displaySize() -> {Width :: integer(), Height :: integer()}
Returns the display size in pixels.
Note: Use of this function is not recommended in the new code as it only works for the primary display. Use wxDisplay:getGeometry/1 to retrieve the size of the appropriate display instead.
Either of output pointers can be NULL if the caller is not interested in the corresponding value.
See: wxGetDisplaySize() (not implemented in wx), wxDisplay