SelectionBasePicker

Internal utility that enhances Scene View object picking by automatically selecting the topmost parent GameObject with a [SelectionBase] component when clicking on any child object in the hierarchy.

Definition

Namespace: Paragon.Editor Assembly: Paragon.Editor.dll

[InitializeOnLoad]
internal static class SelectionBasePicker

Attributes: [InitializeOnLoad] — initializes via static constructor on editor load.

Remarks

Unity's built-in [SelectionBase] attribute marks a component's GameObject as a selection root. However, Unity's default behavior only applies [SelectionBase] for the immediate parent — not for deeply nested hierarchies. This utility extends that behavior by walking the entire parent hierarchy to find the topmost [SelectionBase] component.

Selection Algorithm

1. Input filter — only processes left mouse button clicks (MouseDown, button 0)

2. Object picking — uses HandleUtility.PickGameObject to find the clicked object in the Scene View

3. Hierarchy walk — calls GetParents() on the picked object and reverses the result (topmost parent first)

4. SelectionBase search — finds the first (topmost) parent with any component decorated with [SelectionBase]

5. Selection override — sets Selection.activeGameObject to the selection base and consumes the event

Parent Traversal Order

GetParents().Reverse() produces a top-down order (root → parent → child). FirstOrDefault returns the topmost parent with [SelectionBase], not the nearest. This means clicking any descendant will always select the root selection base.

Quick Lookup

Goal	How
Mark a component as selection base	Add [SelectionBase] attribute to the component class
Behavior	Left-click on any child → topmost [SelectionBase] parent is selected
Event handling	The click event is consumed (Event.current.Use())

Methods

OnSceneGUI (private static)

private static void OnSceneGUI(SceneView sceneView)

Callback for SceneView.duringSceneGui. Processes left-click events by picking the clicked object and selecting its topmost [SelectionBase] ancestor.

HasAnySelectionBaseComponent (private static)

private static bool HasAnySelectionBaseComponent(GameObject gameObject)

Checks if any component on the GameObject has the [SelectionBase] attribute (including inherited).

Parameter	Type	Description
gameObject	GameObject	The object to check

Returns: true if any component has [SelectionBase].

Common Pitfalls

Topmost selection base wins The utility selects the topmost (closest to root) parent with [SelectionBase]. If the hierarchy has multiple [SelectionBase] components at different levels, only the topmost one is selected. To reach a nested selection base, double-click or use the Hierarchy window.

Event consumption The click event is consumed via Event.current.Use() when a selection base is found. This prevents Unity's default object selection from also processing the click, which could result in selecting the wrong object.

Internal class — always active SelectionBasePicker is internal static and cannot be disabled. It runs on every left-click in the Scene View and overrides selection when a [SelectionBase] parent exists.

No selection base found If no parent has [SelectionBase], the utility does nothing and Unity's default selection behavior applies normally.

Examples

Using SelectionBase with a Character

// The Character component is the selection root
[SelectionBase]
public class Character : MonoBehaviour
{
    // Clicking on any child (mesh, collider, weapon)
    // will select this GameObject instead
}

Nested Hierarchy

Root (SelectionBase) ← ALWAYS selected on click
├── Body
│   ├── Head
│   │   └── Hair (clicked here → Root is selected)
│   └── Arms
└── Weapons
    └── Sword (clicked here → Root is selected)

See Also

• Utility Overview — utility subsystem

• Paragon Editor Overview — root editor module