[FEATURE] Menubar to render StyledStrings

[svfat]

Is your feature request related to a problem? Please describe. I'm frustrated because the menubar doesn't render colours from StyledString. Basically, I would like to have ability to highlight keyboard shortcuts (e.g. "F" in "File")

Describe the solution you'd like I would like the menubar to render the colours specified in the StyledString. For example, when passing a StyledString with specific colours, those colours should appear on the menubar.

Describe alternatives you've considered I considered using plain strings instead, but this doesn't allow for the use of colours or styles, which limits the visual customisation options.

Additional context Here is a minimal example demonstrating the issue:

use cursive;
use cursive::utils::markup::StyledString;
use cursive::theme::BaseColor;
use cursive::theme::Color;
use cursive::theme::Style;
use cursive::theme::Effect;

fn main() {
    let mut siv = cursive::default();
    let mut styled = StyledString::plain("Isn't ");
    styled.append(StyledString::styled("that ", Color::Dark(BaseColor::Red)));
    styled.append(StyledString::styled(
        "cool?",
        Style::from(Color::Light(BaseColor::Blue)).combine(Effect::Bold),
    ));
    siv.menubar()
        .add_leaf(styled, |s| s.quit());
    siv.set_autohide_menu(false);
    siv.add_global_callback('q', |s| s.quit());
    siv.run();
}

[gyscos]

Hi, and thanks for the report!

Indeed, it would be very nice to be able to use StyledStrings there! Especially to use bold or underscores to highlight shortcuts.

Right now the menu doesn't support these, mostly because it was written before styled strings were a thing. Shouldn't be too hard to add that!

[svfat]

I can take this on if you could point me in the right direction. I'm not yet familiar with the sources

[gyscos]

Sure!

There's two parts to the menubar:

• The backend menu tree representation, in menu.rs. Looks like I already updated that to support StyledStrings - yay!
• The UI parts. There's 2 views used in the menu: the menubar itself, and the popups that open when a category is selected.
  • The menu popups. Here too, it has already been updated to support styled strings.
  • The menubar. Here too apparently I updated that to support StyledString, but I did not properly update the draw implementation: first we call item.label() which ignores the style, and here we only call printer.print((offset, 0), &format!(" {label} "));, which is not style-aware.

So to fix this last point, I would recommend making 2 changes:

• Adding a menu::Item::styled_label(&self) -> SpannedStr<Style>, which returns either the styled string stored from the item, or an unstyled "|" if it's a delimiter:

  // It's a bit cumbersome, but you can create a static slice of spans:
  const PLAIN_1CHAR_SPAN: &'static [IndexedSpan<Style>] = &[IndexedSpan { 
  content: 
  attr: Style {
      effects: EnumSet::EMPTY,  // This needs a recent enough `enumset` dependency, we should bump the minimum version to 1.1.0
      color: ColorStyle {
          front: ColorType::InheritParent,
          back: ColorType::InheritParent,
      },
  },
  width: 1,
  }];
  // ...
  // ... and here you can create a `SpannedStr<'static, Style>`:
  SpannedStr::new("|", PLAIN_1CHAR_SPAN)

(Note for later: we should really try to make more functions const to help here! Right now we're often using the Into trait so that limits what we can const-ify, but hopefully it'll get better eventually...)

• Updating the Menubar::draw implementation to call this new styled_label() method to get the label, and use Printer::print_styled to print it.
  • Right now we use format!(" {label} ") to add spaces around the label. It may be a better idea to instead make 3 print calls: one (regular Printer::print) for each space, and one (Printer::print_styled) for the styled label.

[svfat]

Wow, thanks for the thorough instructions. The fix seems to work, I will test it and prepare a proper PR soon

[svfat]

merged https://github.com/gyscos/cursive/pull/784