From a0c43e4df998137c94996e799d96d72d087d1708 Mon Sep 17 00:00:00 2001 From: Joe Neeman Date: Fri, 12 Dec 2008 21:34:14 -0800 Subject: [PATCH] Add some comments to Beam::get_beam_segments. --- lily/beam.cc | 33 ++++++++++++++++++++++++++++++--- 1 file changed, 30 insertions(+), 3 deletions(-) diff --git a/lily/beam.cc b/lily/beam.cc index c8adf5694d..b2f015148a 100644 --- a/lily/beam.cc +++ b/lily/beam.cc @@ -341,6 +341,12 @@ Beam::get_beam_segments (Grob *me_grob, Grob **common) Position_stem_segments_map stem_segments; Real lt = me->layout ()->get_dimension (ly_symbol2scm ("line-thickness")); + /* There are two concepts of "rank" that are used in the following code. + The beam_rank is the vertical position of the beam (larger numbers are + closer to the noteheads). Beam_stem_segment.rank_, on the other hand, + is the horizontal position of the segment (this is incremented by two + for each stem; the beam segment on the right side of the stem has + a higher rank (by one) than its neighbour to the left). */ Slice ranks; for (vsize i = 0; i < stems.size (); i++) { @@ -351,6 +357,10 @@ Beam::get_beam_segments (Grob *me_grob, Grob **common) Direction d = LEFT; do { + // Find the maximum and minimum beam ranks. + // Given that RANKS is never reset to empty, the interval will always be + // smallest for the left beamlet of the first stem, and then it might grow. + // Do we really want this? (It only affects the tremolo gaps) --jneem for (SCM s = index_get_cell (beaming, d); scm_is_pair (s); s = scm_cdr (s)) { @@ -400,15 +410,26 @@ Beam::get_beam_segments (Grob *me_grob, Grob **common) Beam_segment current; + // Iterate over all of the segments of the current beam rank, + // merging the adjacent Beam_stem_segments into one Beam_segment + // when appropriate. int vertical_count = (*i).first; for (vsize j = 0; j < segs.size (); j++) { - /* - event_dir == LEFT: left edge of a beamsegment. - */ + // Keeping track of the different directions here is a little tricky. + // segs[j].dir_ is the direction of the beam segment relative to the stem + // (ie. segs[j].dir_ == LEFT if the beam segment sticks out to the left of + // its stem) whereas event_dir refers to the edge of the beam segment that + // we are currently looking at (ie. if segs[j].dir_ == event_dir then we + // are looking at that edge of the beam segment that is furthest from its + // stem). Direction event_dir = LEFT; do { + // TODO: make names clearer? --jneem + // on_line_bound: whether the current segment is on the boundary of the WHOLE beam + // on_beam_bound: whether the current segment is on the boundary of just that part + // of the beam with the current beam_rank bool on_line_bound = (segs[j].dir_ == LEFT) ? segs[j].stem_index_ == 0 : segs[j].stem_index_ == stems.size() - 1; bool on_beam_bound = (event_dir == LEFT) ? j == 0 : @@ -423,11 +444,15 @@ Beam::get_beam_segments (Grob *me_grob, Grob **common) || abs (vertical_count) >= segs[j + event_dir].max_connect_); if (!event) + // Then this edge of the current segment is irrelevent because it will + // be connected with the next segment in the event_dir direction. continue; current.vertical_count_ = vertical_count; current.horizontal_[event_dir] = segs[j].stem_x_; if (segs[j].dir_ == event_dir) + // then we are examining the edge of a beam segment that is furthest + // from its stem. { if (on_line_bound && me->get_bound (event_dir)->break_status_dir ()) @@ -458,6 +483,8 @@ Beam::get_beam_segments (Grob *me_grob, Grob **common) } } else + // we are examining the edge of a beam segment that is closest + // (ie. touching, unless there is a gap) its stem. { current.horizontal_[event_dir] += event_dir * segs[j].width_/2; if (segs[j].gapped_) -- 2.39.2