Initial commit

main.go

@@ -0,0 +1,115 @@
+package main
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/veandco/go-sdl2/sdl"
+)
+
+const (
+	winWidth  int32 = 800
+	winHeight int32 = 600
+)
+
+var (
+	isRunning = true
+	window    *sdl.Window
+)
+
+func main() {
+
+	err := sdl.Init(sdl.INIT_EVERYTHING)
+	if err != nil {
+		panic("Failed to init SDL. Err: " + err.Error())
+	}
+	defer sdl.Quit()
+
+	window, err = sdl.CreateWindow(
+		"test",
+		sdl.WINDOWPOS_CENTERED,
+		sdl.WINDOWPOS_CENTERED,
+		winWidth,
+		winHeight,
+		sdl.WINDOW_SHOWN)
+	if err != nil {
+		panic("Failed to create window. Err: " + err.Error())
+	}
+	defer window.Destroy()
+
+	rend, err := sdl.CreateRenderer(window, -1, sdl.RENDERER_ACCELERATED)
+	if err != nil {
+		panic("Creating renderer failed. Err: " + err.Error())
+	}
+	defer rend.Destroy()
+
+	tex, err := rend.CreateTexture(sdl.PIXELFORMAT_ABGR8888, 0, winWidth, winHeight)
+	if err != nil {
+		panic(err)
+	}
+
+	//x4 to allow for RGBA
+	pixels := make([]byte, winHeight*winWidth*4)
+	for y := 0; y < int(winHeight); y++ {
+		for x := 0; x < int(winWidth); x++ {
+
+			c := sdl.Color{
+				R: byte(int(float64(x)/float64(winWidth)*256) % 256),
+				G: byte(int(float64(y)/float64(winHeight)*256) % 256),
+			}
+
+			setPixel(x, y, c, pixels)
+		}
+	}
+
+	//Update texture with new pixel values
+	tex.Update(nil, pixels, int(winWidth)*4)
+	//Copy texture to renderer
+	rend.Copy(tex, nil, nil)
+	//Blit
+	rend.Present()
+
+	var fps float32 = 60
+	var dt float32 = 1.0 / 60.0
+	var dtLimit float32 = 1.0 / 120.0
+	for isRunning {
+
+		frameStartTime := time.Now()
+
+		handleEvents()
+
+		//If FPS is more than 120 then limit to that
+		dt = float32(time.Since(frameStartTime).Seconds())
+		if dt < dtLimit {
+			sdl.Delay(8 - uint32(dt*1000))
+			dt = float32(time.Since(frameStartTime).Seconds())
+		}
+
+		//Display FPS is the average of the FPS of this frame and the last frame
+		fps = (fps + 1/dt) / 2
+		window.SetTitle(fmt.Sprintf("FPS: %.2f; dt: %.3f", fps, dt))
+	}
+}
+
+func handleEvents() {
+
+	for event := sdl.PollEvent(); event != nil; event = sdl.PollEvent() {
+
+		switch e := event.(type) {
+
+		case *sdl.QuitEvent:
+			println("Quit at ", e.Timestamp)
+			isRunning = false
+		}
+	}
+}
+
+//handleEvents assumes sdl.PIXELFORMAT_ABGR8888
+func setPixel(x, y int, c sdl.Color, pixels []byte) {
+
+	index := (y*int(winWidth) + x) * 4
+	pixels[index] = c.R
+	pixels[index+1] = c.G
+	pixels[index+2] = c.B
+	pixels[index+3] = c.A
+}