FeathersSlider / bevy_ui_widgets/slider fixes

[gagnus]

: Removed value from FeathersSliderProps as it doesn't exist in other controls (use SliderValue component instead) and made SliderPrecision be correctly optional as it is in underlying UI widget rather than silently not updating sliders if not present, in underlying UI widget only send ValueChange if value genuinely changes (matches other controls) rather than every time a SetSliderValue is added

note: slider may end up deprecated in favour of number input, but thought it best to leave it in working state

Objective

• Working way through feathers constructing minimal UIs from the controls I noticed some differences between the slider and other controls (such as FeathersCheckbox) that would confuse users.

Testing

• Feathers Gallery and local testing

---

Showcase

Missing SliderPrecision

(
    @FeathersSlider {
        @min: 0.0,
        @max: 1.0,
    }
    on(slider_self_update)
    on(|change: On<ValueChange<f32>>, mut values: ResMut<TestValues>| {
        info!("value changed {}", change.value);
    })
)

Silently failed to update the slider, now it works.

value property (note: breaking change)

@FeathersSlider {
    @min: 0.0,
    @max: 1.0,
    @value: 0.5,
}

The above is different from other controls which use a component for value

@FeathersSlider {
    @min: 0.0,
    @max: 1.0,
}
SliderValue(0.5)

Is the correct way of setting initial value

SetSliderValue

commands.trigger(SetSliderValue {
     entity,
     change: some_value,
});

Would trigger ValueChange every time, even when some_value is the same as the existing value. Now it doesn't. This is the same as SetChecked

[JosephLassuy]

This seems like a great simple change!

[viridia]

Thank you for doing this.

[JosephLassuy]

Looks good to me!