If you are a Mac or Linux web or cross-platform developer, one of the easiest ways to test your apps on Windows is to use a virtual machine. And you can test Windows in a VM completely for free by using the test VMs provided by Microsoft.
In Xojo 2016 Release 4 we switched our main graphics rendering engine on Windows from GDI and GDI+ to Direct2D/DirectWrite. Direct2D/DirectWrite was first introduced by Microsoft in Windows 7, with support in Vista via a Platform Update. It is (or was at the time) Microsoft’s new high-performance 2D vector Graphics API.