为啥这个 CoreGraphics 绘制代码很慢？

Posted 2023-02-15

【中文标题】为啥这个 CoreGraphics 绘制代码很慢？

【英文标题】：Why is this CoreGraphics drawing code slow?为什么这个 CoreGraphics 绘制代码很慢？

【发布时间】：2020-11-01 10:30:21

【问题描述】：

我根据我的其他一些开源程序编写了这个绘图代码。

它根据用户名将行分成几层。

它有效，只是真的很慢。我认为这是因为我正在添加图层并在绘制时在同一图层上循环它们。这在 C++ 和 javascript 中很快，但在 Swift 中很慢。

忽略 send_point，因为它不会减慢绘图代码的速度。 （Crystal 服务器非常快，目前也忽略了该命令。）

如何优化这段代码？

//
//  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)
    
    

【问题讨论】：

快速版本的例子，看这里github.com/mixflame/Gbaldraw2/blob/master/scribblearea.cpp

你试过通过分析器运行它吗？

我刚刚尝试通过分析器运行，绘图功能占用了 100% 的 CPU。

【参考方案1】：

它很慢，因为我使用了 NSBezierPath。

这是一个更快的 DrawLineTo 方法。

    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()