Pile failing to render anything at all.

[hydra]

This minimal example works:

use cushy::widget::{MakeWidget};
use cushy::widgets::pile::Pile;
use cushy::Run;
use cushy::widgets::label::Displayable;

fn main() -> cushy::Result {
    let pile = Pile::default();

    let handle = pile.push("show a pile!".to_label());
    handle.show(false);

    pile.centered().expand()
        .run()
}

Source: https://github.com/hydra/cushy/blob/pile_fail_1/examples/pile.rs
Screenshot:

This example does not render the pile:

use cushy::widget::{MakeWidget};
use cushy::widgets::pile::Pile;
use cushy::{App, Run};
use cushy::widgets::label::Displayable;
use cushy::window::PendingWindow;

#[cushy::main]
fn main(app: &mut App) -> cushy::Result {
    let pending = PendingWindow::default();

    let pile = Pile::default();

    let handle = pile.push("show a pile!".to_label());
    handle.show(false);

    let ui = pending.with_root(
        pile.centered().expand()
    );

    ui.open_centered(app)?;

    Ok(())
}

Source: https://github.com/hydra/cushy/blob/pile_fail_1/examples/pile_fail_1.rs
Screenshot:

The only difference seems to be how the window is created.

This is blocking me from using Pile in my application.

[hydra]

in Pile::synchronize_widgets, the pile.widgets.entries() does not return any widget entries.

[hydra]

So it seems to be something to do with when the handle is dropped.

This example demonstrates that when there is no reference to the handle, the pile doesn't render the first (and only) widget in the pile, note that the button handler is commented out, and thus handle is free to be drop()ed by the compiler.

#[cushy::main]
fn main(app: &mut App) -> cushy::Result {
    let pending = PendingWindow::default();

    let pile = Pile::default();

    let handle = pile.push("show a pile 1!".to_label());
    handle.show(false);

    let show_first_button = format!("show first")
        .into_button()
        //.on_click({
        //    let section = handle.clone();
        //    move |_| section.show(true)
        //})
        .make_widget();

    println!("pile: {:?}", pile);

    let ui = pending.with_root(
        show_first_button
            .and(pile.centered().expand())
            .into_rows()
            .expand()
    );

    ui.open_centered(app)?;

    Ok(())
}

screenshot:

here's a callstack showing that PiledWidgetData is dropped, before the main window is shown.

however, if you restore the commented-out code, as follows, then it works:

...
    let show_first_button = format!("show first")
        .into_button()
        .on_click({
            let section = handle.clone();
            move |_| section.show(true)
        })
        .make_widget();
...

screenshot:

and here is a screenshot of the callstack showing that PiledWidgetData is dropped only when the application is closed.

I'm guessing this isn't intended and/or needs to be documented. I had to go down the rabbit-hole pretty far to figure this out and we probably don't want other users of Pile to be subjected to the same problem.

[hydra]

this seems to be stemming from the cushy::main macro which injects the main() body into an on_startup handler for the app, so even adding an explicit drop after ui.open_centered(app)?; doesn't help as the macro obfuscates the fact that main is really a closure.

It also feels like Pile::push needs a must_use attribute and/or #[allow(clippy::must_use_candidate)] in the same way impl PendingPiledWidget::finish() does.