Tooltip event

The Tooltip event is sent to check if a visual element underneath the pointer is able to display a tooltip. This is an Editor-only event.

Tooltips are usually set using the tooltip property. You can also respond to the Tooltip event to set tooltips.

You can handle the Tooltip event in two ways:

1. Set a callback to the TooltipEvent. This adds a tooltip to a visual element that doesn’t have one set. This can also override the tooltip set to a visual element.
2. Declare a custom VisualElement (such as declaring a class that extends VisualElement), and override the ExecuteDefaultAction method.

If you set the callback or implement a custom visual element to declare tooltips, don’t set the value for the tooltip property via code or UXML.

When you set a tooltip property, the visual element under the mouse cursor automatically registers a callback to handle the TooltipEvent. This callback also stops further propagation of the event.

If you register a custom callback to handle the TooltipEvent, you must stop the propagation of the event, or the tooltip can be overridden later in the propagation phase.

The base class for Tooltip events is the EventBase class.

Unique properties

rect: Rectangle of the hovered visual element in the panel coordinate system.

tooltip: The tooltip property is a text string to display inside the tooltip box during the tooltip event. The following callback event sets the tooltip property during the event:

   evt.tooltip = "Tooltip set by parent!";

Event list

TooltipEvent

The TooltipEvent is sent just before the Unity Editor displays a tooltip. The handler should set the TooltipEvent.tooltip string and the TooltipEvent.rect.

target: The visual element under the mouse.

Examples

The following examples display the behavior of the ToolTipEvent.

To view an example:

1. Under Assets > Scripts > Editor, create a C# script called SampleWindow.
2. Copy one of the following examples into the C# script.
3. From the Editor Toolbar, select Window > UI Toolkit > SampleWindow.

Example 1: Registering a callback to the TooltipEvent on the parent visual element

using UnityEditor;
using UnityEngine;
using UnityEngine.UIElements;

public class SampleWindow : EditorWindow
{
   [MenuItem("Window/UI Toolkit/SampleWindow")]
   public static void ShowExample()
   {
       SampleWindow wnd = GetWindow<SampleWindow>();
       wnd.titleContent = new GUIContent("SampleWindow");
   }

   public void CreateGUI()
   {
       VisualElement label = new Label("Hello World! This is a UI Toolkit Label.");
       rootVisualElement.Add(label);

       label.tooltip = "And this is a tooltip";

       // If you comment out the registration of the callback, the tooltip that displays for the label is "And this is a tooltip".
       // If you keep the registration of the callback, the tooltip that displays for the label (and any other child of rootVisualElement)
       // is "Tooltip set by parent!".
       rootVisualElement.RegisterCallback<TooltipEvent>(evt =>
       {
           evt.tooltip = "Tooltip set by parent!";
           evt.rect = (evt.target as VisualElement).worldBound;
           evt.StopPropagation();
       }, TrickleDown.TrickleDown); // Pass the TrickleDown.TrickleDown parameter to intercept the event before it reaches the label.
   }
}

Example 2: Declaring a custom visual element and overriding ExecuteDefaultAction

using UnityEditor;
using UnityEngine;
using UnityEngine.UIElements;

public class SampleWindow : EditorWindow
{
   [MenuItem("Window/UI Toolkit/SampleWindow")]
   public static void ShowExample()
   {
       SampleWindow wnd = GetWindow<SampleWindow>();
       wnd.titleContent = new GUIContent("SampleWindow");
   }

   private void CreateGUI()
   {
       CustomLabel custom1 = new CustomLabel("custom 1");
       rootVisualElement.Add(custom1);

       CustomLabel custom2 = new CustomLabel("custom 2");
       rootVisualElement.Add(custom2);
   }
}

public class CustomLabel : Label
{
   private static int m_InstanceCounter = 0;

   private int m_CurrentCounter;

   public CustomLabel(string labelText) : base(labelText)
   {
       m_CurrentCounter = m_InstanceCounter++;
   }

   protected override void ExecuteDefaultAction(EventBase evt)
   {
       // Other events need to be handled as usual.
       base.ExecuteDefaultAction(evt);

       if (evt.eventTypeId == TooltipEvent.TypeId())
       {
           TooltipEvent e = (TooltipEvent)evt;

           // Apply an offset to the tooltip position.
           var tooltipRect = new Rect(worldBound);
           tooltipRect.x += 10;
           tooltipRect.y += 10;
           e.rect = tooltipRect;

           // Set a custom/dynamic tooltip. 
           e.tooltip = $"This is instance # {m_CurrentCounter + 1} of my CustomLabel";

           // Stop propagation avoids other instances of handling of the event that may override the values set here.
           e.StopPropagation();
       }
   }
}