static char help[] = "Demonstrates use of PetscDrawZoom()\n";

#if defined(PETSC_APPLE_FRAMEWORK)

  #include <PETSc/petscsys.h>
  #include <PETSc/petscdraw.h>
#else
  #include <petscsys.h>
  #include <petscdraw.h>
#endif

PetscErrorCode zoomfunction(PetscDraw draw, void *dummy)
{
  MPI_Comm    comm;
  PetscMPIInt size, rank;

  PetscFunctionBeginUser;
  PetscCall(PetscObjectGetComm((PetscObject)draw, &comm));
  PetscCallMPI(MPI_Comm_size(comm, &size));
  PetscCallMPI(MPI_Comm_rank(comm, &rank));
  for (int i = rank; i < 256; i += size) {
    PetscReal y = ((PetscReal)i) / (256 - 1);
    PetscCall(PetscDrawLine(draw, 0.0, y, 1.0, y, i));
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

int main(int argc, char **argv)
{
  int       x = 0, y = 0, width = 256, height = 256;
  PetscDraw draw;

  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc, &argv, NULL, help));
  PetscCall(PetscDrawCreate(PETSC_COMM_WORLD, NULL, "Title", x, y, width, height, &draw));
  PetscCall(PetscDrawSetFromOptions(draw));
  PetscCall(PetscDrawZoom(draw, zoomfunction, NULL));
  PetscCall(PetscDrawDestroy(&draw));
  PetscCall(PetscFinalize());
  return 0;
}

/*TEST

   build:
     requires: x

   test:
     output_file: output/ex1_1.out

   test:
     suffix: db
     args: -draw_double_buffer 0
     output_file: output/ex1_1.out

   test:
     suffix: df
     args: -draw_fast
     output_file: output/ex1_1.out

   test:
     suffix: dv
     args: -draw_virtual
     output_file: output/ex1_1.out

TEST*/