2 This file is part of LilyPond, the GNU music typesetter.
4 Copyright (C) 2005--2012 Erik Sandberg <mandolaerik@gmail.com>
6 LilyPond is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 LilyPond is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with LilyPond. If not, see <http://www.gnu.org/licenses/>.
20 #include "dispatcher.hh"
22 #include "international.hh"
23 #include "ly-smobs.icc"
26 IMPLEMENT_SMOBS (Dispatcher);
27 IMPLEMENT_TYPE_P (Dispatcher, "ly:dispatcher?");
28 IMPLEMENT_DEFAULT_EQUAL_P (Dispatcher);
30 Dispatcher::~Dispatcher ()
34 Dispatcher::Dispatcher ()
38 dispatchers_ = SCM_EOL;
39 listen_classes_ = SCM_EOL;
41 // TODO: use resizable hash (guile 1.8)
42 // listeners_ = scm_c_make_hash_table (0);
43 listeners_ = scm_c_make_hash_table (17);
48 Dispatcher::mark_smob (SCM sm)
50 Dispatcher *me = (Dispatcher *) SCM_CELL_WORD_1 (sm);
51 scm_gc_mark (me->dispatchers_);
52 scm_gc_mark (me->listen_classes_);
53 return me->listeners_;
57 Dispatcher::print_smob (SCM s, SCM p, scm_print_state *)
59 Dispatcher *me = (Dispatcher *) SCM_CELL_WORD_1 (s);
60 scm_puts ("#<Dispatcher ", p);
61 scm_write (scm_call_1 (ly_lily_module_constant ("hash-table->alist"),
69 - Collect a list of listeners for each relevant class
70 - Send the event to each of these listeners, in increasing priority order.
71 This is done by keeping a priority queue of listener lists,
72 and iteratively send the event to the lowest-priority listener.
73 - An event is never sent twice to listeners with equal priority.
74 The only case where listeners with equal priority may exist is when
75 two dispatchers are connected for more than one event type. In that
76 case, the respective listeners all have the same priority, making
77 sure that any event is only dispatched at most once for that
78 combination of dispatchers, even if it matches more than one event
81 IMPLEMENT_LISTENER (Dispatcher, dispatch);
83 Dispatcher::dispatch (SCM sev)
85 Stream_event *ev = unsmob_stream_event (sev);
86 SCM class_list = ev->get_property ("class");
87 if (!scm_is_pair (class_list))
89 ev->origin ()->warning (_ ("Event class should be a list"));
96 int num_classes = scm_ilength (class_list);
99 For each event class there is a list of listeners, which is
100 ordered by priority. Our next task is to call these listeners, in
101 priority order. A priority queue stores the next element in each
102 listener list, and the lowest priority element is repeatedly
103 extracted and called.
105 The priority queue is implemented as an insertion-sorted C
106 array. Using the stack instead of native Scheme datastructures
107 avoids overheads for memory allocation. The queue is usually small
108 (around 2 elements), so the quadratic sorting time is not a
109 problem. (if this changes, it's easy to rewrite this routine using
112 The first step is to collect all listener lists and to initially
113 insert them in the priority queue.
115 struct { int prio; SCM list; } lists[num_classes + 1];
117 for (SCM cl = class_list; scm_is_pair (cl); cl = scm_cdr (cl))
119 SCM list = scm_hashq_ref (listeners_, scm_car (cl), SCM_EOL);
120 if (!scm_is_pair (list))
125 int prio = scm_to_int (scm_caar (list));
127 for (j = i; j > 0 && lists[j - 1].prio > prio; j--)
128 lists[j] = lists[j - 1];
129 lists[j].prio = prio;
130 lists[j].list = list;
134 lists[num_classes].prio = INT_MAX;
136 // Never send an event to two listeners with equal priority.
137 int last_priority = -1;
139 Each iteration extracts the lowest-priority element, which is a
140 list of listeners. The first listener is called, and the tail of
141 the list is pushed back into the priority queue.
145 // Send the event, if we haven't already sent it to this target.
146 if (lists[0].prio != last_priority)
148 // process the listener
149 assert (lists[0].prio > last_priority);
150 last_priority = lists[0].prio;
152 Listener *l = unsmob_listener (scm_cdar (lists[0].list));
153 l->listen (ev->self_scm ());
158 // go to the next listener; bubble-sort the class list.
159 SCM next = scm_cdr (lists[0].list);
160 if (!scm_is_pair (next))
162 int prio = (scm_is_pair (next)) ? scm_to_int (scm_caar (next)) : INT_MAX;
163 for (i = 0; prio > lists[i + 1].prio; i++)
164 lists[i] = lists[i + 1];
165 lists[i].prio = prio;
166 lists[i].list = next;
170 /* TODO: Uncomment. */
172 warning (_f ("Junking event: %s", ly_symbol2string (class_symbol).c_str ()));
177 Dispatcher::is_listened_class (SCM cl)
179 for (; scm_is_pair (cl); cl = scm_cdr (cl))
181 SCM list = scm_hashq_ref (listeners_, scm_car (cl), SCM_EOL);
182 if (scm_is_pair (list))
189 accumulate_types (void * /* closure */,
194 if (scm_is_pair (val))
195 return scm_cons (key, result);
200 Dispatcher::listened_types ()
202 return scm_internal_hash_fold ((scm_t_hash_fold_fn) &accumulate_types,
203 NULL, SCM_EOL, listeners_);
207 Dispatcher::broadcast (Stream_event *ev)
209 dispatch (ev->self_scm ());
212 // add_listener will always assign a new priority for each call
214 Dispatcher::add_listener (Listener l, SCM ev_class)
216 internal_add_listener (l, ev_class, ++priority_count_);
220 Dispatcher::internal_add_listener (Listener l, SCM ev_class, int priority)
222 SCM list = scm_hashq_ref (listeners_, ev_class, SCM_EOL);
223 // if ev_class is not yet listened to, we go through our list of
224 // source dispatchers and register ourselves there with the priority
225 // we have reserved for this dispatcher. The priority system
226 // usually distributes events in the order events are registered.
227 // The reuse of a previous priority when registering another event
228 // for a dispatcher/dispatcher connection bypasses the normal
229 // ordering, but it is the mechanism by which duplicate broadcasts
230 // of the same event from one dispatcher to another are avoided.
231 if (!scm_is_pair (list))
233 /* Tell all dispatchers that we listen to, that we want to hear ev_class
235 for (SCM disp = dispatchers_; scm_is_pair (disp); disp = scm_cdr (disp))
237 int priority = scm_to_int (scm_cdar (disp));
238 Dispatcher *d = unsmob_dispatcher (scm_caar (disp));
239 d->internal_add_listener (GET_LISTENER (dispatch), ev_class, priority);
241 listen_classes_ = scm_cons (ev_class, listen_classes_);
243 SCM entry = scm_cons (scm_from_int (priority), l.smobbed_copy ());
244 list = scm_merge (list, scm_list_1 (entry), ly_lily_module_constant ("car<"));
245 scm_hashq_set_x (listeners_, ev_class, list);
249 Dispatcher::remove_listener (Listener l, SCM ev_class)
251 SCM list = scm_hashq_ref (listeners_, ev_class, SCM_EOL);
255 programming_error ("remove_listener called with incorrect class.");
259 // We just remove the listener once.
262 SCM dummy = scm_cons (SCM_EOL, list);
264 while (scm_is_pair (scm_cdr (e)))
265 if (*unsmob_listener (scm_cdadr (e)) == l && first)
267 scm_set_cdr_x (e, scm_cddr (e));
273 list = scm_cdr (dummy);
274 scm_hashq_set_x (listeners_, ev_class, list);
277 warning (_ ("Attempting to remove nonexisting listener."));
278 else if (!scm_is_pair (list))
280 /* Unregister with all dispatchers. */
281 for (SCM disp = dispatchers_; scm_is_pair (disp); disp = scm_cdr (disp))
283 Dispatcher *d = unsmob_dispatcher (scm_caar (disp));
284 d->remove_listener (GET_LISTENER (dispatch), ev_class);
286 listen_classes_ = scm_delq_x (ev_class, listen_classes_);
290 /* Register as a listener to another dispatcher. */
292 Dispatcher::register_as_listener (Dispatcher *disp)
294 // We are creating and remembering the priority _we_ have with the
295 // foreign dispatcher. All events are dispatched with the same
296 // priority. The result is that, for example, a single event class
297 // will only trigger an event listener once.
298 int priority = ++disp->priority_count_;
300 // Don't register twice to the same dispatcher.
301 if (scm_assq (disp->self_scm (), dispatchers_) != SCM_BOOL_F)
303 warning (_ ("Already listening to dispatcher, ignoring request"));
307 dispatchers_ = scm_acons (disp->self_scm (), scm_from_int (priority), dispatchers_);
309 Listener list = GET_LISTENER (dispatch);
310 for (SCM cl = listen_classes_; scm_is_pair (cl); cl = scm_cdr (cl))
312 disp->internal_add_listener (list, scm_car (cl), priority);
316 /* Unregister as a listener to another dispatcher. */
318 Dispatcher::unregister_as_listener (Dispatcher *disp)
320 dispatchers_ = scm_assq_remove_x (dispatchers_, disp->self_scm ());
322 Listener listener = GET_LISTENER (dispatch);
323 for (SCM cl = listen_classes_; scm_is_pair (cl); cl = scm_cdr (cl))
325 disp->remove_listener (listener, scm_car (cl));