ImVec2ih_ImVec2ih_Nil

Undocumented in source but is binding to C. You might be able to learn more by searching the web for its name.
version(!BindImGui_Static)
extern (C) @nogc nothrow __gshared
pImVec2ih_ImVec2ih_Nil ImVec2ih_ImVec2ih_Nil;

Meta