sdl_layer <-
slices: area*If not @nil
and sdl_layer<-scale
is stretch or tile, the texture is scaled as
nine parts (9-slice scaling), as is common for the frames of
buttons and panels. The area is the centre part, in pixels of the
texture; it is limited to sdl_layer<-source.
The four corners keep their size, the top and bottom edges only stretch
horizontally, the left and right edges only vertically and the centre in
both directions. Using tile, the edges and centre are
repeated instead of stretched. If sdl_layer<-area
is too small for the corners, they are shrunk. Other scales ignore the
slices. With
sdl_layer<-scale_mode linear,
a stretched part blends with the pixels of its neighbours at its border;
use nearest if this is a problem.
