Hi,
It's probably easiest to look at a simplified example:
Rectangle {
id: rect
function myWidth() {
return rect.width
}
height: myWidth()
}
When the engine analyses the binding for height (i.e. myWidth()), it keeps
track of the fact that rect.width was used in the binding (inside the
function), and adds a dependency there -- whenever rect.width changes, it will
update the binding. But if we modify the function to:
Rectangle {
id: rect
function myWidth() {
rect.width = 100;
return rect.width
}
height: myWidth()
}
The engine still adds a dependency on rect.width, but in this case we
manipulate that same property in the function itself, which triggers the engine
to update the binding whenever the function is run. Component.onCompleted works
because it assigns a value, rather than setting up a binding. I'm not sure
whether it makes sense to try and address this in the engine somehow (maybe
some sort of flag you could set in the function that told the engine to ignore
dependancies?) -- for now at least you'll need at least one "imperative" step
in the chain to prevent the loop errors (another option moving forward is for
us to make binding loop detection more relaxed; and/or provide a way to turn
off the warnings).
Regards,
Michael
On 16/11/2010, at 11:43 PM, ext Valentine Silvansky wrote:
> Hi all! I've got some problem...
>
> I have to make a elide for multiline text. Here is the code I wrote:
>
> <pre>
> Text {
> id: tempText
> visible: false
> width: parent.width
> wrapMode: Text.WordWrap
> function elideMultiline(etext, pointSize, linesCount) {
> console.log("elideMultiline: " + etext + " " + pointSize + " "
> + linesCount)
> tempText.font.pointSize = pointSize
> var l = etext.length
> var s = "";
> for (var i = 0; i < linesCount; i++) {
> s += "W";
> if (i < linesCount - 1)
> s += "\n"
> }
> tempText.text = s
> console.log("s = " + s)
> var maxHeight = tempText.paintedHeight
> tempText.text = etext
> while (tempText.paintedHeight > maxHeight) {
> tempText.text = etext.substring(0, l--) + "..."
> }
> return tempText.text
> }
> }
> Text {
> id: longText
> width: parent.width
> wrapMode: Text.WordWrap
> font.pointSize: 16
> text: tempText.elideMultiline("my very-very-very-very and very long
> text with a lot of words in it and which i want to be correctly
> elided", font.pointSize, 2)
> }</pre>
>
> And when running my qml I've got this output:
>
> QML Text: Binding loop detected for property "text"
>
> The resulting qml output is ok, function works as expected, but i've
> got tons of console output messages...
> What's the problem of this code?
>
> PS: if I use Component.onCompleted: { text = "....." } no messages are printed
> _______________________________________________
> Qt-qml mailing list
> Qt-qml@trolltech.com
> http://lists.trolltech.com/mailman/listinfo/qt-qml
_______________________________________________
Qt-qml mailing list
Qt-qml@trolltech.com
http://lists.trolltech.com/mailman/listinfo/qt-qml
