int gdk_surface_get_scale_factor ( GdkSurface* surface )
Returns the internal scale factor that maps from surface coordinates to the actual device pixels.
On traditional systems this is 1, but on very high density outputs this can be a higher value (often 2). A higher value means that drawing is automatically scaled up to a higher resolution, so any code doing drawing will automatically look nicer. However, if you are supplying pixel-based data the scale value can be used to determine whether to use a pixel resource with higher resolution data.
The scale factor may change during the lifetime of the surface.