TextInput rendering of newlines on single-line

[ubruhin]

Edit: Rendering of new-lines in a single line TextInput (the default) is not consistent across renderer.
See also description of #7414

Bug Description

The code below produces this output with winit:

Looks as expected. But with the Qt backend:

The linebreak is ignored.

Reproducible Code (if applicable)

export component AppWindow inherits Window {
    width: 200px;
    height: 200px;

    TextInput {
        wrap: word-wrap;
        text: "Foo\nBar";
    }
}

Environment Details

• Slint Version: 1.9.2
• Platform/OS: Ubuntu 22.04, X11
• Backend/Renderer: Qt

Product Impact

Use-case in LibrePCB (not a blocker for now):

[ogoffart]

The thing is that single-line property defaults to true.
If you add single-line:false; property, it renders correctly with all backend.

Now the question is what to do for slingle-line:true (the default) and our renderer render differently.

With wrap: word-wrap;

Without wrap: word-wrap;

IMHO, word-wrap for a sigle-line edit doesn't make sense.
But what should the \n character do in such case? Qt Just remove it, I think it might make sense.

[ubruhin]

Ahh here the problem comes from! That's totally unexpected but now the strange behavior makes more sense.

But to be honest, now I really wonder if it is a good idea to set single-line: true by default? Given the absolute basic use-case where only text specified, I'd really expect the text gets rendered the most basic way, namely the way it is specified.

IMHO, word-wrap for a sigle-line edit doesn't make sense.

Agree. No strong opinion about it, but probably I'd just give single-line priority (if specified, ignore word-wrap) 🤔

[ogoffart]

But to be honest, now I really wonder if it is a good idea to set single-line: true by default?

I agree. I think it has been the default because at the beginning of the project the component only existed for LineEdit and was only for single line. Then when we added support for TextEdit, we didn't want to break compatibility. And we didn't review that decision later with breaking versions.
Not sure what we can do now.