2020-coding-projects/mandelbrot-webassembly/server/main.go

package main

import (
	"fmt"
	"math"

	"syscall/js"
)

type selection struct {
	startX int
	startY int
	endX   int
	endY   int
}

type mbRender struct {
	doc js.Value
	ctx js.Value

	backCtx []js.Value
	curCtx  int

	width  float64
	height float64
	minX   float64
	minY   float64
	maxX   float64
	maxY   float64

	colorMode string

	imageData               js.Value
	mandelbrot              chan Mandelbrot
	mandelbrotValue         Mandelbrot
	mandelbrotProgress      chan float64
	mandelbrotProgressValue float64

	mouseDown    bool
	hasSelection bool
	selection    selection
}

type Mandelbrot []byte

func (mb *mbRender) getMandelbrot(maxIterations uint) {
	go func() {
		mb.mandelbrot <- mb.CalculateMandelbrot(maxIterations)
	}()
}

func (mb *mbRender) start() {
	mb.doc = js.Global().Get("document")
	canvasEl := mb.doc.Call("getElementById", "canvas")

	//mb.width = mb.doc.Get("body").Get("clientWidth").Float()
	//mb.height = mb.doc.Get("body").Get("clientHeight").Float()
	mb.width = 1000.0
	mb.height = 1000.0

	mb.minX = -2.0
	mb.minY = -2.0
	mb.maxX = 2
	mb.maxY = 2

	canvasEl.Set("width", mb.width)
	canvasEl.Set("height", mb.height)

	mb.ctx = canvasEl.Call("getContext", "2d")
	mb.imageData = mb.ctx.Call("getImageData", 0, 0, mb.width, mb.height)
	mb.mandelbrot = make(chan Mandelbrot)
	mb.getMandelbrot(1000)

	mouseDownEvt := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
		evt := args[0]
		mb.mouseDown = true
		mb.hasSelection = true
		mb.selection = selection{
			startX: evt.Get("clientX").Int() - canvasEl.Get("offsetLeft").Int(),
			startY: evt.Get("clientY").Int() - canvasEl.Get("offsetTop").Int(),
			endX:   evt.Get("clientX").Int() - canvasEl.Get("offsetLeft").Int(),
			endY:   evt.Get("clientY").Int() - canvasEl.Get("offsetTop").Int(),
		}
		return nil
	})
	defer mouseDownEvt.Release()

	mouseMoveEvt := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
		evt := args[0]
		if mb.mouseDown {
			posX := evt.Get("clientX").Int() - canvasEl.Get("offsetLeft").Int()
			posY := evt.Get("clientY").Int() - canvasEl.Get("offsetTop").Int()
			dx := posX - mb.selection.startX
			dy := posY - mb.selection.startY
			if math.Abs(float64(dx)) > math.Abs(float64(dy)) {
				mb.selection.endX = mb.selection.startX + dx
				mb.selection.endY = mb.selection.startY + dx
			} else {
				mb.selection.endX = mb.selection.startX + dy
				mb.selection.endY = mb.selection.startY + dy
			}
		}
		return nil
	})
	defer mouseMoveEvt.Release()

	mouseUpEvt := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
		mb.mouseDown = false
		mb.hasSelection = false

		newMinX := CalcReal(float64(mb.selection.startX), mb.width, mb.minX, mb.maxX)
		newMinY := CalcReal(float64(mb.selection.startY), mb.height, mb.minY, mb.maxY)
		newMaxX := CalcReal(float64(mb.selection.endX), mb.width, mb.minX, mb.maxX)
		newMaxY := CalcReal(float64(mb.selection.endY), mb.height, mb.minY, mb.maxY)

		mb.minX = newMinX
		mb.minY = newMinY
		mb.maxX = newMaxX
		mb.maxY = newMaxY

		mb.getMandelbrot(uint(math.Min(1000*1/math.Sqrt((mb.maxX-mb.minX)), 100000)))

		return nil
	})
	defer mouseUpEvt.Release()

	canvasEl.Call("addEventListener", "mousedown", mouseDownEvt)
	canvasEl.Call("addEventListener", "mousemove", mouseMoveEvt)
	canvasEl.Call("addEventListener", "mouseup", mouseUpEvt)

	var renderFrame js.Func

	renderFrame = js.FuncOf(func(this js.Value, args []js.Value) interface{} {
		//		mb.ctx.Call("clearRect", 0, 0, mb.width, mb.height)

		select {
		case x, ok := <-mb.mandelbrot:
			if ok {
				mb.mandelbrotValue = x
			}
		default:
		}
		select {
		case x, ok := <-mb.mandelbrotProgress:
			if ok {
				mb.mandelbrotProgressValue = x
			}
		default:
		}

		value := js.Global().Get("Uint8Array").New(len(mb.mandelbrotValue))
		js.CopyBytesToJS(value, mb.mandelbrotValue)
		mb.imageData.Get("data").Call("set", value)
		mb.ctx.Call("putImageData", mb.imageData, 0, 0)

		if mb.hasSelection {
			mb.ctx.Set("fillStyle", "rgba(0, 0, 255, 0.8)")
			mb.ctx.Call("fillRect", mb.selection.startX, mb.selection.startY, mb.selection.endX-mb.selection.startX, mb.selection.endY-mb.selection.startY)
		}

		js.Global().Call("requestAnimationFrame", renderFrame)
		return nil
	})

	done := make(chan struct{}, 0)

	js.Global().Call("requestAnimationFrame", renderFrame)
	<-done
}

func (m Mandelbrot) SetPixel(width int, x int, y int, color []byte) {
	start := y*int(width)*4 + x*4
	for i := 0; i < 4; i++ {
		m[start+i] = color[i]
	}
}

func (mb mbRender) GetColor(iteration uint, maxIterations uint) []byte {

	intensity := (math.Pi / 2.0) * float64(iteration) / float64(maxIterations)

	return []byte{
		byte(math.Sin(intensity) * 256),
		byte(math.Sin(intensity*2) * 256),
		byte(math.Cos(intensity) * 256),
		255,
	}

	// HSL - red
	/*c := colorful.Hsl(float64(iteration)/256, 1.0, float64(iteration)/(float64(iteration)+8.0))
	return []byte{
		byte(c.R * 255),
		byte(c.G * 255),
		byte(c.B * 255),
		255,
	}*/
}

func CalcReal(x, width, minX, maxX float64) float64 {
	return (x*(maxX-minX))/width + minX
}
func CalcImaginary(y, height, minY, maxY float64) float64 {
	return (y*(maxY-minY))/height + minY
}

func (mb *mbRender) CalculateMandelbrot(maxIterations uint) Mandelbrot {
	fmt.Println("max iterations", maxIterations)
	mandelbrot := make(Mandelbrot, int(mb.width*mb.height*4))
	mb.mandelbrotProgress = make(chan float64)

	for row := 0; row < int(mb.height); row++ {
		for col := 0; col < int(mb.width); col++ {
			cRe := CalcReal(float64(col), mb.width, mb.minX, mb.maxX)
			cIm := CalcImaginary(float64(row), mb.height, mb.minY, mb.maxY)

			var x float64
			var y float64

			var iteration uint
			for ; x*x+y*y <= 4 && iteration < maxIterations; iteration++ {
				newX := x*x - y*y + cRe
				y = 2*x*y + cIm
				x = newX
			}

			mandelbrot.SetPixel(int(mb.width), col, row, mb.GetColor(iteration, maxIterations))
		}
		go func() {
			mb.mandelbrotProgress <- float64(row) / mb.height
		}()
	}

	return mandelbrot
}

func main() {
	fmt.Println("Hallo fögel")

	mb := mbRender{}
	mb.start()
}