Update to 2Geom revision 2396

(bzr r14059.2.16)

1 files changed, 220 insertions, 0 deletions

diff --git a/src/2geom/sweeper.h b/src/2geom/sweeper.h
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+/** @file
+ * @brief Class for implementing sweepline algorithms
+ *//*
+  * Authors:
+  *   Krzysztof Kosiński <tweenk.pl@gmail.com>
+  *
+  * Copyright 2015 Authors
+  *
+  * This library is free software; you can redistribute it and/or
+  * modify it either under the terms of the GNU Lesser General Public
+  * License version 2.1 as published by the Free Software Foundation
+  * (the "LGPL") or, at your option, under the terms of the Mozilla
+  * Public License Version 1.1 (the "MPL"). If you do not alter this
+  * notice, a recipient may use your version of this file under either
+  * the MPL or the LGPL.
+  *
+  * You should have received a copy of the LGPL along with this library
+  * in the file COPYING-LGPL-2.1; if not, write to the Free Software
+  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+  * You should have received a copy of the MPL along with this library
+  * in the file COPYING-MPL-1.1
+  *
+  * The contents of this file are subject to the Mozilla Public License
+  * Version 1.1 (the "License"); you may not use this file except in
+  * compliance with the License. You may obtain a copy of the License at
+  * http://www.mozilla.org/MPL/
+  *
+  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
+  * OF ANY KIND, either express or implied. See the LGPL or the MPL for
+  * the specific language governing rights and limitations.
+  */
+
+#ifndef LIB2GEOM_SEEN_SWEEPER_H
+#define LIB2GEOM_SEEN_SWEEPER_H
+
+#include <2geom/coord.h>
+#include <algorithm>
+#include <vector>
+#include <boost/intrusive/list.hpp>
+#include <boost/range/algorithm/heap_algorithm.hpp>
+
+namespace Geom {
+
+struct IntervalSweepTraits {
+    typedef Interval Bound;
+    typedef std::less<Coord> Compare;
+    inline static Coord entry_value(Bound const &b) { return b.min(); }
+    inline static Coord exit_value(Bound const &b) { return b.max(); }
+};
+
+template <Dim2 d>
+struct RectSweepTraits {
+    typedef Rect Bound;
+    typedef std::less<Coord> Compare;
+    inline static Coord entry_value(Bound const &b) { return b[d].min(); }
+    inline static Coord exit_value(Bound const &b) { return b[d].max(); }
+};
+
+/** @brief Generic sweepline algorithm.
+ *
+ * This class encapsulates an algorithm that sorts the objects according
+ * to their bounds, then moves an imaginary line (sweepline) over those
+ * bounds from left to right. Objects are added to the active list when
+ * the line starts intersecting their bounds, and removed when it completely
+ * passes over them.
+ *
+ * To use this, create a derived class and reimplement the _enter()
+ * and/or _leave() virtual functions, insert all the objects,
+ * and finally call process(). You can specify the bound type
+ * and how it should be accessed by defining a custom SweepTraits class.
+ *
+ * Look in path.cpp for example usage.
+ */
+template <typename Item, typename SweepTraits = IntervalSweepTraits>
+class Sweeper {
+public:
+    typedef typename SweepTraits::Bound Bound;
+
+    Sweeper() {}
+
+    void insert(Bound const &bound, Item const &item) {
+        assert(!(typename SweepTraits::Compare()(
+            SweepTraits::exit_value(bound),
+            SweepTraits::entry_value(bound))));
+        _items.push_back(Record(bound, item));
+    }
+
+    template <typename Iter, typename BoundFunc>
+    void insert(Iter first, Iter last, BoundFunc f = BoundFunc()) {
+        for (; first != last; ++first) {
+            Bound b = f(*first);
+            assert(!(typename SweepTraits::Compare()(
+                SweepTraits::exit_value(b),
+                SweepTraits::entry_value(b))));
+            _items.push_back(Record(b, *first));
+        }
+    }
+
+    /** @brief Process entry and exit events.
+     * This will iterate over all inserted items, calling the virtual protected
+     * functions _enter() and _leave() according to the order of the boundaries
+     * of each item. */
+    void process() {
+        if (_items.empty()) return;
+
+        typename SweepTraits::Compare cmp;
+
+        for (RecordIter i = _items.begin(); i != _items.end(); ++i) {
+            _entry_events.push_back(i);
+            _exit_events.push_back(i);
+        }
+        boost::make_heap(_entry_events, _entry_heap_compare);
+        boost::make_heap(_exit_events, _exit_heap_compare);
+        boost::pop_heap(_entry_events, _entry_heap_compare);
+        boost::pop_heap(_exit_events, _exit_heap_compare);
+
+        RecordIter next_entry = _entry_events.back();
+        RecordIter next_exit = _exit_events.back();
+        _entry_events.pop_back();
+        _exit_events.pop_back();
+
+        while (next_entry != _items.end() || next_exit != _items.end()) {
+            assert(next_exit != _items.end());
+
+            if (next_entry == _items.end() ||
+                cmp(SweepTraits::exit_value(next_exit->bound),
+                    SweepTraits::entry_value(next_entry->bound)))
+            {
+                // exit event - remove record from active list
+                _leave(*next_exit);
+                _active_items.erase(_active_items.iterator_to(*next_exit));
+                if (!_exit_events.empty()) {
+                    boost::pop_heap(_exit_events, _exit_heap_compare);
+                    next_exit = _exit_events.back();
+                    _exit_events.pop_back();
+                } else {
+                    next_exit = _items.end();
+                    // we should end the loop after this happens
+                }
+            } else {
+                // entry event - add record to active list
+                _enter(*next_entry);
+                _active_items.push_back(*next_entry);
+                if (!_entry_events.empty()) {
+                    boost::pop_heap(_entry_events, _entry_heap_compare);
+                    next_entry = _entry_events.back();
+                    _entry_events.pop_back();
+                } else {
+                    next_entry = _items.end();
+                }
+            }
+        }
+
+        assert(_active_items.empty());
+    }
+
+protected:
+    /// The item and its sweepline boundary.
+    struct Record {
+        boost::intrusive::list_member_hook<> _hook;
+        Bound bound;
+        Item item;
+
+        Record(Bound const &b, Item const &i)
+            : bound(b), item(i)
+        {}
+    };
+    typedef typename std::vector<Record>::iterator RecordIter;
+
+    typedef boost::intrusive::list
+    < Record
+    , boost::intrusive::member_hook
+        < Record
+        , boost::intrusive::list_member_hook<>
+        , &Record::_hook
+        >
+    > RecordList;
+
+    /** @brief Enter an item record.
+     * Override this to process an item as it is about to enter the active list.
+     * When called, the passed record will not be part of the active list. */
+    virtual void _enter(Record const &) {}
+    /** @brief Leave an item record.
+     * Override this to process an item as it is about to leave the active list.
+     * When called, the passed record will be part of the active list. */
+    virtual void _leave(Record const &) {}
+
+    /// The list of all item records undergoing sweeping.
+    std::vector<Record> _items;
+    /// The list of active item records.
+    RecordList _active_items;
+
+private:
+    inline static bool _entry_heap_compare(RecordIter a, RecordIter b) {
+        typename SweepTraits::Compare cmp;
+        return cmp(SweepTraits::entry_value(b->bound), SweepTraits::entry_value(a->bound));
+    }
+    inline static bool _exit_heap_compare(RecordIter a, RecordIter b) {
+        typename SweepTraits::Compare cmp;
+        return cmp(SweepTraits::exit_value(b->bound), SweepTraits::exit_value(a->bound));
+    }
+
+    std::vector<RecordIter> _entry_events;
+    std::vector<RecordIter> _exit_events;
+};
+
+} // namespace Geom
+
+#endif // !LIB2GEOM_SEEN_SWEEPER_H
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :