d3d12: Only support DXGI and GDI APIs on Windows

Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7937>

src/gallium/drivers/d3d12/d3d12_public.h

@@ -32,8 +32,10 @@ typedef struct _LUID LUID;
 extern "C" {
 #endif
 
+#ifdef _WIN32
 struct pipe_screen *
 d3d12_create_dxgi_screen(struct sw_winsys *winsys, LUID *adapter_luid);
+#endif
 
 struct pipe_screen *
 d3d12_create_dxcore_screen(struct sw_winsys *winsys, LUID *adapter_luid);

src/gallium/drivers/d3d12/d3d12_screen.cpp

@@ -633,9 +633,12 @@ d3d12_flush_frontbuffer(struct pipe_screen * pscreen,
       winsys->displaytarget_unmap(winsys, res->dt);
    }
 
+#ifdef _WIN32
+   // WindowFromDC is Windows-only, and this method requires an HWND, so only use it on Windows
    ID3D12SharingContract *sharing_contract;
    if (SUCCEEDED(screen->cmdqueue->QueryInterface(IID_PPV_ARGS(&sharing_contract))))
       sharing_contract->Present(d3d12_res, 0, WindowFromDC((HDC)winsys_drawable_handle));
+#endif
 
    winsys->displaytarget_display(winsys, res->dt, winsys_drawable_handle, sub_box);
 }

src/gallium/drivers/d3d12/meson.build

@@ -28,7 +28,6 @@ files_libd3d12 = files(
   'd3d12_descriptor_pool.cpp',
   'd3d12_draw.cpp',
   'd3d12_dxcore_screen.cpp',
-  'd3d12_dxgi_screen.cpp',
   'd3d12_fence.cpp',
   'd3d12_format.c',
   'd3d12_gs_variant.cpp',
@@ -45,6 +44,10 @@ files_libd3d12 = files(
   'd3d12_surface.cpp',
 )
 
+if host_machine.system() == 'windows'
+  files_libd3d12 += files('d3d12_dxgi_screen.cpp')
+endif
+
 libd3d12 = static_library(
   'd3d12',
   files_libd3d12,