[jamil5454]

After spending hours of reading tutorials and trying understand Cocoa 2d drawing on my own, I've finally given up and decided to see if anyone here can solve my problem.

The point of this small app is to recursively draw rectangles inside rectangles, with each successive rectangle smaller than the one before it. More specifically, each smaller rectangle is either 1/3 the width of its predecessor, or 1/3 the height (depending on a random 0 or 1 value). Each rectangle has a random color assigned to it. The recursive loop runs until the rectangles become smaller than a predetermined size (in this case, it's 5 pixels across and 5 pixels high). So, in effect, you should see the screen being split into smaller and smaller rectangles, until the whole screen is covered with tiny colored rectangles. It's actually really cool, if it'll work.

I've managed to code this using Java, which I'm much more familiar with (2 KB):

http://homepage.mac.com/jboukheir/.P...sProg.java.zip

For some reason, this doesn't work unless you're using the 1.5 version of the java runtime. With 1.4, it just shows a blank screen. Also, to exit the program, just click the mouse. Otherwise it repeats itself forever.


Now, the Cocoa version is a standard Cocoa Application built using XCode 2.2 on Tiger 10.4.3 using my Rev. C DP 2.0 G5. I'm using an NSTimer to try to slow it down to a rate of 24 fps (or 24 rectangles drawn per second). The problem is that the rectangles are being drawn to the view all at once, and then the view is displayed when it's done. I've tried using '[self setNeedsDisplay:YES]' and '[self display]' after each rectangle I draw, but to no avail. So here's the XCode project (1.7 MB):

http://homepage.mac.com/jboukheir/.P...aphicsProg.zip

I congratulate you if you've gotten this far. I've been yearning to learn Cocoa so I could port a few games I wrote in Java to run natively on my Mac. Much thanks, and replies are appreciated.

[Catfish_Man]

You should never call [self display].

I think the confusion here is between stateful and stateless canvases. Java's assumption is that you "paint" onto the window, and it stays there. Cocoa instead asks you application to redraw *all* of the contents of a certain rectangle (your view's entire bounds if you called setNeedsDisplay, or a "dirty rectangle" if you called setNeedsDisplayInRect:). Probably the way I would implement this is to have an array of NSRects and have stepAnimation: add the next level of rects to the array. drawRect: would then just either loop over the array calling NSRectFill() or NSRectFillWithOperation(), or just call NSRectFillList() on the whole array. That's just my off-the-top-of-my-head idea, there are probably other ways of doing it.


Actually, come to think of it, you might be able to get away with just having each run through drawRect add the next level of rects. It wouldn't be 24fps (iirc it'd be 30, but I might be misremembering), and it wouldn't redraw correctly if you did something that would normally require the view to be redisplayed, but it would be much faster and simpler.

Definitely switch over to using NSRectFill rather than instantiating a new NSBezierPath for each rect.

[jamil5454]

Thanks for the suggestions. Hopefully I'll have some time to try them tomorrow evening after class