1/* gtksizerequest.c
2 * Copyright (C) 2007-2010 Openismus GmbH
3 *
4 * Authors:
5 * Mathias Hasselmann <mathias@openismus.com>
6 * Tristan Van Berkom <tristan.van.berkom@gmail.com>
7 *
8 * This library is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Library General Public
10 * License as published by the Free Software Foundation; either
11 * version 2 of the License, or (at your option) any later version.
12 *
13 * This library is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Library General Public License for more details.
17 *
18 * You should have received a copy of the GNU Library General Public
19 * License along with this library. If not, see <http://www.gnu.org/licenses/>.
20 */
21
22#include <config.h>
23
24#include "gtksizerequest.h"
25
26#include "gtkdebug.h"
27#include "gtkintl.h"
28#include "gtkprivate.h"
29#include "gtksizegroup-private.h"
30#include "gtksizerequestcacheprivate.h"
31#include "gtkwidgetprivate.h"
32#include "gtkcssnodeprivate.h"
33#include "gtkcssnumbervalueprivate.h"
34#include "gtklayoutmanagerprivate.h"
35
36
37#ifdef G_ENABLE_CONSISTENCY_CHECKS
38static GQuark recursion_check_quark = 0;
39
40static void
41push_recursion_check (GtkWidget *widget,
42 GtkOrientation orientation)
43{
44 gboolean in_measure = FALSE;
45
46 if (recursion_check_quark == 0)
47 recursion_check_quark = g_quark_from_static_string ("gtk-size-request-in-progress");
48
49 in_measure = GPOINTER_TO_INT (g_object_get_qdata (G_OBJECT (widget), recursion_check_quark));
50
51 if (in_measure)
52 {
53 g_warning ("%s %p: widget tried to gtk_widget_measure inside "
54 " GtkWidget::measure implementation. "
55 "Should just invoke GTK_WIDGET_GET_CLASS(widget)->measure "
56 "directly rather than using gtk_widget_measure",
57 G_OBJECT_TYPE_NAME (widget), widget);
58 }
59
60 g_object_set_qdata (G_OBJECT (widget), recursion_check_quark, GINT_TO_POINTER(TRUE));
61}
62
63static void
64pop_recursion_check (GtkWidget *widget,
65 GtkOrientation orientation)
66{
67 g_object_set_qdata (G_OBJECT (widget), recursion_check_quark, NULL);
68}
69#else
70#define push_recursion_check(widget, orientation)
71#define pop_recursion_check(widget, orientation)
72#endif /* G_ENABLE_CONSISTENCY_CHECKS */
73
74static GtkSizeRequestMode
75fetch_request_mode (GtkWidget *widget)
76{
77 GtkLayoutManager *layout_manager = gtk_widget_get_layout_manager (widget);
78
79 if (layout_manager != NULL)
80 return gtk_layout_manager_get_request_mode (manager: layout_manager);
81 else
82 return GTK_WIDGET_GET_CLASS (widget)->get_request_mode (widget);
83}
84
85static int
86get_number (GtkCssValue *value)
87{
88 double d = _gtk_css_number_value_get (number: value, one_hundred_percent: 100);
89
90 if (d < 1)
91 return ceil (x: d);
92 else
93 return floor (x: d);
94}
95
96/* Special-case min-width|height to round upwards, to avoid underalloc by 1px */
97static int
98get_number_ceil (GtkCssValue *value)
99{
100 return ceil (x: _gtk_css_number_value_get (number: value, one_hundred_percent: 100));
101}
102
103static void
104get_box_margin (GtkCssStyle *style,
105 GtkBorder *margin)
106{
107 margin->top = get_number (value: style->size->margin_top);
108 margin->left = get_number (value: style->size->margin_left);
109 margin->bottom = get_number (value: style->size->margin_bottom);
110 margin->right = get_number (value: style->size->margin_right);
111}
112
113static void
114get_box_border (GtkCssStyle *style,
115 GtkBorder *border)
116{
117 border->top = get_number (value: style->border->border_top_width);
118 border->left = get_number (value: style->border->border_left_width);
119 border->bottom = get_number (value: style->border->border_bottom_width);
120 border->right = get_number (value: style->border->border_right_width);
121}
122
123static void
124get_box_padding (GtkCssStyle *style,
125 GtkBorder *border)
126{
127 border->top = get_number (value: style->size->padding_top);
128 border->left = get_number (value: style->size->padding_left);
129 border->bottom = get_number (value: style->size->padding_bottom);
130 border->right = get_number (value: style->size->padding_right);
131}
132
133static void
134gtk_widget_query_size_for_orientation (GtkWidget *widget,
135 GtkOrientation orientation,
136 int for_size,
137 int *minimum,
138 int *natural,
139 int *minimum_baseline,
140 int *natural_baseline)
141{
142 SizeRequestCache *cache;
143 int min_size = 0;
144 int nat_size = 0;
145 int min_baseline = -1;
146 int nat_baseline = -1;
147 gboolean found_in_cache;
148
149 gtk_widget_ensure_resize (widget);
150
151 /* We check the request mode first, to determine whether the widget even does
152 * any wfh/hfw handling. If it doesn't, we reset for_size to -1 and ensure
153 * that we only cache one size for the widget (i.e. a lot more cache hits). */
154 cache = _gtk_widget_peek_request_cache (widget);
155 if (G_UNLIKELY (!cache->request_mode_valid))
156 {
157 cache->request_mode = fetch_request_mode (widget);
158 cache->request_mode_valid = TRUE;
159 }
160
161 if (cache->request_mode == GTK_SIZE_REQUEST_CONSTANT_SIZE)
162 for_size = -1;
163
164 found_in_cache = _gtk_size_request_cache_lookup (cache,
165 orientation,
166 for_size,
167 minimum: &min_size,
168 natural: &nat_size,
169 minimum_baseline: &min_baseline,
170 natural_baseline: &nat_baseline);
171
172 if (!found_in_cache)
173 {
174 GtkWidgetClass *widget_class;
175 GtkCssStyle *style;
176 GtkBorder margin, border, padding;
177 int adjusted_min, adjusted_natural;
178 int reported_min_size = 0;
179 int reported_nat_size = 0;
180 int css_min_size;
181 int css_min_for_size;
182 int css_extra_for_size;
183 int css_extra_size;
184 int widget_margins_for_size;
185
186 style = gtk_css_node_get_style (cssnode: gtk_widget_get_css_node (widget));
187 get_box_margin (style, margin: &margin);
188 get_box_border (style, border: &border);
189 get_box_padding (style, border: &padding);
190
191 widget_class = GTK_WIDGET_GET_CLASS (widget);
192
193 if (orientation == GTK_ORIENTATION_HORIZONTAL)
194 {
195 css_extra_size = margin.left + margin.right + border.left + border.right + padding.left + padding.right;
196 css_extra_for_size = margin.top + margin.bottom + border.top + border.bottom + padding.top + padding.bottom;
197 css_min_size = get_number_ceil (value: style->size->min_width);
198 css_min_for_size = get_number_ceil (value: style->size->min_height);
199 widget_margins_for_size = widget->priv->margin.top + widget->priv->margin.bottom;
200 }
201 else
202 {
203 css_extra_size = margin.top + margin.bottom + border.top + border.bottom + padding.top + padding.bottom;
204 css_extra_for_size = margin.left + margin.right + border.left + border.right + padding.left + padding.right;
205 css_min_size = get_number_ceil (value: style->size->min_height);
206 css_min_for_size = get_number_ceil (value: style->size->min_width);
207 widget_margins_for_size = widget->priv->margin.left + widget->priv->margin.right;
208 }
209
210 GtkLayoutManager *layout_manager = gtk_widget_get_layout_manager (widget);
211
212 if (layout_manager != NULL)
213 {
214 if (for_size < 0)
215 {
216 push_recursion_check (widget, orientation);
217 gtk_layout_manager_measure (manager: layout_manager, widget,
218 orientation, for_size: -1,
219 minimum: &reported_min_size, natural: &reported_nat_size,
220 minimum_baseline: &min_baseline, natural_baseline: &nat_baseline);
221 pop_recursion_check (widget, orientation);
222 }
223 else
224 {
225 int adjusted_for_size;
226 int minimum_for_size = 0;
227 int natural_for_size = 0;
228
229 /* Pull the minimum for_size from the cache as it's needed to adjust
230 * the proposed 'for_size' */
231 gtk_layout_manager_measure (manager: layout_manager, widget,
232 OPPOSITE_ORIENTATION (orientation), for_size: -1,
233 minimum: &minimum_for_size, natural: &natural_for_size,
234 NULL, NULL);
235
236 if (minimum_for_size < css_min_for_size)
237 minimum_for_size = css_min_for_size;
238
239 if (for_size < minimum_for_size)
240 for_size = minimum_for_size;
241
242 adjusted_for_size = for_size - widget_margins_for_size;
243 adjusted_for_size -= css_extra_for_size;
244 if (adjusted_for_size < 0)
245 adjusted_for_size = minimum_for_size;
246
247 push_recursion_check (widget, orientation);
248 gtk_layout_manager_measure (manager: layout_manager, widget,
249 orientation,
250 for_size: adjusted_for_size,
251 minimum: &reported_min_size, natural: &reported_nat_size,
252 minimum_baseline: &min_baseline, natural_baseline: &nat_baseline);
253 pop_recursion_check (widget, orientation);
254 }
255 }
256 else
257 {
258 if (for_size < 0)
259 {
260 push_recursion_check (widget, orientation);
261 widget_class->measure (widget, orientation, -1,
262 &reported_min_size, &reported_nat_size,
263 &min_baseline, &nat_baseline);
264 pop_recursion_check (widget, orientation);
265 }
266 else
267 {
268 int adjusted_for_size;
269 int minimum_for_size = 0;
270 int natural_for_size = 0;
271
272 /* Pull the minimum for_size from the cache as it's needed to adjust
273 * the proposed 'for_size' */
274 gtk_widget_measure (widget, OPPOSITE_ORIENTATION (orientation), for_size: -1,
275 minimum: &minimum_for_size, natural: &natural_for_size, NULL, NULL);
276
277 if (minimum_for_size < css_min_for_size)
278 minimum_for_size = css_min_for_size;
279
280 if (for_size < minimum_for_size)
281 for_size = minimum_for_size;
282
283 adjusted_for_size = for_size - widget_margins_for_size;
284 adjusted_for_size -= css_extra_for_size;
285 if (adjusted_for_size < 0)
286 adjusted_for_size = minimum_for_size;
287
288 push_recursion_check (widget, orientation);
289 widget_class->measure (widget,
290 orientation,
291 adjusted_for_size,
292 &reported_min_size, &reported_nat_size,
293 &min_baseline, &nat_baseline);
294 pop_recursion_check (widget, orientation);
295 }
296 }
297
298 min_size = MAX (0, MAX (reported_min_size, css_min_size)) + css_extra_size;
299 nat_size = MAX (0, MAX (reported_nat_size, css_min_size)) + css_extra_size;
300
301 if (G_UNLIKELY (min_size > nat_size))
302 {
303 if (orientation == GTK_ORIENTATION_HORIZONTAL)
304 {
305 g_warning ("%s %p (%s) reported min width %d and natural width %d in measure() with for_size=%d; natural size must be >= min size",
306 G_OBJECT_TYPE_NAME (widget), widget,
307 g_quark_to_string (gtk_css_node_get_name (gtk_widget_get_css_node (widget))),
308 min_size, nat_size, for_size);
309 }
310 else
311 {
312 g_warning ("%s %p (%s) reported min height %d and natural height %d in measure() with for_size=%d; natural size must be >= min size",
313 G_OBJECT_TYPE_NAME (widget), widget,
314 g_quark_to_string (gtk_css_node_get_name (gtk_widget_get_css_node (widget))),
315 min_size, nat_size, for_size);
316
317 }
318
319 nat_size = min_size;
320 }
321 else if (G_UNLIKELY (min_size < 0))
322 {
323 g_warning ("%s %p (%s) reported min %s %d, but sizes must be >= 0",
324 G_OBJECT_TYPE_NAME (widget), widget,
325 g_quark_to_string (gtk_css_node_get_name (gtk_widget_get_css_node (widget))),
326 orientation == GTK_ORIENTATION_HORIZONTAL ? "width" : "height",
327 min_size);
328 min_size = 0;
329 nat_size = MAX (0, min_size);
330 }
331
332 adjusted_min = min_size;
333 adjusted_natural = nat_size;
334 gtk_widget_adjust_size_request (widget, orientation,
335 minimum_size: &adjusted_min, natural_size: &adjusted_natural);
336
337 if (adjusted_min < min_size ||
338 adjusted_natural < nat_size)
339 {
340 g_warning ("%s %p adjusted size %s min %d natural %d must not decrease below min %d natural %d",
341 G_OBJECT_TYPE_NAME (widget), widget,
342 orientation == GTK_ORIENTATION_VERTICAL ? "vertical" : "horizontal",
343 adjusted_min, adjusted_natural,
344 min_size, nat_size);
345 /* don't use the adjustment */
346 }
347 else if (adjusted_min > adjusted_natural)
348 {
349 g_warning ("%s %p adjusted size %s min %d natural %d original min %d natural %d has min greater than natural",
350 G_OBJECT_TYPE_NAME (widget), widget,
351 orientation == GTK_ORIENTATION_VERTICAL ? "vertical" : "horizontal",
352 adjusted_min, adjusted_natural,
353 min_size, nat_size);
354 /* don't use the adjustment */
355 }
356 else
357 {
358 /* adjustment looks good */
359 min_size = adjusted_min;
360 nat_size = adjusted_natural;
361 }
362
363 if (min_baseline != -1 || nat_baseline != -1)
364 {
365 if (orientation == GTK_ORIENTATION_HORIZONTAL)
366 {
367 g_warning ("%s %p reported a horizontal baseline",
368 G_OBJECT_TYPE_NAME (widget), widget);
369 min_baseline = -1;
370 nat_baseline = -1;
371 }
372 else if (min_baseline == -1 || nat_baseline == -1)
373 {
374 g_warning ("%s %p reported baseline for only one of min/natural (min: %d, natural: %d)",
375 G_OBJECT_TYPE_NAME (widget), widget,
376 min_baseline, nat_baseline);
377 min_baseline = -1;
378 nat_baseline = -1;
379 }
380 else if (min_baseline > reported_min_size ||
381 nat_baseline > reported_nat_size ||
382 min_baseline < 0 ||
383 nat_baseline < 0)
384 {
385 g_warning ("%s %p reported baselines of minimum %d and natural %d, but sizes of "
386 "minimum %d and natural %d. Baselines must be inside the widget size.",
387 G_OBJECT_TYPE_NAME (widget), widget, min_baseline, nat_baseline,
388 reported_min_size, reported_nat_size);
389 min_baseline = -1;
390 nat_baseline = -1;
391 }
392 else
393 {
394 if (css_min_size > reported_min_size)
395 {
396 min_baseline += (css_min_size - reported_min_size) / 2;
397 nat_baseline += (css_min_size - reported_min_size) / 2;
398 }
399
400 min_baseline += margin.top + border.top + padding.top;
401 nat_baseline += margin.top + border.top + padding.top;
402
403 gtk_widget_adjust_baseline_request (widget, minimum_baseline: &min_baseline, natural_baseline: &nat_baseline);
404 }
405 }
406
407 _gtk_size_request_cache_commit (cache,
408 orientation,
409 for_size,
410 minimum_size: min_size,
411 natural_size: nat_size,
412 minimum_baseline: min_baseline,
413 natural_baseline: nat_baseline);
414 }
415
416 if (minimum)
417 *minimum = min_size;
418
419 if (natural)
420 *natural = nat_size;
421
422 if (minimum_baseline)
423 *minimum_baseline = min_baseline;
424
425 if (natural_baseline)
426 *natural_baseline = nat_baseline;
427
428 g_assert (min_size <= nat_size);
429
430 GTK_DISPLAY_NOTE (_gtk_widget_get_display (widget), SIZE_REQUEST, {
431 GString *s;
432
433 s = g_string_new ("");
434 g_string_append_printf (s, "[%p] %s\t%s: %d is minimum %d and natural: %d",
435 widget, G_OBJECT_TYPE_NAME (widget),
436 orientation == GTK_ORIENTATION_HORIZONTAL
437 ? "width for height"
438 : "height for width",
439 for_size, min_size, nat_size);
440 if (min_baseline != -1 || nat_baseline != -1)
441 {
442 g_string_append_printf (s, ", baseline %d/%d",
443 min_baseline, nat_baseline);
444 }
445 g_string_append_printf (s, " (hit cache: %s)\n",
446 found_in_cache ? "yes" : "no");
447 g_printerr ("%s", s->str);
448 g_string_free (s, TRUE);
449 });
450}
451
452/**
453 * gtk_widget_measure:
454 * @widget: A `GtkWidget` instance
455 * @orientation: the orientation to measure
456 * @for_size: Size for the opposite of @orientation, i.e.
457 * if @orientation is %GTK_ORIENTATION_HORIZONTAL, this is
458 * the height the widget should be measured with. The %GTK_ORIENTATION_VERTICAL
459 * case is analogous. This way, both height-for-width and width-for-height
460 * requests can be implemented. If no size is known, -1 can be passed.
461 * @minimum: (out) (optional): location to store the minimum size
462 * @natural: (out) (optional): location to store the natural size
463 * @minimum_baseline: (out) (optional): location to store the baseline
464 * position for the minimum size, or -1 to report no baseline
465 * @natural_baseline: (out) (optional): location to store the baseline
466 * position for the natural size, or -1 to report no baseline
467 *
468 * Measures @widget in the orientation @orientation and for the given @for_size.
469 *
470 * As an example, if @orientation is %GTK_ORIENTATION_HORIZONTAL and @for_size
471 * is 300, this functions will compute the minimum and natural width of @widget
472 * if it is allocated at a height of 300 pixels.
473 *
474 * See [GtkWidget’s geometry management section](class.Widget.html#height-for-width-geometry-management) for
475 * a more details on implementing `GtkWidgetClass.measure()`.
476 */
477void
478gtk_widget_measure (GtkWidget *widget,
479 GtkOrientation orientation,
480 int for_size,
481 int *minimum,
482 int *natural,
483 int *minimum_baseline,
484 int *natural_baseline)
485{
486 g_return_if_fail (GTK_IS_WIDGET (widget));
487 g_return_if_fail (for_size >= -1);
488 g_return_if_fail (orientation == GTK_ORIENTATION_HORIZONTAL ||
489 orientation == GTK_ORIENTATION_VERTICAL);
490
491 if (for_size >= 0)
492 {
493 int min_opposite_size;
494 gtk_widget_measure (widget, OPPOSITE_ORIENTATION (orientation), for_size: -1, minimum: &min_opposite_size, NULL, NULL, NULL);
495 if (for_size < min_opposite_size)
496 for_size = min_opposite_size;
497 }
498
499 /* This is the main function that checks for a cached size and
500 * possibly queries the widget class to compute the size if it's
501 * not cached.
502 */
503 if (!_gtk_widget_get_visible (widget) && !GTK_IS_ROOT (ptr: widget))
504 {
505 if (minimum)
506 *minimum = 0;
507 if (natural)
508 *natural = 0;
509 if (minimum_baseline)
510 *minimum_baseline = -1;
511 if (natural_baseline)
512 *natural_baseline = -1;
513 return;
514 }
515
516 if (G_LIKELY (!_gtk_widget_get_sizegroups (widget)))
517 {
518 gtk_widget_query_size_for_orientation (widget, orientation, for_size, minimum, natural,
519 minimum_baseline, natural_baseline);
520 }
521 else
522 {
523 GHashTable *widgets;
524 GHashTableIter iter;
525 gpointer key;
526 int min_result = 0, nat_result = 0;
527
528 widgets = _gtk_size_group_get_widget_peers (for_widget: widget, orientation);
529
530 g_hash_table_iter_init (iter: &iter, hash_table: widgets);
531 while (g_hash_table_iter_next (iter: &iter, key: &key, NULL))
532 {
533 GtkWidget *tmp_widget = key;
534 int min_dimension, nat_dimension;
535
536 gtk_widget_query_size_for_orientation (widget: tmp_widget, orientation, for_size,
537 minimum: &min_dimension, natural: &nat_dimension, NULL, NULL);
538
539 min_result = MAX (min_result, min_dimension);
540 nat_result = MAX (nat_result, nat_dimension);
541 }
542
543 g_hash_table_destroy (hash_table: widgets);
544
545 /* Baselines make no sense with sizegroups really */
546 if (minimum_baseline)
547 *minimum_baseline = -1;
548
549 if (natural_baseline)
550 *natural_baseline = -1;
551
552 if (minimum)
553 *minimum = min_result;
554
555 if (natural)
556 *natural = nat_result;
557 }
558}
559
560/**
561 * gtk_widget_get_request_mode:
562 * @widget: a `GtkWidget` instance
563 *
564 * Gets whether the widget prefers a height-for-width layout
565 * or a width-for-height layout.
566 *
567 * Single-child widgets generally propagate the preference of
568 * their child, more complex widgets need to request something
569 * either in context of their children or in context of their
570 * allocation capabilities.
571 *
572 * Returns: The `GtkSizeRequestMode` preferred by @widget.
573 */
574GtkSizeRequestMode
575gtk_widget_get_request_mode (GtkWidget *widget)
576{
577 SizeRequestCache *cache;
578
579 cache = _gtk_widget_peek_request_cache (widget);
580
581 if (G_UNLIKELY (!cache->request_mode_valid))
582 {
583 cache->request_mode = fetch_request_mode (widget);
584 cache->request_mode_valid = TRUE;
585 }
586
587 return cache->request_mode;
588}
589
590/**
591 * gtk_widget_get_preferred_size:
592 * @widget: a `GtkWidget` instance
593 * @minimum_size: (out) (optional): location for storing the minimum size
594 * @natural_size: (out) (optional): location for storing the natural size
595 *
596 * Retrieves the minimum and natural size of a widget, taking
597 * into account the widget’s preference for height-for-width management.
598 *
599 * This is used to retrieve a suitable size by container widgets which do
600 * not impose any restrictions on the child placement. It can be used
601 * to deduce toplevel window and menu sizes as well as child widgets in
602 * free-form containers such as `GtkFixed`.
603 *
604 * Handle with care. Note that the natural height of a height-for-width
605 * widget will generally be a smaller size than the minimum height, since
606 * the required height for the natural width is generally smaller than the
607 * required height for the minimum width.
608 *
609 * Use [id@gtk_widget_measure] if you want to support baseline alignment.
610 */
611void
612gtk_widget_get_preferred_size (GtkWidget *widget,
613 GtkRequisition *minimum_size,
614 GtkRequisition *natural_size)
615{
616 int min_width, nat_width;
617 int min_height, nat_height;
618
619 g_return_if_fail (GTK_IS_WIDGET (widget));
620
621 if (gtk_widget_get_request_mode (widget) == GTK_SIZE_REQUEST_HEIGHT_FOR_WIDTH)
622 {
623 gtk_widget_measure (widget, orientation: GTK_ORIENTATION_HORIZONTAL, for_size: -1,
624 minimum: &min_width, natural: &nat_width, NULL, NULL);
625
626 if (minimum_size)
627 {
628 minimum_size->width = min_width;
629 gtk_widget_measure (widget,
630 orientation: GTK_ORIENTATION_VERTICAL, for_size: min_width,
631 minimum: &minimum_size->height, NULL, NULL, NULL);
632 }
633
634 if (natural_size)
635 {
636 natural_size->width = nat_width;
637 gtk_widget_measure (widget,
638 orientation: GTK_ORIENTATION_VERTICAL, for_size: nat_width,
639 NULL, natural: &natural_size->height, NULL, NULL);
640 }
641 }
642 else /* GTK_SIZE_REQUEST_WIDTH_FOR_HEIGHT or CONSTANT_SIZE */
643 {
644 gtk_widget_measure (widget, orientation: GTK_ORIENTATION_VERTICAL,
645 for_size: -1, minimum: &min_height, natural: &nat_height, NULL, NULL);
646
647 if (minimum_size)
648 {
649 minimum_size->height = min_height;
650 gtk_widget_measure (widget, orientation: GTK_ORIENTATION_HORIZONTAL, for_size: min_height,
651 minimum: &minimum_size->width, NULL, NULL, NULL);
652 }
653
654 if (natural_size)
655 {
656 natural_size->height = nat_height;
657 gtk_widget_measure (widget, orientation: GTK_ORIENTATION_HORIZONTAL, for_size: nat_height,
658 NULL, natural: &natural_size->width, NULL, NULL);
659 }
660 }
661}
662
663static int
664compare_gap (gconstpointer p1,
665 gconstpointer p2,
666 gpointer data)
667{
668 GtkRequestedSize *sizes = data;
669 const guint *c1 = p1;
670 const guint *c2 = p2;
671
672 const int d1 = MAX (sizes[*c1].natural_size -
673 sizes[*c1].minimum_size,
674 0);
675 const int d2 = MAX (sizes[*c2].natural_size -
676 sizes[*c2].minimum_size,
677 0);
678
679 int delta = (d2 - d1);
680
681 if (0 == delta)
682 delta = (*c2 - *c1);
683
684 return delta;
685}
686
687/**
688 * gtk_distribute_natural_allocation:
689 * @extra_space: Extra space to redistribute among children after subtracting
690 * minimum sizes and any child padding from the overall allocation
691 * @n_requested_sizes: Number of requests to fit into the allocation
692 * @sizes: (array length=n_requested_sizes): An array of structs with a client pointer and a minimum/natural size
693 * in the orientation of the allocation.
694 *
695 * Distributes @extra_space to child @sizes by bringing smaller
696 * children up to natural size first.
697 *
698 * The remaining space will be added to the @minimum_size member of the
699 * `GtkRequestedSize` struct. If all sizes reach their natural size then
700 * the remaining space is returned.
701 *
702 * Returns: The remainder of @extra_space after redistributing space
703 * to @sizes.
704 */
705int
706gtk_distribute_natural_allocation (int extra_space,
707 guint n_requested_sizes,
708 GtkRequestedSize *sizes)
709{
710 guint *spreading;
711 int i;
712
713 g_return_val_if_fail (extra_space >= 0, 0);
714
715 if (n_requested_sizes == 0)
716 return extra_space;
717
718 spreading = g_newa (guint, n_requested_sizes);
719
720 for (i = 0; i < n_requested_sizes; i++)
721 spreading[i] = i;
722
723 /* Distribute the container's extra space c_gap. We want to assign
724 * this space such that the sum of extra space assigned to children
725 * (c^i_gap) is equal to c_cap. The case that there's not enough
726 * space for all children to take their natural size needs some
727 * attention. The goals we want to achieve are:
728 *
729 * a) Maximize number of children taking their natural size.
730 * b) The allocated size of children should be a continuous
731 * function of c_gap. That is, increasing the container size by
732 * one pixel should never make drastic changes in the distribution.
733 * c) If child i takes its natural size and child j doesn't,
734 * child j should have received at least as much gap as child i.
735 *
736 * The following code distributes the additional space by following
737 * these rules.
738 */
739
740 /* Sort descending by gap and position. */
741 g_qsort_with_data (pbase: spreading,
742 total_elems: n_requested_sizes, size: sizeof (guint),
743 compare_func: compare_gap, user_data: sizes);
744
745 /* Distribute available space.
746 * This masterpiece of a loop was conceived by Behdad Esfahbod.
747 */
748 for (i = n_requested_sizes - 1; extra_space > 0 && i >= 0; --i)
749 {
750 /* Divide remaining space by number of remaining children.
751 * Sort order and reducing remaining space by assigned space
752 * ensures that space is distributed equally.
753 */
754 int glue = (extra_space + i) / (i + 1);
755 int gap = sizes[(spreading[i])].natural_size
756 - sizes[(spreading[i])].minimum_size;
757
758 int extra = MIN (glue, gap);
759
760 sizes[spreading[i]].minimum_size += extra;
761
762 extra_space -= extra;
763 }
764
765 return extra_space;
766}
767

source code of gtk/gtk/gtksizerequest.c