Remove the Val::try_* arithmetic functions

[ickshonpe]

What problem does this solve or what need does it fill?

Wondering if these are useful at all, or even make sense.
They aren't used internally or in any of the examples.

let mut r = UiRect::new(Val::Px(10.), Val::Percent(5.), Val::Auto, Val::VMin(50.));

// Just feels like nonsense; they don't compose or handle failure well
r.left.try_sub_assign(Val::Px(10.).unwrap();
r.right = r.right.try_add(Val::Px(10.)).unwrap_or(r.right.try_add(Val::Percent(10.)));

The try_*_assign_with_size functions seem problematic too:

r.bottom.try_add_assign_with_context(Val::Px(50.), 100., vec2(800., 600.));

r.bottom equals Val::VMin(50.) and is resolved to 600. * 50. / 100. = 300..

So r.bottom is assigned the value: Val::Px(350.).

This might seem like it's okay. But now r.bottom is no longer responsive to changes in the viewport size.

[772]

I use try_add_asign() and try_sub_assign() to move some background cloud images in my game from the right side to the left side.

fn move_background_cloud_images(
    mut background_images: Query<&mut Style, With<IsBackgroundImage1>>,
    time: Res<Time>,
) {
    let speed = 10.0;
    for mut image in background_images.iter_mut() {
        image
            .left
            .try_sub_assign(Val::Px(speed * time.delta_seconds()))
            .unwrap();
        let Val::Px(bar) = image.left else { unreachable!() };
        if bar < -1000.0 {
            image.left.try_add_assign(Val::Px(1000.0)).unwrap();
        }
    }
}

I agree that useless functions should be removed from the engine. And there are likely other ways to to what I did, but this is what I came up with using bevy docs.

[alice-i-cecile]

I'm fine to defer to you and remove these.

[ickshonpe]

I agree that useless functions should be removed from the engine. And there are likely other ways to to what I did, but this is what I came up with using bevy docs.

That's a really helpful example. Rewritten using pattern matching it feels much more natural to me (hopefully I understood the intent of your code correctly):

fn move_background_cloud_images_3(
    mut background_images: Query<&mut Style, With<IsBackgroundImage1>>,
    time: Res<Time>,
) {
    let speed = 10.0;
    for mut style in background_images.iter_mut() {
        let Val::Px(ref mut bar) = style.left else { unreachable!(); };
        *bar -= speed * time.delta_seconds();
        if *bar < -1000. {
            *bar += 1000.;
        }
    }
}

[772]

Yes, that does the same job. Sorry for the poor variable name.

[ickshonpe]

I'm fine to defer to you and remove these.

Definitely think this is the way to go. They seem actively unhelpful and confusing.