Question

In a program I am working on I am performing a large amount of data crunching, and want to be able draw a custom NSView to represent the process visually.

The data crunching is processed off the main thread by using GCD (using dispatch_sync as the order needs to be preserved):

for (int i=0; i<iterations; i++) {

    dispatch_sync(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        // Add a data crunching task to the queue!
    });
}

When the processing is started I initialise a timer, which is used to ask the custom display to redraw at regular intervals (this timer is invalidated once all of the processing tasks are completed):

-(void)onTick:(NSTimer *)timer {

    [_customView setNeedsDisplay:YES];
    // Update some other UI object (labels etc.)    
}

I have this working as expected, however the only problem I notice now is that if I do something like click and hold on a button on the same window, or begin dragging a slider while the process is going on, the redrawing of the custom view is prevented until I let go of the mouse!

Is there any way I can prevent this from happening, preferably without moving all of the controls onto a separate window!

Answer 1

yip the timer is on the runloop and while in the drag drop / tracking mode it doesnt get fired because the runloop isnt advanced for the common mode

add it to the modes needed:

NSRunLoop *runloop = [NSRunLoop currentRunLoop];
NSTimer *timer = [NSTimer timerWithTimeInterval:0.1 target:self selector:@selector(myTimerAction:) userInfo:nil repeats:YES];
[runloop addTimer:timer forMode:NSRunLoopCommonModes];
[runloop addTimer:timer forMode: NSEventTrackingRunLoopMode];

edit: the runloop is basically apple’s while loop for dispatch ANY event to an app. and it filters the events it dispatches based on so called modes.