Fix gizmo depth sorting (#46)

Small patch for the `GizmoMaterial` that fixes depth sorting for
non-translucent elements by setting their blend mode to
`AlphaMode::Opaque`

studio/src/interaction/gizmos/material.rs

@@ -15,7 +15,7 @@ impl From<Color> for GizmoMaterial {
     fn from(color: Color) -> Self {
         GizmoMaterial {
             color,
-            blend_mode: AlphaMode::Blend,
+            blend_mode: AlphaMode::Opaque,
         }
     }
 }

studio/src/interaction/gizmos/resources.rs

@@ -102,9 +102,13 @@ pub(super) fn init_resources(
     let rotate_x = ra_mats.add(design_system::Color::RED.into());
     let rotate_y = ra_mats.add(design_system::Color::GREEN.into());
     let rotate_z = ra_mats.add(design_system::Color::BLUE.into());
-    let rotate_trackball = ra_mats.add(Color::WHITE.with_a(0.0).into());
     let rotate_ss = ra_mats.add(Color::WHITE.into());
 
+    let rotate_trackball = ra_mats.add(GizmoMaterial {
+        color: Color::WHITE.with_a(0.0),
+        blend_mode: AlphaMode::Blend,
+    });
+
     cmd.insert_resource(GizmoMats {
         translate_x,
         translate_y,

studio/src/interaction/gizmos/rotation.rs

@@ -239,11 +239,17 @@ pub(super) fn on_rotate(
     q_widget: Query<&RotationWidget>,
 ) {
     // Components from the gizmo root (the entity being transformed)
-    let (mut xform, parent, init_xform, init_point, mut last_point, mut last_rotation) =
-        q_root.single_mut();
-
-    let gizmo_xform = q_gizmo.single();
-    let (cam, cam_xform) = q_camera.single();
+    let Ok((mut xform, parent, init_xform, init_point, mut last_point, mut last_rotation)) =
+        q_root.get_single_mut()
+    else {
+        return;
+    };
+    let Ok(gizmo_xform) = q_gizmo.get_single() else {
+        return;
+    };
+    let Ok((cam, cam_xform)) = q_camera.get_single() else {
+        return;
+    };
 
     // `Transform::rotate_axis` takes an axis vector relative to the transform's
     // _parent_. We'll use the gizmo root's parent's global transform (if it