You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: Form1Impl.go
    path of file: ./repos/govcl/samples/drawrose
    
    the code of the file until where you have to start completion: // 在这里写你的事件

package main

import (
	"fmt"
	"math"
	"math/rand"
	"time"

	"github.com/ying32/govcl/vcl/types"

	"github.com/ying32/govcl/vcl/types/colors"

	"github.com/ying32/govcl/vc
    
func (f *TForm1) drawRose() {
	var zBuffer []int
	var i, j, x, y, z, zBufferIndex int
	var dot TDOT
	var r, g, b int

	zBuffer = make([]int, urosesize*urosesize)
	canvas := f.Canvas()

	canvas.Brush().SetColor(colors.ClWhite)
	canvas.FillRect(types.TRect{0, 0, f.Width(), f.Height()})
	rand.Seed(time.Now().UnixNano())
	for j = 0; j <= 1999; j++ {
		for i = 0; i <= 9999; i++ {
			if calc(float64(rand.Intn(RAND_MAX))/RAND_MAX, float64(rand.Intn(RAND_MAX))/RAND_MAX, float64(rand.Intn(RAND_MAX)%46)/0.74, &dot) {
				z = int(math.Trunc(dot.z + 0.5))
				x = int(math.Trunc(dot.x*float64(urosesize)/float64(z) - uh + 0.5))
				y = int(math.Trunc(dot.y*float64(urosesize)/float64(z) - uh + 0.5))
				if y >= urosesize {
					continue
				}
				zBufferIndex = y*urosesize + x
				if (!(zBuffer[zBufferIndex] != 0)) || (zBuffer[zBufferIndex] > z) {
					zBuffer[zBufferIndex] = z

					// 画点
					r = ^int(math.Trunc(dot.r * uh))
					if r < 0 {
						r = 0
					}
					if r > 255 {
						r = 255
					}
					g = ^int(math.Trunc(dot.g * uh))
					if g < 0 {
						g = 0
					}
					if g > 255 {
						g = 255
					}
					b = ^int(math.Trunc(dot.r * dot.r * -80))
					if b < 0 {
						b = 0
					}
					if b > 255 {
						b = 255
					}
					var color types.TColor
					canvas.SetPixels(int32(x+50), int32(y-20), color.RGB(byte(r), byte(g), byte(b)))
				}
			}
			vcl.Application.ProcessMessages()
		}
		time.Sleep(time.Millisecond)
	}
	fmt.Println("done.")
}