ui: Adjust cursor positoin on fullscreen mode (#374)

internal/ui/input.go

@@ -28,7 +28,7 @@ func CurrentInput() *Input {
 func (i *Input) CursorPosition() (x, y int) {
 	i.m.RLock()
 	defer i.m.RUnlock()
-	return i.cursorX, i.cursorY
+	return adjustCursorPosition(i.cursorX, i.cursorY)
 }
 
 func (i *Input) GamepadAxisNum(id int) int {

internal/ui/ui_glfw.go

@@ -214,6 +214,20 @@ func ScreenOffset() (float64, float64) {
 	return ox, oy
 }
 
+func adjustCursorPosition(x, y int) (int, int) {
+	u := currentUI
+	if !u.isRunning() {
+		return x, y
+	}
+	ox, oy := ScreenOffset()
+	s := 0.0
+	_ = currentUI.runOnMainThread(func() error {
+		s = currentUI.actualScreenScale()
+		return nil
+	})
+	return x - int(ox/s), y - int(oy/s)
+}
+
 func SetCursorVisibility(visible bool) {
 	// This can be called before Run: change the state asyncly.
 	go func() {

internal/ui/ui_js.go

@@ -70,6 +70,10 @@ func ScreenOffset() (float64, float64) {
 	return 0, 0
 }
 
+func adjustCursorPosition(x, y int) (int, int) {
+	return x, y
+}
+
 func SetCursorVisibility(visibility bool) {
 	if visibility {
 		canvas.Get("style").Set("cursor", "auto")

internal/ui/ui_mobile.go

@@ -110,6 +110,10 @@ func ScreenOffset() (float64, float64) {
 	return 0, 0
 }
 
+func adjustCursorPosition(x, y int) (int, int) {
+	return x, y
+}
+
 func SetCursorVisibility(visibility bool) {
 	// Do nothing
 }