A rectangle is considered "empty" for this function if r is NULL, or if
r's width and/or height are <= 0.
Note that this is a forced-inline function in a header, and not a public
API function available in the SDL library (which is to say, the code is
embedded in the calling program and the linker and dynamic loader will not
be able to find this function inside SDL itself).
Determine whether a rectangle has no area.
A rectangle is considered "empty" for this function if r is NULL, or if r's width and/or height are <= 0.
Note that this is a forced-inline function in a header, and not a public API function available in the SDL library (which is to say, the code is embedded in the calling program and the linker and dynamic loader will not be able to find this function inside SDL itself).