Make it possible to forward key events to components

[skilvingr]

Feature Description

It would be great to be able to forward key events to other elements.

The following demo simulates an application where we have a list which takes the majority of the space in the page and a text input field to filter the elements in the list.
It would be convenient to be able to filter the lines in the list by typing in the whole page, not only in the dedicated LineEdit.

Demo:

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

export component Demo {
    FocusScope {
        // Example 1
        key-pressed(event) => {
            filter.focus();
            reject
        }

        // Example 2
        //key-pressed(event) => {
        //    filter.text += event.text;
        //    reject
        //}

        VerticalBox {
            ListView {
                for e in ["First", "Second", "Third"] : Text {
                    text: e;
                }
            }

            filter := LineEdit {
                placeholder-text: "Insert filter";
            }
        }
    }
}

A the moment it's possible to manually focus the destination, but such a focus becomes effective only after the event has been discarded, so a character gets lost (Example 1).
Example 2 manually edits filter's text, but doing so the LineEdit cannot react to special keys, such as backspace.

Having a forward_key_event method on TextInput-related components (or maybe on every component) would solve the issue and would make it possible to build interfaces fully controlled by keyboard.

Product Impact

[tronical]

Could it be that you're looking for a way to capture key events before they reach the line-edit to then act on them?

See also https://docs.slint.dev/latest/docs/slint/reference/keyboard-input/focusscope/#key-event-delivery

Perhaps you'll want to let the filter LineEdit have the focus (use forward-focus: filter; in your Demo) but capture events before than to act on them? (such as up/down for scrolling)

[skilvingr]

Sorry for the delay.

For keyboard-controlled interfaces, I still think it would make sense to just forward the events, leaving the focus as it is. Most of all because one could use a central hub-component to control the whole view, without having to manually re-change the focus.

However, regarding your suggestion, yes, I've already tried that, but it doesn't seem to work, both with and without a FocusScope.

Am I reading this wrong?