EnsureCapacity_QuadTreeMesh2D Subroutine

  subroutine EnsureCapacity_QuadTreeMesh2D(this,need)
    !! Grow the node arrays (amortized doubling) so at least `need` nodes fit.
    implicit none
    class(QuadTreeMesh2D),intent(inout) :: this
    integer,intent(in) :: need
    ! Local
    integer :: newCap
    integer,allocatable :: itmp(:),ctmp(:,:)

    if(need <= this%capacity) return

    newCap = this%capacity
    do while(newCap < need)
      newCap = 2*newCap
    enddo

    allocate(itmp(1:newCap))
    itmp = 0; itmp(1:this%nNodes) = this%level(1:this%nNodes); call move_alloc(itmp,this%level)
    allocate(itmp(1:newCap))
    itmp = 0; itmp(1:this%nNodes) = this%parent(1:this%nNodes); call move_alloc(itmp,this%parent)
    allocate(itmp(1:newCap))
    itmp = 0; itmp(1:this%nNodes) = this%quadrant(1:this%nNodes); call move_alloc(itmp,this%quadrant)
    allocate(itmp(1:newCap))
    itmp = 0; itmp(1:this%nNodes) = this%rootElem(1:this%nNodes); call move_alloc(itmp,this%rootElem)
    allocate(ctmp(1:4,1:newCap))
    ctmp = 0; ctmp(1:4,1:this%nNodes) = this%child(1:4,1:this%nNodes); call move_alloc(ctmp,this%child)

    this%capacity = newCap

  endsubroutine EnsureCapacity_QuadTreeMesh2D