draw2d/samples/helloworldgl/helloworldgl.go

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// Open an OpenGl window and display a rectangle using a OpenGl GraphicContext
package main
import (
"image/color"
"log"
"runtime"
"github.com/go-gl/gl/v2.1/gl"
"github.com/go-gl/glfw/v3.1/glfw"
"github.com/llgcode/draw2d"
"github.com/llgcode/draw2d/draw2dgl"
"github.com/llgcode/draw2d/draw2dkit"
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)
var (
// global rotation
rotate int
width, height int
redraw = true
font draw2d.FontData
)
func reshape(window *glfw.Window, w, h int) {
gl.ClearColor(1, 1, 1, 1)
/* Establish viewing area to cover entire window. */
gl.Viewport(0, 0, int32(w), int32(h))
/* PROJECTION Matrix mode. */
gl.MatrixMode(gl.PROJECTION)
/* Reset project matrix. */
gl.LoadIdentity()
/* Map abstract coords directly to window coords. */
gl.Ortho(0, float64(w), 0, float64(h), -1, 1)
/* Invert Y axis so increasing Y goes down. */
gl.Scalef(1, -1, 1)
/* Shift origin up to upper-left corner. */
gl.Translatef(0, float32(-h), 0)
gl.Enable(gl.BLEND)
gl.BlendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA)
gl.Disable(gl.DEPTH_TEST)
width, height = w, h
redraw = true
}
// Ask to refresh
func invalidate() {
redraw = true
}
func display() {
gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)
gl.LineWidth(1)
gc := draw2dgl.NewGraphicContext(width, height)
gc.SetFontData(draw2d.FontData{
Name: "luxi",
Family: draw2d.FontFamilyMono,
Style: draw2d.FontStyleBold | draw2d.FontStyleItalic})
gc.BeginPath()
draw2dkit.RoundedRectangle(gc, 200, 200, 600, 600, 100, 100)
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gc.SetFillColor(color.RGBA{0, 0, 0, 0xff})
gc.Fill()
gl.Flush() /* Single buffered, so needs a flush. */
}
func init() {
runtime.LockOSThread()
}
func main() {
err := glfw.Init()
if err != nil {
panic(err)
}
defer glfw.Terminate()
width, height = 800, 800
window, err := glfw.CreateWindow(width, height, "Show RoundedRect", nil, nil)
if err != nil {
panic(err)
}
window.MakeContextCurrent()
window.SetSizeCallback(reshape)
window.SetKeyCallback(onKey)
window.SetCharCallback(onChar)
glfw.SwapInterval(1)
err = gl.Init()
if err != nil {
panic(err)
}
reshape(window, width, height)
for !window.ShouldClose() {
if redraw {
display()
window.SwapBuffers()
redraw = false
}
glfw.PollEvents()
// time.Sleep(2 * time.Second)
}
}
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func onChar(w *glfw.Window, char rune) {
log.Println(char)
}
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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)
}
}