Descendants of a disabled View apply disabled behavior, but not disabled styling

[pieterdd]

I observed the following when putting a View into a disabled state:

• Its descendants exhibit disabled behavior, i.e. the buttons in my test no longer respond to clicks (makes sense)
• Its descendants don't look disabled, i.e. they don't apply disabled styling

Here's a live demo:

tmp.mp4

Source code for the demo:

use floem::kurbo::Size;
use floem::peniko::Color;
use floem::reactive::{create_signal, ReadSignal, WriteSignal};
use floem::style::AlignItems;
use floem::view::View;
use floem::views::{h_stack, label, v_stack, Decorators};
use floem::widgets::{button, checkbox};
use floem::window::WindowConfig;
use floem::EventPropagation;

fn my_button(label: &'static str) -> impl View {
    button(move || label).style(|s| {
        s.background(Color::GREEN)
            .color(Color::WHITE)
            .disabled(|s| s.background(Color::DARK_GRAY))
            .font_size(18.0)
            .padding(5.0)
    })
}

fn spinbox(counter: ReadSignal<i32>, set_counter: WriteSignal<i32>) -> impl View {
    h_stack((
        my_button("-").on_click(move |_| {
            set_counter.update(|value| *value -= 1);
            EventPropagation::Stop
        }),
        label(move || counter.get()),
        my_button("+").on_click(move |_| {
            set_counter.update(|value| *value += 1);
            EventPropagation::Stop
        }),
    ))
    .style(|s| {
        s.align_items(AlignItems::Center)
            .disabled(|s| s.background(Color::DIM_GRAY))
            .gap(10.0, 0.0)
    })
}

fn app_view() -> impl View {
    let (spinbox_enabled, set_spinbox_enabled) = create_signal(true);
    let (counter, set_counter) = create_signal(0);

    v_stack((
        checkbox(spinbox_enabled)
            .on_click_stop(move |_| set_spinbox_enabled.set(!spinbox_enabled.get())),
        spinbox(counter, set_counter).disabled(move || !spinbox_enabled.get()),
    ))
}

fn main() {
    let window_config = WindowConfig::default().size(Size {
        width: 200.0,
        height: 100.0,
    });

    floem::Application::new()
        .window(move |_| app_view(), Some(window_config))
        .run()
}

To be consistent, I think disabled styling should apply whenever disabled behavior is into effect.

I'll see if I can write a fix and submit a PR, but I'm still pretty new to Floem. Fix ready at #231.

[pieterdd]

Addressed by e795021.