1 files changed, 72 insertions, 0 deletions
diff --git a/layout/generic/nsIntervalSet.h b/layout/generic/nsIntervalSet.h
new file mode 100644
index 0000000000..0d89357bd7
--- /dev/null
+++ b/layout/generic/nsIntervalSet.h
@@ -0,0 +1,72 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+// vim:cindent:ts=8:et:sw=4:
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* a set of ranges on a number-line */
+
+#ifndef nsIntervalSet_h___
+#define nsIntervalSet_h___
+
+#include "nsCoord.h"
+
+namespace mozilla {
+class PresShell;
+}  // namespace mozilla
+
+/*
+ * A list-based class (hopefully tree-based when I get around to it)
+ * for representing a set of ranges on a number-line.
+ */
+class nsIntervalSet {
+ public:
+  typedef nscoord coord_type;
+
+  explicit nsIntervalSet(mozilla::PresShell* aPresShell);
+  ~nsIntervalSet();
+
+  /*
+   * Include the interval [aBegin, aEnd] in the set.
+   *
+   * Removal of intervals added is not supported because that would
+   * require keeping track of the individual intervals that were
+   * added (nsIntervalMap should do that).  It would be simple to
+   * implement ExcludeInterval if anyone wants it, though.
+   */
+  void IncludeInterval(coord_type aBegin, coord_type aEnd);
+
+  /*
+   * Are _some_ points in [aBegin, aEnd] contained within the set
+   * of intervals?
+   */
+  bool Intersects(coord_type aBegin, coord_type aEnd) const;
+
+  /*
+   * Are _all_ points in [aBegin, aEnd] contained within the set
+   * of intervals?
+   */
+  bool Contains(coord_type aBegin, coord_type aEnd) const;
+
+  bool IsEmpty() const { return !mList; }
+
+ private:
+  class Interval {
+   public:
+    Interval(coord_type aBegin, coord_type aEnd)
+        : mBegin(aBegin), mEnd(aEnd), mPrev(nullptr), mNext(nullptr) {}
+
+    coord_type mBegin;
+    coord_type mEnd;
+    Interval* mPrev;
+    Interval* mNext;
+  };
+
+  void* AllocateInterval();
+  void FreeInterval(Interval* aInterval);
+
+  Interval* mList;
+  mozilla::PresShell* mPresShell;
+};
+
+#endif  // !defined(nsIntervalSet_h___)