2 This file is part of LilyPond, the GNU music typesetter.
4 Copyright (C) 2005--2015 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"
25 const char Dispatcher::type_p_name_[] = "ly:dispatcher?";
27 Dispatcher::~Dispatcher ()
31 Dispatcher::Dispatcher ()
34 dispatchers_ = SCM_EOL;
35 listen_classes_ = SCM_EOL;
37 // TODO: use resizable hash (guile 1.8)
38 // listeners_ = scm_c_make_hash_table (0);
39 listeners_ = scm_c_make_hash_table (17);
44 Dispatcher::mark_smob ()
46 scm_gc_mark (dispatchers_);
47 scm_gc_mark (listen_classes_);
52 Dispatcher::print_smob (SCM p, scm_print_state *)
54 scm_puts ("#<Dispatcher ", p);
55 scm_write (scm_call_1 (ly_lily_module_constant ("hash-table->alist"),
63 - Collect a list of listeners for each relevant class
64 - Send the event to each of these listeners, in increasing priority order.
65 This is done by keeping a priority queue of listener lists,
66 and iteratively send the event to the lowest-priority listener.
67 - An event is never sent twice to listeners with equal priority.
68 The only case where listeners with equal priority may exist is when
69 two dispatchers are connected for more than one event type. In that
70 case, the respective listeners all have the same priority, making
71 sure that any event is only dispatched at most once for that
72 combination of dispatchers, even if it matches more than one event
76 Dispatcher::dispatch (SCM sev)
78 Stream_event *ev = Stream_event::unsmob (sev);
79 SCM class_list = ev->get_property ("class");
80 if (!scm_is_pair (class_list))
82 ev->origin ()->warning (_ ("Event class should be a list"));
89 int num_classes = scm_ilength (class_list);
92 For each event class there is a list of listeners, which is
93 ordered by priority. Our next task is to call these listeners, in
94 priority order. A priority queue stores the next element in each
95 listener list, and the lowest priority element is repeatedly
98 The priority queue is implemented as an insertion-sorted C
99 array. Using the stack instead of native Scheme datastructures
100 avoids overheads for memory allocation. The queue is usually small
101 (around 2 elements), so the quadratic sorting time is not a
102 problem. (if this changes, it's easy to rewrite this routine using
105 The first step is to collect all listener lists and to initially
106 insert them in the priority queue.
108 struct { int prio; SCM list; } lists[num_classes + 1];
110 for (SCM cl = class_list; scm_is_pair (cl); cl = scm_cdr (cl))
112 SCM list = scm_hashq_ref (listeners_, scm_car (cl), SCM_EOL);
113 if (!scm_is_pair (list))
118 int prio = scm_to_int (scm_caar (list));
120 for (j = i; j > 0 && lists[j - 1].prio > prio; j--)
121 lists[j] = lists[j - 1];
122 lists[j].prio = prio;
123 lists[j].list = list;
127 lists[num_classes].prio = INT_MAX;
129 // Never send an event to two listeners with equal priority.
130 int last_priority = -1;
132 Each iteration extracts the lowest-priority element, which is a
133 list of listeners. The first listener is called, and the tail of
134 the list is pushed back into the priority queue.
138 // Send the event, if we haven't already sent it to this target.
139 if (lists[0].prio != last_priority)
141 // process the listener
142 assert (lists[0].prio > last_priority);
143 last_priority = lists[0].prio;
145 SCM l = scm_cdar (lists[0].list);
146 scm_call_1 (l, ev->self_scm ());
151 // go to the next listener; bubble-sort the class list.
152 SCM next = scm_cdr (lists[0].list);
153 if (!scm_is_pair (next))
155 int prio = (scm_is_pair (next)) ? scm_to_int (scm_caar (next)) : INT_MAX;
156 for (i = 0; prio > lists[i + 1].prio; i++)
157 lists[i] = lists[i + 1];
158 lists[i].prio = prio;
159 lists[i].list = next;
163 /* TODO: Uncomment. */
165 warning (_f ("Junking event: %s", ly_symbol2string (class_symbol).c_str ()));
170 Dispatcher::is_listened_class (SCM cl)
172 for (; scm_is_pair (cl); cl = scm_cdr (cl))
174 SCM list = scm_hashq_ref (listeners_, scm_car (cl), SCM_EOL);
175 if (scm_is_pair (list))
182 accumulate_types (void * /* closure */,
187 if (scm_is_pair (val))
188 return scm_cons (key, result);
193 Dispatcher::listened_types ()
195 return scm_internal_hash_fold ((scm_t_hash_fold_fn) &accumulate_types,
196 NULL, SCM_EOL, listeners_);
200 Dispatcher::broadcast (Stream_event *ev)
202 dispatch (ev->self_scm ());
205 // add_listener will always assign a new priority for each call
207 Dispatcher::add_listener (Listener l, SCM ev_class)
209 add_listener (l.smobbed_copy (), ev_class);
213 Dispatcher::add_listener (SCM callback, SCM ev_class)
215 internal_add_listener (callback, ev_class, ++priority_count_);
219 Dispatcher::internal_add_listener (SCM callback, SCM ev_class, int priority)
221 SCM list = scm_hashq_ref (listeners_, ev_class, SCM_EOL);
222 // if ev_class is not yet listened to, we go through our list of
223 // source dispatchers and register ourselves there with the priority
224 // we have reserved for this dispatcher. The priority system
225 // usually distributes events in the order events are registered.
226 // The reuse of a previous priority when registering another event
227 // for a dispatcher/dispatcher connection bypasses the normal
228 // ordering, but it is the mechanism by which duplicate broadcasts
229 // of the same event from one dispatcher to another are avoided.
230 if (!scm_is_pair (list))
232 /* Tell all dispatchers that we listen to, that we want to hear ev_class
234 for (SCM disp = dispatchers_; scm_is_pair (disp); disp = scm_cdr (disp))
236 int priority = scm_to_int (scm_cdar (disp));
237 Dispatcher *d = Dispatcher::unsmob (scm_caar (disp));
238 d->internal_add_listener (GET_LISTENER (Dispatcher, dispatch).smobbed_copy (),
241 listen_classes_ = scm_cons (ev_class, listen_classes_);
243 SCM entry = scm_cons (scm_from_int (priority), callback);
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);
253 if (scm_is_null (list))
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 (*Listener::unsmob (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 = Dispatcher::unsmob (scm_caar (disp));
284 d->remove_listener (GET_LISTENER (Dispatcher, 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_is_true (scm_assq (disp->self_scm (), dispatchers_)))
303 warning (_ ("Already listening to dispatcher, ignoring request"));
307 dispatchers_ = scm_acons (disp->self_scm (), scm_from_int (priority), dispatchers_);
309 SCM list = GET_LISTENER (Dispatcher, dispatch).smobbed_copy ();
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 (Dispatcher, dispatch);
323 for (SCM cl = listen_classes_; scm_is_pair (cl); cl = scm_cdr (cl))
325 disp->remove_listener (listener, scm_car (cl));