How to monitor the change of focus of a LineEdit?

[Horbin-Magician]

I have seen that "Added focus-changed-event callback to FocusScope." in the Changelog of Slint 1.3.0. But I want to do something when the focus of a LineEdit changed, Is there any way we can do that now? Perhaps I should wait for #3811 to be implemented?

[ogoffart]

What are you trying to achieve? Is it to pop up a virtual keyboard? What platform are you using?

[Horbin-Magician]

I'm trying to achieve a search tool in Win11. Pressing Ctrl+F displays a search box coantaining a LineEdit, which hides when the LineEdit loses focus.

[ogoffart]

I see. Then #3811 might not help you since that is only for writing your own platform.
I think what you want is maybe a callback in the Window itself when the window gets de-activated, would that help?

[Horbin-Magician]

Yes, I remember that you give me a good trick to achieve this purpose. It like:

pure callback lose_focus_trick(bool) -> bool;
always-on-top: lose_focus_trick(input.has-focus);

This is do not work well all the time, and sometimes it is called when no change has occurred.

[Tsuiban]

Adding on another use case, I want to do a my_line_edit.select_all() whenever my LineEdit gains focus. I can do this with a TextEdit via the FocusScope. However, LineEdit doesn't accept a FocusScope due to not allowing it to have any children.

I tried surrounding it with a Rectangle and putting the FocusScope there, but that causes lots of other problems such as being unable to tab out of the field to the next field.

Closest I've gotten was this:

GridBox {
        spacing: 0;
        Row {
            Text { text: "Start Time: "; }
            Rectangle {
                forward-focus: start_time_focus_handler;
                start_time_focus_handler := FocusScope {
                    focus-changed-event() => {
                        if self.has_focus {
                            st.select-all();
                        }
                    } }

                st := LineEdit {
                    placeholder-text: "hh:mm:ss";
                    accepted => { root.data-changed(); }
                    width: 100px;
                }
            }
        }

[FischLu]

Any news of this issue??

[ogoffart]

With Slint 1.8 you can do:

 LineEdit {
    changed has-focus => { ... }
 }

[FischLu]

Hi, thanks for the info, however, it doesn't work, the app just crash with the following error

thread 'main' panicked at /Users/xxx/.cargo/registry/src/index.crates.io-6f17d22bba15001f/i-slint-compiler-1.8.0/llr/expression.rs:676:89:
  called `Option::unwrap()` on a `None` value

I just add

LineEdit {
      width: 50px;
      input-type: number;
      changed has-focus => { debug("hello") }
  }

to a slint offical template, If I remove the line changed has-focus => { debug("hello") } , the app works without any issues. Actually, if I add just changed has-focus => {}, the app crashes as well. By the way, in LineEdit documentation there is no changed callback mentioned, does this callback support all widgets??

[FischLu]

tried more about changed callback, changed text => { debug("hello") } works, but has-focus doesn't, is it a bug?

[hunger]

Yes, that looks like a bug. Could you please file an issue, ideally with a short snippet of code reproducing the problem? That would help a lot!

[FischLu]

Okay

[felipetesc]

Even though that's not what you asked, what about using TextEdit and configuring its height, wrap, x, and y, (other stuff too), so you mimic LineEdit ?

[FischLu]

but TextEdit doesn't have onfocus callback as well