text_layout.krk?

This file has been sitting in ~local for quite some time now, always there for new users running ls in a fresh terminal. Running it presents a Yutani window with decorations, a menubar, and a Douglas Adams quote covered in colorful boxes.

So what's it for?

If its name wasn't self-explanatory, this is a demo of a text layout engine. Users may select the text justification, hide the colorful boxes representing the ascenders, descenders, and baseline, change the font size, and - more interestingly - resize the window to watch it reflow text.

Why is it in local's home directory?

I occasionally try to experiment with new ideas in the layout engine entirely within a ToaruOS VM. It's been a while since one of those experiments has warranted exporting the changes from the VM and committing them, but we'll see how things go.

What's the plan for it?

Originally, the plan was to build a full replacement for the Python layout engine from ToaruOS 1.2.x. That one had the assistance of a full HTML parser, and was using Freetype.

That's still on the table, but I am also using text_layout.krk to prototype something simpler that can be re-written in C, so that we can get better text layout with wrapping in various applications.

[IAmTheNerdNextDoor]

Related but still off-topic but why not just use the wiki stuff in GitHub?

[klange]

I actually have a change to text_layout.krk, for the first time in years, that I might commit. It moves the responsibility of calculating a line's baseline to after all of the 'words' have been added, which is important for mixing text with different metrics on a single line.

The result is we can do this:

The "line height" is the distance between the highest ascender and the lowest descender. The baseline remains constant through the line, but is set appropriately for that highest ascender.

Which sure looks a lot like what a browser spits out for a similar text (this is a different font, mind you):

With some tweaks on both sides to render outlines, we can get this:

And now it looks nearly identical.