Re: Removing/Adding views in drawRect:

FROM : Mike R. Manzano
DATE : Thu Aug 31 20:05:54 2006

Hi all,

Thanks for the replies thus far. I suppose I wasn't specific enough 
with my question. Here's what seems to be fouling up my app:

(1) I start resizing my window.
(2) The window resize causes NSTextViews to resize in response.
(3) This forces the text within the text views to do a re-layout.
(4) In response to the re-layout, my delegates add/remove NSTextViews 
to accommodate the new text layout.

It seems that somewhere in here things are getting all fouled up. The 
NSTextViews  don't render properly. Is what I'm doing bad?

I seemed to have gotten around this problem by:

(A) Having the subview that arranges the view not pay attention to 
frame resizes, but instead a special notification that I post myself.
(2) Posting this special notification in the parent view's 
viewDidEndLiveResize, and also in my window's zoom:.
(iii) For whatever reasons, views still seemed to get fouled up 
until, in my layoutManager:didCompleteLayoutForTextContainer:atEnd: 
delegate method, I deferred my NSTextView addition/removal thusly:

// [ self appendOneTextView ] ;
    [ self performSelector:@selector( appendOneTextView ) 
withObject:nil afterDelay:0.0f ] ;


This seems to workn consistently, but:

(x) (obviously) live resize is now ugly, because my views don't 
refresh until AFTER the live resize is finished
(x+1) I have no clue why I had to defer appendOneTextView, which 
makes me uneasy.



I hope that wasn't too detailed. Any thoughts?


    ~    Mike
        alephx01 (at) mac (dot) com





On Aug 30, 2006, at 9:58 PM, Andrew Merenbach wrote:

> Hi, Mike.  In regard to (2), you may wish to do something like (in 
> accordance with Uli's suggestion) in the class that handles the 
> adding and removing of subviews:
>
> [[NSNotificationCenter defaultCenter] addObserver:self 
> selector:@selector(addOrRemoveSubviewsDuringResize:) 
> name:NSWindowDidResizeNotification object:myWindow];
>
> This will cause -addOrRemoveSubviewsDuringResize: to be called 
> whenever the pixel dimensions of myWindow change.  Change the 
> observer if you need a different object to handle the adding or 
> removing of subviews.
>
> Cheers,
>     Andrew
>
> On Aug 30, 2006, at 1:56 PM, Uli Kusterer wrote:
>

>> Am 30.08.2006 um 20:40 schrieb Mike R. Manzano:

>>> (1) Is it prudent to add or remove subviews in drawRect:?

>>
>>  No. Moving views can cause a view to be invalidated, which would 
>> cause drawRect: to be called again. If you search the list 
>> archives you'll se epostings from lots of people who did it anyway 
>> and got hilarious endless loops, dropped updates and other odd 
>> behaviour.
>>

>>> If not,
>>>
>>> (2) Is it prudent to add or remove views somewhere else during a 
>>> window live resize?

>>
>>  I think there's a notification sent when auto-resizing happens. 
>> Alternatively, you could just override that method (don't remember 
>> the name, but a quick read of NSView.h should make it obvious) 
>> that's called when a superview is resized and asked to resize its 
>> subviews. That should be a safe place to show/hide subviews before 
>> calling through to super.
>>
>> Cheers,
>> -- M. Uli Kusterer
>> http://www.zathras.de
>>
>>
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