Drag component for windows in Unity

WindowDragHandle.cs

using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

namespace SmolderSoft.Gists
{
	/// <summary>
	/// Add this component to a Graphic to allow dragging. Keeps within the bounds of the screen.
	/// </summary>
	public class DraggableWindow : MonoBehaviour, IDragHandler, IBeginDragHandler
	{
		public bool resetToOriginalPositionOnShow = true;

		private RectTransform windowRectTransform;
		private Vector2 offset;
		public Vector2 OriginalPosition { get; private set; }

		#region Unity Messages

		private void Awake()
		{
			windowRectTransform = GetComponent<RectTransform>();
			OriginalPosition = windowRectTransform.anchoredPosition;
		}

		private void OnEnable()
		{
			if (resetToOriginalPositionOnShow)
				windowRectTransform.anchoredPosition = OriginalPosition;
		}

		#endregion Unity Messages

		public void OnBeginDrag(PointerEventData eventData)
		{
			// don't start dragging if something like a button was pressed
			if (eventData.pointerPress && eventData.pointerPress.TryGetComponent<Selectable>(out _))
				return;

			// Calculate the initial offset from the window's position to the mouse position
			offset = windowRectTransform.position.ToVector2() - eventData.position;
		}

		public void OnDrag(PointerEventData eventData)
		{
			// Calculate the clamped position based on the screen bounds
			Rect bounds = windowRectTransform.rect.Scale(0.9f);
			Vector2 clampedPosition = eventData.position + offset;

			// modify lower bounds so window can be moved off screen up to the title bar
			float lowerBounds = -bounds.height * 0.3f;

			// horizontal bounds such that window never leaves viewport
			clampedPosition.x = QuickMath.Clamp(clampedPosition.x, -bounds.xMin, Screen.width - bounds.xMax);

			// vertical bounds such that the title bar never leaves viewport
			clampedPosition.y = QuickMath.Clamp(clampedPosition.y, lowerBounds, Screen.height - bounds.yMax);

			// Update the window's position based on the clamped position
			windowRectTransform.position = clampedPosition;
		}
	}

	public static class Rect_Extensions
	{
		/// <summary>
		/// Creates a new rect scaled by <paramref name="scaleFactor"/>.
		/// </summary>
		public static Rect Scale(this Rect originalRect, float scaleFactor)
		{
			// Calculate the new dimensions
			float newWidth = originalRect.width * scaleFactor;
			float newHeight = originalRect.height * scaleFactor;

			// Calculate the new position to keep the Rect centered
			float newX = originalRect.x + (originalRect.width - newWidth) / 2;
			float newY = originalRect.y + (originalRect.height - newHeight) / 2;

			// Create the new Rect
			return new Rect(newX, newY, newWidth, newHeight);
		}
	}
}