change the behavior of ui.cursor.insert and ui.cursor.select when ui.cursor.primary is present

[oati]

Fixes #1337

Previously, ui.cursor.insert and ui.cursor.select only applied to non-primary cursors when ui.cursor.primary was present.
This PR changes this behavior to make ui.cursor.insert and ui.cursor.select only affect the primary cursor when ui.cursor.primary is set.

[oati]

The motivation is that ui.cursor.{insert,select} are currently useless when ui.cursor.primary is set. The effect of ui.cursor.{insert,select} is only visible in non-primary cursors.

This change would make ui.cursor.{insert,select} "play better" with ui.cursor.primary, making the behavior closer to how cursor shapes work.

Another option to consider is adding the options ui.cursor.{insert,select}.primary to allow more complex theming.

[archseer]

Another option to consider is adding the options ui.cursor.{insert,select}.primary to allow more complex theming.

This seems more reasonable to me but it's tricky. What would the fallback there be? ui.cursor.primary? Or ui.cursor.insert

[archseer]

I'm a bit confused by the conditionals here.

[oati]

this chooses between mode_cursor_scope and base_cursor_scope/base_primary_cursor_scope depending on whether ui.cursor.primary is present.

I'm considering making a new PR that cleans up the code to make all of the defaults and fallbacks clearer, and adding code for ui.cursor.{insert,select}.primary over it.

[oati]

This seems more reasonable to me but it's tricky. What would the fallback there be? ui.cursor.primary? Or ui.cursor.insert

The current behavior chooses ui.cursor.primary. Ideally, there shouldn't be any situation where ui.cursor.primary and ui.cursor.insert are both present without ui.cursor.insert.primary.

One argument for making ui.cursor.primary first is that people might want a consistent primary cursor color with varying cursor shape, while having colors for non-primary cursors.

Falling back to ui.cursor.insert would make you explicitly specify the primary cursor for each mode, which might be better for forcing themes to make sense (i.e. avoid situations where only the non-primary cursors change colors between modes). It would also make more sense given the name ui.cursor.insert.primary. But we do have the alternative name ui.cursor.primary.insert.

[archseer]

Replaced by #5130