delete_cells slow in some cases

[klayoutmatthias]

This is related to this discussion: https://www.klayout.de/forum/discussion/2147/find-and-delete-the-empty-cells-in-the-gds#latest

It appears as if this method call:

ly.delete_cells([ c.cell_index() for c in ly.each_cell() if c.is_empty() ])

is very slow sometimes.

[klayoutmatthias]

There is a simple workaround:

  ly.start_changes()
  ly.delete_cells([ c.cell_index() for c in ly.each_cell() if c.is_empty() ])
  ly.end_changes()

However, the delete_cells method should internally disable layout updates.