Module'd up.

manager.go

@@ -0,0 +1,106 @@
+package groovy
+
+import (
+	"os"
+
+	"github.com/hajimehoshi/ebiten/v2"
+)
+
+const (
+	defaultWidth  = 1024
+	defaultHeight = 768
+)
+
+type Area struct {
+	Width  int
+	Height int
+}
+
+type GameInfo struct {
+	Name      string
+	Version   string
+	Dimension Area
+}
+
+type Manager struct {
+	Info           GameInfo
+	currentScene   Scene
+	currentSceneId int
+	scenes         []Scene
+}
+
+// can be used to create default manager instance
+func NewManager() Manager {
+	return Manager{
+		Info: GameInfo{
+			Name:    "groovy",
+			Version: "1.0",
+			Dimension: Area{
+				Width:  defaultWidth,
+				Height: defaultHeight},
+		},
+		currentSceneId: 0,
+	}
+}
+
+// ebitengine update proxy
+// manages scene transition and exists, then calls scene's update method
+func (m *Manager) Update() error {
+	if m.currentScene == nil {
+		return nil
+	}
+
+	m.CheckTransitions()
+	m.CheckExit()
+
+	//call the current scene's update method
+	return m.currentScene.Update()
+
+}
+
+// check for exit condition
+func (m *Manager) CheckExit() {
+	if m.currentSceneId >= len(m.scenes) {
+		os.Exit(0)
+	}
+}
+
+// check for scene completion and if reached, set up next scene (if available)
+func (m *Manager) CheckTransitions() {
+	if m.currentScene.Completed() {
+		m.currentSceneId++
+		if m.currentSceneId < len(m.scenes) {
+			m.currentScene = m.scenes[m.currentSceneId]
+		}
+	}
+}
+
+// calls current scene's draw method if the currentscene is valid
+func (m *Manager) Draw(screen *ebiten.Image) {
+	if m.currentScene != nil {
+		m.currentScene.Draw(screen)
+	}
+}
+
+// ebitengine proxy for layout
+func (m *Manager) Layout(outsideWidth, outsideHeight int) (screenWidth, screenHeight int) {
+	return m.Info.Dimension.Width, m.Info.Dimension.Height
+}
+
+// appends scene to the managed scenes
+func (m *Manager) AddScene(s Scene) {
+	m.scenes = append(m.scenes, s)
+}
+
+// sets the current scene, based on sceneindex
+func (m *Manager) SetCurrentScene(sceneId int) {
+	if sceneId >= 0 && sceneId < len(m.scenes) {
+		m.currentSceneId = sceneId
+		m.currentScene = m.scenes[m.currentSceneId]
+	}
+}
+
+// check for exit condition
+func (m *Manager) SetDimensions(a Area) {
+	m.Info.Dimension = a
+}

scene.go

@@ -0,0 +1,9 @@
+package groovy
+
+import "github.com/hajimehoshi/ebiten/v2"
+
+type Scene interface {
+	Update() error
+	Draw(screen *ebiten.Image)
+	Completed() bool
+}