/
glfps.go
130 lines (100 loc) · 2.31 KB
/
glfps.go
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// Simple fps overlay for opengl.
package glfps
import (
"github.com/banthar/Go-SDL/sdl"
"github.com/banthar/gl"
"image"
"image/png"
"bytes"
)
var (
digitImages []*image.NRGBA
t0, frames uint32
digitStore [5]int8
)
func init() {
img, err := readImage()
if err != nil { panic(err) }
digitImages = cutImage(img)
}
// Draws the average fps (frames per second).
// (x, y) sets the right top corner of the drawing area.
// (0, 0) is left top on the screen.
func Draw(x, y int) {
drawNumber(x, y, int(fps()))
}
func fps() uint32 {
t := sdl.GetTicks()
frames++
if t0 == 0 { t0 = t; frames = 0; return 0 }
if t - t0 > 2000 {
t0 += (t - t0) / 2; frames /= 2
}
if t - t0 == 0 { return 0 }
fps := 1000 * frames / (t - t0)
return fps
}
func readImage() (rgb *image.NRGBA, err error) {
b := bytes.NewBuffer(digits_png[:])
img, err := png.Decode(b)
if err != nil { return }
rgb = img.(*image.NRGBA)
return
}
func cutImage(img *image.NRGBA) []*image.NRGBA {
r := image.Rect(0, 0, 6, 11)
cuts := make([]*image.NRGBA, 10)
for i := 0; i < 10; i++ {
cuts[i] = img.SubImage(r).(*image.NRGBA)
r = r.Add(image.Pt(7, 0))
}
return cuts
}
func countDigits(n int) (d int) {
d = 0
for n != 0 { n /= 10; d++ }
return
}
func getDigits(n int) (digits []int8) {
count := countDigits(n)
digits = digitStore[:count]
for i := 0; i < count; i++ {
digits[i] = int8(n % 10)
n /= 10
}
return
}
func drawNumber(x, y int, n int) {
digits := getDigits(n)
drawDigits(x, y, digits)
}
func drawDigits(x, y int, digits []int8) {
s := sdl.GetVideoSurface()
lft, rgt, btm, top := 0.0, float64(s.W), float64(s.H), 0.0
gl.Enable(gl.BLEND)
gl.BlendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA)
gl.MatrixMode(gl.PROJECTION)
gl.PushMatrix()
gl.LoadIdentity()
gl.Ortho(lft, rgt, btm, top, 0.0, 1.0)
gl.MatrixMode(gl.MODELVIEW)
gl.PushMatrix()
gl.LoadIdentity()
w := digitImages[0].Rect.Dx()
for i := 0; i < len(digits); i++ {
img := digitImages[digits[i]]
drawImage(x - w*i-i, y, img)
}
gl.MatrixMode(gl.MODELVIEW)
gl.PopMatrix()
gl.MatrixMode(gl.PROJECTION)
gl.PopMatrix()
}
func drawImage(x, y int, img *image.NRGBA) {
w, h := img.Rect.Dx(), img.Rect.Dy()
stride := img.Stride
for line := 0; line < h; line++ {
gl.RasterPos2i(x, y + line)
gl.DrawPixels(w, 1, gl.RGBA, gl.UNSIGNED_BYTE, &img.Pix[line*stride])
}
}