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src/svg_geom.cpp

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+/*
+ * This program source code file is part of KICAD, a free EDA CAD application.
+ *
+ * Copyright (C) 2021 Jan Sebastian Götte <kicad@jaseg.de>
+ * Copyright (C) 2021 KiCad Developers, see AUTHORS.txt for contributors.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, you may find one here:
+ * http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+ * or you may search the http://www.gnu.org website for the version 2 license,
+ * or you may write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
+ */
+
+#include "svg_geom.h"
+
+#include <cmath>
+#include <string>
+#include <sstream>
+#include <assert.h>
+#include <cairo.h>
+#include "svg_import_defs.h"
+
+using namespace ClipperLib;
+using namespace std;
+
+/* Get bounding box of a Clipper Paths */
+IntRect svg_plugin::get_paths_bounds(const Paths &paths) {
+    if (paths.empty()) {
+        return {0, 0, 0, 0};
+    }
+
+    if (paths[0].empty()) {
+        return {0, 0, 0, 0};
+    }
+
+    IntPoint p0 = paths[0][0];
+    cInt x0=p0.X, y0=p0.Y, x1=p0.X, y1=p0.Y;
+
+    for (const Path &p : paths) {
+        for (const IntPoint ip : p) {
+            if (ip.X < x0)
+                x0 = ip.X;
+
+            if (ip.Y < y0)
+                y0 = ip.Y;
+
+            if (ip.X > x1)
+                x1 = ip.X;
+
+            if (ip.Y > y1)
+                y1 = ip.Y;
+        }
+    }
+
+    return {x0, y0, x1, y1};
+}
+
+enum ClipperLib::PolyFillType svg_plugin::clipper_fill_rule(const pugi::xml_node &node) {
+    string val(node.attribute("fill-rule").value());
+    if (val == "evenodd")
+        return ClipperLib::pftEvenOdd;
+    else
+        return ClipperLib::pftNonZero; /* default */
+}
+
+enum ClipperLib::EndType svg_plugin::clipper_end_type(const pugi::xml_node &node) {
+    string val(node.attribute("stroke-linecap").value());
+    if (val == "round")
+        return ClipperLib::etOpenRound;
+
+    if (val == "square")
+        return ClipperLib::etOpenSquare;
+
+    return ClipperLib::etOpenButt;
+}
+
+enum ClipperLib::JoinType svg_plugin::clipper_join_type(const pugi::xml_node &node) {
+    string val(node.attribute("stroke-linejoin").value());
+    if (val == "round")
+        return ClipperLib::jtRound;
+
+    if (val == "bevel")
+        return ClipperLib::jtSquare;
+
+    return ClipperLib::jtMiter;
+}
+
+/* Take a Clipper polytree, i.e. a description of a set of polygons, their holes and their inner polygons, and remove
+ * all holes from it. We remove holes by splitting each polygon that has a hole into two or more pieces so that the hole
+ * is no more. These pieces perfectly fit each other so there is no visual or functional difference.
+ */
+void svg_plugin::dehole_polytree(PolyNode &ptree, Paths &out) {
+    for (int i=0; i<ptree.ChildCount(); i++) {
+        PolyNode *nod = ptree.Childs[i];
+        assert(nod);
+        assert(!nod->IsHole());
+
+        /* First, recursively process inner polygons. */
+        for (int j=0; j<nod->ChildCount(); j++) {
+            PolyNode *child = nod->Childs[j];
+            assert(child);
+            assert(child->IsHole());
+
+            if (child->ChildCount() > 0) {
+                dehole_polytree(*child, out);
+            }
+        }
+
+        if (nod->ChildCount() == 0) {
+            out.push_back(nod->Contour);
+
+        } else {
+
+            /* Do not add children's children, those were handled in the recursive call above */
+            Clipper c;
+            c.AddPath(nod->Contour, ptSubject, /* closed= */ true);
+            for (int k=0; k<nod->ChildCount(); k++) {
+                c.AddPath(nod->Childs[k]->Contour, ptSubject, /* closed= */ true);
+            }
+
+            /* 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);
+
+            PolyTree solution;
+            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, solution, pftNonZero);
+            dehole_polytree(solution, out);
+
+            c.Execute(ctIntersection, solution, pftNonZero);
+            dehole_polytree(solution, out);
+        }
+    }
+}
+
+/* Intersect two clip paths. Both must share a coordinate system. */
+void svg_plugin::combine_clip_paths(Paths &in_a, Paths &in_b, Paths &out) {
+    Clipper c;
+    c.StrictlySimple(true);
+    c.AddPaths(in_a, ptClip, /* closed */ true);
+    c.AddPaths(in_b, ptSubject, /* closed */ true);
+    /* Nonzero fill since both input clip paths must already have been preprocessed by clipper. */
+    c.Execute(ctIntersection, out, pftNonZero);
+}
+
+/* Transform given clipper paths under the given cairo transform. If no transform is given, use cairo's current
+ * user-to-device transform. */
+void svg_plugin::transform_paths(cairo_t *cr, Paths &paths, cairo_matrix_t *mat) {
+    cairo_save(cr);
+    if (mat != nullptr) {
+        cairo_set_matrix(cr, mat);
+    }
+    
+    for (Path &p : paths) {
+        transform(p.begin(), p.end(), p.begin(),
+                [cr](IntPoint p) -> IntPoint {
+                    double x = p.X / clipper_scale, y = p.Y / clipper_scale;
+                    cairo_user_to_device(cr, &x, &y);
+                    return { (cInt)round(x * clipper_scale), (cInt)round(y * clipper_scale) };
+                });
+    }
+
+    cairo_restore(cr);
+}
+
+