i3
tree.c
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1 #undef I3__FILE__
2 #define I3__FILE__ "tree.c"
3 /*
4  * vim:ts=4:sw=4:expandtab
5  *
6  * i3 - an improved dynamic tiling window manager
7  * © 2009-2011 Michael Stapelberg and contributors (see also: LICENSE)
8  *
9  * tree.c: Everything that primarily modifies the layout tree data structure.
10  *
11  */
12 #include "all.h"
13 
14 struct Con *croot;
15 struct Con *focused;
16 
17 struct all_cons_head all_cons = TAILQ_HEAD_INITIALIZER(all_cons);
18 
19 /*
20  * Create the pseudo-output __i3. Output-independent workspaces such as
21  * __i3_scratch will live there.
22  *
23  */
24 static Con *_create___i3(void) {
25  Con *__i3 = con_new(croot, NULL);
26  FREE(__i3->name);
27  __i3->name = sstrdup("__i3");
28  __i3->type = CT_OUTPUT;
29  __i3->layout = L_OUTPUT;
30  con_fix_percent(croot);
31  x_set_name(__i3, "[i3 con] pseudo-output __i3");
32  /* For retaining the correct position/size of a scratchpad window, the
33  * dimensions of the real outputs should be multiples of the __i3
34  * pseudo-output. Ensuring that is the job of scratchpad_fix_resolution()
35  * which gets called after this function and after detecting all the
36  * outputs (or whenever an output changes). */
37  __i3->rect.width = 1280;
38  __i3->rect.height = 1024;
39 
40  /* Add a content container. */
41  DLOG("adding main content container\n");
42  Con *content = con_new(NULL, NULL);
43  content->type = CT_CON;
44  FREE(content->name);
45  content->name = sstrdup("content");
46  content->layout = L_SPLITH;
47 
48  x_set_name(content, "[i3 con] content __i3");
49  con_attach(content, __i3, false);
50 
51  /* Attach the __i3_scratch workspace. */
52  Con *ws = con_new(NULL, NULL);
53  ws->type = CT_WORKSPACE;
54  ws->num = -1;
55  ws->name = sstrdup("__i3_scratch");
56  ws->layout = L_SPLITH;
57  con_attach(ws, content, false);
58  x_set_name(ws, "[i3 con] workspace __i3_scratch");
59  ws->fullscreen_mode = CF_OUTPUT;
60 
61  return __i3;
62 }
63 
64 /*
65  * Loads tree from 'path' (used for in-place restarts).
66  *
67  */
68 bool tree_restore(const char *path, xcb_get_geometry_reply_t *geometry) {
69  char *globbed = resolve_tilde(path);
70 
71  if (!path_exists(globbed)) {
72  LOG("%s does not exist, not restoring tree\n", globbed);
73  free(globbed);
74  return false;
75  }
76 
77  /* TODO: refactor the following */
78  croot = con_new(NULL, NULL);
79  croot->rect = (Rect){
80  geometry->x,
81  geometry->y,
82  geometry->width,
83  geometry->height
84  };
85  focused = croot;
86 
87  tree_append_json(globbed);
88 
89  printf("appended tree, using new root\n");
90  croot = TAILQ_FIRST(&(croot->nodes_head));
91  printf("new root = %p\n", croot);
92  Con *out = TAILQ_FIRST(&(croot->nodes_head));
93  printf("out = %p\n", out);
94  Con *ws = TAILQ_FIRST(&(out->nodes_head));
95  printf("ws = %p\n", ws);
96 
97  /* For in-place restarting into v4.2, we need to make sure the new
98  * pseudo-output __i3 is present. */
99  if (strcmp(out->name, "__i3") != 0) {
100  DLOG("Adding pseudo-output __i3 during inplace restart\n");
101  Con *__i3 = _create___i3();
102  /* Ensure that it is the first output, other places in the code make
103  * that assumption. */
104  TAILQ_REMOVE(&(croot->nodes_head), __i3, nodes);
105  TAILQ_INSERT_HEAD(&(croot->nodes_head), __i3, nodes);
106  }
107 
108  return true;
109 }
110 
111 /*
112  * Initializes the tree by creating the root node. The CT_OUTPUT Cons below the
113  * root node are created in randr.c for each Output.
114  *
115  */
116 void tree_init(xcb_get_geometry_reply_t *geometry) {
117  croot = con_new(NULL, NULL);
118  FREE(croot->name);
119  croot->name = "root";
120  croot->type = CT_ROOT;
121  croot->layout = L_SPLITH;
122  croot->rect = (Rect){
123  geometry->x,
124  geometry->y,
125  geometry->width,
126  geometry->height
127  };
128 
129  _create___i3();
130 }
131 
132 /*
133  * Opens an empty container in the current container
134  *
135  */
136 Con *tree_open_con(Con *con, i3Window *window) {
137  if (con == NULL) {
138  /* every focusable Con has a parent (outputs have parent root) */
139  con = focused->parent;
140  /* If the parent is an output, we are on a workspace. In this case,
141  * the new container needs to be opened as a leaf of the workspace. */
142  if (con->parent->type == CT_OUTPUT && con->type != CT_DOCKAREA) {
143  con = focused;
144  }
145 
146  /* If the currently focused container is a floating container, we
147  * attach the new container to the currently focused spot in its
148  * workspace. */
149  if (con->type == CT_FLOATING_CON) {
151  if (con->type != CT_WORKSPACE)
152  con = con->parent;
153  }
154  DLOG("con = %p\n", con);
155  }
156 
157  assert(con != NULL);
158 
159  /* 3. create the container and attach it to its parent */
160  Con *new = con_new(con, window);
161  new->layout = L_SPLITH;
162 
163  /* 4: re-calculate child->percent for each child */
164  con_fix_percent(con);
165 
166  return new;
167 }
168 
169 static bool _is_con_mapped(Con *con) {
170  Con *child;
171 
172  TAILQ_FOREACH(child, &(con->nodes_head), nodes)
173  if (_is_con_mapped(child))
174  return true;
175 
176  return con->mapped;
177 }
178 
179 /*
180  * Closes the given container including all children.
181  * Returns true if the container was killed or false if just WM_DELETE was sent
182  * and the window is expected to kill itself.
183  *
184  * The dont_kill_parent flag is specified when the function calls itself
185  * recursively while deleting a containers children.
186  *
187  * The force_set_focus flag is specified in the case of killing a floating
188  * window: tree_close() will be invoked for the CT_FLOATINGCON (the parent
189  * container) and focus should be set there.
190  *
191  */
192 bool tree_close(Con *con, kill_window_t kill_window, bool dont_kill_parent, bool force_set_focus) {
193  bool was_mapped = con->mapped;
194  Con *parent = con->parent;
195 
196  if (!was_mapped) {
197  /* Even if the container itself is not mapped, its children may be
198  * mapped (for example split containers don't have a mapped window on
199  * their own but usually contain mapped children). */
200  was_mapped = _is_con_mapped(con);
201  }
202 
203  /* Get the container which is next focused */
204  Con *next = con_next_focused(con);
205  DLOG("next = %p, focused = %p\n", next, focused);
206 
207  DLOG("closing %p, kill_window = %d\n", con, kill_window);
208  Con *child, *nextchild;
209  bool abort_kill = false;
210  /* We cannot use TAILQ_FOREACH because the children get deleted
211  * in their parent’s nodes_head */
212  for (child = TAILQ_FIRST(&(con->nodes_head)); child; ) {
213  nextchild = TAILQ_NEXT(child, nodes);
214  DLOG("killing child=%p\n", child);
215  if (!tree_close(child, kill_window, true, false))
216  abort_kill = true;
217  child = nextchild;
218  }
219 
220  if (abort_kill) {
221  DLOG("One of the children could not be killed immediately (WM_DELETE sent), aborting.\n");
222  return false;
223  }
224 
225  if (con->window != NULL) {
226  if (kill_window != DONT_KILL_WINDOW) {
227  x_window_kill(con->window->id, kill_window);
228  return false;
229  } else {
230  xcb_void_cookie_t cookie;
231  /* un-parent the window */
232  cookie = xcb_reparent_window(conn, con->window->id, root, 0, 0);
233 
234  /* Ignore X11 errors for the ReparentWindow request.
235  * X11 Errors are returned when the window was already destroyed */
236  add_ignore_event(cookie.sequence, 0);
237 
238  /* We are no longer handling this window, thus set WM_STATE to
239  * WM_STATE_WITHDRAWN (see ICCCM 4.1.3.1) */
240  long data[] = { XCB_ICCCM_WM_STATE_WITHDRAWN, XCB_NONE };
241  cookie = xcb_change_property(conn, XCB_PROP_MODE_REPLACE,
242  con->window->id, A_WM_STATE, A_WM_STATE, 32, 2, data);
243 
244  /* Ignore X11 errors for the ReparentWindow request.
245  * X11 Errors are returned when the window was already destroyed */
246  add_ignore_event(cookie.sequence, 0);
247  }
248  FREE(con->window->class_class);
249  FREE(con->window->class_instance);
250  i3string_free(con->window->name);
251  free(con->window);
252  }
253 
254  /* kill the X11 part of this container */
255  x_con_kill(con);
256 
257  con_detach(con);
258 
259  /* disable urgency timer, if needed */
260  if (con->urgency_timer != NULL) {
261  DLOG("Removing urgency timer of con %p\n", con);
263  ev_timer_stop(main_loop, con->urgency_timer);
264  FREE(con->urgency_timer);
265  }
266 
267  if (con->type != CT_FLOATING_CON) {
268  /* If the container is *not* floating, we might need to re-distribute
269  * percentage values for the resized containers. */
270  con_fix_percent(parent);
271  }
272 
273  if (con_is_floating(con)) {
274  Con *ws = con_get_workspace(con);
275  DLOG("Container was floating, killing floating container\n");
276  tree_close(parent, DONT_KILL_WINDOW, false, (con == focused));
277  DLOG("parent container killed\n");
278  if (con == focused) {
279  DLOG("This is the focused container, i need to find another one to focus. I start looking at ws = %p\n", ws);
280  /* go down the focus stack as far as possible */
281  next = con_descend_focused(ws);
282 
283  dont_kill_parent = true;
284  DLOG("Alright, focusing %p\n", next);
285  } else {
286  next = NULL;
287  }
288  }
289 
290  free(con->name);
291  FREE(con->deco_render_params);
293  free(con);
294 
295  /* in the case of floating windows, we already focused another container
296  * when closing the parent, so we can exit now. */
297  if (!next) {
298  DLOG("No next container, i will just exit now\n");
299  return true;
300  }
301 
302  if (was_mapped || con == focused) {
303  if ((kill_window != DONT_KILL_WINDOW) || !dont_kill_parent || con == focused) {
304  DLOG("focusing %p / %s\n", next, next->name);
305  if (next->type == CT_DOCKAREA) {
306  /* Instead of focusing the dockarea, we need to restore focus to the workspace */
308  } else {
309  if (!force_set_focus && con != focused)
310  DLOG("not changing focus, the container was not focused before\n");
311  else con_focus(next);
312  }
313  }
314  else {
315  DLOG("not focusing because we're not killing anybody\n");
316  }
317  } else {
318  DLOG("not focusing, was not mapped\n");
319  }
320 
321  /* check if the parent container is empty now and close it */
322  if (!dont_kill_parent)
323  CALL(parent, on_remove_child);
324 
325  return true;
326 }
327 
328 /*
329  * Closes the current container using tree_close().
330  *
331  */
332 void tree_close_con(kill_window_t kill_window) {
333  assert(focused != NULL);
334  if (focused->type == CT_WORKSPACE) {
335  LOG("Cannot close workspace\n");
336  return;
337  }
338 
339  /* There *should* be no possibility to focus outputs / root container */
340  assert(focused->type != CT_OUTPUT);
341  assert(focused->type != CT_ROOT);
342 
343  /* Kill con */
344  tree_close(focused, kill_window, false, false);
345 }
346 
347 /*
348  * Splits (horizontally or vertically) the given container by creating a new
349  * container which contains the old one and the future ones.
350  *
351  */
352 void tree_split(Con *con, orientation_t orientation) {
353  /* for a workspace, we just need to change orientation */
354  if (con->type == CT_WORKSPACE) {
355  DLOG("Workspace, simply changing orientation to %d\n", orientation);
356  con->layout = (orientation == HORIZ) ? L_SPLITH : L_SPLITV;
357  return;
358  }
359  else if (con->type == CT_FLOATING_CON) {
360  DLOG("Floating containers can't be split.\n");
361  return;
362  }
363 
364  Con *parent = con->parent;
365 
366  /* Force re-rendering to make the indicator border visible. */
367  FREE(con->deco_render_params);
368  FREE(parent->deco_render_params);
369 
370  /* if we are in a container whose parent contains only one
371  * child (its split functionality is unused so far), we just change the
372  * orientation (more intuitive than splitting again) */
373  if (con_num_children(parent) == 1 &&
374  (parent->layout == L_SPLITH ||
375  parent->layout == L_SPLITV)) {
376  parent->layout = (orientation == HORIZ) ? L_SPLITH : L_SPLITV;
377  DLOG("Just changing orientation of existing container\n");
378  return;
379  }
380 
381  DLOG("Splitting in orientation %d\n", orientation);
382 
383  /* 2: replace it with a new Con */
384  Con *new = con_new(NULL, NULL);
385  TAILQ_REPLACE(&(parent->nodes_head), con, new, nodes);
386  TAILQ_REPLACE(&(parent->focus_head), con, new, focused);
387  new->parent = parent;
388  new->layout = (orientation == HORIZ) ? L_SPLITH : L_SPLITV;
389 
390  /* 3: swap 'percent' (resize factor) */
391  new->percent = con->percent;
392  con->percent = 0.0;
393 
394  /* 4: add it as a child to the new Con */
395  con_attach(con, new, false);
396 }
397 
398 /*
399  * Moves focus one level up. Returns true if focus changed.
400  *
401  */
402 bool level_up(void) {
403  /* Skip over floating containers and go directly to the grandparent
404  * (which should always be a workspace) */
405  if (focused->parent->type == CT_FLOATING_CON) {
406  con_focus(focused->parent->parent);
407  return true;
408  }
409 
410  /* We can focus up to the workspace, but not any higher in the tree */
411  if ((focused->parent->type != CT_CON &&
412  focused->parent->type != CT_WORKSPACE) ||
413  focused->type == CT_WORKSPACE) {
414  ELOG("'focus parent': Focus is already on the workspace, cannot go higher than that.\n");
415  return false;
416  }
417  con_focus(focused->parent);
418  return true;
419 }
420 
421 /*
422  * Moves focus one level down. Returns true if focus changed.
423  *
424  */
425 bool level_down(void) {
426  /* Go down the focus stack of the current node */
427  Con *next = TAILQ_FIRST(&(focused->focus_head));
428  if (next == TAILQ_END(&(focused->focus_head))) {
429  DLOG("cannot go down\n");
430  return false;
431  }
432  else if (next->type == CT_FLOATING_CON) {
433  /* Floating cons shouldn't be directly focused; try immediately
434  * going to the grandchild of the focused con. */
435  Con *child = TAILQ_FIRST(&(next->focus_head));
436  if (child == TAILQ_END(&(next->focus_head))) {
437  DLOG("cannot go down\n");
438  return false;
439  }
440  else
441  next = TAILQ_FIRST(&(next->focus_head));
442  }
443 
444  con_focus(next);
445  return true;
446 }
447 
448 static void mark_unmapped(Con *con) {
449  Con *current;
450 
451  con->mapped = false;
452  TAILQ_FOREACH(current, &(con->nodes_head), nodes)
453  mark_unmapped(current);
454  if (con->type == CT_WORKSPACE) {
455  /* We need to call mark_unmapped on floating nodes aswell since we can
456  * make containers floating. */
457  TAILQ_FOREACH(current, &(con->floating_head), floating_windows)
458  mark_unmapped(current);
459  }
460 }
461 
462 /*
463  * Renders the tree, that is rendering all outputs using render_con() and
464  * pushing the changes to X11 using x_push_changes().
465  *
466  */
467 void tree_render(void) {
468  if (croot == NULL)
469  return;
470 
471  DLOG("-- BEGIN RENDERING --\n");
472  /* Reset map state for all nodes in tree */
473  /* TODO: a nicer method to walk all nodes would be good, maybe? */
474  mark_unmapped(croot);
475  croot->mapped = true;
476 
477  render_con(croot, false);
478 
479  x_push_changes(croot);
480  DLOG("-- END RENDERING --\n");
481 }
482 
483 /*
484  * Recursive function to walk the tree until a con can be found to focus.
485  *
486  */
487 static bool _tree_next(Con *con, char way, orientation_t orientation, bool wrap) {
488  /* When dealing with fullscreen containers, it's necessary to go up to the
489  * workspace level, because 'focus $dir' will start at the con's real
490  * position in the tree, and it may not be possible to get to the edge
491  * normally due to fullscreen focusing restrictions. */
492  if (con->fullscreen_mode == CF_OUTPUT && con->type != CT_WORKSPACE)
493  con = con_get_workspace(con);
494 
495  /* Stop recursing at workspaces after attempting to switch to next
496  * workspace if possible. */
497  if (con->type == CT_WORKSPACE) {
498  if (con_get_fullscreen_con(con, CF_GLOBAL)) {
499  DLOG("Cannot change workspace while in global fullscreen mode.\n");
500  return false;
501  }
502  Output *current_output = get_output_containing(con->rect.x, con->rect.y);
503  Output *next_output;
504 
505  if (!current_output)
506  return false;
507  DLOG("Current output is %s\n", current_output->name);
508 
509  /* Try to find next output */
510  direction_t direction;
511  if (way == 'n' && orientation == HORIZ)
512  direction = D_RIGHT;
513  else if (way == 'p' && orientation == HORIZ)
514  direction = D_LEFT;
515  else if (way == 'n' && orientation == VERT)
516  direction = D_DOWN;
517  else if (way == 'p' && orientation == VERT)
518  direction = D_UP;
519  else
520  return false;
521 
522  next_output = get_output_next(direction, current_output, CLOSEST_OUTPUT);
523  if (!next_output)
524  return false;
525  DLOG("Next output is %s\n", next_output->name);
526 
527  /* Find visible workspace on next output */
528  Con *workspace = NULL;
529  GREP_FIRST(workspace, output_get_content(next_output->con), workspace_is_visible(child));
530 
531  /* Show next workspace and focus appropriate container if possible. */
532  if (!workspace)
533  return false;
534 
535  workspace_show(workspace);
536 
537  /* If a workspace has an active fullscreen container, one of its
538  * children should always be focused. The above workspace_show()
539  * should be adequate for that, so return. */
540  if (con_get_fullscreen_con(workspace, CF_OUTPUT))
541  return true;
542 
543  Con *focus = con_descend_direction(workspace, direction);
544  if (focus) {
545  con_focus(focus);
546  x_set_warp_to(&(focus->rect));
547  }
548  return true;
549  }
550 
551  Con *parent = con->parent;
552 
553  if (con->type == CT_FLOATING_CON) {
554  /* left/right focuses the previous/next floating container */
555  if (orientation == HORIZ) {
556  Con *next;
557  if (way == 'n')
558  next = TAILQ_NEXT(con, floating_windows);
559  else next = TAILQ_PREV(con, floating_head, floating_windows);
560 
561  /* If there is no next/previous container, wrap */
562  if (!next) {
563  if (way == 'n')
564  next = TAILQ_FIRST(&(parent->floating_head));
565  else next = TAILQ_LAST(&(parent->floating_head), floating_head);
566  }
567 
568  /* Still no next/previous container? bail out */
569  if (!next)
570  return false;
571 
573  return true;
574  } else {
575  /* up/down cycles through the Z-index */
576  /* TODO: implement cycling through the z-index */
577  return false;
578  }
579  }
580 
581  /* If the orientation does not match or there is no other con to focus, we
582  * need to go higher in the hierarchy */
583  if (con_orientation(parent) != orientation ||
584  con_num_children(parent) == 1)
585  return _tree_next(parent, way, orientation, wrap);
586 
587  Con *current = TAILQ_FIRST(&(parent->focus_head));
588  /* TODO: when can the following happen (except for floating windows, which
589  * are handled above)? */
590  if (TAILQ_EMPTY(&(parent->nodes_head))) {
591  DLOG("nothing to focus\n");
592  return false;
593  }
594 
595  Con *next;
596  if (way == 'n')
597  next = TAILQ_NEXT(current, nodes);
598  else next = TAILQ_PREV(current, nodes_head, nodes);
599 
600  if (!next) {
602  /* If there is no next/previous container, we check if we can focus one
603  * when going higher (without wrapping, though). If so, we are done, if
604  * not, we wrap */
605  if (_tree_next(parent, way, orientation, false))
606  return true;
607 
608  if (!wrap)
609  return false;
610  }
611 
612  if (way == 'n')
613  next = TAILQ_FIRST(&(parent->nodes_head));
614  else next = TAILQ_LAST(&(parent->nodes_head), nodes_head);
615  }
616 
617  /* Don't violate fullscreen focus restrictions. */
619  return false;
620 
621  /* 3: focus choice comes in here. at the moment we will go down
622  * until we find a window */
623  /* TODO: check for window, atm we only go down as far as possible */
625  return true;
626 }
627 
628 /*
629  * Changes focus in the given way (next/previous) and given orientation
630  * (horizontal/vertical).
631  *
632  */
633 void tree_next(char way, orientation_t orientation) {
634  _tree_next(focused, way, orientation, true);
635 }
636 
637 /*
638  * tree_flatten() removes pairs of redundant split containers, e.g.:
639  * [workspace, horizontal]
640  * [v-split] [child3]
641  * [h-split]
642  * [child1] [child2]
643  * In this example, the v-split and h-split container are redundant.
644  * Such a situation can be created by moving containers in a direction which is
645  * not the orientation of their parent container. i3 needs to create a new
646  * split container then and if you move containers this way multiple times,
647  * redundant chains of split-containers can be the result.
648  *
649  */
650 void tree_flatten(Con *con) {
651  Con *current, *child, *parent = con->parent;
652  DLOG("Checking if I can flatten con = %p / %s\n", con, con->name);
653 
654  /* We only consider normal containers without windows */
655  if (con->type != CT_CON ||
656  parent->layout == L_OUTPUT || /* con == "content" */
657  con->window != NULL)
658  goto recurse;
659 
660  /* Ensure it got only one child */
661  child = TAILQ_FIRST(&(con->nodes_head));
662  if (child == NULL || TAILQ_NEXT(child, nodes) != NULL)
663  goto recurse;
664 
665  DLOG("child = %p, con = %p, parent = %p\n", child, con, parent);
666 
667  /* The child must have a different orientation than the con but the same as
668  * the con’s parent to be redundant */
669  if (!con_is_split(con) ||
670  !con_is_split(child) ||
671  con_orientation(con) == con_orientation(child) ||
672  con_orientation(child) != con_orientation(parent))
673  goto recurse;
674 
675  DLOG("Alright, I have to flatten this situation now. Stay calm.\n");
676  /* 1: save focus */
677  Con *focus_next = TAILQ_FIRST(&(child->focus_head));
678 
679  DLOG("detaching...\n");
680  /* 2: re-attach the children to the parent before con */
681  while (!TAILQ_EMPTY(&(child->nodes_head))) {
682  current = TAILQ_FIRST(&(child->nodes_head));
683  DLOG("detaching current=%p / %s\n", current, current->name);
684  con_detach(current);
685  DLOG("re-attaching\n");
686  /* We don’t use con_attach() here because for a CT_CON, the special
687  * case handling of con_attach() does not trigger. So all it would do
688  * is calling TAILQ_INSERT_AFTER, but with the wrong container. So we
689  * directly use the TAILQ macros. */
690  current->parent = parent;
691  TAILQ_INSERT_BEFORE(con, current, nodes);
692  DLOG("attaching to focus list\n");
693  TAILQ_INSERT_TAIL(&(parent->focus_head), current, focused);
694  current->percent = con->percent;
695  }
696  DLOG("re-attached all\n");
697 
698  /* 3: restore focus, if con was focused */
699  if (focus_next != NULL &&
700  TAILQ_FIRST(&(parent->focus_head)) == con) {
701  DLOG("restoring focus to focus_next=%p\n", focus_next);
702  TAILQ_REMOVE(&(parent->focus_head), focus_next, focused);
703  TAILQ_INSERT_HEAD(&(parent->focus_head), focus_next, focused);
704  DLOG("restored focus.\n");
705  }
706 
707  /* 4: close the redundant cons */
708  DLOG("closing redundant cons\n");
709  tree_close(con, DONT_KILL_WINDOW, true, false);
710 
711  /* Well, we got to abort the recursion here because we destroyed the
712  * container. However, if tree_flatten() is called sufficiently often,
713  * there can’t be the situation of having two pairs of redundant containers
714  * at once. Therefore, we can safely abort the recursion on this level
715  * after flattening. */
716  return;
717 
718 recurse:
719  /* We cannot use normal foreach here because tree_flatten might close the
720  * current container. */
721  current = TAILQ_FIRST(&(con->nodes_head));
722  while (current != NULL) {
723  Con *next = TAILQ_NEXT(current, nodes);
724  tree_flatten(current);
725  current = next;
726  }
727 
728  current = TAILQ_FIRST(&(con->floating_head));
729  while (current != NULL) {
730  Con *next = TAILQ_NEXT(current, floating_windows);
731  tree_flatten(current);
732  current = next;
733  }
734 }