Metal: class type detection problem

[funatsufumiya]

Related to this code:

bgfx.nim/examples/graphics.nim

Line 103 in eeb8b17

pd.nwh = info.cocoa.window

Probably because of wrapping (casting) pointer with nim, class type detection of init.platformData.nwh below seems to be failing on Metal backend (so finally becomes Noop backend), when interop with SDL2 or GLFW.

https://github.com/bkaradzic/bgfx/blob/7b3e1ebf626fc6ecb5ba777173c56dddac9a5726/src/renderer_mtl.mm#L3561

It's working when bypassing this process with modifying bgfx-shared-lib (by forcefully casting as NSWindow* in ObjC), so I think assigning init.platformData.nwh should be done by calling C code from Nim, in example code.