Add ability to theme cursor and primary selection

[vv9k]

Perhaps this might be a solution for #323 ?

[sudormrfbin]

This would allow changing the cursor styling but to change the shape itself we'll have to change this:

helix/helix-view/src/editor.rs

Lines 285 to 297 in fc39a6c

	pub fn cursor(&self) -> (Option<Position>, CursorKind) {
	const OFFSET: u16 = 7; // 1 diagnostic + 5 linenr + 1 gutter
	let view = view!(self);
	let doc = &self.documents[view.doc];
	let cursor = doc.selection(view.id).cursor();
	if let Some(mut pos) = view.screen_coords_at_pos(doc, doc.text().slice(..), cursor) {
	pos.col += view.area.x as usize + OFFSET as usize;
	pos.row += view.area.y as usize;
	(Some(pos), CursorKind::Hidden)
	} else {
	(None, CursorKind::Hidden)
	}
	}

[vv9k]

So currently this PR adds 5 new theme scopes

• ui.cursor
• ui.cursor.insert
• ui.cursor.select
• ui.cursor.match
• ui.selection.primary

Here's a demo of the selection:

[pickfire]

I am confused in the last image, why is there two white bold cursor? Shouldn't the original cursor be brighter? Other than the blue and purple which can't distinguish easily which is the main selection, how does one determine which is the cursor for the primary selection just by looking at the cursor?

[vv9k]

I am confused in the last image, why is there two white bold cursor? Shouldn't the original cursor be brighter?

There is no original cursor, all cursors have the same styling.

Other than the blue and purple which can't distinguish easily which is the main selection

I'm not really proposing this colors, I just wanted to demo it. Perhaps should've used more distinguishable colors.

how does one determine which is the cursor for the primary selection just by looking at the cursor?

Just from the cursor I don't think you can for now, the selection might be helpful here.

[vv9k]

Perhaps this might be better as a preview

[pickfire]

Yeah, this looks clear to me. Just wondering, what does ui.cursor since there are specializations?

[archseer]

You can have both ui.cursor.primary and ui.cursor.insert and merge the two styles using patch, this is how I do it on my branch:

helix/helix-term/src/ui/editor.rs

Line 320 in d1ac1a5

acc.patch(style)

The question is just which one should take precedence.

I'm significantly changing selection rendering so I haven't had time to test this branch out yet. I'll probably merge it then rebase mine

[archseer]

Note: for the most part it's not important which selection is primary, which is why they are/were all styled the same by default. But it's good to have this as a theming option. (I actually found the first preview to be nice and subtle)

[pickfire]

Why shouldn't this be ui.cursor.normal?

[archseer]

Was thinking that too at first. I would actually keep it as ui.cursor, this way the insert and select ones can fall back to it if they're not defined

[vv9k]

I was also considering making it ui.cursor.normal but I think as @archseer said it makes more sense as a fallback.

[pickfire]

But the issue is users would not understand the heuristic if all of us here "think that too at first". Then users have to go through our thought process to know why was the decision made this way. Do you think that is a better tradeoff for visibility vs simplicity?

[vv9k]

I didn't say I considered it first, I just said I considered it as an option. Actually at first I came up with ui.cursor because that is what for example vim does, you have Cursor and iCursor as highlight groups and not nCursor but perhaps in this case with 3 this is a bit different. I thought vim also had the vCursor but that seems to only be for gui.

[archseer]

I think it makes sense, you're defining a color for ui.cursor but if you'd like to change the style for ui.cursor.insert or ui.cursor.select you can override it. I anticipate most themes should just define a ui.cursor.