bindings inside Repeater to outside properties don't work (?)

jimav

[https://doc.qt.io/qt-5/qml-qtqml-qt.html](link url) has a non-working example for using Qt.callLater() which purports to show a Column of strings and make them all display with the width of the widest string (the widths of the string do not change as intended).

I tried to figure out why. It has nothing to do with Qt.callLater(), but a seemingly fundamental issue of how bindings work (did that example ever work in older releases?)

Here is a cut-down example of the problem:

import QtQuick 2.12
import QtQuick.Controls 2.12

ApplicationWindow {
    visible:true

    Column {
        id: column
        property real widestChild: 50
        Repeater {
            id: repeater
            model: 4
            delegate: Rectangle {
              width: column.widestChild  //*** DOES NOT WORK
              height: 20
              color: "lightblue" 
              border.width: 1
            }
        }
    }
}

The binding

width: column.widestChild

seems to have no effect. Nothing is displayed at all, as if width were zero (in the non-working example cited above "widestChild" is computed and set on a onChildrenChanged signal, but in this cut-down example it is a constant).

Why doesn't this work?

dheerendra

You can try width: parent.widestChild. It should work.

Shrinidhi Upadhyaya

Hi @jimav , i think Qt actually treats "column" as a keyword,so if you replace the id with something else for example:-

 Column {
   id: sampleColumn
   property real widestChild: 50
   [..]
   [..]
   delegate: Rectangle {
   width: sampleColumn.widestChild
   height: 20
    [..]
    [..]
  }
}

it works. And if you try to print it, it is "undefined"
For Example:-

 Component.onCompleted: {
       console.log(column.widestChild)
 }

And if you take the example given in the [https://doc.qt.io/qt-5/qml-qtqml-qt.html], actually that also does not work, if you try to print "column.widestChild" in that example it comes as "undefined", you can try it by pasting the above code inside the Text like i have done below:-

[..]
[..]
Repeater {
           id: repeater
           model:columnTexts[currentTextModel%3]
           delegate: Text {
               color: "white"
               text: modelData
               width: column.widestChild
               horizontalAlignment: Text.Center

               //####Try this####
               Component.onCompleted: {
                   console.log(column.widestChild)
               }

               Rectangle { anchors.fill: parent; z: -1; color: index%2 ? "red" : "darkgray" }
           }
       }
[..]
[..]

The only reason the why text or the rectangle is visible to you is because the Text is taking width with respect to the length of strings inside "property var columnTexts:[..]"

jimav

Ok, it looks like a bug introduced since Qt 5.8. I filed a bug report:
https://bugreports.qt.io/browse/QTBUG-74332