Re: Third time I ask - please help. How to trace visible change in a UIView (UIWebView)
Re: Third time I ask - please help. How to trace visible change in a UIView (UIWebView)
- Subject: Re: Third time I ask - please help. How to trace visible change in a UIView (UIWebView)
- From: Sandor Szatmari <email@hidden>
- Date: Mon, 22 Apr 2013 13:48:31 -0400
I had thought about this too, but was afraid that -drawRect: would be called more often than the actual content of the view was being changed.
If you could limit the calls within -drawRect: perhaps by setting a content did change flag in the subclass this might reduce the notifications to be meaningful.
Like: (written in mail)
-drawRect:(NSRect)rect
{
if ( contentDidChange )
// post notification
[super drawRect:rect];
}
Sandor Szatmari
On Apr 22, 2013, at 13:30, Jens Alfke <email@hidden> wrote:
>
> On Apr 22, 2013, at 12:26 AM, Motti Shneor <email@hidden> wrote:
>
>> I already succeeded in capturing the contents of the view as an image-buffer (out of the CALAyer's context) and I can (brutally) solve my problem by setting up a timer that will sample the view's contents N times a second. However, I'd like to avoid transmitting anything when the view doesn't change
>
> A quick & naive idea is to subclass UIWebView and override -drawRect: to call the inherited method and then set a timer that will capture the view's pixels a fraction of a second later. (You'd want a timer for coalescing purposes, since there are likely to be multiple calls in a short time interval.)
>
> The reason I say this is naive is because UIWebView almost certainly has a whole tree of views inside it that do the actual drawing, so the actual -drawRect: calls are probably going to those instead. But you could give this a try and see if you get anything useful.
>
> —Jens
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