fix: multi object selection support for axis to synchronize toggles in network transform (#3781)

* fix editing of the axis to synchronize toggles in network transform

- with multi object selection the last object selected was overriding the other objects
- enabled multi select support on the toggle fields so it will properly show a dash when a mix of values is present

* update changelog

---------

Co-authored-by: Noel Stephens <noel.stephens@unity3d.com>

Author: larus

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -24,6 +24,8 @@ Additional documentation and release notes are available at [Multiplayer Documen
 
 ### Fixed
 
+- Fixed issue where the `Axis to Synchronize` toggles didn't work with multi object editing in `NetworkTransform`. (#3781)
+
 
 ### Security
 

com.unity.netcode.gameobjects/Editor/NetworkTransformEditor.cs

@@ -107,11 +107,11 @@ private void DisplayNetworkTransformProperties()
                 rect = EditorGUI.PrefixLabel(rect, ctid, s_PositionLabel);
                 rect.width = s_ToggleOffset;
 
-                m_SyncPositionXProperty.boolValue = EditorGUI.ToggleLeft(rect, "X", m_SyncPositionXProperty.boolValue);
+                DrawToggleProperty(rect, "X", m_SyncPositionXProperty);
                 rect.x += s_ToggleOffset;
-                m_SyncPositionYProperty.boolValue = EditorGUI.ToggleLeft(rect, "Y", m_SyncPositionYProperty.boolValue);
+                DrawToggleProperty(rect, "Y", m_SyncPositionYProperty);
                 rect.x += s_ToggleOffset;
-                m_SyncPositionZProperty.boolValue = EditorGUI.ToggleLeft(rect, "Z", m_SyncPositionZProperty.boolValue);
+                DrawToggleProperty(rect, "Z", m_SyncPositionZProperty);
 
                 GUILayout.EndHorizontal();
             }
@@ -126,11 +126,11 @@ private void DisplayNetworkTransformProperties()
                 rect = EditorGUI.PrefixLabel(rect, ctid, s_RotationLabel);
                 rect.width = s_ToggleOffset;
 
-                m_SyncRotationXProperty.boolValue = EditorGUI.ToggleLeft(rect, "X", m_SyncRotationXProperty.boolValue);
+                DrawToggleProperty(rect, "X", m_SyncRotationXProperty);
                 rect.x += s_ToggleOffset;
-                m_SyncRotationYProperty.boolValue = EditorGUI.ToggleLeft(rect, "Y", m_SyncRotationYProperty.boolValue);
+                DrawToggleProperty(rect, "Y", m_SyncRotationYProperty);
                 rect.x += s_ToggleOffset;
-                m_SyncRotationZProperty.boolValue = EditorGUI.ToggleLeft(rect, "Z", m_SyncRotationZProperty.boolValue);
+                DrawToggleProperty(rect, "Z", m_SyncRotationZProperty);
 
                 GUILayout.EndHorizontal();
             }
@@ -150,11 +150,11 @@ private void DisplayNetworkTransformProperties()
                 rect = EditorGUI.PrefixLabel(rect, ctid, s_ScaleLabel);
                 rect.width = s_ToggleOffset;
 
-                m_SyncScaleXProperty.boolValue = EditorGUI.ToggleLeft(rect, "X", m_SyncScaleXProperty.boolValue);
+                DrawToggleProperty(rect, "X", m_SyncScaleXProperty);
                 rect.x += s_ToggleOffset;
-                m_SyncScaleYProperty.boolValue = EditorGUI.ToggleLeft(rect, "Y", m_SyncScaleYProperty.boolValue);
+                DrawToggleProperty(rect, "Y", m_SyncScaleYProperty);
                 rect.x += s_ToggleOffset;
-                m_SyncScaleZProperty.boolValue = EditorGUI.ToggleLeft(rect, "Z", m_SyncScaleZProperty.boolValue);
+                DrawToggleProperty(rect, "Z", m_SyncScaleZProperty);
 
                 GUILayout.EndHorizontal();
             }
@@ -281,6 +281,28 @@ private void DisplayNetworkTransformProperties()
 #endif // COM_UNITY_MODULES_PHYSICS2D
         }
 
+        /// <summary>
+        /// Draw a ToggleLeft property field so it will support multi selection editing if applicable.
+        /// </summary>
+        private void DrawToggleProperty(Rect rect, string label, SerializedProperty property)
+        {
+            if (property.hasMultipleDifferentValues)
+            {
+                EditorGUI.showMixedValue = true;
+                EditorGUI.BeginChangeCheck();
+                bool enabled = EditorGUI.ToggleLeft(rect, label, property.boolValue);
+                if (EditorGUI.EndChangeCheck())
+                {
+                    property.boolValue = enabled;
+                }
+                EditorGUI.showMixedValue = false;
+            }
+            else
+            {
+                property.boolValue = EditorGUI.ToggleLeft(rect, label, property.boolValue);
+            }
+        }
+
         /// <inheritdoc/>
         public override void OnInspectorGUI()
         {