Start work on menu interactivity.

With this commit, we get a ui.Interface and ui.Widget type. The
interface monitors hover and mouse click state and tells the widgets
about them; the widgets execute code specified by the application when
events occur.

Next step: have wh40k load the main menu and play sound, etc.

internal/ui/window.go

@@ -12,6 +12,11 @@ import (
 	"github.com/hajimehoshi/ebiten/inpututil"
 )
 
+type Game interface {
+	Update(screenX, screenY int) error
+	Draw(*ebiten.Image) error
+}
+
 var (
 	screenScale = flag.Float64("screen-scale", 1.0, "Scale the window by this factor")
 
@@ -26,9 +31,8 @@ type Window struct {
 	KeyUpHandlers     map[ebiten.Key]func()
 	MouseWheelHandler func(float64, float64)
 
-	// User-provided update actions
-	updateFn func() error
-	drawFn   func(*ebiten.Image) error
+	// Allow the "game" to be switched out at any time
+	game Game
 
 	debug    bool
 	firstRun bool
@@ -37,7 +41,7 @@ type Window struct {
 // 0,0 is the *top left* of the window
 //
 // ebiten assumes a single window, so only call this once...
-func NewWindow(title string) (*Window, error) {
+func NewWindow(game Game, title string) (*Window, error) {
 	ebiten.SetRunnableInBackground(true)
 
 	return &Window{
@@ -45,6 +49,7 @@ func NewWindow(title string) (*Window, error) {
 		KeyUpHandlers: make(map[ebiten.Key]func()),
 		debug:         true,
 		firstRun:      true,
+		game:          game,
 	}, nil
 }
 
@@ -57,13 +62,12 @@ func (w *Window) OnMouseWheel(f func(x, y float64)) {
 	w.MouseWheelHandler = f
 }
 
-func (w *Window) run(screen *ebiten.Image) error {
-	if w.firstRun {
-		ebiten.SetScreenScale(*screenScale)
-		w.firstRun = false
-	}
+func (w *Window) Layout(_, _ int) (int, int) {
+	return *winX, *winY
+}
 
-	if err := w.updateFn(); err != nil {
+func (w *Window) Update(screen *ebiten.Image) error {
+	if err := w.game.Update(screen.Size()); err != nil {
 		return err
 	}
 
@@ -83,16 +87,18 @@ func (w *Window) run(screen *ebiten.Image) error {
 		}
 	}
 
-	if !ebiten.IsDrawingSkipped() {
-		if err := w.drawFn(screen); err != nil {
-			return err
-		}
+	if ebiten.IsDrawingSkipped() {
+		return nil
+	}
 
-		if w.debug {
-			// Draw FPS, etc, to the screen
-			msg := fmt.Sprintf("tps=%0.2f fps=%0.2f", ebiten.CurrentTPS(), ebiten.CurrentFPS())
-			ebitenutil.DebugPrint(screen, msg)
-		}
+	if err := w.game.Draw(screen); err != nil {
+		return err
+	}
+
+	if w.debug {
+		// Draw FPS, etc, to the screen
+		msg := fmt.Sprintf("tps=%0.2f fps=%0.2f", ebiten.CurrentTPS(), ebiten.CurrentFPS())
+		ebitenutil.DebugPrint(screen, msg)
 	}
 
 	return nil
@@ -101,10 +107,7 @@ func (w *Window) run(screen *ebiten.Image) error {
 // TODO: a stop or other cancellation mechanism
 //
 // Note that this must be called on the main OS thread
-func (w *Window) Run(updateFn func() error, drawFn func(*ebiten.Image) error) error {
-	w.updateFn = updateFn
-	w.drawFn = drawFn
-
+func (w *Window) Run() error {
 	if *cpuprofile != "" {
 		f, err := os.Create(*cpuprofile)
 		if err != nil {
@@ -117,5 +120,7 @@ func (w *Window) Run(updateFn func() error, drawFn func(*ebiten.Image) error) er
 		defer pprof.StopCPUProfile()
 	}
 
-	return ebiten.Run(w.run, *winX, *winY, 1, w.Title) // Native game resolution: 640x480
+	ebiten.SetWindowSize(int(float64(*winX)**screenScale), int(float64(*winY)**screenScale))
+	ebiten.SetWindowTitle(w.Title)
+	return ebiten.RunGame(w) // Native game resolution: 640x480
 }