prevent moving window out of bounds

Still a bug in KDE: taskbar pushes the boundary inward but that
difference isn't reflected in ebiten.ScreenSizeInFullscreen().

main.go

@@ -49,6 +49,7 @@ type Position struct{ x, y int }
 
 var DurationTillHungry time.Duration
 var WalkChance, StopChance int
+var WindowWidth, WindowHeight int
 
 type Vector struct{ x, y int }
 
@@ -118,9 +119,11 @@ func main() {
 	DurationTillHungry = time.Duration(secondsUntilHungryFlag) * 1_000_000_000
 
 	ebiten.SetWindowPosition(xFlag, yFlag)
-	ebiten.SetWindowSize(SPRITE_X*sizeFlag, SPRITE_Y*sizeFlag)
+	WindowWidth = SPRITE_X * sizeFlag
+	WindowHeight = SPRITE_Y * sizeFlag
+	ebiten.SetWindowSize(WindowWidth, WindowHeight)
 	ebiten.SetWindowTitle("Shark!")
-	//ebiten.SetWindowDecorated(false)
+	ebiten.SetWindowDecorated(false)
 	ebiten.SetWindowFloating(true)
 
 	AppIcon, _ := must.Two(image.Decode(bytes.NewReader(IconFile)))

states.go

@@ -8,6 +8,8 @@ import (
 	"github.com/hajimehoshi/ebiten/v2/inpututil"
 )
 
+var screenW, screenH = ebiten.ScreenSizeInFullscreen()
+
 type StateMachine struct {
 	state          State
 	anim           *Anim
@@ -48,6 +50,8 @@ func (sm *StateMachine) Update() error {
 
 	sm.state.Update(sm)
 
+	sm.x = min(max(sm.x, 0), screenW-WindowWidth)
+	sm.y = min(max(sm.y, 0), screenH-WindowHeight)
 	ebiten.SetWindowPosition(sm.x, sm.y)
 
 	// Advance to next animation frame