Optimize NSView's drawRect

NSView_optimize_drawRect.swift

class MyView: NSView {

override func draw(_ dirtyRect: NSRect) {
	super.draw(dirtyRect)
	
	guard let ctx = NSGraphicsContext.current?.cgContext else {return}
	
	var rects: UnsafePointer<NSRect>?
	var count = 0
	self.getRectsBeingDrawn(&rects, count: &count)
	if let rects = rects {
		for i in 0..<count {
			let rect = rects[i]
			let objectFrame: NSRect = <#object's frame#>
			if NSIntersectsRect(objectFrame, rect) {
			  // drawing code for object
			}
		}
	}
}
  
}

// https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/CocoaViewsGuide/Optimizing/Optimizing.html

NSView_optimize_drawRect2.swift

class MyView: NSView {

    override func draw(_ dirtyRect: NSRect) {
        super.draw(dirtyRect)
	
        guard let ctx = NSGraphicsContext.current?.cgContext else {return}
        
        let objectFrame: NSRect = <#object's frame#>
        if self.needsToDraw(objectFrame) {
            // drawing code for object
        }
    }
  
}

// https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/CocoaViewsGuide/Optimizing/Optimizing.html