Repetition with condition

[landaire]

I'm trying to implement a tree view where tree nodes that should not be visible have their visible flag set to false. I'd like to check this in the slint code by doing something like the following:

import { ListView} from "std-widgets.slint";

export struct Box {
    visible: bool,
}

export component Example inherits Window {
    in property<[Box]> boxes: [{visible: false}, {visible: true},];
    preferred-width: 50px;
    preferred-height: 50px;
    ListView { 
        for box[i] in root.boxes: if box.visible: Rectangle {
                height: 25px;
                background: i == 0 ? blue : green;
        }
    }
    
}

This results in a syntax error, however.

Is there a workaround that anyone can suggest?

[landaire]

I now see that there's a visible property that can be set... but even for a very simple example this causes an application hang:

import { ListView} from "std-widgets.slint";

export struct Box {
    visible: bool,
}

export component Example inherits Window {
    in property<[Box]> boxes: [{visible: false}, {visible: true},];
    preferred-width: 50px;
    preferred-height: 50px;
    ListView { 
        for box[i] in root.boxes: Rectangle {
                visible: box.visible;
                height: 25px;
                background: i == 0 ? blue : green;
        }
    }
}

Seems related to #2516

Hacking up the workaround presented there to be something like the following for my scenario:

import { ListView, Button } from "std-widgets.slint";

export struct Box {
    visible: bool,
}

export component Example inherits Window {
    in property<[Box]> boxes: [{visible: false}, {visible: true}, {visible: true}];
    preferred-width: 50px;
    preferred-height: 50px;
    ListView {
        for box[i] in root.boxes: HorizontalLayout {
                if box.visible: HorizontalLayout {
                    width: self.preferred-width;
                    spacing: 5px;
                    Text {
                        text: "foo";
                        vertical-alignment: center;
                    }

                    Button {
                        text: "Click!";
                    }
                }
        }
    }
}

This unfortunately causes the application to hang with a sufficiently large number of conditional elements.

[ogoffart]

Looks like bug #2516 indeed.
It should be possible to fix it now.

As a workaround, i can suggest to set the height to 0 when it is not visible.