Hi Arno,
On 7/23/20, 4:14 PM, "Arno Rehn" <a.r...@menlosystems.com> wrote:
I think much of the confusion stems from the fact that you can get
notifications (i.e. callbacks) without evaluating the whole binding.
From what I grok from the code, you can subscribe to "dirty" flag
changes with onValueChanged/subscribe - but this does not evaluate the
property binding. Evaluation is only done when your handler routine
actually requests the property value.
(Note that in that case "onValueChanged" might be a misnomer - the value
might not have actually changed, even though a changed dependency has
lead to it being flagged dirty).
Thanks for this explanation. My question below is related to your comment, but
not necessarily directed at you (Arno).
If I subscribe a callback to a QProperty, does it get called once or more than
once? I.e., if the property is area, which depends on x and y, and both x and
y are changed, do I get called only when the first is updated? Or both?
If the goal is, however, to really get rid of all the ways to get
notified about (possibly) changed properties, then this system is
defective IMHO. Constant-rate polling with a timer might be a good
solution for *some* problems, but it leads to absolutely abysimal
performance in others (or many wasted resources). But I don't think this
is what is proposed.
Agreed.
Brett
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