SDL_GL_GetDrawableSize was introduced after 2.0.0, so we need to check for that version before we call this method. Fixes MethodNotFounException on vanilla libsdl2-2.0.0 on linux.
When HiDPI is enabled, the size of the OpenGL surface (specified in
pixels) may no longer correspond to the size of the window (specified
in points). Width, Height, ClientSize and ClientRectangle return the
size of the OpenGL surface in device-dependent pixel coordinates
(origin: top-left pixel of the surface). Bounds and Size return the
size of the window in device-independent point coordinates (origin:
desktop).