AbstractCustomPainter issue in UIWidgetsEditorWindow

[JustinFincher]

Environment

macOS 10.14.5 Unity 2018.4.0 UIWidgets 6cd480a4b1c780a634c24f0e751d3bd3595faf0d

Expect Behaviour

AbstractCustomPainter should draw canvas in UIWidgetsEditorWindow as it in UIWidgetsPanel would draw, like this when the scroll view is zoomed in:

Current Behaviour

Reproduce Step

1. Add ScrollView to the Unity Package Manager. The ScrollView is just a custom class in a single file that zooms the canvas using GestureDetecter & Transform.scale, which you can inspect the source code on GitHub.
2. Unzip the file to the Asset folder. FinGameWorks.zip
3. Open FinGameWorks/Scenes/Main.unity to see the UIWidgetsPanel.
4. Open FinGameWorks/NodeEditor menu to see the UIWidgetsEditorWindow.
5. Zoom to the scale factor x2 on both UIWidgets views.

Very appreciated!