Fix 3D manipulator the gizmo growing too large on small viewports

This closes #27112. This closes #19116.

editor/plugins/spatial_editor_plugin.cpp

@@ -2922,8 +2922,14 @@ void SpatialEditorViewport::update_transform_gizmo_view() {
 	if (dd == 0)
 		dd = 0.0001;
 
-	float gsize = EditorSettings::get_singleton()->get("editors/3d/manipulator_gizmo_size");
-	gizmo_scale = (gsize / Math::abs(dd)) * MAX(1, EDSCALE) / viewport_container->get_stretch_shrink();
+	float gizmo_size = EditorSettings::get_singleton()->get("editors/3d/manipulator_gizmo_size");
+	// At low viewport heights, multiply the gizmo scale based on the viewport height.
+	// This prevents the gizmo from growing very large and going outside the viewport.
+	const int viewport_base_height = 400 * MAX(1, EDSCALE);
+	gizmo_scale =
+			(gizmo_size / Math::abs(dd)) * MAX(1, EDSCALE) *
+			MIN(viewport_base_height, viewport_container->get_size().height) / viewport_base_height /
+			viewport_container->get_stretch_shrink();
 	Vector3 scale = Vector3(1, 1, 1) * gizmo_scale;
 
 	xform.basis.scale(scale);