make Window and ImgUi into singletons; there will only ever be one of each

platform/imgui/context.go

@@ -1,9 +1,9 @@
 package imgui
 
-// #cgo linux LDFLAGS: -L./cimgui -l:cimgui.a -lstdc++ -lm
 // #include "native.h"
 import "C"
 import (
+	"errors"
 	"log"
 	"unsafe"
 
@@ -12,6 +12,10 @@ import (
 	"github.com/veandco/go-sdl2/sdl"
 )
 
+var (
+	ErrNotInit = errors.New("imgui context was not created")
+)
+
 const (
 	pointerSize     = unsafe.Sizeof(C.uintptr_t(0))
 	drawCommandSize = unsafe.Sizeof(C.ImDrawCmd{})
@@ -46,159 +50,162 @@ var keyMapping = map[int]C.int{
 	C.ImGuiKey_Z:          sdl.SCANCODE_Z,
 }
 
-var singleton struct {
+var imguiState struct {
-	nativeContext *C.ImGuiContext
+	imguiContext *C.ImGuiContext
-	nativeIo      *C.ImGuiIO
+	imguiIo      *C.ImGuiIO
-	refCount      int
-}
 
-type Context struct {
-	buttonsDown [3]bool
-	lastTime    uint64
 	fontTexture uint32
 	displaySize math.Vec2i
 	bufferSize  math.Vec2i
+	buttonsDown [3]bool
+	lastTime    uint64
 }
 
-func New(displaySize, bufferSize math.Vec2i) (*Context, error) {
+func Create() error {
-	singleton.refCount++
+	if IsCreated() {
-	if singleton.refCount == 1 {
+		return nil
-		log.Println("imgui global create")
-		singleton.nativeContext = C.igCreateContext(nil)
-		singleton.nativeIo = C.igGetIO()
-
-		for imguiKey, nativeKey := range keyMapping {
-			singleton.nativeIo.KeyMap[imguiKey] = nativeKey
-		}
 	}
 
-	log.Println("imgui context create")
+	log.Println("imgui create")
-	c := &Context{displaySize: displaySize, bufferSize: bufferSize}
+	imguiState.imguiContext = C.igCreateContext(nil)
+	imguiState.imguiIo = C.igGetIO()
+
+	for imguiKey, nativeKey := range keyMapping {
+		imguiState.imguiIo.KeyMap[imguiKey] = nativeKey
+	}
 
 	var imageData *C.uchar
 	var imageWidth, imageHeight C.int
-	C.ImFontAtlas_GetTexDataAsRGBA32(singleton.nativeIo.Fonts, &imageData, &imageWidth, &imageHeight, nil)
+	C.ImFontAtlas_GetTexDataAsRGBA32(imguiState.imguiIo.Fonts, &imageData, &imageWidth, &imageHeight, nil)
 
 	var lastTexture int32
 	gl.GetIntegerv(gl.TEXTURE_BINDING_2D, &lastTexture)
-	gl.GenTextures(1, &c.fontTexture)
+	gl.GenTextures(1, &imguiState.fontTexture)
-	gl.BindTexture(gl.TEXTURE_2D, c.fontTexture)
+	gl.BindTexture(gl.TEXTURE_2D, imguiState.fontTexture)
 	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR)
 	gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR)
 	gl.PixelStorei(gl.UNPACK_ROW_LENGTH, 0)
 	gl.TexImage2D(gl.TEXTURE_2D, 0, gl.RGBA, int32(imageWidth), int32(imageHeight), 0, gl.RGBA, gl.UNSIGNED_BYTE, unsafe.Pointer(imageData))
 	gl.BindTexture(gl.TEXTURE_2D, uint32(lastTexture))
 
-	return c, nil
+	return nil
 }
 
-func (c *Context) Destroy() error {
+func IsCreated() bool {
-	if c == nil || c.fontTexture == 0 {
+	return imguiState.imguiContext != nil
+}
+
+func Destroy() error {
+	if !IsCreated() {
 		return nil
 	}
 
-	log.Println("imgui context destroy")
+	gl.DeleteTextures(1, &imguiState.fontTexture)
-	gl.DeleteTextures(1, &c.fontTexture)
+	imguiState.imguiIo.Fonts.TexID = C.nativeHandleCast(C.uintptr_t(imguiState.fontTexture))
-	singleton.nativeIo.Fonts.TexID = C.nativeHandleCast(C.uintptr_t(c.fontTexture))
+	imguiState.fontTexture = 0
-	c.fontTexture = 0
 
-	singleton.refCount--
+	log.Println("imgui destroy")
-	if singleton.refCount == 0 {
+	C.igDestroyContext(imguiState.imguiContext)
-		log.Println("imgui global destroy")
+	imguiState.imguiContext = nil
-		C.igDestroyContext(singleton.nativeContext)
+	imguiState.imguiIo = nil
-		singleton.nativeContext = nil
-		singleton.nativeIo = nil
-	}
 
 	return nil
 }
 
-func (c *Context) SetDisplaySize(displaySize math.Vec2i) {
+func BeginFrame(displaySize, bufferSize math.Vec2i) error {
-	c.displaySize = displaySize
+	if !IsCreated() {
-}
+		return ErrNotInit
+	}
 
-func (c *Context) SetBufferSize(bufferSize math.Vec2i) {
+	imguiState.displaySize = displaySize
-	c.bufferSize = bufferSize
+	imguiState.bufferSize = bufferSize
-}
 
-func (c *Context) BeginFrame() {
+	imguiState.imguiIo.Fonts.TexID = C.nativeHandleCast(C.uintptr_t(imguiState.fontTexture))
-	singleton.nativeIo.Fonts.TexID = C.nativeHandleCast(C.uintptr_t(c.fontTexture))
+	imguiState.imguiIo.DisplaySize.x = C.float(displaySize.X)
-	singleton.nativeIo.DisplaySize.x = C.float(c.displaySize.X)
+	imguiState.imguiIo.DisplaySize.y = C.float(displaySize.Y)
-	singleton.nativeIo.DisplaySize.y = C.float(c.displaySize.Y)
 
 	currentTime := sdl.GetPerformanceCounter()
-	if c.lastTime > 0 {
+	if imguiState.lastTime > 0 {
-		singleton.nativeIo.DeltaTime = C.float(float32(currentTime-c.lastTime) / float32(sdl.GetPerformanceFrequency()))
+		imguiState.imguiIo.DeltaTime = C.float(float32(currentTime-imguiState.lastTime) / float32(sdl.GetPerformanceFrequency()))
 	} else {
-		singleton.nativeIo.DeltaTime = C.float(1.0 / 60.0)
+		imguiState.imguiIo.DeltaTime = C.float(1.0 / 60.0)
 	}
-	c.lastTime = currentTime
+	imguiState.lastTime = currentTime
 
 	x, y, state := sdl.GetMouseState()
-	singleton.nativeIo.MousePos.x = C.float(x)
+	imguiState.imguiIo.MousePos.x = C.float(x)
-	singleton.nativeIo.MousePos.y = C.float(y)
+	imguiState.imguiIo.MousePos.y = C.float(y)
 	for i, button := range []uint32{sdl.BUTTON_LEFT, sdl.BUTTON_RIGHT, sdl.BUTTON_MIDDLE} {
-		singleton.nativeIo.MouseDown[i] = C.bool(c.buttonsDown[i] || (state&sdl.Button(button)) != 0)
+		imguiState.imguiIo.MouseDown[i] = C.bool(imguiState.buttonsDown[i] || (state&sdl.Button(button)) != 0)
-		c.buttonsDown[i] = false
+		imguiState.buttonsDown[i] = false
 	}
 
 	C.igNewFrame()
+	return nil
 }
 
-func (c *Context) ProcessEvent(event sdl.Event) (bool, error) {
+func ProcessEvent(event sdl.Event) (bool, error) {
+	if !IsCreated() {
+		return false, ErrNotInit
+	}
+
 	switch event.GetType() {
 	case sdl.MOUSEWHEEL:
 		wheelEvent := event.(*sdl.MouseWheelEvent)
 		if wheelEvent.X > 0 {
-			singleton.nativeIo.MouseDelta.x++
+			imguiState.imguiIo.MouseDelta.x++
 		} else if wheelEvent.X < 0 {
-			singleton.nativeIo.MouseDelta.x--
+			imguiState.imguiIo.MouseDelta.x--
 		}
 		if wheelEvent.Y > 0 {
-			singleton.nativeIo.MouseDelta.y++
+			imguiState.imguiIo.MouseDelta.y++
 		} else if wheelEvent.Y < 0 {
-			singleton.nativeIo.MouseDelta.y--
+			imguiState.imguiIo.MouseDelta.y--
 		}
 		return true, nil
 	case sdl.MOUSEBUTTONDOWN:
 		buttonEvent := event.(*sdl.MouseButtonEvent)
 		switch buttonEvent.Button {
 		case sdl.BUTTON_LEFT:
-			c.buttonsDown[0] = true
+			imguiState.buttonsDown[0] = true
 			break
 		case sdl.BUTTON_RIGHT:
-			c.buttonsDown[1] = true
+			imguiState.buttonsDown[1] = true
 			break
 		case sdl.BUTTON_MIDDLE:
-			c.buttonsDown[2] = true
+			imguiState.buttonsDown[2] = true
 			break
 		}
 		return true, nil
 	case sdl.TEXTINPUT:
 		inputEvent := event.(*sdl.TextInputEvent)
-		C.ImGuiIO_AddInputCharactersUTF8(singleton.nativeIo, (*C.char)(unsafe.Pointer(&inputEvent.Text[0])))
+		C.ImGuiIO_AddInputCharactersUTF8(imguiState.imguiIo, (*C.char)(unsafe.Pointer(&inputEvent.Text[0])))
 		return true, nil
 	case sdl.KEYDOWN:
 		keyEvent := event.(*sdl.KeyboardEvent)
-		singleton.nativeIo.KeysDown[keyEvent.Keysym.Scancode] = true
+		imguiState.imguiIo.KeysDown[keyEvent.Keysym.Scancode] = true
 		modState := sdl.GetModState()
-		singleton.nativeIo.KeyCtrl = C.bool(modState&sdl.KMOD_CTRL != 0)
+		imguiState.imguiIo.KeyCtrl = C.bool(modState&sdl.KMOD_CTRL != 0)
-		singleton.nativeIo.KeyAlt = C.bool(modState&sdl.KMOD_ALT != 0)
+		imguiState.imguiIo.KeyAlt = C.bool(modState&sdl.KMOD_ALT != 0)
-		singleton.nativeIo.KeyShift = C.bool(modState&sdl.KMOD_SHIFT != 0)
+		imguiState.imguiIo.KeyShift = C.bool(modState&sdl.KMOD_SHIFT != 0)
 	case sdl.KEYUP:
 		keyEvent := event.(*sdl.KeyboardEvent)
-		singleton.nativeIo.KeysDown[keyEvent.Keysym.Scancode] = false
+		imguiState.imguiIo.KeysDown[keyEvent.Keysym.Scancode] = false
 		modState := sdl.GetModState()
-		singleton.nativeIo.KeyCtrl = C.bool(modState&sdl.KMOD_CTRL != 0)
+		imguiState.imguiIo.KeyCtrl = C.bool(modState&sdl.KMOD_CTRL != 0)
-		singleton.nativeIo.KeyAlt = C.bool(modState&sdl.KMOD_ALT != 0)
+		imguiState.imguiIo.KeyAlt = C.bool(modState&sdl.KMOD_ALT != 0)
-		singleton.nativeIo.KeyShift = C.bool(modState&sdl.KMOD_SHIFT != 0)
+		imguiState.imguiIo.KeyShift = C.bool(modState&sdl.KMOD_SHIFT != 0)
 		return true, nil
 	}
 
 	return false, nil
 }
 
-func (c *Context) EndFrame() error {
+func EndFrame() error {
+	if !IsCreated() {
+		return ErrNotInit
+	}
+
 	C.igRender()
 
 	var lastTexture int32
@@ -223,11 +230,11 @@ func (c *Context) EndFrame() error {
 	gl.Enable(gl.TEXTURE_2D)
 	gl.PolygonMode(gl.FRONT_AND_BACK, gl.FILL)
 
-	gl.Viewport(0, 0, int32(c.bufferSize.X), int32(c.bufferSize.Y))
+	gl.Viewport(0, 0, int32(imguiState.bufferSize.X), int32(imguiState.bufferSize.Y))
 	gl.MatrixMode(gl.PROJECTION)
 	gl.PushMatrix()
 	gl.LoadIdentity()
-	gl.Ortho(0, float64(c.displaySize.X), float64(c.displaySize.Y), 0, -1, 1)
+	gl.Ortho(0, float64(imguiState.displaySize.X), float64(imguiState.displaySize.Y), 0, -1, 1)
 	gl.MatrixMode(gl.MODELVIEW)
 	gl.PushMatrix()
 	gl.LoadIdentity()
@@ -236,8 +243,8 @@ func (c *Context) EndFrame() error {
 	C.ImDrawData_ScaleClipRects(
 		drawData,
 		C.ImVec2{
-			x: C.float(float32(c.bufferSize.X) / float32(c.displaySize.X)),
+			x: C.float(float32(imguiState.bufferSize.X) / float32(imguiState.displaySize.X)),
-			y: C.float(float32(c.bufferSize.Y) / float32(c.displaySize.Y)),
+			y: C.float(float32(imguiState.bufferSize.Y) / float32(imguiState.displaySize.Y)),
 		},
 	)
 
@@ -257,7 +264,7 @@ func (c *Context) EndFrame() error {
 			command := (*C.ImDrawCmd)(unsafe.Pointer(uintptr(unsafe.Pointer(commandList.CmdBuffer.Data)) + drawCommandSize*uintptr(j)))
 			gl.Scissor(
 				int32(command.ClipRect.x),
-				int32(c.bufferSize.Y)-int32(command.ClipRect.w),
+				int32(imguiState.bufferSize.Y)-int32(command.ClipRect.w),
 				int32(command.ClipRect.z-command.ClipRect.x),
 				int32(command.ClipRect.w-command.ClipRect.y),
 			)

platform/imgui/imgui.go

@@ -1,5 +1,6 @@
 package imgui
 
+// #cgo linux LDFLAGS: -L./cimgui -l:cimgui.a -lstdc++ -lm
 // #include "native.h"
 import "C"
 import (
@@ -9,27 +10,27 @@ import (
 	"github.com/FooSoft/lazarus/math"
 )
 
-func (*Context) DialogBegin(label string) bool {
+func DialogBegin(label string) bool {
 	labelC := C.CString(label)
 	defer C.free(unsafe.Pointer(labelC))
 	return bool(C.igBegin(labelC, nil, 0))
 }
 
-func (*Context) DialogEnd() {
+func DialogEnd() {
 	C.igEnd()
 }
 
-func (*Context) Button(label string) bool {
+func Button(label string) bool {
 	labelC := C.CString(label)
 	defer C.free(unsafe.Pointer(labelC))
 	return bool(C.igButton(labelC, C.ImVec2{}))
 }
 
-func (c *Context) Image(texture graphics.Texture) {
+func Image(texture graphics.Texture) {
-	c.ImageSized(texture, texture.Size())
+	ImageSized(texture, texture.Size())
 }
 
-func (*Context) ImageSized(texture graphics.Texture, size math.Vec2i) {
+func ImageSized(texture graphics.Texture, size math.Vec2i) {
 	C.igImage(
 		C.nativeHandleCast(C.uintptr_t(texture.Id())),
 		C.ImVec2{x: C.float(size.X), y: C.float(size.Y)},
@@ -40,7 +41,7 @@ func (*Context) ImageSized(texture graphics.Texture, size math.Vec2i) {
 	)
 }
 
-func (*Context) SliderInt(label string, value *int, min, max int) bool {
+func SliderInt(label string, value *int, min, max int) bool {
 	labelC := C.CString(label)
 	defer C.free(unsafe.Pointer(labelC))
 	valueC := C.int(*value)
@@ -49,7 +50,7 @@ func (*Context) SliderInt(label string, value *int, min, max int) bool {
 	return result
 }
 
-func (*Context) Text(label string) {
+func Text(label string) {
 	labelStartC := C.CString(label)
 	labelEndC := (*C.char)(unsafe.Pointer(uintptr(unsafe.Pointer(labelStartC)) + uintptr(len(label))))
 	defer C.free(unsafe.Pointer(labelStartC))

platform/platform.go

@@ -4,99 +4,45 @@ import (
 	"log"
 	"runtime"
 
-	"github.com/FooSoft/lazarus/math"
 	"github.com/veandco/go-sdl2/sdl"
 )
 
-var singleton struct {
+var platfromState struct {
 	sdlIsInit bool
-	windows   []*Window
 }
 
 func Advance() (bool, error) {
-	if err := advanceWindows(); err != nil {
-		return false, err
-	}
-
 	for event := sdl.PollEvent(); event != nil; event = sdl.PollEvent() {
 		switch event.(type) {
 		case *sdl.QuitEvent:
 			return false, nil
 		default:
-			if err := processWindowEvents(event); err != nil {
+			if _, err := windowProcessEvent(event); err != nil {
 				return false, err
 			}
 		}
 	}
 
-	return len(singleton.windows) > 0, nil
+	run, err := windowAdvance()
+	if !run {
+		WindowDestroy()
+	}
+
+	return run, err
 }
 
-func NewWindow(title string, size math.Vec2i, scene Scene) (*Window, error) {
+func platformInit() error {
-	if !singleton.sdlIsInit {
+	if platfromState.sdlIsInit {
-		runtime.LockOSThread()
+		return nil
-
-		log.Println("sdl global init")
-		if err := sdl.Init(sdl.INIT_VIDEO); err != nil {
-			return nil, err
-		}
-
-		sdl.GLSetAttribute(sdl.GL_CONTEXT_MAJOR_VERSION, 2)
-		sdl.GLSetAttribute(sdl.GL_CONTEXT_MINOR_VERSION, 1)
-		sdl.GLSetAttribute(sdl.GL_DOUBLEBUFFER, 1)
-
-		singleton.sdlIsInit = true
 	}
 
-	w, err := newWindow(title, size, scene)
+	runtime.LockOSThread()
-	if err != nil {
+
-		return nil, err
+	log.Println("sdl init")
-	}
+	if err := sdl.Init(sdl.INIT_VIDEO); err != nil {
-
+		return err
-	appendWindow(w)
-	return w, err
-}
-
-func appendWindow(window *Window) {
-	singleton.windows = append(singleton.windows, window)
-}
-
-func removeWindow(window *Window) bool {
-	for i, w := range singleton.windows {
-		if w == window {
-			singleton.windows = append(singleton.windows[:i], singleton.windows[i+1:]...)
-			return true
-		}
-	}
-
-	return false
-}
-
-func advanceWindows() error {
-	var windowsToRemove []*Window
-	for _, window := range singleton.windows {
-		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 {
-	for _, window := range singleton.windows {
-		if _, err := window.processEvent(event); err != nil {
-			return err
-		}
 	}
 
+	platfromState.sdlIsInit = true
 	return nil
 }

platform/scene.go

@@ -5,21 +5,13 @@ type Scene interface {
 }
 
 type SceneCreator interface {
-	Create(window *Window) error
+	Create() error
 }
 
 type SceneAdvancer interface {
-	Advance(window *Window) error
+	Advance() error
 }
 
 type SceneDestroyer interface {
-	Destroy(window *Window) error
+	Destroy() error
-}
-
-func sceneName(scene Scene) string {
-	if scene == nil {
-		return "<nil>"
-	} else {
-		return scene.Name()
-	}
 }

platform/texture.go

@@ -9,11 +9,15 @@ import (
 )
 
 type texture struct {
-	size      math.Vec2i
 	glTexture uint32
+	size      math.Vec2i
 }
 
-func newTextureFromRgba(colors []math.Color4b, size math.Vec2i) (graphics.Texture, error) {
+func NewTextureFromRgba(colors []math.Color4b, size math.Vec2i) (graphics.Texture, error) {
+	if !WindowIsCreated() {
+		return nil, ErrWindowNotExists
+	}
+
 	var glLastTexture int32
 	gl.GetIntegerv(gl.TEXTURE_BINDING_2D, &glLastTexture)
 
@@ -26,10 +30,14 @@ func newTextureFromRgba(colors []math.Color4b, size math.Vec2i) (graphics.Textur
 	gl.TexImage2D(gl.TEXTURE_2D, 0, gl.RGBA, int32(size.X), int32(size.Y), 0, gl.RGBA, gl.UNSIGNED_BYTE, unsafe.Pointer(&colors[0]))
 
 	gl.BindTexture(gl.TEXTURE_2D, uint32(glLastTexture))
-	return &texture{size, glTexture}, nil
+	return &texture{glTexture, size}, nil
 }
 
-func newTextureFromRgb(colors []math.Color3b, size math.Vec2i) (graphics.Texture, error) {
+func NewTextureFromRgb(colors []math.Color3b, size math.Vec2i) (graphics.Texture, error) {
+	if !WindowIsCreated() {
+		return nil, ErrWindowNotExists
+	}
+
 	var glLastTexture int32
 	gl.GetIntegerv(gl.TEXTURE_BINDING_2D, &glLastTexture)
 
@@ -43,7 +51,7 @@ func newTextureFromRgb(colors []math.Color3b, size math.Vec2i) (graphics.Texture
 	gl.TexImage2D(gl.TEXTURE_2D, 0, gl.RGB, int32(size.X), int32(size.Y), 0, gl.RGB, gl.UNSIGNED_BYTE, unsafe.Pointer(&colors[0]))
 
 	gl.BindTexture(gl.TEXTURE_2D, uint32(glLastTexture))
-	return &texture{size, glTexture}, nil
+	return &texture{glTexture, size}, nil
 }
 
 func (t *texture) Id() graphics.TextureId {

platform/window.go

@@ -1,6 +1,7 @@
 package platform
 
 import (
+	"errors"
 	"log"
 
 	"github.com/FooSoft/lazarus/graphics"
@@ -10,78 +11,88 @@ import (
 	"github.com/veandco/go-sdl2/sdl"
 )
 
-type Window struct {
+var (
+	ErrWindowExists    = errors.New("only one window can exist at a time")
+	ErrWindowNotExists = errors.New("no window has been created")
+)
+
+var windowState struct {
 	sdlWindow    *sdl.Window
 	sdlGlContext sdl.GLContext
-	imguiContext *imgui.Context
 	scene        Scene
 }
 
-func newWindow(title string, size math.Vec2i, scene Scene) (*Window, error) {
+func WindowCreate(title string, size math.Vec2i, scene Scene) error {
+	if WindowIsCreated() {
+		return ErrWindowExists
+	}
+
+	platformInit()
+
+	var err error
 	log.Println("window create")
-	sdlWindow, err := sdl.CreateWindow(
+	if windowState.sdlWindow, err = sdl.CreateWindow(title, sdl.WINDOWPOS_CENTERED, sdl.WINDOWPOS_CENTERED, int32(size.X), int32(size.Y), sdl.WINDOW_OPENGL); err != nil {
-		title,
+		return err
-		sdl.WINDOWPOS_CENTERED,
-		sdl.WINDOWPOS_CENTERED,
-		int32(size.X),
-		int32(size.Y),
-		sdl.WINDOW_OPENGL,
-	)
-	if err != nil {
-		return nil, err
 	}
 
-	sdlGlContext, err := sdlWindow.GLCreateContext()
+	log.Println("window gl context create")
-	if err != nil {
+	if windowState.sdlGlContext, err = windowState.sdlWindow.GLCreateContext(); err != nil {
-		sdlWindow.Destroy()
+		WindowDestroy()
-		return nil, err
+		return err
 	}
 
-	w := &Window{
+	log.Println("window gl context make current")
-		sdlWindow:    sdlWindow,
+	windowState.sdlWindow.GLMakeCurrent(windowState.sdlGlContext)
-		sdlGlContext: sdlGlContext,
-	}
 
-	w.makeCurrent()
+	log.Println("window gl init")
-
-	log.Println("opengl init")
 	if err := gl.Init(); err != nil {
-		return nil, err
+		WindowDestroy()
+		return err
 	}
 
-	w.imguiContext, err = imgui.New(w.DisplaySize(), w.BufferSize())
+	if err := imgui.Create(); err != nil {
-	if err != nil {
+		WindowDestroy()
-		w.Destroy()
+		return err
-		return nil, err
 	}
 
-	if err := w.SetScene(scene); err != nil {
+	if err := WindowSetScene(scene); err != nil {
-		w.Destroy()
+		WindowDestroy()
-		return nil, err
+		return err
 	}
 
-	return w, nil
+	return nil
 }
 
-func (w *Window) SetScene(scene Scene) error {
+func WindowSetScene(scene Scene) error {
-	if w.scene == scene {
+	if !WindowIsCreated() {
+		return ErrWindowNotExists
+	}
+
+	if windowState.scene == scene {
 		return nil
 	}
 
-	log.Printf("scene transition \"%v\" => \"%v\"\n", sceneName(w.scene), sceneName(scene))
+	sceneName := func(s Scene) string {
+		if s == nil {
+			return "<nil>"
+		} else {
+			return s.Name()
+		}
+	}
 
-	if sceneDestroyer, ok := w.scene.(SceneDestroyer); ok {
+	if sceneDestroyer, ok := windowState.scene.(SceneDestroyer); ok {
-		log.Printf("scene notify destroy \"%s\"\n", sceneName(w.scene))
+		log.Printf("window scene notify destroy \"%s\"\n", sceneName(windowState.scene))
-		if err := sceneDestroyer.Destroy(w); err != nil {
+		if err := sceneDestroyer.Destroy(); err != nil {
 			return err
 		}
 	}
 
-	w.scene = scene
+	log.Printf("window scene transition \"%v\" => \"%v\"\n", sceneName(windowState.scene), sceneName(scene))
+	windowState.scene = scene
 
 	if sceneCreator, ok := scene.(SceneCreator); ok {
-		log.Printf("scene notify create \"%s\"\n", sceneName(w.scene))
+		log.Printf("window scene notify create \"%s\"\n", sceneName(windowState.scene))
-		if err := sceneCreator.Create(w); err != nil {
+		if err := sceneCreator.Create(); err != nil {
 			return err
 		}
 	}
@@ -89,52 +100,41 @@ func (w *Window) SetScene(scene Scene) error {
 	return nil
 }
 
-func (w *Window) Destroy() error {
+func WindowDestroy() error {
-	if w == nil || w.sdlWindow == nil {
+	if !WindowIsCreated() {
 		return nil
 	}
 
-	w.makeCurrent()
+	if err := WindowSetScene(nil); err != nil {
-
-	if err := w.SetScene(nil); err != nil {
 		return err
 	}
 
-	if err := w.imguiContext.Destroy(); err != nil {
+	if err := imgui.Destroy(); err != nil {
 		return err
 	}
-	w.imguiContext = nil
 
-	sdl.GLDeleteContext(w.sdlGlContext)
+	log.Println("window gl context destroy")
-	w.sdlGlContext = nil
+	sdl.GLDeleteContext(windowState.sdlGlContext)
-
+	windowState.sdlGlContext = nil
-	if err := w.sdlWindow.Destroy(); err != nil {
-		return err
-	}
-	w.sdlWindow = nil
 
 	log.Println("window destroy")
-	removeWindow(w)
+	if err := windowState.sdlWindow.Destroy(); err != nil {
+		return err
+	}
+	windowState.sdlWindow = nil
 
 	return nil
 }
 
-func (w *Window) CreateTextureRgba(colors []math.Color4b, size math.Vec2i) (graphics.Texture, error) {
+func WindowRenderTexture(texture graphics.Texture, position math.Vec2i) error {
-	w.makeCurrent()
+	if !WindowIsCreated() {
-	return newTextureFromRgba(colors, size)
+		return ErrWindowNotExists
-}
+	}
 
-func (w *Window) CreateTextureRgb(colors []math.Color3b, size math.Vec2i) (graphics.Texture, error) {
-	w.makeCurrent()
-	return newTextureFromRgb(colors, size)
-}
-
-func (w *Window) RenderTexture(texture graphics.Texture, position math.Vec2i) {
 	size := texture.Size()
 
 	gl.Enable(gl.TEXTURE_2D)
 	gl.BindTexture(gl.TEXTURE_2D, uint32(texture.Id()))
-
 	gl.Begin(gl.QUADS)
 	gl.TexCoord2f(0, 0)
 	gl.Vertex2f(0, 0)
@@ -145,31 +145,48 @@ func (w *Window) RenderTexture(texture graphics.Texture, position math.Vec2i) {
 	gl.TexCoord2f(1, 0)
 	gl.Vertex2f(float32(size.X), 0)
 	gl.End()
+
+	return nil
 }
 
-func (w *Window) DisplaySize() math.Vec2i {
+func WindowDisplaySize() (math.Vec2i, error) {
-	width, height := w.sdlWindow.GetSize()
+	if !WindowIsCreated() {
-	return math.Vec2i{X: int(width), Y: int(height)}
+		return math.Vec2i{}, ErrWindowNotExists
+	}
+
+	width, height := windowState.sdlWindow.GetSize()
+	return math.Vec2i{X: int(width), Y: int(height)}, nil
 }
 
-func (w *Window) BufferSize() math.Vec2i {
+func WindowIsCreated() bool {
-	width, height := w.sdlWindow.GLGetDrawableSize()
+	return windowState.sdlWindow != nil
-	return math.Vec2i{X: int(width), Y: int(height)}
 }
 
-func (w *Window) Imgui() *imgui.Context {
+func windowBufferSize() (math.Vec2i, error) {
-	return w.imguiContext
+	if !WindowIsCreated() {
+		return math.Vec2i{}, ErrWindowNotExists
+	}
+
+	width, height := windowState.sdlWindow.GLGetDrawableSize()
+	return math.Vec2i{X: int(width), Y: int(height)}, nil
 }
 
-func (w *Window) advance() (bool, error) {
+func windowAdvance() (bool, error) {
-	w.makeCurrent()
+	if !WindowIsCreated() {
+		return false, ErrWindowNotExists
+	}
 
-	displaySize := w.DisplaySize()
+	displaySize, err := WindowDisplaySize()
-	w.imguiContext.SetDisplaySize(displaySize)
+	if err != nil {
-	bufferSize := w.BufferSize()
+		return false, err
-	w.imguiContext.SetBufferSize(bufferSize)
+	}
 
-	w.imguiContext.BeginFrame()
+	bufferSize, err := windowBufferSize()
+	if err != nil {
+		return false, err
+	}
+
+	imgui.BeginFrame(displaySize, bufferSize)
 
 	gl.Viewport(0, 0, int32(displaySize.X), int32(displaySize.Y))
 	gl.Clear(gl.COLOR_BUFFER_BIT)
@@ -179,23 +196,22 @@ func (w *Window) advance() (bool, error) {
 	gl.MatrixMode(gl.MODELVIEW)
 	gl.LoadIdentity()
 
-	if sceneAdvancer, ok := w.scene.(SceneAdvancer); ok {
+	if sceneAdvancer, ok := windowState.scene.(SceneAdvancer); ok {
-		if err := sceneAdvancer.Advance(w); err != nil {
+		if err := sceneAdvancer.Advance(); err != nil {
 			return false, err
 		}
 	}
 
-	w.imguiContext.EndFrame()
+	imgui.EndFrame()
-	w.sdlWindow.GLSwap()
+	windowState.sdlWindow.GLSwap()
 
-	return w.scene != nil, nil
+	return windowState.scene != nil, nil
 }
 
-func (w *Window) processEvent(event sdl.Event) (bool, error) {
+func windowProcessEvent(event sdl.Event) (bool, error) {
-	return w.imguiContext.ProcessEvent(event)
+	if !WindowIsCreated() {
-}
+		return false, ErrWindowNotExists
-
+	}
-func (w *Window) makeCurrent() {
-	w.sdlWindow.GLMakeCurrent(w.sdlGlContext)
 
+	return imgui.ProcessEvent(event)
 }

tools/viewer/viewer.go

@@ -12,6 +12,7 @@ import (
 	"github.com/FooSoft/lazarus/graphics"
 	"github.com/FooSoft/lazarus/math"
 	"github.com/FooSoft/lazarus/platform"
+	"github.com/FooSoft/lazarus/platform/imgui"
 )
 
 func loadPalette(path string) (*dat.DatPalette, error) {
@@ -45,7 +46,7 @@ func (s *scene) Name() string {
 	return "viewer"
 }
 
-func (s *scene) Destroy(window *platform.Window) error {
+func (s *scene) Destroy() error {
 	if s.texture != nil {
 		return s.texture.Destroy()
 	}
@@ -53,20 +54,18 @@ func (s *scene) Destroy(window *platform.Window) error {
 	return nil
 }
 
-func (s *scene) Advance(window *platform.Window) error {
+func (s *scene) Advance() error {
 	var (
 		directionIndex = s.directionIndex
 		frameIndex     = s.frameIndex
 	)
 
 	if s.texture == nil {
-		if err := s.updateTexture(window); err != nil {
+		if err := s.updateTexture(); err != nil {
 			return err
 		}
 	}
 
-	imgui := window.Imgui()
-
 	imgui.DialogBegin("DC6 Viewer")
 	imgui.Image(s.texture)
 	direction := s.animation.Directions[directionIndex]
@@ -78,20 +77,20 @@ 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)
+		platform.WindowSetScene(nil)
 	}
 	imgui.DialogEnd()
 
 	if directionIndex != s.directionIndex || frameIndex != s.frameIndex {
 		s.directionIndex = directionIndex
 		s.frameIndex = frameIndex
-		s.updateTexture(window)
+		s.updateTexture()
 	}
 
 	return nil
 }
 
-func (s *scene) updateTexture(window *platform.Window) error {
+func (s *scene) updateTexture() error {
 	frame := s.animation.Directions[s.directionIndex].Frames[s.frameIndex]
 	colors := make([]math.Color3b, frame.Size.X*frame.Size.Y)
 	for y := 0; y < frame.Size.Y; y++ {
@@ -107,7 +106,7 @@ func (s *scene) updateTexture(window *platform.Window) error {
 	}
 
 	var err error
-	s.texture, err = window.CreateTextureRgb(colors, frame.Size)
+	s.texture, err = platform.NewTextureFromRgb(colors, frame.Size)
 	if err != nil {
 		return err
 	}
@@ -151,12 +150,11 @@ func main() {
 	}
 
 	scene := &scene{animation: animation, palette: palette}
-	window, err := platform.NewWindow("Viewer", math.Vec2i{X: 1024, Y: 768}, scene)
+	if err := platform.WindowCreate("Viewer", math.Vec2i{X: 1024, Y: 768}, scene); err != nil {
-	if err != nil {
 		fmt.Fprintln(os.Stderr, err)
 		os.Exit(1)
 	}
-	defer window.Destroy()
+	defer platform.WindowDestroy()
 
 	for {
 		run, err := platform.Advance()