Thanks for your reply Andrew. Unfortunately it still doesn't work. The
text or slider don't update at all if I click and hold on the resize
widget. It will only update if I move the mouse and it is very 'jerky'
even when I do that.
Here is what I have. UpdatePosition is called from my thread and I
have simplified a few things.:
- (void)updatePosition:(id)anObject{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
while (1) {
myStopWatch->updatePosition();
[self performSelectorOnMainThread:@selector(updateGUI)
withObject:nil waitUntilDone:NO];
[NSThread sleepForTimeInterval:.001];
std::cout << "MainThread " << myStopWatch->getPosition(); <<
std::endl;
}
[pool release];
}
- (void)updateGUI{
double currentPosition;
currentPosition = myStopWatch->getPosition();
[ positionLabel setDoubleValue: currentPosition];
[ positionLabel setNeedsDisplay:YES];
std::cout << "GUI Thread" << currentPosition << std::endl; <-- this
doesn't block
}
As you can see updateGUI is being called all the time as std::cout
keeps spitting out data, but my text label doesn't update at all. It
is as if clicking on the resize widget runs in its own loop and only
updates the window when it actually changes size. Interestingly an app
such as GarageBand also stops updating its GUI if a song is playing
and you click and hold on the resize widget.
Peter
On 19/10/2008, at 1:36 PM, Andrew Merenbach wrote:
On Oct 18, 2008, at 7:27 PM, Andrew Merenbach wrote:
On Oct 18, 2008, at 4:23 AM, Peter Zegelin wrote:
Hi,
Still fairly new to Cocoa here.
I have a high priority thread that that for the moment just calls
back as often as possible to a method that updates a static text
object with the current time. A slider is also updated to a new
value. Its a bit like a stop watch with a position indicator. This
all works well until I resize a window or invoke a menu when the
whole thing just grinds to a halt. If I call std::cout with the
value the debugger shows a continuous stream of data so I know the
thread is still being called as often as possible but the text and
slider aren't updating. Is there any way to get these items to
update under these circumstances? I tried calling [label
setNeedsDisplay] but that just caused a crash.
thanks!
Peter Zegelin
Hi, Peter,
Is it possible that your GUI objects are being updated from the
secondary thread? You'll need to use -performSelectorOnMainThread:
to channel updates from the high-priority thread to the main
thread, since only the main thread is allowed to touch the
graphical AppKit classes (which are generally not threadsafe, with
the possible exception of NSProgressIndicators). Hopefully this
solves your issue!
Cheers,
Andrew
Erm, sorry to respond to myself, but I was lazy -- just for clarity,
the full methods available are (from the docs):
- (void)performSelectorOnMainThread:(SEL)aSelector withObject:
(id)arg waitUntilDone:(BOOL)wait;
- (void)performSelectorOnMainThread:(SEL)aSelector withObject:
(id)arg waitUntilDone:(BOOL)wait modes:(NSArray *)array;
-- Andrew
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