fix: correct mouse coordinates in stretch mode

Added a method to transform mouse coordinates for games using
fullscreen stretch mode, updated mouse driver extensions to transform
coordinates when constructing InputEvents. Fixes mouse clicks not
being correctly delivered in fullscreen stretch mode.

GodotTestDriver/Input/MouseInputExtensions.cs

@@ -29,11 +29,13 @@ public static void ClickMouseAt(this Viewport viewport, Vector2 position, MouseB
     public static void MoveMouseTo(this Viewport viewport, Vector2 position)
     {
         var oldPosition = viewport.GetMousePosition();
+        var stretchedPosition = viewport.StretchedPosition(position);
+
         viewport.WarpMouse(position);
         var inputEvent = new InputEventMouseMotion
         {
-            GlobalPosition = position,
-            Position = position,
+            GlobalPosition = stretchedPosition,
+            Position = stretchedPosition,
             Relative = position - oldPosition
         };
         Input.ParseInputEvent(inputEvent);
@@ -88,12 +90,14 @@ public static void ReleaseMouse(this Viewport _, MouseButton button = MouseButto
     private static void PressMouseAt(this Viewport viewport, Vector2 position, MouseButton button = MouseButton.Left)
     {
         viewport.MoveMouseTo(position);
+        var stretchedPosition = viewport.StretchedPosition(position);
 
         var action = new InputEventMouseButton
         {
             ButtonIndex = button,
             Pressed = true,
-            Position = position
+            Position = stretchedPosition,
+            GlobalPosition = stretchedPosition
         };
         Input.ParseInputEvent(action);
         Input.FlushBufferedEvents();
@@ -102,14 +106,24 @@ private static void PressMouseAt(this Viewport viewport, Vector2 position, Mouse
     private static void ReleaseMouseAt(this Viewport viewport, Vector2 position, MouseButton button = MouseButton.Left)
     {
         viewport.MoveMouseTo(position);
+        var stretchedPosition = viewport.StretchedPosition(position);
 
         var action = new InputEventMouseButton
         {
             ButtonIndex = button,
             Pressed = false,
-            Position = position
+            Position = stretchedPosition,
+            GlobalPosition = stretchedPosition
         };
         Input.ParseInputEvent(action);
         Input.FlushBufferedEvents();
     }
+
+    // Correct for viewport's stretch transform
+    // see https://docs.godotengine.org/en/stable/tutorials/2d/2d_transforms.html#stretch-transform
+    private static Vector2 StretchedPosition(this Viewport viewport, Vector2 position)
+    {
+        var screenTransform = viewport.GetFinalTransform();
+        return screenTransform.BasisXform(position) + screenTransform.Origin;
+    }
 }