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package main
import (
"fmt"
"log"
"os"
"path/filepath"
"runtime"
"time"
"github.com/veandco/go-sdl2/sdl"
"crecher.net/gones/v2/cart"
"crecher.net/gones/v2/nes"
"crecher.net/gones/v2/ppu"
)
const (
windowScale = 3
// nes: 1789773 cpu cycles per sec / 29780.5 cycles per frame
framesPerSecond = 60.0988
)
func init() {
// sdl wants to be driven from the main thread
runtime.LockOSThread()
}
func main() {
if len(os.Args) != 2 {
fmt.Fprintf(os.Stderr, "usage: %s <rom.nes>\n", os.Args[0])
os.Exit(2)
}
if err := run(os.Args[1]); err != nil {
log.Fatal(err)
}
}
func run(romPath string) error {
c, err := cart.Load(romPath)
if err != nil {
return err
}
console := nes.New(c)
name := filepath.Base(romPath)
if err := sdl.Init(sdl.INIT_VIDEO); err != nil {
return err
}
defer sdl.Quit()
window, err := sdl.CreateWindow("gones - "+name,
sdl.WINDOWPOS_CENTERED, sdl.WINDOWPOS_CENTERED,
ppu.ScreenWidth*windowScale, ppu.ScreenHeight*windowScale,
sdl.WINDOW_SHOWN|sdl.WINDOW_RESIZABLE)
if err != nil {
return err
}
defer window.Destroy()
renderer, err := sdl.CreateRenderer(window, -1, sdl.RENDERER_ACCELERATED|sdl.RENDERER_PRESENTVSYNC)
if err != nil {
return err
}
defer renderer.Destroy()
// the window can be resized freely, sdl scales (and letterboxes) the 256x240 picture
if err := renderer.SetLogicalSize(ppu.ScreenWidth, ppu.ScreenHeight); err != nil {
return err
}
// framebuffer is ARGB8888, streaming since we rewrite it every frame
texture, err := renderer.CreateTexture(sdl.PIXELFORMAT_ARGB8888, sdl.TEXTUREACCESS_STREAMING,
ppu.ScreenWidth, ppu.ScreenHeight)
if err != nil {
return err
}
defer texture.Destroy()
fps := framesPerSecond // a variable, a constant would have to be a whole number of nanoseconds
frameTime := time.Duration(float64(time.Second) / fps)
next := time.Now()
fpsStart, frames := next, 0
jamShown := false
for {
for e := sdl.PollEvent(); e != nil; e = sdl.PollEvent() {
switch ev := e.(type) {
case *sdl.QuitEvent:
return nil
case *sdl.KeyboardEvent:
if ev.Type == sdl.KEYDOWN && ev.Keysym.Sym == sdl.K_ESCAPE {
return nil
}
}
}
console.StepFrame()
// UpdateRGBA multiplies the pitch by 4 itself, so this is in pixels, not bytes
if err := texture.UpdateRGBA(nil, console.PPU.Framebuffer(), ppu.ScreenWidth); err != nil {
return err
}
renderer.Clear()
renderer.Copy(texture, nil, nil)
renderer.Present()
if console.CPU.Jammed && !jamShown {
window.SetTitle("gones - " + name + " - CPU jammed (reset needed)")
jamShown = true
}
frames++
if elapsed := time.Since(fpsStart); elapsed >= time.Second && !jamShown {
window.SetTitle(fmt.Sprintf("gones - %s - %.1f fps", name, float64(frames)/elapsed.Seconds()))
fpsStart, frames = time.Now(), 0
}
// vsync alone would run too fast on a 120/144hz monitor, so pace to the nes frame rate
next = next.Add(frameTime)
if wait := time.Until(next); wait > 0 {
time.Sleep(wait)
} else if wait < -100*time.Millisecond {
next = time.Now() // fell far behind (window drag etc), don't try to catch up
}
}
}
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