ebiten: keep TouchID int by using a generics function

input.go

@@ -348,7 +348,7 @@ func UpdateStandardGamepadLayoutMappings(mappings string) (bool, error) {
 }
 
 // TouchID represents a touch's identifier.
-type TouchID = ui.TouchID
+type TouchID int
 
 // AppendTouchIDs appends the current touch states to touches, and returns the extended buffer.
 // Giving a slice that already has enough capacity works efficiently.
@@ -361,7 +361,7 @@ type TouchID = ui.TouchID
 //
 // AppendTouchIDs is concurrent-safe.
 func AppendTouchIDs(touches []TouchID) []TouchID {
-	return inputstate.Get().AppendTouchIDs(touches)
+	return inputstate.AppendTouchIDs(touches)
 }
 
 // TouchIDs returns the current touch states.

internal/inputstate/inputstate.go

@@ -88,12 +88,12 @@ func (i *inputState) IsMouseButtonPressed(mouseButton ui.MouseButton) bool {
 	return i.state.MouseButtonPressed[mouseButton]
 }
 
-func (i *inputState) AppendTouchIDs(touches []ui.TouchID) []ui.TouchID {
-	i.m.Lock()
-	defer i.m.Unlock()
+func AppendTouchIDs[T ~int](touches []T) []T {
+	theInputState.m.Lock()
+	defer theInputState.m.Unlock()
 
-	for _, t := range i.state.Touches {
-		touches = append(touches, ui.TouchID(t.ID))
+	for _, t := range theInputState.state.Touches {
+		touches = append(touches, T(t.ID))
 	}
 	return touches
 }