draw2d/cmd/draw2dgl.go

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// Ported from GLUT's samples. Original copyright below applies.
/* Copyright (c) Mark J. Kilgard, 1996. */
/* This program is freely distributable without licensing fees
and is provided without guarantee or warrantee expressed or
implied. This program is -not- in the public domain. */
/* 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
lines of code". */
package main
import (
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"code.google.com/p/draw2d/draw2dgl"
"code.google.com/p/draw2d/postscript"
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"gl"
"glut"
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"io/ioutil"
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"log"
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"math"
"os"
"strings"
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"time"
)
var postscriptContent string
var (
width, height int
rotate int
)
func reshape(w, h int) {
/* 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
coordinate system. */
gl.ClearColor(1, 1, 1, 1)
//fmt.Println(gl.GetString(gl.EXTENSIONS))
gl.Viewport(0, 0, w, h) /* Establish viewing area to cover entire window. */
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. */
glut.PostRedisplay()
}
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)
glut.Init()
glut.InitWindowSize(800, 800)
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glut.CreateWindow("Show Tiger in Opengl")
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glut.DisplayFunc(display)
glut.ReshapeFunc(reshape)
glut.MainLoop()
}