When a workspace overflows the screen, allow offscreen columns to "peek" the edge

[agausmann]

EDIT: This was originally written as a feature request, but it turns out that option A was already implemented as struts.

Motivation

When your column widths perfectly fit the screen, I've noticed as a new user that it's easy to forget if there are any columns offscreen. Other users have mentioned similar things in the discussions of the "overview" feature request: #352 (comment), #352 (comment)

High-level description

There is a solution that doesn't require overviews - we could reserve some space on the edges of the output, where if there is an offscreen column, it peeks over the edge, so the user can see it.

As a side effect, this would make navigation with a mouse a little bit easier - the user can see and click on the edge of offscreen columns to focus them and bring them onscreen.

(Note, this is mainly applicable to the mode center-focused-column "never" - I will assume it is in this mode for this discussion)

Implementation

A) Easy user configs

Just add this as a config parameter - how much width should each output reserve for column peeking? Then niri does all the math internally (adjusting the proportional column widths to make it work, calculating where a newly-focused column needs to scroll in order to keep a peek next to it)

B) Hacky user configs, but maybe simpler to implement internally

Recognize that part of the solution to this is already available to users - instead of using preset widths at exactly 1/2, 1/3, etc. of the output width, we could make them slightly smaller. For example, remove 4% from each width preset (i.e. scale the values by 96%). That way, if all columns use preset widths that add up to 96%, they leave 4% of the width for peeking.

Then, if the onscreen content is perfectly centered, that would be 2% on both sides for offscreen peeking. However, there isn't currently a setting in Niri that can quite do this. With center-focused-column "never", it will only scroll just far enough to put the newly-focused column onscreen.

The minimum change that would enable something like this: Add a configuration option to set a "scroll offset" or a "margin" to be used by center-focused-column "never". When it needs to focus an offscreen column, bring it onscreen and scroll an additional offset to put a peek next to the newly-focused column. (Additionally, consider any column that intersects that offset region as "offscreen", even if it is technically fully visible, forcing it to scroll further onscreen to satisfy the offset value)

Alternatives

Hot-edges - when the cursor is on/near the edge of the output, scroll slightly so the user can see the column that is off that edge (if any).

Main drawbacks:

• This may not work well for multi-monitor setups where the outputs are laid out side-by-side.
• Could be an annoying behavior if the user was trying to interact with a window, overshoots a bit, and hits the edge.

[maggster165]

Adding left and right struts to your config should do what you want, making them 32px will always leave 32px at the left and right of the screen for other windows. It does not peek though

[agausmann]

This is what I was looking for! (And it does automatically reduce the proportional width sizes - basically option A as I described)

This is exactly what i meant when I said "peek", so it does peek though 😝

thanks for pointing me in the right direction!

[maggster165]

no problem! glad to have helped