Background

This is the first implementation of what I call "Savablz", layout windows that can be saved.
I think this is a required feature for many of us : #201, someone on gitter asked, this, I needed this, and you also had to do that too in doobry.

I'm pretty new to the project so I admit I've no idea if I cover all the cases.

Implementation

I've read what you did in https://github.com/ButchersBoy/doobry/blob/master/Doobry/MainWindowViewModel.cs , but this implementation:

• Doesn't need tab ID, the tree is written as-is in the object hierarchy, which doesn't require id manipulations, and serializes well, at least in JSON
• Works with multiple windows
• Saves the position and the state (maximized, restored...) of the windows
• Is flexible (User have control of how this is serialized and what kind of model/viewmodel has a tab)

Note: this PR is based on top of #207, feel free to cherry pick if you don't want that.

I also implemented a new Sample project that demonstrates how that works.

How it works

• You need to have a ViewModel that represents your tab.
• Create a Model type that is a POCO object, used to serialize the state of your tab. Include all details that helps you to recreate the state of the ViewModel
• Call WindowsStateSaver.GetWindowsState<TModel, TViewModel>(viewModelToModelConversionFunction) to get the state of all windows in this app.
• The state is serialization agnostic, so that you can save that the way you want (JSON, XML...)
• Restore the state at startup by calling WindowsStateSaver.RestoreWindowsState(window.InitialTabablz, state, modelToViewModelConversionFunction). The window must be shown beforehand for this to work.
• Enjoy!

About the new sample project

This sample is aimed at providing a simple getting started for the common scenario. It is not meant to provide a full documentation. It is however a good way to get started.

Tabs are just showing a GUID in the header and in the content. The view model is very simple, and so is the Model, but it is here to demonstrate how things work together. When the "main" window is closed, the state is saved and is restored at next startup, thanks to the .net's Settings mechanism.

When the last tab of the main window is closed, the settings are reset and a fresh configuration is generated on the next startup.

Questions

• Does it work well in all cases?
• I'm only tackling the simple case of one Partition. What happen when we have multiple partitions? What should be done?
• We should probably implement a method that can get the state of a window which don't have a Layout (we currently enumerate the layouts to get the windows). The model is ready for that scenario.