state control through scenes

platform/platform.go

@@ -1,57 +1,25 @@
 package platform
 
 import (
-	"errors"
 	"runtime"
 
+	"github.com/FooSoft/lazarus/math"
 	"github.com/go-gl/gl/v2.1/gl"
 	"github.com/veandco/go-sdl2/sdl"
 )
 
-var (
-	ErrAlreadyInit = errors.New("platform is already initialized")
-	ErrWasNotInit  = errors.New("platform was not initialized")
-)
-
 var singleton struct {
-	isInit  bool
+	sdlIsInit bool
 	windows   []*Window
 }
 
 type Handle uintptr
 
-type Scene interface {
-	Init(window *Window) error
-	Advance(window *Window) error
-	Shutdown(window *Window) error
-}
-
-func Init() error {
-	if singleton.isInit {
-		return ErrAlreadyInit
-	}
-
-	runtime.LockOSThread()
-
-	if err := sdl.Init(sdl.INIT_VIDEO); err != nil {
-		return err
-	}
-
-	if err := gl.Init(); err != nil {
-		return err
-	}
-
-	singleton.isInit = true
-	return nil
-}
-
 func Advance() (bool, error) {
-	if !singleton.isInit {
-		return false, ErrWasNotInit
+	if err := advanceWindows(); err != nil {
+		return false, err
 	}
 
-	advanceWindows()
-
 	for event := sdl.PollEvent(); event != nil; event = sdl.PollEvent() {
 		switch event.(type) {
 		case *sdl.QuitEvent:
@@ -63,32 +31,25 @@ func Advance() (bool, error) {
 		}
 	}
 
-	return true, nil
+	return len(singleton.windows) > 0, nil
 }
 
-func Shutdown() error {
-	if !singleton.isInit {
-		return ErrWasNotInit
+func NewWindow(title string, size math.Vec2i, scene Scene) (*Window, error) {
+	if !singleton.sdlIsInit {
+		runtime.LockOSThread()
+
+		if err := sdl.Init(sdl.INIT_VIDEO); err != nil {
+			return nil, err
 		}
 
-	for _, w := range singleton.windows {
-		if err := w.Destroy(); err != nil {
-			return err
-		}
+		if err := gl.Init(); err != nil {
+			return nil, err
 		}
 
-	singleton.windows = nil
-	singleton.isInit = false
-
-	return nil
-}
-
-func CreateWindow(title string, width, height int, scene Scene) (*Window, error) {
-	if !singleton.isInit {
-		return nil, ErrWasNotInit
+		singleton.sdlIsInit = true
 	}
 
-	w, err := newWindow(title, width, height, scene)
+	w, err := newWindow(title, size, scene)
 	if err != nil {
 		return nil, err
 	}
@@ -112,10 +73,23 @@ func removeWindow(window *Window) bool {
 	return false
 }
 
-func advanceWindows() {
+func advanceWindows() error {
+	var windowsToRemove []*Window
 	for _, window := range singleton.windows {
-		window.advance()
+		run, err := window.advance()
+		if err != nil {
+			return err
 		}
+		if !run {
+			windowsToRemove = append(windowsToRemove, window)
+		}
+	}
+
+	for _, window := range windowsToRemove {
+		removeWindow(window)
+	}
+
+	return nil
 }
 
 func processWindowEvents(event sdl.Event) error {

platform/scene.go

@@ -0,0 +1,15 @@
+package platform
+
+type Scene interface{}
+
+type SceneCreator interface {
+	Create(window *Window) error
+}
+
+type SceneAdvancer interface {
+	Advance(window *Window) error
+}
+
+type SceneDestroyer interface {
+	Destroy(window *Window) error
+}

platform/window.go

@@ -14,7 +14,7 @@ type Window struct {
 	scene        Scene
 }
 
-func newWindow(title string, width, height int, scene Scene) (*Window, error) {
+func newWindow(title string, size math.Vec2i, scene Scene) (*Window, error) {
 	sdl.GLSetAttribute(sdl.GL_CONTEXT_MAJOR_VERSION, 2)
 	sdl.GLSetAttribute(sdl.GL_CONTEXT_MINOR_VERSION, 1)
 	sdl.GLSetAttribute(sdl.GL_DOUBLEBUFFER, 1)
@@ -23,8 +23,8 @@ func newWindow(title string, width, height int, scene Scene) (*Window, error) {
 		title,
 		sdl.WINDOWPOS_CENTERED,
 		sdl.WINDOWPOS_CENTERED,
-		int32(width),
-		int32(height),
+		int32(size.X),
+		int32(size.Y),
 		sdl.WINDOW_OPENGL,
 	)
 	if err != nil {
@@ -40,16 +40,17 @@ func newWindow(title string, width, height int, scene Scene) (*Window, error) {
 	w := &Window{
 		sdlWindow:    sdlWindow,
 		sdlGlContext: sdlGlContext,
-		scene:        scene,
 	}
 
+	w.makeCurrent()
+
 	w.imguiContext, err = imgui_backend.New(w.DisplaySize(), w.BufferSize())
 	if err != nil {
 		w.Destroy()
 		return nil, err
 	}
 
-	if err := scene.Init(w); err != nil {
+	if err := w.SetScene(scene); err != nil {
 		w.Destroy()
 		return nil, err
 	}
@@ -57,15 +58,43 @@ func newWindow(title string, width, height int, scene Scene) (*Window, error) {
 	return w, nil
 }
 
+func (w *Window) SetScene(scene Scene) error {
+	if w.scene == scene {
+		return nil
+	}
+
+	if sceneDestroyer, ok := w.scene.(SceneDestroyer); ok {
+		if err := sceneDestroyer.Destroy(w); err != nil {
+			return err
+		}
+	}
+
+	w.scene = scene
+
+	if sceneCreator, ok := scene.(SceneCreator); ok {
+		if err := sceneCreator.Create(w); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 func (w *Window) Destroy() error {
 	if w == nil || w.sdlWindow == nil {
 		return nil
 	}
 
-	if err := w.scene.Shutdown(w); err != nil {
+	w.makeCurrent()
+
+	if err := w.SetScene(nil); err != nil {
 		return err
 	}
-	w.scene = nil
+
+	if err := w.imguiContext.Destroy(); err != nil {
+		return err
+	}
+	w.imguiContext = nil
 
 	sdl.GLDeleteContext(w.sdlGlContext)
 	w.sdlGlContext = nil
@@ -115,8 +144,8 @@ func (w *Window) BufferSize() math.Vec2i {
 	return math.Vec2i{X: int(width), Y: int(height)}
 }
 
-func (w *Window) advance() {
-	w.sdlWindow.GLMakeCurrent(w.sdlGlContext)
+func (w *Window) advance() (bool, error) {
+	w.makeCurrent()
 
 	displaySize := w.DisplaySize()
 	w.imguiContext.SetDisplaySize(displaySize)
@@ -133,12 +162,23 @@ func (w *Window) advance() {
 	gl.MatrixMode(gl.MODELVIEW)
 	gl.LoadIdentity()
 
-	w.scene.Advance(w)
+	if sceneAdvancer, ok := w.scene.(SceneAdvancer); ok {
+		if err := sceneAdvancer.Advance(w); err != nil {
+			return false, err
+		}
+	}
 
 	w.imguiContext.EndFrame()
 	w.sdlWindow.GLSwap()
+
+	return w.scene != nil, nil
 }
 
 func (w *Window) processEvent(event sdl.Event) (bool, error) {
 	return w.imguiContext.ProcessEvent(event)
 }
+
+func (w *Window) makeCurrent() {
+	w.sdlWindow.GLMakeCurrent(w.sdlGlContext)
+
+}

tools/viewer/main.go

@@ -41,15 +41,7 @@ type scene struct {
 	frameIndex     int32
 }
 
-func (s *scene) Init(window *platform.Window) error {
-	return nil
-}
-
-func (s *scene) Shutdown(window *platform.Window) error {
-	if s.texture == nil {
-		return nil
-	}
-
+func (s *scene) Destroy(window *platform.Window) error {
 	return s.texture.Destroy()
 }
 
@@ -77,6 +69,10 @@ func (s *scene) Advance(window *platform.Window) error {
 	imgui.Text(fmt.Sprintf("Size: %+v", frame.Size))
 	imgui.Text(fmt.Sprintf("Offset: %+v", frame.Offset))
 
+	if imgui.Button("Exit") {
+		window.SetScene(nil)
+	}
+
 	if directionIndex != s.directionIndex || frameIndex != s.frameIndex {
 		s.directionIndex = directionIndex
 		s.frameIndex = frameIndex
@@ -146,11 +142,8 @@ func main() {
 		palette = dat.NewFromGrayscale()
 	}
 
-	platform.Init()
-	defer platform.Shutdown()
-
 	scene := &scene{sprite: sprite, palette: palette}
-	window, err := platform.CreateWindow("Viewer", 1280, 720, scene)
+	window, err := platform.NewWindow("Viewer", math.Vec2i{X: 1024, Y: 768}, scene)
 	if err != nil {
 		fmt.Fprintln(os.Stderr, err)
 		os.Exit(1)