Issue #18996 has been updated by st0012 (Stan Lo). hsbt (Hiroshi SHIBATA) wrote in #note-10:

```ruby Reline.completion_colors = { foreground: :white, background: :black, selected_text: :black, selection: :white } ```

I agree that `color` postfix is a bit redundant. But I still lean *slightly* toward having it because it makes passing values easier: ```rb DialogRenderInfo.new( pos: Reline::CursorPos.new(x, y), contents: contents, width: width, **Reline.completion_colors ) ``` And when doing so, users get errors when they have typos or unsupported attributes in their `Reline.completion_colors`, for example. But I'll take either one decided in the dev meeting. ---------------------------------------- Feature #18996: Proposal: Introduce new APIs to reline for changing dialog UI colours https://bugs.ruby-lang.org/issues/18996#change-100332 * Author: st0012 (Stan Lo) * Status: Open * Priority: Normal ---------------------------------------- ### TL;DR I want to add APIs to `reline` for changing its dialog item's colors. The APIs I want to add actually have been merged but becaue: 1. This is a design change 2. The maintainer @aycabta is not available to approve nor reject them I want to raise it here to decide if we should: 1. Drop them 2. Modify them 3. Officiallty accept them ### Background After version `1.4`, `irb` provides autocompletion support, which is a great feature and has increased many developers' productivity significantly. But there's an user-experience issue: the completion items' UI colors (set in `reline`) [are not configurable](https://github.com/ruby/reline/blob/9ab5850444b49aff8e360a84eb1dfa425e96ced1...). So depending on the user's terminal theme, some may find it hard to use because the background and the text having low-contrast colors, like this:  And if that happens, the user has no way to fix it. This caused users to open issues like: - https://github.com/ruby/irb/issues/351 - https://github.com/ruby/irb/issues/328 for being able to change it. Some users even decided to disable it completely because the colors are unreadable to them. I have also seen people sharingtips for disabling this feature: [example](https://twitter.com/sdogruyol/status/1538512030449254400). So I believe it may be bothering many developers. Personally I really like this feature but the background also bothers me:  And that's why I want to improve it by making the colors configurable and potentially also by providing simple light/dark themes from `irb`. ### Proposal For the dialog UI, there are 2 element states: `highlighted` and `default`. In `irb`'s case, the selected completion candidate will be `highlighted`, and the rest of options will be `default`. And each state has 2 colors: `foreground (text)` and `background (block)`. This means the `reline` should allow `irb` and/or users to configure: - Default items' foreground color - Default items' background color - Highlighted items' foreground color - Highlighted items' background color That brings us to these APIs: - `Reline.dialog_default_fg_color` - `Reline.dialog_default_bg_color` - `Reline.dialog_highlight_fg_color` - `Reline.dialog_highlight_bg_color` And because `reline` only supports coloring through ANSI sequences, these APIs only has 8 available colors if we exclude their bright variants: - Black - Red - Green - Yellow - Blue - Magenta - Cyan - White Given the limited options and also to prevent users from entering non-color ANSI sequences, these APIs only take color names directly: - :black - :red - :green - :yellow - :blue - :magenta - :cyan - :white Example: ```rb Reline.dialog_default_bg_color = :black puts Reline.dialog_default_bg_color_sequence #=> 40 Reline.dialog_default_fg_color = :white puts Reline.dialog_default_fg_color_sequence #=> 37 Reline.dialog_highlight_bg_color = :blue puts Reline.dialog_highlight_bg_color_sequence #=> 34 Reline.dialog_highlight_fg_color = :black puts Reline.dialog_highlight_fg_color_sequence #=> 30 ``` I have made a [proof of concept PR](https://github.com/ruby/irb/pull/380) on `irb` to show what these APIs can achieve if they or similar ones are adopted. #### Related PRs The related changes are made through multiple PRs: - [Initial APIs PR by @pocari](https://github.com/ruby/reline/pull/413) - [PR to improve the APIs and make them safer to use](https://github.com/ruby/reline/pull/454) - [PR to rename the APIs](https://github.com/ruby/reline/pull/456) #### Other Thoughts This is more of a concern on the `irb` part, but to make the UI looks comfortable, I think it's better to follow these conditions: 1. An item's foreground and background colors should have high contrast with each other so the texts (foreground) are readable. 2. For the `highlighted` item, its background color should be easily distinguishable from the rest of `default` items. 3. When using dark terminal themes, the `default` items' background is better to be dark as well. ---Files-------------------------------- Screenshot 2022-10-18 at 15.25.36.png (9.7 KB) -- https://bugs.ruby-lang.org/