draw2d/cmd/draw2dgl.go

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// Ported from GLUT's samples. Original copyright below applies.
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/* Copyright (c) Mark J. Kilgard, 1996. */
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/* This program is freely distributable without licensing fees
and is provided without guarantee or warrantee expressed or
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implied. This program is -not- in the public domain. */
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/* This program is a response to a question posed by Gil Colgate
<gcolgate@sirius.com> about how lengthy a program is required using
OpenGL compared to using Direct3D immediate mode to "draw a
triangle at screen coordinates 0,0, to 200,200 to 20,200, and I
want it to be blue at the top vertex, red at the left vertex, and
green at the right vertex". I'm not sure how long the Direct3D
program is; Gil has used Direct3D and his guess is "about 3000
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lines of code". */
package main
import (
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"io/ioutil"
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"log"
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"math"
"os"
"runtime"
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"strings"
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"time"
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"github.com/go-gl/gl/v2.1/gl"
"github.com/go-gl/glfw/v3.1/glfw"
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"github.com/llgcode/draw2d/draw2dgl"
"github.com/llgcode/draw2d/postscript"
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)
var postscriptContent string
var (
width, height int
rotate int
window *glfw.Window
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)
func reshape(window *glfw.Window, w, h int) {
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/* Because Gil specified "screen coordinates" (presumably with an
upper-left origin), this short bit of code sets up the coordinate
system to correspond to actual window coodrinates. This code
wouldn't be required if you chose a (more typical in 3D) abstract
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coordinate system. */
gl.ClearColor(1, 1, 1, 1)
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//fmt.Println(gl.GetString(gl.EXTENSIONS))
gl.Viewport(0, 0, int32(w), int32(h)) /* Establish viewing area to cover entire window. */
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gl.MatrixMode(gl.PROJECTION) /* Start modifying the projection matrix. */
gl.LoadIdentity() /* Reset project matrix. */
gl.Ortho(0, float64(w), 0, float64(h), -1, 1) /* Map abstract coords directly to window coords. */
gl.Scalef(1, -1, 1) /* Invert Y axis so increasing Y goes down. */
gl.Translatef(0, float32(-h), 0) /* Shift origin up to upper-left corner. */
gl.Enable(gl.BLEND)
gl.BlendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA)
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gl.Disable(gl.DEPTH_TEST)
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width, height = w, h
}
func display() {
gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)
gl.LineWidth(1)
gc := draw2dgl.NewGraphicContext(width, height)
gc.Translate(380, 400)
gc.Scale(1, -1)
rotate = (rotate + 1) % 360
gc.Rotate(float64(rotate) * math.Pi / 180)
gc.Translate(-380, -400)
interpreter := postscript.NewInterpreter(gc)
reader := strings.NewReader(postscriptContent)
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lastTime := time.Now()
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interpreter.Execute(reader)
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dt := time.Now().Sub(lastTime)
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log.Printf("Redraw in : %f ms\n", float64(dt)*1e-6)
gl.Flush() /* Single buffered, so needs a flush. */
window.SwapBuffers()
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}
func main() {
src, err := os.OpenFile("../resource/postscript/tiger.ps", 0, 0)
if err != nil {
log.Println("can't find postscript file.")
return
}
defer src.Close()
bytes, err := ioutil.ReadAll(src)
postscriptContent = string(bytes)
err = glfw.Init()
if err != nil {
panic(err)
}
defer glfw.Terminate()
window, err = glfw.CreateWindow(800, 800, "Show Tiger in OpenGL", nil, nil)
if err != nil {
panic(err)
}
window.MakeContextCurrent()
window.SetSizeCallback(reshape)
window.SetKeyCallback(onKey)
glfw.SwapInterval(1)
err = gl.Init()
if err != nil {
panic(err)
}
for !window.ShouldClose() {
display()
glfw.PollEvents()
window.SwapBuffers()
// time.Sleep(2 * time.Second)
}
}
func onKey(w *glfw.Window, key glfw.Key, scancode int, action glfw.Action, mods glfw.ModifierKey) {
switch {
case key == glfw.KeyEscape && action == glfw.Press,
key == glfw.KeyQ && action == glfw.Press:
w.SetShouldClose(true)
}
}
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func init() {
runtime.LockOSThread()
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}