New styling API (0.13) inside of a function

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1

So I am creating a function that returns an Element. Which works perfectly fine, it has the trait restrictions:

where
    Message: 'a + Clone,
    Theme: 'a + button::Catalog + iced::widget::text::Catalog,
    Renderer: 'a + iced::advanced::Renderer + iced::advanced::text::Renderer,

And when I attempt to apply some of my custom styles, like this:

pub fn punge_button_style(status: Status) -> Style {
    match status {
        Status::Disabled => Style {
            background: None,
            text_color: Color {
                r: 0.85,
                g: 0.85,
                b: 0.85,
                a: 1.0,
            },
            border: Border {
                color: Color {
                    r: 0.0,
                    g: 0.0,
                    b: 0.0,
                    a: 0.0,
                },
                radius: Radius::default(),
                width: 1.0,
            },
            shadow: Shadow::default(),
        },

        _ => Style::default(),
    }
}

I get an error:

.style(|_t, status| punge_button_style(status))
^^^^^ the trait `From<std::boxed::Box<dyn for<'a> std::ops::Fn(&'a Theme, iced::widget::button::Status) -> iced::widget::button::Style>>` is not implemented for `<Theme as iced::widget::button::Catalog>::Class<'_>`

note: required by a bound in `iced::widget::Button::<'a, Message, Theme, Renderer>::style`

I’ve searched through to try to find examples of people doing similar things, but I haven’t found many projects that have upgraded to the new styling api. (given it hasn’t had a release yet).

Again, this works fine when I use my styling in my view function, but doesn’t seem to like being in a regular function. Any help would be great!

2

Can you share you full code, so we can run it by our self and play with it?

Where do these restrictions come from?

where
Message: 'a + Clone,
Theme: 'a + button::Catalog + iced::widget::text::Catalog,
Renderer: 'a + iced::advanced::Renderer + iced::advanced::text::Renderer,

3

Here, this replicates the problem I had:

use iced::border::{Border, Radius};
use iced::widget::button::{Status, Style};
use iced::widget::{button, container, row, text};
use iced::Element;
use iced::{Color, Shadow};

fn main() -> iced::Result {
    iced::run("testing", App::update, App::view)
}

#[derive(Default)]
struct App {}

#[derive(Debug, Clone)]
enum Message {
    Test,
}

fn create_stuff<'a, Message, Theme, Renderer>() -> Element<'a, Message, Theme, Renderer>
where
    Message: 'a + Clone,
    Theme: 'a + button::Catalog + iced::widget::text::Catalog,
    Renderer: 'a + iced::advanced::Renderer + iced::advanced::text::Renderer,
{
    row![button(text("here is some content!!")).style(|_t, status| custom_button(status))].into()
}

impl App {
    fn update(&mut self, message: Message) {
        println!("ignore")
    }

    fn view(&self) -> Element<Message> {
        container(row![
            button(text("my content!")).style(|_t, status| custom_button(status)),
            create_stuff(),
        ])
        .into()
    }
}

fn custom_button(status: iced::widget::button::Status) -> iced::widget::button::Style {
    match status {
        Status::Disabled => Style {
            background: None,
            text_color: Color {
                r: 0.85,
                g: 0.85,
                b: 0.85,
                a: 1.0,
            },
            border: Border {
                color: Color {
                    r: 0.0,
                    g: 0.0,
                    b: 0.0,
                    a: 0.0,
                },
                radius: Radius::default(),
                width: 1.0,
            },
            shadow: Shadow::default(),
        },

        _ => Style::default(),
    }
}

With the iced version being:

iced = {git = "https://github.com/iced-rs/iced", branch = "feature/list-widget-reloaded", features = ["advanced"] }

(using the master branch caused some dependency errors for me, I’m not sure if there is a different specific 0.13 branch, but the one I use has the styling changes)

4

The style methods need additional bounds:

pub fn style(
    self,
    style: impl Fn(&Theme, Status) -> Style + 'a,
) -> Button<'a, Message, Theme, Renderer>
where
    <Theme as Catalog>::Class<'a>: From<Box<dyn Fn(&Theme, Status) -> Style + 'a>>,

Make sure you add them.

5

I got it.

Was sort of confused as what Catalog refers to (I recall people making their own trait for it).

fn create_stuff<'a, Message, Theme, Renderer>() -> Element<'a, Message, Theme, Renderer>
where
    <Theme as iced::widget::button::Catalog>::Class<'a>:
        From<Box<dyn Fn(&Theme, Status) -> Style + 'a>>,
    Message: 'a + Clone,
    Theme: 'a + button::Catalog + iced::widget::text::Catalog,
    Renderer: 'a + iced::advanced::Renderer + iced::advanced::text::Renderer,
{

Was all it needed.

Thanks!