diff options
| -rw-r--r-- | svg-flatten/src/svg_geom.cpp | 39 |
1 files changed, 31 insertions, 8 deletions
diff --git a/svg-flatten/src/svg_geom.cpp b/svg-flatten/src/svg_geom.cpp index a36c881..3825775 100644 --- a/svg-flatten/src/svg_geom.cpp +++ b/svg-flatten/src/svg_geom.cpp @@ -122,14 +122,37 @@ static void dehole_polytree_worker(PolyNode &ptree, Paths &out, queue<PolyTree> /* Find a viable cut: Cut from top-left bounding box corner, through two subsequent points on the hole * outline and to top-right bbox corner. */ IntRect bbox = c.GetBounds(); - Path tri = { { bbox.left, bbox.top }, nod->Childs[0]->Contour[0], nod->Childs[0]->Contour[1], { bbox.right, bbox.top } }; - c.AddPath(tri, ptClip, true); - - c.StrictlySimple(true); - /* Execute twice, once for intersection fragment and once for difference fragment. Note that this will yield - * at least two, but possibly more polygons. */ - c.Execute(ctDifference, todo.emplace(), pftNonZero); - c.Execute(ctIntersection, todo.emplace(), pftNonZero); + + /* Clipper might return a polygon with a zero-length, or an exactly vertical outline segment. We iterate + * until we find a point that has a different X coordinate than our starting point. If we can't find one + * because the polygon only consists only of points on a vertical line, we can safely discard it and do + * nothing since it has zero area anyway. */ + for (size_t i=0; i<nod->Childs[0]->Contour.size(); i++) { + if (nod->Childs[0]->Contour[i].X == nod->Childs[0]->Contour[0].X) { + continue; + } + + /* We now have found that Contour[0] - Contour[i] has a non-zero horizontal component, and is a + * candidate for our cut. However, we have to make sure that the first point is left (lower X + * coordinate) of the second point, or the cutting polygon we create here would have a + * self-intersection, which with high likelihood would lead to a new hole being created when cutting. + */ + int a=0, b=i; + if (nod->Childs[0]->Contour[i].X < nod->Childs[0]->Contour[0].X) { + /* Swap points */ + a = i; + b = 0; + } + Path tri = { { bbox.left, bbox.top }, nod->Childs[0]->Contour[a], nod->Childs[0]->Contour[b], { bbox.right, bbox.top } }; + c.AddPath(tri, ptClip, true); + + /* Execute twice, once for intersection fragment and once for difference fragment. Note that this will yield + * at least two, but possibly more polygons. */ + c.StrictlySimple(true); + c.Execute(ctDifference, todo.emplace(), pftNonZero); + c.Execute(ctIntersection, todo.emplace(), pftNonZero); + break; + } } } } |