Function ImGuiPlatformIO_Set_Platform_GetWindowFramebufferScale_OutParam 

pub unsafe fn ImGuiPlatformIO_Set_Platform_GetWindowFramebufferScale_OutParam(
    platform_io: *mut ImGuiPlatformIO,
    user_callback: Option<unsafe extern "C" fn(vp: *mut ImGuiViewport, out_scale: *mut ImVec2)>,
)

Install a C-compatible out-parameter callback for ImGuiPlatformIO::Platform_GetWindowFramebufferScale.

See ImGuiPlatformIO_Set_Platform_GetWindowPos_OutParam for the ABI rationale.

Safety

platform_io must be null or point to a live ImGuiPlatformIO. user_callback, when present, must obey Dear ImGui’s platform callback contract and must not unwind.