lily/dispatcher.cc

   1 /*
   2   This file is part of LilyPond, the GNU music typesetter.
   3
   4   Copyright (C) 2005--2011 Erik Sandberg  <mandolaerik@gmail.com>
   5
   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.
  10
  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.
  15
  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/>.
  18 */
  19
  20 #include "dispatcher.hh"
  21 #include "input.hh"
  22 #include "international.hh"
  23 #include "ly-smobs.icc"
  24 #include "warn.hh"
  25
  26 IMPLEMENT_SMOBS (Dispatcher);
  27 IMPLEMENT_TYPE_P (Dispatcher, "ly:dispatcher?");
  28 IMPLEMENT_DEFAULT_EQUAL_P (Dispatcher);
  29
  30 Dispatcher::~Dispatcher ()
  31 {
  32 }
  33
  34 Dispatcher::Dispatcher ()
  35 {
  36   self_scm_ = SCM_EOL;
  37   listeners_ = SCM_EOL;
  38   dispatchers_ = SCM_EOL;
  39   listen_classes_ = SCM_EOL;
  40   smobify_self ();
  41 // TODO: use resizable hash (guile 1.8)
  42 //  listeners_ = scm_c_make_hash_table (0);
  43   listeners_ = scm_c_make_hash_table (17);
  44   priority_count_ = 0;
  45 }
  46
  47 SCM
  48 Dispatcher::mark_smob (SCM sm)
  49 {
  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_;
  54 }
  55
  56 int
  57 Dispatcher::print_smob (SCM s, SCM p, scm_print_state*)
  58 {
  59   Dispatcher *me = (Dispatcher *) SCM_CELL_WORD_1 (s);
  60   scm_puts ("#<Dispatcher ", p);
  61   scm_write (scm_vector_to_list (me->listeners_), p);
  62   scm_puts (">", p);
  63   return 1;
  64 }
  65
  66 /*
  67 Event dispatching:
  68 - Collect a list of listeners for each relevant class
  69 - Send the event to each of these listeners, in increasing priority order.
  70   This is done by keeping a priority queue of listener lists,
  71   and iteratively send the event to the lowest-priority listener.
  72 - An event is never sent twice to listeners with equal priority.
  73 */
  74 IMPLEMENT_LISTENER (Dispatcher, dispatch);
  75 void
  76 Dispatcher::dispatch (SCM sev)
  77 {
  78   Stream_event *ev = unsmob_stream_event (sev);
  79   SCM class_symbol = ev->get_property ("class");
  80   if (!scm_symbol_p (class_symbol))
  81     {
  82       warning (_ ("Event class should be a symbol"));
  83       return;
  84     }
  85
  86   SCM class_list = scm_call_1 (ly_lily_module_constant ("ly:make-event-class"), class_symbol);
  87   if (!scm_is_pair (class_list))
  88     {
  89       ev->origin ()->warning (_f ("Unknown event class %s", ly_symbol2string (class_symbol).c_str ()));
  90       return;
  91     }
  92   bool sent = false;
  93   int num_classes = scm_ilength (class_list);
  94
  95   /*
  96     For each event class there is a list of listeners, which is
  97     ordered by priority. Our next task is to call these listeners, in
  98     priority order.  A priority queue stores the next element in each
  99     listener list, and the lowest priority element is repeatedly
 100     extracted and called.
 101
 102     The priority queue is implemented as a bubble-sorted C
 103     array. Using the stack instead of native Scheme datastructures
 104     avoids overheads for memory allocation. The queue is usually small
 105     (around 2 elements), so the quadratic sorting time is not a
 106     problem. (if this changes, it's easy to rewrite this routine using
 107     a heap)
 108
 109     The first step is to collect all listener lists and to initially
 110     insert them in the priority queue.
 111   */
 112   struct { int prio; SCM list; } lists[num_classes+1];
 113   int i = 0;
 114   for (SCM cl = class_list; scm_is_pair (cl); cl = scm_cdr (cl))
 115     {
 116       SCM list = scm_hashq_ref (listeners_, scm_car (cl), SCM_EOL);
 117       if (!scm_is_pair (list))
 118         num_classes--;
 119       else
 120         {
 121           // bubblesort.
 122           int prio = scm_to_int (scm_caar (list));
 123           int j;
 124           for (j = i; j > 0 && lists[j-1].prio > prio; j--)
 125             lists[j] = lists[j-1];
 126           lists[j].prio = prio;
 127           lists[j].list = list;
 128           i++;
 129         }
 130     }
 131   lists[num_classes].prio = INT_MAX;
 132
 133   // Never send an event to two listeners with equal priority.
 134   int last_priority = -1;
 135   /*
 136     Each iteration extracts the lowest-priority element, which is a
 137     list of listeners. The first listener is called, and the tail of
 138     the list is pushed back into the priority queue.
 139   */
 140   while (num_classes)
 141     {
 142       // Send the event, if we haven't already sent it to this target.
 143       if (lists[0].prio != last_priority)
 144         {
 145           // process the listener
 146           assert (lists[0].prio > last_priority);
 147           last_priority = lists[0].prio;
 148
 149           Listener *l = unsmob_listener (scm_cdar (lists[0].list));
 150           l->listen (ev->self_scm ());
 151           sent = true;
 152         }
 153       // go to the next listener; bubble-sort the class list.
 154       SCM next = scm_cdr (lists[0].list);
 155       if (!scm_is_pair (next))
 156         num_classes--;
 157       int prio = (scm_is_pair (next)) ? scm_to_int (scm_caar (next)) : INT_MAX;
 158       for (i = 0; prio > lists[i+1].prio; i++)
 159         lists[i] = lists[i+1];
 160       lists[i].prio = prio;
 161       lists[i].list = next;
 162     }
 163
 164 /* TODO: Uncomment.
 165   if (!sent)
 166     warning (_f ("Junking event: %s", ly_symbol2string (class_symbol).c_str ()));
 167 */
 168 }
 169
 170 void
 171 Dispatcher::broadcast (Stream_event *ev)
 172 {
 173   dispatch (ev->self_scm ());
 174 }
 175
 176 void
 177 Dispatcher::add_listener (Listener l, SCM ev_class)
 178 {
 179   internal_add_listener (l, ev_class, ++priority_count_);
 180 }
 181
 182 inline void
 183 Dispatcher::internal_add_listener (Listener l, SCM ev_class, int priority)
 184 {
 185   SCM list = scm_hashq_ref (listeners_, ev_class, SCM_EOL);
 186   if (!scm_is_pair (list))
 187     {
 188       /* Tell all dispatchers that we listen to, that we want to hear ev_class
 189          events */
 190       for (SCM disp = dispatchers_; scm_is_pair (disp); disp = scm_cdr (disp))
 191         {
 192           int priority = scm_to_int (scm_cdar (disp));
 193           Dispatcher *d = unsmob_dispatcher (scm_caar (disp));
 194           d->internal_add_listener (GET_LISTENER (dispatch), ev_class, priority);
 195         }
 196       listen_classes_ = scm_cons (ev_class, listen_classes_);
 197     }
 198   SCM entry = scm_cons (scm_from_int (priority), l.smobbed_copy ());
 199   list = scm_merge (list, scm_list_1 (entry), ly_lily_module_constant ("car<"));
 200   scm_hashq_set_x (listeners_, ev_class, list);
 201 }
 202
 203 void
 204 Dispatcher::remove_listener (Listener l, SCM ev_class)
 205 {
 206   SCM list = scm_hashq_ref (listeners_, ev_class, SCM_EOL);
 207
 208   if (list == SCM_EOL)
 209     {
 210       programming_error ("remove_listener called with incorrect class.");
 211       return;
 212     }
 213
 214   // We just remove the listener once.
 215   bool first = true;
 216
 217   SCM dummy = scm_cons (SCM_EOL, list);
 218   SCM e = dummy;
 219   while (scm_is_pair (scm_cdr (e)))
 220     if (*unsmob_listener (scm_cdadr (e)) == l && first)
 221       {
 222         scm_set_cdr_x (e, scm_cddr (e));
 223         first = false;
 224         break;
 225       }
 226     else
 227       e = scm_cdr (e);
 228   list = scm_cdr (dummy);
 229   scm_hashq_set_x (listeners_, ev_class, list);
 230
 231   if (first)
 232     warning ("Attempting to remove nonexisting listener.");
 233   else if (!scm_is_pair (list))
 234     {
 235       /* Unregister with all dispatchers. */
 236       for (SCM disp = dispatchers_; scm_is_pair (disp); disp = scm_cdr (disp))
 237         {
 238           Dispatcher *d = unsmob_dispatcher (scm_caar (disp));
 239           d->remove_listener (GET_LISTENER (dispatch), ev_class);
 240         }
 241       listen_classes_ = scm_delq_x (ev_class, listen_classes_);
 242     }
 243 }
 244
 245 /* Register as a listener to another dispatcher. */
 246 void
 247 Dispatcher::register_as_listener (Dispatcher *disp)
 248 {
 249   int priority = ++disp->priority_count_;
 250
 251   // Don't register twice to the same dispatcher.
 252   if (scm_assq (disp->self_scm (), dispatchers_) != SCM_BOOL_F)
 253     {
 254       warning ("Already listening to dispatcher, ignoring request");
 255       return;
 256     }
 257
 258   dispatchers_ = scm_acons (disp->self_scm (), scm_from_int (priority), dispatchers_);
 259
 260   Listener list = GET_LISTENER (dispatch);
 261   for (SCM cl = listen_classes_; scm_is_pair (cl); cl = scm_cdr (cl))
 262     {
 263       disp->internal_add_listener (list, scm_car (cl), priority);
 264     }
 265 }
 266
 267 /* Unregister as a listener to another dispatcher. */
 268 void
 269 Dispatcher::unregister_as_listener (Dispatcher *disp)
 270 {
 271   dispatchers_ = scm_assq_remove_x (dispatchers_, disp->self_scm ());
 272
 273   Listener listener = GET_LISTENER (dispatch);
 274   for (SCM cl = listen_classes_; scm_is_pair (cl); cl = scm_cdr (cl))
 275     {
 276       disp->remove_listener (listener, scm_car (cl));
 277     }
 278 }