Why is this CoreGraphics drawing code slow? - swift

Question

I wrote this drawing code based on some of my other open source programs.
It separates the lines into layers based on username.
It works, it's just really slow. I think it's because I'm adding to the layers and looping through them on the same layer as I draw. This was fast in C++ and Javascript but slow in Swift.
Ignore send_point as it's not slowing down the drawing code. (The Crystal server is very fast and currently ignores the command as well.)
How can I optimize this code?
//
// GlobalDrawController.swift
// GlobalChat
//
// Created by Jonathan Silverman on 7/9/20.
// Copyright © 2020 Jonathan Silverman. All rights reserved.
//
import Cocoa
class GlobalDrawController: NSViewController {
#IBOutlet weak var drawing_view: NSView!
var gcc: GlobalChatController?
override func viewDidLoad() {
super.viewDidLoad()
// Do view setup here.
print("viewDidLoad: gdc")
}
}
class LineDrawer : NSView {
var newLinear = NSBezierPath()
var points : [[String : Any]] = []
var nameHash : [String : Int] = [:] // which layer is this handle on
var layerOrder : [String] = [] // which order to draw layers
var layers : [String : Any] = [:] // which points are in a layer
// var username : String = ""
var scribbling : Bool = false
var pen_color : NSColor = NSColor.black.usingColorSpace(NSColorSpace.deviceRGB)!
var pen_width : CGFloat = CGFloat(1)
func addClick(_ x: CGFloat, y: CGFloat, dragging: Bool, red: CGFloat, green: CGFloat, blue: CGFloat, alpha: CGFloat, width: CGFloat, clickName: String) {
var point : [String : Any] = [:]
point["x"] = x
point["y"] = y
point["dragging"] = dragging
point["red"] = red
point["green"] = green
point["blue"] = blue
point["alpha"] = alpha
point["width"] = width
point["clickName"] = clickName
points.append(point)
var layerName : String = ""
if(nameHash[clickName] == nil) {
let layer = 0
nameHash[clickName] = layer
layerName = "\(clickName)_\(layer)"
let layerArray : [[String : Any]] = []
layers[layerName] = layerArray
} else {
if(dragging == false) {
let layer = nameHash[clickName]! + 1
nameHash[clickName] = layer
layerName = "\(clickName)_\(layer)"
let layerArray : [[String : Any]] = []
layers[layerName] = layerArray
} else {
let layer = nameHash[clickName]!
layerName = "\(clickName)_\(layer)"
}
}
var tempLayers = layers[layerName] as! [[String : Any]]
tempLayers.append(point)
layers[layerName] = tempLayers
if(!layerOrder.contains(layerName)) {
layerOrder.append(layerName)
}
}
func drawLineTo(_ lastPoint : CGPoint, _ endPoint : CGPoint, _ penColor : NSColor, _ penWidth : CGFloat) {
newLinear.move(to: lastPoint)
newLinear.line(to: endPoint)
penColor.set()
newLinear.lineWidth = penWidth
newLinear.stroke()
}
func redraw() {
NSColor.white.setFill() // allow configuration of this later
bounds.fill()
for layer in layerOrder {
let layerArray = layers[layer] as! [[String : Any]]
for i in 1...layerArray.count - 1 {
let lastObj = layerArray[i - 1] as [String : Any]
var lastPoint : CGPoint = CGPoint()
lastPoint.x = lastObj["x"] as! CGFloat
lastPoint.y = lastObj["y"] as! CGFloat
let thisObj = layerArray[i] as [String : Any]
var thisPoint : CGPoint = CGPoint()
thisPoint.x = thisObj["x"] as! CGFloat
thisPoint.y = thisObj["y"] as! CGFloat
if(thisObj["dragging"] as! Bool && lastObj["dragging"] as! Bool) {
let red = lastObj["red"] as! CGFloat
let green = lastObj["green"] as! CGFloat
let blue = lastObj["blue"] as! CGFloat
let alpha = lastObj["alpha"] as! CGFloat
let penColor : NSColor = NSColor.init(red: red, green: green, blue: blue, alpha: alpha)
let penWidth = lastObj["width"] as! CGFloat
drawLineTo(lastPoint, thisPoint, penColor, penWidth)
}
}
}
}
override func draw(_ dirtyRect: NSRect) {
super.draw(dirtyRect)
let objectFrame: NSRect = self.frame
if self.needsToDraw(objectFrame) {
// drawing code for object
redraw()
}
}
override func mouseDown(with event: NSEvent) {
let gdc = self.window?.contentViewController as! GlobalDrawController
super.mouseDown(with: event)
scribbling = true
var lastPt = convert(event.locationInWindow, from: nil)
lastPt.x -= frame.origin.x
lastPt.y -= frame.origin.y
addClick(lastPt.x, y: lastPt.y, dragging: false, red: pen_color.redComponent, green: pen_color.greenComponent, blue: pen_color.blueComponent, alpha: pen_color.alphaComponent, width: pen_width, clickName: gdc.gcc!.handle)
send_point(lastPt.x, y: lastPt.y, dragging: false, red: pen_color.redComponent, green: pen_color.greenComponent, blue: pen_color.blueComponent, alpha: pen_color.alphaComponent, width: pen_width, clickName: gdc.gcc!.handle)
}
override func mouseDragged(with event: NSEvent) {
let gdc = self.window?.contentViewController as! GlobalDrawController
super.mouseDragged(with: event)
var newPt = convert(event.locationInWindow, from: nil)
newPt.x -= frame.origin.x
newPt.y -= frame.origin.y
addClick(newPt.x, y: newPt.y, dragging: true, red: pen_color.redComponent, green: pen_color.greenComponent, blue: pen_color.blueComponent, alpha: pen_color.alphaComponent, width: pen_width, clickName: gdc.gcc!.handle)
send_point(newPt.x, y: newPt.y, dragging: true, red: pen_color.redComponent, green: pen_color.greenComponent, blue: pen_color.blueComponent, alpha: pen_color.alphaComponent, width: pen_width, clickName: gdc.gcc!.handle)
needsDisplay = true
}
override func mouseUp(with event: NSEvent) {
super.mouseUp(with: event)
scribbling = false
}
func send_point(_ x: CGFloat, y: CGFloat, dragging: Bool, red: CGFloat, green: CGFloat, blue: CGFloat, alpha: CGFloat, width: CGFloat, clickName: String) {
let gdc = self.window?.contentViewController as! GlobalDrawController
var point : [String] = []
point.append(String(x.description))
point.append(String(y.description))
point.append(String(dragging.description))
point.append(String(red.description))
point.append(String(green.description))
point.append(String(blue.description))
point.append(String(alpha.description))
point.append(String(width.description))
point.append(String(gdc.gcc!.chat_token))
gdc.gcc?.send_message("POINT", args: point)
}
}

Answer 1

Its slow because I used NSBezierPath.
Here is a faster DrawLineTo method.
func drawLineTo(_ lastPoint : CGPoint, _ endPoint : CGPoint, _ penColor : NSColor, _ penWidth : CGFloat) {
guard let context = NSGraphicsContext.current?.cgContext else { return }
context.setStrokeColor(penColor.cgColor)
context.setLineWidth(penWidth)
context.move(to: lastPoint)
context.addLine(to: endPoint)
context.strokePath()
}