With respect to API incompatibilities you can do something like this in your code:
#include <vtkVersion.h>
//...
#if VTK_MAJOR_VERSION > 8 || VTK_MAJOR_VERSION == 8 && VTK_MINOR_VERSION >= 90
// ...
#ielse
// ...
#endif
With respect to API incompatibilities you can do something like this in your code:
#include <vtkVersion.h>
//...
#if VTK_MAJOR_VERSION > 8 || VTK_MAJOR_VERSION == 8 && VTK_MINOR_VERSION >= 90
// ...
#ielse
// ...
#endif