FWIW, the logic for this stuff is already rather complex:

I'm not eager to try adding more options in here unless there is a really clear and pressing need.
There would need to be answers for questions like:

• How do you treat reverse video cursor coupled with reverse video selection?

and other combinations of factors/configs.

Hmmm, I don't really know much about this so I'll take you word for it about complexity, but for reverse video cursor coupled with reverse video selection couldn't you disallow having both for a start? Since you already have the cursor one you could let that one take priority, and so if both are set the selection one would have no effect.

There's obviously no clear and pressing need, it's just a look thing, I can definitely go without it, I'm just trying to replicate my old Konsole look on WezTerm.

As far as I know, the logic for this should be fairly simple. If reverse video for selection is enabled in config, simply swap foreground and background color for selected text. I looked at the code, here is what that would look like IMO:

            // Selected text overrides colors
            (true, _, _, CursorVisibility::Hidden) => if self.config.force_reverse_video_selection {(
                params.bg_color,
                params.fg_color,
                params.cursor_bg,
            )} else {(
                params.selection_fg.when_fully_transparent(params.fg_color),
                params.selection_bg,
                params.cursor_bg,
            )},

While it is not a pressing need, this is the default behavior in gnome terminal, terminator, konsole, kitty and a couple more I think. It ensures that selected text is always very easy to read and contrasts the background nicely (no matter the colors), since the selection is simply the user theme color swapped. I am used to it to the point, that I actually can't live without it 😅

I tried to implement this feature myself. I ran into an issue however, right now the selection in a line is rendered as a rectangle with a single color:

            let mut quad = self
                .filled_rectangle(
                    layers,
                    0,
                    euclid::rect(start, params.top_pixel_y, width, cell_height),
                    params.selection_bg,
                )
                .context("filled_rectangle")?;

This feature would require that selection background color depends on the color of the text in front of it. So if you have a line with first white text, then red text, then more white text, that would require 3 separate rectangles each with its own color. I don't know the performance implications of this, I thought background color was rendered on a per character basis.

How would I go about implementing this?

if you're interested in working on this, the only changes you need to make are in the compute_cell_fg_bg method I linked to above; the struct that it returns tells the rest of the code what the effect fg and bg colors should be for the cell:

it is passed this set of information that encodes all of the pertinent information for that cell:

Okay, I checked the compute_cell_fg_bg method. I can successfully swap the color of the selected text like I want, but I am having issues swapping the color of the selection background. It seems to me like bg_color the method compute_cell_fg_bg() returns is not used for drawing anything to the screen at all and is only used to prevent anti-aliasing ghostly outline. Am I missing something?

The only place where selection background is drawn is with a color set in the config file, am I correct?

ah, then I think you'll need use compute_cell_fg_bg for the background painting logic which is a bit further up in the code:

the thing to be careful about here is that we paint the background first, then composite the selection rectangle over the top; the selection color can have an alpha component and blend together, so it isn't valid to simply draw the selection background instead of the main background. There needs to be two separate rectangles of different colors.

They can be both draw in the same loop, so maybe the thing to try is adding a compute_cell_fg_bg just before:

and using that to draw the selection color. Then this logic can be removed:

Hey, I added a PR for this feature #4093. When the new config option I added is set to true, the selection behaves exactly as it does in Terminator (what I used before Wezterm). I left comments in the code, so hopefully my code makes sense. Let me know what you think about it.

There is one more thing to address here and that is the cursor itself. When the cursor itself is selected, and force reverse video cursor config is enabled, colors should be swapped again for the cursor. Otherwise the cursor and the text is covers has the same color as the selection making it illegible.

Here is the example of PR in action. Notice how the reverse video cursor is the same color as the selection itself. That needs fixing, otherwise I think it's perfect.

Thank you for working on this @Tomiyou !