Bspwm: Render the preselection feedback in the borders

[baskerville]

The preselection feedback can be drawn in the border pixmap of each of the window that touches the preselected node's boundary.

This design doesn't require transparency.

[sudo-nice]

If this kind of design is going to replace the current one, there might be a problem for those who use very thin boarders (1px, e.g.).

[ikselven]

Tried to recreate the layout from above and added the yellow and blue borders as shown above. I'm using a border size of 1px and no gaps between windows. The result looks like this:

Even though the border is tiny, it's visible, at least when window contents have a dark background. However, the border is barely visible at the bottom side of Firefox (middle column) and between Firefox and Chromium (upper right).

[pjvds]

What's the best way to get this? Would love to the the pre select hint visible on my borders only.