Implementation of preview callback

[alexxbb]

The preview feature of skim is great, however when skim is used as a library, there's no way to render a preview from Rust code.

This PR adds a new option to SkimOptionsBuilder:

.preview_fn(| items: Vec<String> | -> Vec<AnsiString<'static>> {})

The closure will be called with the currently selected items to render.

[alexxbb]

Hey @lotabout, could you please take a look at this PR and see if you want to merge it? I'm not sure why it's failing on one test, I'm happy to fix it if you could give me a hint.

Alex.

[kkharji]

Interesting, but does it allow for pre-processing of entry before handing it to preview command. In my case I have paths that I abbreviated and I have a rust function that perform some adjustment to make absolute path again. Then I'd pass it to bat

[alexxbb]

Interesting, but does it allow for pre-processing of entry before handing it to preview command. In my case I have paths that I abbreviated and I have a rust function that perform some adjustment to make absolute path again. Then I'd pass it to bat

If you want to pre-precess before sending to bat it could be possible to do with this PR, but you'd have to spawn bat yourself in this callback and returns its output. It would be nice to have a filtering function before sending to preview. Looks like there's no way to achive that atm.

[kkharji]

Interesting, but does it allow for pre-processing of entry before handing it to preview command. In my case I have paths that I abbreviated and I have a rust function that perform some adjustment to make absolute path again. Then I'd pass it to bat

If you want to pre-precess before sending to bat it could be possible to do with this PR, but you'd have to spawn bat yourself in this callback and returns its output. It would be nice to have a filtering function before sending to preview. Looks like there's no way to achive that atm.

Thanks @alexxbb I'll drop preview requirement for the moment.