Swift: NSBezier

Question

This is the code inside my custom view class:

func drawTestingPoint(_ point: CGPoint, target: Int, output: Int) {
    let path = NSBezierPath()
    path.appendArc(withCenter: point, radius: 5, startAngle: 0, endAngle: 360)
    NSColor.black.setStroke()
    if target == output {
        NSColor.green.setFill()
    } else {
        NSColor.red.setFill()
    }
    path.lineWidth = 3
    path.fill()
    path.stroke()
}

override func draw(_ dirtyRect: NSRect) {
    //If I call the drawTestingPoint function here it works
}

Inside my viewDidLoad method in my NSViewController class I set up the custom view and try to draw the testing point:

let size = getDataViewSize()
let origin = CGPoint(x: view.frame.width/2-size.width/2, y: view.frame.height/2-size.height/2)
dataView = DataView(frame: CGRect(origin: origin, size: size))
view.addSubview(dataView)
dataView.drawTestingPoint(CGPoint(x: view.frame.width/2 y: view.frame.height/2), target: target, output: output)
dataView.needsDisplay = true

My problem is that no point is getting drawn. I think there can't be anything wrong with my drawTestingPoint function because when I call it inside my draw(_ dirtyRect: NSRect) function in my custom NSView class, it works. What can I do so I can call this function inside my viewDidLoad function how you can see in the codes snippets above so my point gets drawn

What you are trying to do isn't clear. First, nobody knows what DataView is. Assuming that it's a subclass of NSView, one still doesn't know if it's an existing NSView object that is connected to a view controller. — El Tomato, Dec 14 '18 at 02:57
I've already been drawing sth. on my custom NSView so that is not the problem. Yes your assumptions were right. I am trying to draw on my custom NSView after adding it to my view controllers view — l30c0d35, Dec 14 '18 at 03:06

score 1 · Answer 1 · edited Jun 20 '20 at 09:12

1

You can't just draw any time you want. Normally you set up a view and implement draw(_:) as you've done. The system calls the draw method when it needs the view to draw its contents. Before calling your draw(_:) method it sets up the drawing context correctly to draw inside your view and clip if you draw outside of the view. That's the bit you're missing.

As a general rule you should NOT draw outside of the view's draw(_:) method. I've done drawing outside of the draw(_:) method so infrequently that I don't remember what you'd need to do to set up the drawing context correctly. (To be fair I do mostly iOS development these days and my MacOS is getting rusty.)

So the short answer is "Don't do that."

EDIT:

Instead, set up your custom view to save the information it needs to draw itself. As others have suggested, when you make changes to the view, set needsDisplay=true on the view. That will cause the system to call the view's draw(_:) method on the next pass through the event loop

edited Jun 20 '20 at 09:12

Community

1
1

answered Dec 14 '18 at 03:10

Duncan C

128,072
22
173
272

so what would you recommend to do when you want to draw something in a NSView afterwards? – l30c0d35 Dec 14 '18 at 03:23
1

Set `view.needsDisplay = true`. AppKit will call your view's `drawRect:` method during the next display update pass. – rob mayoff Dec 14 '18 at 04:24
i did call `dataView.needsDisplay = true` (last line in my code snippets) – l30c0d35 Dec 14 '18 at 05:29
You need to save off the parameters you want to send to `drawTestingPoint()` and then pass them to `drawTestingPoint()` from `drawRect()`. – user1118321 Dec 14 '18 at 05:40
See the edit to my answer. I would suggest having the view save it's own stat information rather than having `draw(_:)` pass parameters to `drawTestingPoint()` as @user1118321 suggests above. – Duncan C Dec 14 '18 at 13:05

Swift: NSBezier

1 Answers1

EDIT: