Subtracting two polygons in C++

david234589

I know you intentionally don't publish the C++ API, but I have a quick question.

I'm looking at Basic.ROUND_PATH Pcell code, and just need to make a minor modification - so instead of a rounded path it creates two co-linear paths, one wide and one narrow, then subtracts the wide path from the narrow path.

I believe it'd be far easier to do a minor modification of the existing C++ Pcell than to write the whole thing in Ruby from scratch.

So basically if this were Ruby I'd do the following:

    ep = RBA::EdgeProcessor::new
    wide_minus_narrow = ep.boolean_p2p(wide_wire, narrow_wire, RBA::EdgeProcessor::ModeANotB, false, false)
    wide_minus_narrow.each do |p|
      out_cell.shapes(out_layer).insert(p)
    end

Could you perhaps make an exception in this case with your non-API-publishing rule and let me know how I can find out what C++ commands to do that?

Thanks!

david234589

Never mind, I think I figured it out -- so you don't have to break your rules on publicizing C++ APIs :-). However I have another question.

But first, my attempt at the code. Basically I found libBasicStrokedPolygon to be using an edge processor, so it was easy to copy that.

So the only additions to the libBasicRoundPaths is the following..?

/* Existing code */
db::Polygon poly;
poly.assign_hull (hull.begin (), hull.end (), db::cast_op<db::Point, db::DPoint> ());
cell.shapes (layer_ids [p_layer]).insert (poly);

/* New code */
db::Polygon poly2;
poly2 = poly;
cell.shapes (layer_ids [p_layer]).insert (poly2);

std::vector <db::Polygon> shapes;
db::EdgeProcessor ep; 
shapes.clear ();
ep.boolean (poly, poly2, shapes, db::BooleanOp::ANotB, true /*resolve holes*/);

Of course I added these two declarations to the start:

#include "dbPolygonTools.h"
#include "dbEdgeProcessor.h"

Now just missing two small things:

1) How to make poly2 have larger width than poly? So that the ep.boolean actually does something useful? Note that poly2 should be a rounded wire with width w2, converted to polygon. And poly should be a rounded wire with width w, converted to polygon. I just can't see where to set the width.

2) This is a .cc file -- how to compile it to be included with an existing KLayout installation, if possible? Or do I have to build the whole KLayout from scratch with this extra file included?

Thanks!

Matthias

Hi,

Here is a sketch (not tested):

std::vector<db::Polygon> a;
a.push_back (db::Polygon ());
a.back ().assign_hull (hull.begin (), hull.end (), db::cast_op<db::Point, db::DPoint> ());

db::EdgeProcessor ep;

//  Produce small version (d = compensation per edge)
std::vector<db::Polygon> b;
ep.size (a, -d, -d, b);

//  subtract (a = a-b)
ep.boolean (a, b, a, db::EdgeProcessor::ANotB, true /*resolve holes*/);

//  Produce the shapes
for (std::vector<db::Polygon>::const_iterator p = a.begin (); p != a.end (); ++p) {
  cell.shapes (layer_ids [p_layer]).insert (*p);
}

If you change anything in a C++ program, you'll have to rebuild the whole application. You cannot just exchange a single file. If you add a new file, you'll have to include it in the Makefile so it's built too.

Matthias