[WPF] Context backend handler about xwt

[lytico]

As far as I can see, you use Gdi (System.Drawing) to implement Wpf.ContextBackendHandler.
I have already started some Xwt.Gdi-Backends;
https://github.com/lytico/xwt/tree/8912f007355620a194c46c99e6511d0250f0bee9/Xwt.Gdi
You can take whatever you need, I think you'l need fonts for drawing Text.
I think my ContextBackendHandler is less finished than yours, but maybe you find something usefull...

Later on it would be nice to refactor that it can be used in Xwt.Wpf and
Xwt.Winform (http://limada.git.sourceforge.net/git/gitweb.cgi?p=limada/limada;a=tree;f=src/Xwt.SWF;h=faa369bffe0edc77c977a9fff19625e0b48fc725;hb=HEAD)
but I'll make a proposal then

[lytico]

Current state of Xwt.Gdi:
https://github.com/lytico/xwt/blob/7666d3ed8a2a6383b1192e605b4094447468964a/Xwt.Gdi/Mono.Xwt.Drawing.Gtk.Gdi.PNG?raw=true

[lytico]

Current state of Xwt.Gdi:
lytico@def0499
It runs the Samples.DrawingTransforms complete now:
https://github.com/lytico/xwt/blob/def049952e483fda284fb3cc820e3e3a8c8e429a/Xwt.Gdi/Mono.Xwt.Drawing.Gtk.Gdi.PNG?raw=true

[lytico]

@ermau I have a working Xwt.Drawing-Windows.Drawing backend now. It runs the DrawingTransforms-Sample without errors. I had to continue cause of a presentation tomorrow. Missing is the integration into Xwt.Wpf, I have to finish this until next week. Just to inform you, as we are working parallel now...