From 5f8de423f190bbb79a62f804151bc24824fa32d8 Mon Sep 17 00:00:00 2001
From: "Matt A. Tobin" <mattatobin@localhost.localdomain>
Date: Fri, 2 Feb 2018 04:16:08 -0500
Subject: Add m-esr52 at 52.6.0

---
 gfx/layers/BSPTree.h | 106 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 106 insertions(+)
 create mode 100644 gfx/layers/BSPTree.h

(limited to 'gfx/layers/BSPTree.h')

diff --git a/gfx/layers/BSPTree.h b/gfx/layers/BSPTree.h
new file mode 100644
index 000000000..24a82f2ac
--- /dev/null
+++ b/gfx/layers/BSPTree.h
@@ -0,0 +1,106 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * 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/. */
+
+#ifndef MOZILLA_LAYERS_BSPTREE_H
+#define MOZILLA_LAYERS_BSPTREE_H
+
+#include "mozilla/gfx/Polygon.h"
+#include "mozilla/Move.h"
+#include "mozilla/UniquePtr.h"
+#include "nsTArray.h"
+
+#include <deque>
+
+namespace mozilla {
+namespace layers {
+
+class Layer;
+
+// Represents a layer that might have a non-rectangular geometry.
+struct LayerPolygon {
+  explicit LayerPolygon(Layer *aLayer)
+    : layer(aLayer) {}
+
+  LayerPolygon(Layer *aLayer,
+               gfx::Polygon3D&& aGeometry)
+    : layer(aLayer), geometry(Some(aGeometry)) {}
+
+  LayerPolygon(Layer *aLayer,
+               nsTArray<gfx::Point3D>&& aPoints, const gfx::Point3D& aNormal)
+    : layer(aLayer), geometry(Some(gfx::Polygon3D(Move(aPoints), aNormal))) {}
+
+  Layer *layer;
+  Maybe<gfx::Polygon3D> geometry;
+};
+
+LayerPolygon PopFront(std::deque<LayerPolygon>& aLayers);
+
+// Represents a node in a BSP tree. The node contains at least one layer with
+// associated geometry that is used as a splitting plane, and at most two child
+// nodes that represent the splitting planes that further subdivide the space.
+struct BSPTreeNode {
+  explicit BSPTreeNode(LayerPolygon&& layer)
+  {
+    layers.push_back(Move(layer));
+  }
+
+  const gfx::Polygon3D& First() const
+  {
+    MOZ_ASSERT(layers[0].geometry);
+    return *layers[0].geometry;
+  }
+
+  UniquePtr<BSPTreeNode> front;
+  UniquePtr<BSPTreeNode> back;
+  std::deque<LayerPolygon> layers;
+};
+
+// BSPTree class takes a list of layers as an input and uses binary space
+// partitioning algorithm to create a tree structure that can be used for
+// depth sorting.
+//
+// Sources for more information:
+// https://en.wikipedia.org/wiki/Binary_space_partitioning
+// ftp://ftp.sgi.com/other/bspfaq/faq/bspfaq.html
+class BSPTree {
+public:
+  // This constructor takes the ownership of layers in the given list.
+  explicit BSPTree(std::deque<LayerPolygon>& aLayers)
+  {
+    MOZ_ASSERT(!aLayers.empty());
+    mRoot.reset(new BSPTreeNode(PopFront(aLayers)));
+
+    BuildTree(mRoot, aLayers);
+  }
+
+  // Returns the root node of the BSP tree.
+  const UniquePtr<BSPTreeNode>& GetRoot() const
+  {
+    return mRoot;
+  }
+
+  // Builds and returns the back-to-front draw order for the created BSP tree.
+  nsTArray<LayerPolygon> GetDrawOrder() const
+  {
+    nsTArray<LayerPolygon> layers;
+    BuildDrawOrder(mRoot, layers);
+    return layers;
+  }
+
+private:
+  UniquePtr<BSPTreeNode> mRoot;
+
+  // BuildDrawOrder and BuildTree are called recursively. The depth of the
+  // recursion depends on the amount of polygons and their intersections.
+  void BuildDrawOrder(const UniquePtr<BSPTreeNode>& aNode,
+                      nsTArray<LayerPolygon>& aLayers) const;
+  void BuildTree(UniquePtr<BSPTreeNode>& aRoot,
+                 std::deque<LayerPolygon>& aLayers);
+};
+
+} // namespace layers
+} // namespace mozilla
+
+#endif /* MOZILLA_LAYERS_BSPTREE_H */
-- 
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