Added the bulk of the algorithm for GPU accelerated 2D vector curve...

core/cross/gpu2d/path_processor.h

+/*
+ * Copyright 2010, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+// The main entry point for Loop and Blinn's GPU accelerated curve
+// rendering algorithm.
+
+#ifndef O3D_CORE_CROSS_GPU2D_PATH_PROCESSOR_H_
+#define O3D_CORE_CROSS_GPU2D_PATH_PROCESSOR_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+
+class SkPath;
+
+namespace o3d {
+namespace gpu2d {
+
+class Arena;
+class Contour;
+class PathCache;
+class Segment;
+
+// The PathProcessor turns an SkPath (assumed to contain one or more
+// closed regions) into a set of exterior and interior triangles,
+// stored in the PathCache. The exterior triangles have associated 3D
+// texture coordinates which are used to evaluate the curve's
+// inside/outside function on a per-pixel basis. The interior
+// triangles are filled with 100% opacity.
+//
+// Note that the fill style and management of multiple layers are
+// separate concerns, handled at a higher level with shaders and
+// polygon offsets.
+class PathProcessor {
+ public:
+  PathProcessor();
+  explicit PathProcessor(Arena* arena);
+  ~PathProcessor();
+
+  // Transforms the given path into a triangle mesh for rendering
+  // using Loop and Blinn's shader, placing the result into the given
+  // PathCache.
+  void Process(const SkPath& path, PathCache* cache);
+
+  // Enables or disables verbose logging in debug mode.
+  void set_verbose_logging(bool on_or_off);
+
+ private:
+  // Builds a list of contours for the given path.
+  void BuildContours(const SkPath& path);
+
+  // Determines whether the left or right side of each contour should
+  // be filled.
+  void DetermineSidesToFill();
+
+  // Determines whether the given (closed) contour is oriented
+  // clockwise or counterclockwise.
+  void DetermineOrientation(Contour* contour);
+
+  // Subdivides the curves so that there are no overlaps of the
+  // triangles associated with the curves' control points.
+  void SubdivideCurves();
+
+  // Helper function used during curve subdivision.
+  void ConditionallySubdivide(Segment* seg,
+                              std::vector<Segment*>* next_segments);
+
+  // Tessellates the interior regions of the contours.
+  void TessellateInterior(PathCache* cache);
+
+  // For debugging the orientation computation. Returns all of the
+  // segments overlapping the given Y coordinate.
+  std::vector<Segment*> AllSegmentsOverlappingY(float y);
+
+  // For debugging the curve subdivision algorithm. Subdivides the
+  // curves using an alternate, slow (O(n^3)) algorithm.
+  void SubdivideCurvesSlow();
+
+  // Arena from which to allocate temporary objects.
+  Arena* arena_;
+
+  // Whether to delete the arena upon deletion of the PathProcessor.
+  bool should_delete_arena_;
+
+  // The contours described by the path.
+  std::vector<Contour*> contours_;
+
+  // Whether or not to perform verbose logging in debug mode.
+  bool verbose_logging_;
+
+  DISALLOW_COPY_AND_ASSIGN(PathProcessor);
+};
+
+}  // namespace gpu2d
+}  // namespace o3d
+
+#endif  // O3D_CORE_CROSS_GPU2D_PATH_PROCESSOR_H_
+