WIP: flat region tests, partially working

src/db/db/dbAsIfFlatRegion.cc

@@ -364,6 +364,7 @@ AsIfFlatRegion::filtered (const PolygonFilterBase &filter) const
     }
   }
 
+  new_region->set_is_merged (true);
   return new_region.release ();
 }
 
@@ -1017,7 +1018,7 @@ AsIfFlatRegion::snapped (db::Coord gx, db::Coord gy)
     throw tl::Exception (tl::to_string (tr ("Grid snap requires a positive grid value")));
   }
 
-  std::unique_ptr<FlatRegion> new_region (new FlatRegion (merged_semantics ()));
+  std::unique_ptr<FlatRegion> new_region (new FlatRegion ());
 
   gx = std::max (db::Coord (1), gx);
   gy = std::max (db::Coord (1), gy);
@@ -1386,7 +1387,7 @@ AsIfFlatRegion::sized (coord_type dx, coord_type dy, unsigned int mode) const
   } else if (! merged_semantics () || is_merged ()) {
 
     //  Generic case
-    std::unique_ptr<FlatRegion> new_region (new FlatRegion (false /*output isn't merged*/));
+    std::unique_ptr<FlatRegion> new_region (new FlatRegion ());
 
     db::ShapeGenerator pc (new_region->raw_polygons (), false);
     db::PolygonGenerator pg (pc, false, true);
@@ -1395,6 +1396,12 @@ AsIfFlatRegion::sized (coord_type dx, coord_type dy, unsigned int mode) const
       sf.put (*p);
     }
 
+    //  in case of negative sizing the output polygons will still be merged (on positive sizing they might
+    //  overlap after size and are not necessarily merged)
+    if (dx < 0 && dy < 0 && is_merged ()) {
+      new_region->set_is_merged (true);
+    }
+
     return new_region.release ();
 
   } else {
@@ -1416,7 +1423,7 @@ AsIfFlatRegion::sized (coord_type dx, coord_type dy, unsigned int mode) const
       ep.insert (*p, n);
     }
 
-    std::unique_ptr<FlatRegion> new_region (new FlatRegion (false /*output isn't merged*/));
+    std::unique_ptr<FlatRegion> new_region (new FlatRegion ());
     db::ShapeGenerator pc (new_region->raw_polygons (), true /*clear*/);
     db::PolygonGenerator pg2 (pc, false /*don't resolve holes*/, true /*min. coherence*/);
     db::SizingPolygonFilter siz (pg2, dx, dy, mode);
@@ -1424,6 +1431,12 @@ AsIfFlatRegion::sized (coord_type dx, coord_type dy, unsigned int mode) const
     db::BooleanOp op (db::BooleanOp::Or);
     ep.process (pg, op);
 
+    //  in case of negative sizing the output polygons will still be merged (on positive sizing they might
+    //  overlap after size and are not necessarily merged)
+    if (dx < 0 && dy < 0 && merged_semantics ()) {
+      new_region->set_is_merged (true);
+    }
+
     return new_region.release ();
 
   }

src/db/unit_tests/dbAsIfFlatRegionTests.cc

@@ -350,7 +350,7 @@ TEST(5_BoolXOR)
   db::Region r42xor3  = r42 ^ r3;
   db::Region r42xor42 = r42 ^ r42;
 
-  EXPECT_EQ (r2xor3.is_merged (), false);
+  EXPECT_EQ (r2xor3.is_merged (), true);
 
   db::Layout target;
   unsigned int target_top_cell_index = target.add_cell (ly.cell_name (top_cell_index));