+ /*
+ * The following explanations are mostly taken from the article
+ *
+ * Real-Time Grid Fitting of Typographic Outlines
+ *
+ * by David Turner and Werner Lemberg
+ *
+ * http://www.tug.org/TUGboat/Articles/tb24-3/lemberg.pdf
+ *
+ *
+ * Segments
+ *
+ * `af_{cjk,latin,...}_hints_compute_segments' are the functions to
+ * find segments in an outline. A segment is a series of consecutive
+ * points that are approximately aligned along a coordinate axis. The
+ * analysis to do so is specific to a script.
+ *
+ * A segment must have at least two points, except in the case of
+ * `fake' segments that are generated to hint metrics appropriately,
+ * and which consist of a single point.
+ *
+ *
+ * Edges
+ *
+ * As soon as segments are defined, the auto-hinter groups them into
+ * edges. An edge corresponds to a single position on the main
+ * dimension that collects one or more segments (allowing for a small
+ * threshold).
+ *
+ * The auto-hinter first tries to grid fit edges, then to align
+ * segments on the edges unless it detects that they form a serif.
+ *
+ * `af_{cjk,latin,...}_hints_compute_edges' are the functions to find
+ * edges; they are specific to a script.
+ *
+ *
+ * A H
+ * | |
+ * | |
+ * | |
+ * | |
+ * C | | F
+ * +------<-----+ +-----<------+
+ * | B G |
+ * | |
+ * | |
+ * +--------------->------------------+
+ * D E
+ *
+ *
+ * Stems
+ *
+ * Segments need to be `linked' to other ones in order to detect stems.
+ * A stem is made of two segments that face each other in opposite
+ * directions and that are sufficiently close to each other. Using
+ * vocabulary from the TrueType specification, stem segments form a
+ * `black distance'.
+ *
+ * In the above ASCII drawing, the horizontal segments are BC, DE, and
+ * FG; the vertical segments are AB, CD, EF, and GH.
+ *
+ * Each segment has at most one `best' candidate to form a black
+ * distance, or no candidate at all. Notice that two distinct segments
+ * can have the same candidate, which frequently means a serif.
+ *
+ * A stem is recognized by the following condition:
+ *
+ * best segment_1 = segment_2 && best segment_2 = segment_1
+ *
+ * The best candidate is stored in field `link' in structure
+ * `AF_Segment'.
+ *
+ * Stems are detected by `af_{cjk,latin,...}_hint_edges'.
+ *
+ * In the above ASCII drawing, the best candidate for both AB and CD is
+ * GH, while the best candidate for GH is AB. Similarly, the best
+ * candidate for EF and GH is AB, while the best candidate for AB is
+ * GH.
+ *
+ *
+ * Serifs
+ *
+ * On the opposite, a serif has
+ *
+ * best segment_1 = segment_2 && best segment_2 != segment_1
+ *
+ * where segment_1 corresponds to the serif segment (CD and EF in the
+ * above ASCII drawing).
+ *
+ * The best candidate is stored in field `serif' in structure
+ * `AF_Segment' (and `link' is set to NULL).
+ *
+ * Serifs are detected by `af_{cjk,latin,...}_hint_edges'.
+ *
+ *
+ * Touched points
+ *
+ * A point is called `touched' if it has been processed somehow by the
+ * auto-hinter. It basically means that it shouldn't be moved again
+ * (or moved only under certain constraints to preserve the already
+ * applied processing).
+ *
+ *
+ * Flat and round segments
+ *
+ * Segments are `round' or `flat', depending on the series of points
+ * that define them. A segment is round if the next and previous point
+ * of an extremum (which can be either a single point or sequence of
+ * points) are both conic or cubic control points. Otherwise, a
+ * segment with an extremum is flat.
+ *
+ *
+ * Strong Points
+ *
+ * Experience has shown that points which are not part of an edge need
+ * to be interpolated linearly between their two closest edges, even if
+ * these are not part of the contour of those particular points.
+ * Typical candidates for this are
+ *
+ * - angle points (i.e., points where the `in' and `out' direction
+ * differ greatly)
+ *
+ * - inflection points (i.e., where the `in' and `out' angles are the
+ * same, but the curvature changes sign)
+ *
+ * `af_glyph_hints_align_strong_points' is the function which takes
+ * care of such situations; it is equivalent to the TrueType `IP'
+ * hinting instruction.
+ *
+ *
+ * Weak Points
+ *
+ * Other points in the outline must be interpolated using the
+ * coordinates of their previous and next unfitted contour neighbours.
+ * These are called `weak points' and are touched by the function
+ * `af_glyph_hints_align_weak_points', equivalent to the TrueType `IUP'
+ * hinting instruction. Typical candidates are control points and
+ * points on the contour without a major direction.
+ *
+ * The major effect is to reduce possible distortion caused by
+ * alignment of edges and strong points, thus weak points are processed
+ * after strong points.
+ */
+
+