[davecom]

I've been trying and trying and trying. But I can't draw even a simple little circle in Cocoa. I make the subclass. In IB I make a NSView that gets customized to extend the subclass I make. And then in Project Builder I call the display method of the NSView and then draw an NSBezierPath that I call a fill method on. It compiles fine, but when I click the button that calls the display method nothing happens. I'm thinking maybe the problem is that the NSView I drag and drop from the pallete and that then becomes a subclass of NSView.

If anyone could show me the most simple way to just draw a circle when a button it clicked using NSBezierPath I would greatly appreciate and would be in debt to you for quite a while.

Thank you ever so much,
Dave

------------------
Think Different.

[parallax]

Have you tried looking at SonOfSillyBalls at Apple's source code repository? It's a Cocoa App which draws silly balls using (I think) NSBezierPath. You may want to check that out.
http://developer.apple.com/samplecod...SillyBalls.htm

[Apocalypse]

Son of Silly Balls is helpful yet a little over-complicated for what most of us may want to do because of how it side-steps the "drawRect" method. If you create the subclass of NSView and then implement the drawRect method in it to make a few calls to NSBezierPath to draw the circle it should just draw it (I did something like that a few days ago and it worked great). As far as the button, I would just create a global boolean and get the button to set it when pressed and the drawRect to only draw the circle when the flag is set. I am not sure which is the best way to implement that button trigger but for straight drawing just use drawRect.

Hope that helps,
Jeff.

[This message has been edited by Apocalypse (edited 01-31-2001).]

[davecom]

[self display] calls the drawRect method right?

[ali]

You basically override drawRect: and implement your drawing, everything else should be automatic... Below is a snippet of code from a view which draws a circle where the user clicks.
Ali


The interface:

@interface MyView : NSView {
NSPoint center;
float radius;
}


And part of the code:

@implementation MyView

- (id)initWithFrameNSRect)frame {
[super initWithFrame:frame];
center.x = 50.0;
center.y = 50.0;
radius = 10.0;
return self;
}


// Recommended way to handle events is to override NSResponder (superclass
// of NSView) methods in the NSView subclass. One such method is mouseUp:.
// These methods get the event as the argument. The event has the mouse
// location in window coordinates; use convertPoint:fromView: (with "nil"
// as the view argument) to convert this point to local view coordinates.
//
// Note that once we get the new center, we call setNeedsDisplay:YES to
// mark that the view needs to be redisplayed (which is done automatically
// by the AppKit).

- (void)mouseUpNSEvent *)event {
NSPoint eventLocation = [event locationInWindow];
center = [self convertPoint:eventLocation fromView:nil];
[self setNeedsDisplay:YES];
}


// setRadiusFromControl: is an action method which lets you change the radius of the dot.
// We assume the sender is a control capable of returning a floating point
// number; so we ask for it's value, and mark the view as needing to be
// redisplayed. A possible optimization is to check to see if the old and
// new value is the same, and not do anything if so.

- (void)setRadiusFromControlid)sender {
radius = [sender floatValue];
[self setNeedsDisplay:YES];
}


// drawRect: should be overridden in subclassers of NSView to do necessary
// drawing in order to recreate the the look of the view. It will be called
// to draw the whole view or parts of it (pay attention the rect argument);
// it will also be called during printing if your app is set up to print.
// Here we first clear the view to white, then draw a red dot at its
// current location.

- (void)drawRectNSRect)rect {
NSRect dotRect;

[[NSColor whiteColor] set];
NSRectFill([self bounds]); // Same as [[NSBezierPath bezierPathWithRect:[self bounds]] fill]

dotRect.origin.x = center.x - radius;
dotRect.origin.y = center.y - radius;
dotRect.size.width = 2 * radius;
dotRect.size.height = 2 * radius;

[[NSColor redColor] set];
[[NSBezierPath bezierPathWithOvalInRect:dotRect] fill];
}


// Views which totally redraw their whole bounds without needing any of the
// views behind it should override isOpaque to return YES. This is a performance
// optimization hint for the display subsystem.

- (BOOL)isOpaque {
return YES;
}

@end

[ali]

You basically override drawRect: and implement your drawing, everything else should be automatic... Below is a snippet of code from a view which draws a circle where the user clicks.
Ali


The interface:

@interface MyView : NSView {
NSPoint center;
float radius;
}


And part of the code:

@implementation MyView

- (id)initWithFrameNSRect)frame {
[super initWithFrame:frame];
center.x = 50.0;
center.y = 50.0;
radius = 10.0;
return self;
}


// Recommended way to handle events is to override NSResponder (superclass
// of NSView) methods in the NSView subclass. One such method is mouseUp:.
// These methods get the event as the argument. The event has the mouse
// location in window coordinates; use convertPoint:fromView: (with "nil"
// as the view argument) to convert this point to local view coordinates.
//
// Note that once we get the new center, we call setNeedsDisplay:YES to
// mark that the view needs to be redisplayed (which is done automatically
// by the AppKit).

- (void)mouseUpNSEvent *)event {
NSPoint eventLocation = [event locationInWindow];
center = [self convertPoint:eventLocation fromView:nil];
[self setNeedsDisplay:YES];
}


// setRadiusFromControl: is an action method which lets you change the radius of the dot.
// We assume the sender is a control capable of returning a floating point
// number; so we ask for it's value, and mark the view as needing to be
// redisplayed. A possible optimization is to check to see if the old and
// new value is the same, and not do anything if so.

- (void)setRadiusFromControlid)sender {
radius = [sender floatValue];
[self setNeedsDisplay:YES];
}


// drawRect: should be overridden in subclassers of NSView to do necessary
// drawing in order to recreate the the look of the view. It will be called
// to draw the whole view or parts of it (pay attention the rect argument);
// it will also be called during printing if your app is set up to print.
// Here we first clear the view to white, then draw a red dot at its
// current location.

- (void)drawRectNSRect)rect {
NSRect dotRect;

[[NSColor whiteColor] set];
NSRectFill([self bounds]); // Same as [[NSBezierPath bezierPathWithRect:[self bounds]] fill]

dotRect.origin.x = center.x - radius;
dotRect.origin.y = center.y - radius;
dotRect.size.width = 2 * radius;
dotRect.size.height = 2 * radius;

[[NSColor redColor] set];
[[NSBezierPath bezierPathWithOvalInRect:dotRect] fill];
}


// Views which totally redraw their whole bounds without needing any of the
// views behind it should override isOpaque to return YES. This is a performance
// optimization hint for the display subsystem.

- (BOOL)isOpaque {
return YES;
}

@end

[davecom]

Thank you Ali! This is exactly what I needed! I think this will be helpful to quite a few people.

------------------
Think Different.