ScrollView.mouseWheelScrollSize

Description

This property controls the scrolling speed only when using a mouse scroll wheel, based on the size of the page.

This property takes precedence over the --unity-metrics-single_line-height USS variable. If both the property and the variable are set, the property value is used.

The following example demonstrates how to use the mouseWheelScrollSize property to control the "speed" of a scroll when using the mouse wheel. Notice the difference in feel when selecting different values:

using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UIElements;

[RequireComponent(typeof(UIDocument))]
public class ScrollView_MouseWheelScrollSize : MonoBehaviour
{
    // To use this example in runtime, add a UIDocument component to your Scene and attach a UXML file to the UIDocument component.
    // The UXML file can be empty.
    public UIDocument uiDocument;
    public int numberOfPotions = 100;

    void Start()
    {
        // Create a dropdown to change the mouse wheel scroll size.
        var mouseWheelScrollSizeDropdown = new DropdownField("Select a Mouse Wheel Scroll Size");

        var scrollView = new ScrollView { name = "MyPotionsInventory" };
        scrollView.style.height = 200;

        var initialMouseWheelScrollSize = scrollView.mouseWheelScrollSize;

        // Set the choices of the dropdown to different values of the mouse wheel scroll size.
        mouseWheelScrollSizeDropdown.choices = new List<string>() { $"{initialMouseWheelScrollSize * 0.5f}", $"{initialMouseWheelScrollSize}",
            $"{initialMouseWheelScrollSize * 2}", $"{initialMouseWheelScrollSize * 10}", $"{initialMouseWheelScrollSize * 20}" };
        mouseWheelScrollSizeDropdown.value = $"{initialMouseWheelScrollSize}";

        // Register a ValueChangedCallback to change the mouse wheel scroll size.
        mouseWheelScrollSizeDropdown.RegisterValueChangedCallback(evt =>
        {
            // We know the choices are all floats, so we can parse them directly.
            var newValue = float.Parse(evt.newValue);
            scrollView.mouseWheelScrollSize = newValue;

        });

        var inventoryColor = new Color(0.65f, 0.3f, 0.2f, 1f);

        // Create a list of labels representing potions.
        for (int i = 0; i < numberOfPotions; i++)
        {
            var label = new Label { text = " Unnamed Potion #" + (i) };
            label.style.backgroundColor = inventoryColor;
            scrollView.Add(label);
        }

        // Add a title for the list and make it noticeable.
        var title = new Label { text = "Potions Inventory" };
        title.style.unityFontStyleAndWeight = FontStyle.Bold;
        title.style.fontSize = 20;
        title.style.color = inventoryColor;
        title.style.unityTextAlign = TextAnchor.MiddleCenter;

        uiDocument.rootVisualElement.Add(mouseWheelScrollSizeDropdown);
        uiDocument.rootVisualElement.Add(title);
        uiDocument.rootVisualElement.Add(scrollView);
    }
}