On 09/13/2010 12:31 PM, danovics wrote:
>
> Hi
>
> I've found an intresting issue. Hope someone could help me with it.
> I've a label which changes its value in runtime.
> I added a 'changeValue' to this label, with a function to get the actual
> width of the label using getBounds().
> The proplem is that it does't return the width of the label with new value,
> but the width corresponding to the label's old value.
>
> I made a little playground example for this: http://tinyurl.com/39sgmlb
Playground sample nicely done.
The issue here is that the label listener is invoked as soon as the
'value' *property* changes - which does *not* imply that the rendering
of that property has already changed (as all rendering is done
asynchronously in qooxdoo). So the DOM is typically not updated at this
point in time, and the .getBounds() call (which operates on the DOM)
retrieves the old value.
One way to get around that is to explicitly flush the rendering queues:
this.label.addListener("changeValue", function(e)
{
var bounds = this.getBounds();
qx.ui.core.queue.Manager.flush(); // <-- HERE
that.log.setValue("widht of red label: " + this.getBounds().width);
});
Here is the full example: http://tinyurl.com/266woeq
Mind, though, that both .getBounds and .flush methods are expensive, so
you shouldn't be doing this in a tight loop or a recurring timer with
high frequency. In an event handler that reacts on user input it should
be ok.
T.
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