FIX: Don't show action properties view when there's no actions (ISX-1497). (#1819)

* Fix showing action properties view when there's no actions (ISX-1497).

* Address feedback: Keep header visible for properties pane.

* Access scrollview directly.

Author: graham-huws

Packages/com.unity.inputsystem/CHANGELOG.md

@@ -34,6 +34,7 @@ however, it has to be formatted properly to pass verification tests.
 - Fixed issue where composite part dropdown manipulates binding path and leaves composite part field unchanged.
 - Fixed lingering highlight effect on Save Asset button after clicking.
 - Fixed missing name in window title for Input Action assets.
+- Fixed showing action properties view when there were no actions.
 - Fixed "Listen" functionality for selecting an input sometimes expecting the wrong input type.
 
 ## [1.8.0-pre.2] - 2023-11-09

Packages/com.unity.inputsystem/InputSystem/Editor/UITKAssetEditor/Resources/InputActionsEditor.uxml

@@ -42,7 +42,7 @@
                     <ui:VisualElement name="header" class="body-panel-header">
                         <ui:Label text="Action Properties" display-tooltip-when-elided="true" name="properties-header-label" />
                     </ui:VisualElement>
-                    <ui:ScrollView>
+                    <ui:ScrollView name="properties-scrollview">
                         <ui:Foldout text="Action Properties" name="properties-foldout" class="properties-foldout" />
                         <ui:Foldout text="Interactions" name="interactions-foldout" class="properties-foldout name-and-parameters-list-view">
                             <ui:Label text="No interactions have been added." name="no-parameters-added-label" display-tooltip-when-elided="true" class="name-and-parameter-empty-label" style="display: flex;" />

Packages/com.unity.inputsystem/InputSystem/Editor/UITKAssetEditor/Views/ActionsTreeView.cs

@@ -203,6 +203,9 @@ public override void RedrawUI(ViewState viewState)
             }
             RenameNewAction(viewState.newElementID);;
             addActionButton.SetEnabled(viewState.actionMapCount > 0);
+
+            // Don't want to show action properties if there's no actions.
+            m_Root.Q<VisualElement>("properties-scrollview").visible = m_ActionsTreeView.GetTreeCount() > 0;
         }
 
         private void RenameNewAction(int id)