Value of begin_shapes_rec variable changes if new shapes added to cell.

Comments

• Matthias

  January 24

  Hi Giovanni,

  yes, that is intended.

  Actually, when you create a Region with a recursive shape iterator, it becomes a special kind of Region called an "original layer region". It is not a replica of the layer, but represents the actual layer inside the source layout. This feature is preventing unnecessary and expensive copies. Also, such a region remains hierarchical, hence saving memory.

  In order to "freeze" a Region, you can use "flatten". But beware, this will do what it says and may explode your hierarchy.

  For example, this code reproduces your problem:

  ly = pya.Layout()
  l1 = ly.layer(1, 0)
  top = ly.create_cell("TOP")
  
  top.shapes(l1).insert(pya.Box(0, 0, 100, 100))
  
  r1 = pya.Region(top.begin_shapes_rec(l1))
  
  top.shapes(l1).insert(pya.Box(200, 0, 300, 100))
  
  r2 = pya.Region(top.begin_shapes_rec(l1))
  
  print(r1)
  print(r2)
  

  As you experienced, it will print the same shapes, although the second shape was added after the region 1 was created:

  (0,0;0,100;100,100;100,0);(200,0;200,100;300,100;300,0)
  (0,0;0,100;100,100;100,0);(200,0;200,100;300,100;300,0)
  

  With "flatten", the copy is frozen:

  ly = pya.Layout()
  l1 = ly.layer(1, 0)
  top = ly.create_cell("TOP")
  
  top.shapes(l1).insert(pya.Box(0, 0, 100, 100))
  
  r1 = pya.Region(top.begin_shapes_rec(l1)).flatten()
  
  top.shapes(l1).insert(pya.Box(200, 0, 300, 100))
  
  r2 = pya.Region(top.begin_shapes_rec(l1)).flatten()
  
  print(r1)
  print(r2)
  

  and it prints:

  (0,0;0,100;100,100;100,0)
  (0,0;0,100;100,100;100,0);(200,0;200,100;300,100;300,0)
  

  Matthias
• Giovanni

  January 27

  Thank you Matthias for the detailed explanation.
  I wil change my code and make shure that I add .flatten() when I need to freeze the content of the region.

  Thank you again
  Best regards
  Giovanni