Re: Textview is overwriting itself
Re: Textview is overwriting itself
- Subject: Re: Textview is overwriting itself
- From: Ross Carter <email@hidden>
- Date: Mon, 24 Mar 2008 12:21:57 -0400
On Mar 21, 2008, at 2:37 PM, Christopher Woodruff wrote:
I used a textview to work as an automatically scrolling log window
for a real time data output feed. I limit the size of the
textstorage programmatically. When I fill the textstorage to my
programmatic size limit (currently is 16384 characters), the
textview overwrites itself momentarily. By overwrite, I mean that
the new text displays on top of the existing text, such that you
can't read it anymore. The rate I update the textview is about 1-3
times a second.
I have posted a few screenshots of this behavior here: http://picasaweb.google.com/cswoodruff/CocoaTroubleshooting/photo#5180264259131797666
.
Here are the relevent code chunks:
- (void)handleNewData:(id)newData
{
scrollPos [[receiverScroll verticalScroller] floatValue]; //Get
the current scrollbar position
if(newData ! nil)
{
NSRange endRange;
endRange.location [[receiverConsole textStorage] length];
endRange.length 0;
[receiverConsole replaceCharactersInRange:endRange
withString:newData]; //Append the new text to the textStorage
mutableString
}
if([[receiverConsole textStorage] length] > TEXT_SIZE)
{
[self deleteToSize];
}
}
- (void)deleteToSize
{
int charToDelete [[receiverConsole textStorage] length] - TEXT_SIZE;
[[receiverConsole textStorage]
deleteCharactersInRange:NSMakeRange(0, charToDelete)];
}
- (void)scrollToBottom
{
//if the scrollbar *was all the way at the bottom before the new
text was appended, then scroll down to the bottom
if( scrollPos == 1.0 )
{
NSRange endRange;
endRange.location [[receiverConsole textStorage] length];
endRange.length 0;
[receiverConsole scrollRangeToVisible:endRange];
}
}
In the Init method:
[receiverScroll setPostsFrameChangedNotifications:YES];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(scrollToBottom)
name:NSViewFrameDidChangeNotification object:nil];
I am running this code on OSX 10.4.11 on a MacBook Pro 2.4 GHz. If
anyone has any idea of what I'm doing wrong here, please let me
know. I still consider myself a beginner at Objective-C / Cocoa, so
I welcome ideas on how to make this better.
Chris, since no one else has chimed in, I'll make a suggestion. Rather
than use NSViewFrameDidChangeNotification and scrollRangeToVisible,
try NSViewBoundsDidChangeNotification and scrollToPoint:. The
technique is described in the Scroll View Programming Guide under
"Synchronizing Scroll Views," http://developer.apple.com/documentation/Cocoa/Conceptual/NSScrollViewGuide/Articles/SynchroScroll.html#/
/apple_ref/doc/uid/TP40003537
If that doesn't work then I'd give the layout manager a chance to
finish layout before adjusting the scroll view. The NSLayoutManager
delegate method didCompleteLayoutForTextContainer:atEnd: will tell you
when layout is complete.
Ross
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