Class used to implement content for a popup window.
Additional resources: PopupWindow with full example.
| editorWindow | The EditorWindow that contains the popup content. |
| CreateGUI | Creates custom GUI with UI Toolkit for the popup. |
| GetWindowSize | The size of the popup window. |
| OnClose | Callback when the popup window is closed. |
| OnGUI | Callback for drawing GUI controls for the popup window. |
| OnOpen | Callback when the popup window is opened. |