Animating a nice backbuffer. Thank you Casey Muratori of Handmade Hero fame (https://www.youtube.com/watch?v=hNKU8Jiza2g)

gb/console.go

@@ -1,17 +1,40 @@
 package gb
 
+import (
+	"image"
+	"image/color"
+)
+
+const (
+	ConsoleWidth  = 160
+	ConsoleHeight = 144
+)
+
 type Console struct {
 	Cartridge *Cartridge
+	front     *image.RGBA
 }
 
 func NewConsole(path string) (*Console, error) {
 	cartridge := InsertCartridge(path)
+	buffer := image.NewRGBA(image.Rect(0, 0, ConsoleWidth, ConsoleHeight))
 
-	console := Console{cartridge}
+	console := Console{Cartridge: cartridge, front: buffer}
 
 	return &console, nil
 }
 
-func (console *Console) Update(dt uint64) {
-	console.StepSeconds(dt)
+func (console *Console) StepMilliSeconds(ms uint64) {
+	speed := int(ms / 3)
+	for y := 0; y < ConsoleHeight; y++ {
+		for x := 0; x < ConsoleWidth; x++ {
+			console.front.Set(x, y, color.RGBA{0, uint8(y + speed), uint8(x + speed), 255})
+		}
+	}
+
+}
+
+func (console *Console) Buffer() *image.RGBA {
+
+	return console.front
 }

ui/controller.go

@@ -1,25 +1,37 @@
 package ui
 
 import (
-	"gb-player/gb"
+	"fmt"
+	"log"
 
 	"github.com/veandco/go-sdl2/sdl"
+	"github.com/veandco/go-sdl2/ttf"
+
+	"gb-player/gb"
 )
 
 type Controller struct {
+	window    *sdl.Window
 	renderer  *sdl.Renderer
+	font      *ttf.Font
 	view      *View
 	timestamp uint64
 }
 
-func NewController(renderer *sdl.Renderer) *Controller {
+func NewController(window *sdl.Window, renderer *sdl.Renderer, font *ttf.Font) *Controller {
 	controller := Controller{}
+	controller.window = window
 	controller.renderer = renderer
+	controller.font = font
 	return &controller
 }
 
 func (c *Controller) Start(path string) {
-	console := gb.NewConsole(path)
+	console, err := gb.NewConsole(path)
+	if err != nil {
+		log.Fatal(err)
+	}
+
 	c.view = NewView(c, console)
 	c.Run()
 }
@@ -27,17 +39,14 @@ func (c *Controller) Start(path string) {
 func (c *Controller) Step() {
 	timestamp := sdl.GetTicks64()
 	dt := timestamp - c.timestamp
-	c.view.Update(timestamp, dt)
+	c.timestamp = timestamp
+	c.view.Update(dt)
 }
 
 func (c *Controller) Run() {
 	var fps float64
 	var frameCount uint32
-	var startTicks = sdl.GetTicks64()
-	var now, last uint64
-
-	// cartridge := gb.Insert(romPath)
-	// fmt.Println(cartridge)
+	var frameStart = sdl.GetTicks64()
 
 	running := true
 	for running {
@@ -49,38 +58,49 @@ func (c *Controller) Run() {
 			}
 		}
 
-		last = now
-		now = sdl.GetPerformanceCounter()
-		deltaTime := float64((now - last) * 1000.0 / sdl.GetPerformanceFrequency())
-		_ = deltaTime
-
 		// Clear screen
-		renderer.SetDrawColor(0x63, 0x94, 0xED, 0xff)
-		renderer.Clear()
+		c.renderer.SetDrawColor(0x63, 0x94, 0xED, 0xff)
+		c.renderer.Clear()
 
 		// Update state
 		c.Step()
-		rect := sdl.Rect{X: 100, Y: 100, W: 200, H: 150}
-		renderer.SetDrawColor(0, 0, 255, 255)
-		renderer.FillRect(&rect)
-
-		drawDebugWindow(fps)
+		c.drawDebugWindow(fps)
 
 		// Present to screen
-		renderer.Present()
+		c.renderer.Present()
 
 		// Calculate framerate
 		frameCount++
-		currentTicks := sdl.GetTicks64()
-		elapsed := currentTicks - startTicks
+		frameEnd := sdl.GetTicks64()
+		elapsed := frameEnd - frameStart
 
 		if elapsed >= 1000 {
 			fps = float64(frameCount) / (float64(elapsed) / 1000.0)
 
-			// Reset counters
+			// Reset framerate counters
 			frameCount = 0
-			startTicks = currentTicks
+			frameStart = frameEnd
 		}
 	}
-
+}
+
+func (c *Controller) drawDebugWindow(fps float64) {
+	renderer := c.renderer
+	font := c.font
+
+	// FPS
+	textSurface, err := font.RenderUTF8Blended(fmt.Sprintf("FPS: %.2f", fps), sdl.Color{R: 0, G: 0, B: 0, A: 255})
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer textSurface.Free()
+
+	textTexture, err := renderer.CreateTextureFromSurface(textSurface)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer textTexture.Destroy()
+
+	textRect := sdl.Rect{X: 0, Y: 0, W: textSurface.W, H: textSurface.H}
+	renderer.Copy(textTexture, nil, &textRect)
 }

ui/run.go

@@ -1,7 +1,6 @@
 package ui
 
 import (
-	"fmt"
 	"log"
 	"runtime"
 
@@ -9,8 +8,10 @@ import (
 	"github.com/veandco/go-sdl2/ttf"
 )
 
-var renderer *sdl.Renderer
-var font *ttf.Font
+const (
+	windowWidth  = 800
+	windowHeight = 600
+)
 
 func init() {
 	runtime.LockOSThread()
@@ -31,45 +32,27 @@ func Run(romPath string) {
 		"GB Player",
 		sdl.WINDOWPOS_UNDEFINED,
 		sdl.WINDOWPOS_UNDEFINED,
-		800, 600,
+		windowWidth, windowHeight,
 		sdl.WINDOW_SHOWN)
 	if err != nil {
 		panic(err)
 	}
 	defer window.Destroy()
 
-	renderer, err = sdl.CreateRenderer(window, -1, 0)
+	renderer, err := sdl.CreateRenderer(window, -1, 0)
 	if err != nil {
 		panic(err)
 	}
 	defer renderer.Destroy()
 	renderer.RenderSetVSync(true)
 
-	font, err = ttf.OpenFont("SourceCodePro.ttf", 18)
+	font, err := ttf.OpenFont("SourceCodePro.ttf", 18)
 	if err != nil {
 		log.Fatal(err)
 	}
 	defer font.Close()
 	font.SetStyle(ttf.STYLE_BOLD)
 
-	controller := NewController(renderer)
+	controller := NewController(window, renderer, font)
 	controller.Start(romPath)
 }
-
-func drawDebugWindow(fps float64) {
-	// FPS
-	textSurface, err := font.RenderUTF8Blended(fmt.Sprintf("FPS: %.2f", fps), sdl.Color{R: 0, G: 0, B: 0, A: 255})
-	if err != nil {
-		log.Fatal(err)
-	}
-	defer textSurface.Free()
-
-	textTexture, err := renderer.CreateTextureFromSurface(textSurface)
-	if err != nil {
-		log.Fatal(err)
-	}
-	defer textTexture.Destroy()
-
-	textRect := sdl.Rect{X: 0, Y: 0, W: textSurface.W, H: textSurface.H}
-	renderer.Copy(textTexture, nil, &textRect)
-}

ui/view.go

@@ -1,6 +1,11 @@
 package ui
 
 import (
+	"image"
+	"log"
+
+	"github.com/veandco/go-sdl2/sdl"
+
 	"gb-player/gb"
 )
 
@@ -12,3 +17,45 @@ type View struct {
 func NewView(controller *Controller, console *gb.Console) *View {
 	return &View{controller, console}
 }
+
+func (view *View) Update(dt uint64) {
+	console := view.console
+	renderer := view.controller.renderer
+
+	// console.StepMilliSeconds(dt)
+	console.StepMilliSeconds(sdl.GetTicks64())
+
+	buffer := console.Buffer()
+
+	drawBuffer(renderer, buffer)
+}
+
+func drawBuffer(renderer *sdl.Renderer, buffer *image.RGBA) {
+	width, height := gb.ConsoleWidth, gb.ConsoleHeight
+
+	imageTexture, err := renderer.CreateTexture(
+		uint32(sdl.PIXELFORMAT_RGBA32),
+		sdl.TEXTUREACCESS_STREAMING,
+		int32(width), int32(height))
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer imageTexture.Destroy()
+
+	pixels, pitch, err := imageTexture.Lock(nil)
+	if err != nil {
+		log.Fatal(err)
+	}
+	for y := range height {
+		start := y * buffer.Stride
+		end := start + width*4
+		copy(pixels[y*pitch:y*pitch+width*4], buffer.Pix[start:end])
+	}
+	imageTexture.Unlock()
+
+	x := (windowWidth / 2) - width
+	y := (windowHeight / 2) - height
+	imageRect := sdl.Rect{X: int32(x), Y: int32(y), W: 2 * int32(width), H: 2 * int32(height)}
+
+	renderer.Copy(imageTexture, nil, &imageRect)
+}