Scribble is a simple paintbrush like tool which is a wpf sample application built using MVVM pattern and PRISM framework. I wrote this sample in 2014 to learn how to build a composite application using WPF and PRISM. Later posted the sample in codeproject. The complete article / documentation is available at the below link
https://www.codeproject.com/Articles/617868/Scribble
The sample runs in Visual Studio 2017 with the target framework set to .Net Framework 4 Client Profile