This is an experiment investigating using the awesome CsWin32 Nuget package to draw to a Windows Forms form using Direct Write through a GDI DC.
While CsWin32 is a huge help with generating PInvoke boilerplate, it is still in Beta, so it has a few bugs to work out and some things to work around.
To get Direct Write to work the following interfaces have had to be overridden from what CsWin32 generates because of a couple of methods that currently don't work as generated:
ID2D1BitmapRenderTargetID2D1DCRenderTargetID2D1DeviceContextID2D1DeviceContext1ID2D1DeviceContext2ID2D1DeviceContext3ID2D1DeviceContext4ID2D1DeviceContext5ID2D1DeviceContext6ID2D1HwndRenderTargetID2D1RenderTarget
Specifically the GetSize and GetPixelSize methods both crash because they are generated to return their respective structs rather than an HRESULT. See CsWin32 Issue #167 on incorrect generation. When the GetSize and GetPixelSize methods aren't called, it still manifests as memory corruption in later calls because the returned structs in the interfaces are not the same size as the HRESULT and struct. For example calling textLayout = DirectWriteFactory?.CreateTextLayout(text, textFormat, renderTarget?.GetSize() ?? default); results in:
[!ERROR]
System.AccessViolationException: 'Attempted to read or write protected memory. This is often an indication that other memory is corrupt.'
To see the results of CsWin32 generated PInvokes, exclude the Overrides folder in the AutoGenDirectWriteLibrary project and compile.