Modals show up behind images in kitty terminal

[mfontanini]

The kitty graphics protocol treats images as non cell-based entities and therefore if you write an image at position (x, y) and then move the cursor back to (x, y) and write text, it won't overwrite the image. In order to control image stacking, it uses z-indexes so that you can specify whether an image is on top of text, in between the text and the background, or behind the background (and also image over image stacking but we don't care). This causes every application that uses the kitty protocol and needs the use of a modal to have extra code to deal with this, see the discussion here kovidgoyal/kitty#6988.

Unfortunately, viuer doesn't currently support z-indexes (I created a PR for this here atanunq/viuer#53), so the plan to get around this behavior in kitty is:

• Wait until that viuer PR is merged or alternatively fork viuer as the project seems quite dead and there's other things I've thought of adding/I think its API could use some rework so it's more flexible and more tailored to apps that want to write multiple images/the same image multiple times.
• Once we can control z-indexes via either of the solutions above, create a new RenderOperation that's something like "fill.. with... transparent...something" which takes a rect and will, only if we're in kitty mode, print a semi transparent image over that rect with a z-index greater than what we normally use but also negative so it shows up behind text.