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[subset] comment cleanup in hb-repacker.hh

This commit is contained in:
Garret Rieger 2020-11-11 13:50:18 -08:00
parent 832f2b599b
commit d3e2ba7c01
1 changed files with 24 additions and 11 deletions
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35
src/hb-repacker.hh
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@ -288,9 +288,6 @@ struct graph_t
check_success (removed_edges.resize (vertices_.length)); check_success (removed_edges.resize (vertices_.length));
update_incoming_edge_count (); update_incoming_edge_count ();
// Object graphs are in reverse order, the first object is at the end
// of the vector. Since the graph is topologically sorted it's safe to
// assume the first object has no incoming edges.
queue.insert (root_idx (), root ().modified_distance (0)); queue.insert (root_idx (), root ().modified_distance (0));
int new_id = root_idx (); int new_id = root_idx ();
unsigned order = 1; unsigned order = 1;
@ -308,7 +305,7 @@ struct graph_t
// Add the order that the links were encountered to the priority. // Add the order that the links were encountered to the priority.
// This ensures that ties between priorities objects are broken in a consistent // This ensures that ties between priorities objects are broken in a consistent
// way. More specifically this is set up so that if a set of objects have the same // way. More specifically this is set up so that if a set of objects have the same
// distance they'll be added to the topolical order in the order that they are // distance they'll be added to the topological order in the order that they are
// referenced from the parent object. // referenced from the parent object.
queue.insert (link.objidx, queue.insert (link.objidx,
vertices_[link.objidx].modified_distance (order++)); vertices_[link.objidx].modified_distance (order++));
@ -486,7 +483,7 @@ struct graph_t
} }
/* /*
* Finds the distance too each object in the graph * Finds the distance to each object in the graph
* from the initial node. * from the initial node.
*/ */
void update_distances () void update_distances ()
@ -657,17 +654,27 @@ struct graph_t
/* /*
* Re-serialize the provided object graph into the serialization context * Attempts to modify the topological sorting of the provided object graph to
* using BFS (Breadth First Search) to produce the topological ordering. * eliminate offset overflows in the links between objects of the graph. If a
* non-overflowing ordering is found the updated graph is serialized it into the
* provided serialization context.
*
* If necessary the structure of the graph may be modified in ways that do not
* affect the functionality of the graph. For example shared objects may be
* duplicated.
*/ */
inline void inline void
hb_resolve_overflows (const hb_vector_t<hb_serialize_context_t::object_t *>& packed, hb_resolve_overflows (const hb_vector_t<hb_serialize_context_t::object_t *>& packed,
hb_serialize_context_t* c) { hb_serialize_context_t* c) {
// Kahn sort is ~twice as fast as shortest distance sort and works for many fonts // Kahn sort is ~twice as fast as shortest distance sort and works for many fonts
// so try it first. // so try it first to save time.
graph_t sorted_graph (packed); graph_t sorted_graph (packed);
sorted_graph.sort_kahn (); sorted_graph.sort_kahn ();
if (!sorted_graph.will_overflow ()) return; if (!sorted_graph.will_overflow ())
{
sorted_graph.serialize (c);
return;
}
sorted_graph.sort_shortest_distance (); sorted_graph.sort_shortest_distance ();
@ -693,13 +700,19 @@ hb_resolve_overflows (const hb_vector_t<hb_serialize_context_t::object_t *>& pac
// by duplicating it. // by duplicating it.
sorted_graph.duplicate (r.parent, r.link->objidx); sorted_graph.duplicate (r.parent, r.link->objidx);
resolution_attempted = true; resolution_attempted = true;
// Stop processing overflows for this round so that object order can be
// updated to account for the newly added object.
break; break;
} }
if (child.is_leaf () && !priority_bumped_parents.has (r.parent)) if (child.is_leaf () && !priority_bumped_parents.has (r.parent))
{ {
// TODO(garretrieger): initially limiting this to leaf's but likely // This object is too far from it's parent, attempt to move it closer.
// can be used for non-leafs as well. //
// TODO(garretrieger): initially limiting this to leaf's since they can be
// moved closer with fewer consequences. However, this can
// likely can be used for non-leafs as well.
// TODO(garretrieger): add a maximum priority, don't try to raise past this. // TODO(garretrieger): add a maximum priority, don't try to raise past this.
// TODO(garretrieger): also try lowering priority of the parent. Make it // TODO(garretrieger): also try lowering priority of the parent. Make it
// get placed further up in the ordering, closer to it's children. // get placed further up in the ordering, closer to it's children.