Allowing for SSR is a good step, but does this also render the other controls in their native style? The window border is one important place for styling, and I'm glad GTK4 will improve the situation once it hits the mainstream distros, but as far as I can tell, the rest of the controls (buttons, textboxes, etc.) are still rendered by the application rather than by the system.
I've given GTK4 a try on Windows, and all enabling the top level decorations seem to do is to disable the window border. All controls are still Adwaita, so you'd still need to fake a Windows UI style if you want to make the application feel any kind of native.
I'm sorry, I misunderstood. I thought you meant the toplevel window controls like close, minimize, maximize. There is currently no way to make all the widgets render using the Win32 API to look like Windows widgets. You probably don't want to do that anyway, it will start to look and act really inconsistent when an application uses custom widgets.
Somebody could definitely fake a theme that makes the widgets look like Windows, and ship that with their windows builds, if that was desired. That to me is a much more viable option. There are multiple themes like this for GTK3. [0] [1] I don't know if any have been ported to GTK4 yet, but they could.
I've given GTK4 a try on Windows, and all enabling the top level decorations seem to do is to disable the window border. All controls are still Adwaita, so you'd still need to fake a Windows UI style if you want to make the application feel any kind of native.