source: libcaca/trunk/caca/dirty.c @ 4369

Last change on this file since 4369 was 4369, checked in by sam, 5 years ago

Add the copyright unit test and update copyright information everywhere.

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1/*
2 *  libcaca       Colour ASCII-Art library
3 *  Copyright (c) 2002-2010 Sam Hocevar <sam@hocevar.net>
4 *                All Rights Reserved
5 *
6 *  This library is free software. It comes without any warranty, to
7 *  the extent permitted by applicable law. You can redistribute it
8 *  and/or modify it under the terms of the Do What The Fuck You Want
9 *  To Public License, Version 2, as published by Sam Hocevar. See
10 *  http://sam.zoy.org/wtfpl/COPYING for more details.
11 */
12
13/*
14 *  This file contains the dirty rectangle handling functions.
15 *
16 *
17 *  About dirty rectangles:
18 *
19 *  * Dirty rectangles MUST NOT be larger than the canvas. If the user
20 *  provides a large rectangle through caca_add_dirty_rect(), or if the
21 *  canvas changes size to become smaller, all dirty rectangles MUST
22 *  immediately be clipped to the canvas size.
23 */
24
25#include "config.h"
26
27#if !defined(__KERNEL__)
28#   include <stdio.h>
29#   include <string.h>
30#endif
31
32#include "caca.h"
33#include "caca_internals.h"
34
35static void merge_new_rect(caca_canvas_t *cv, int n);
36
37/** \brief Disable dirty rectangles.
38 *
39 *  Disable dirty rectangle handling for all \e libcaca graphic calls. This
40 *  is handy when the calling application needs to do slow operations within
41 *  a known area. Just call caca_add_dirty_rect() afterwards.
42 *
43 *  This function is recursive. Dirty rectangles are only reenabled when
44 *  caca_enable_dirty_rect() is called as many times.
45 *
46 *  This function never fails.
47 *
48 *  \param cv A libcaca canvas.
49 *  \return This function always returns 0.
50 */
51int caca_disable_dirty_rect(caca_canvas_t *cv)
52{
53    cv->dirty_disabled++;
54
55    return 0;
56}
57
58/** \brief Enable dirty rectangles.
59 *
60 *  This function can only be called after caca_disable_dirty_rect() was
61 *  called.
62 *
63 *  If an error occurs, -1 is returned and \b errno is set accordingly:
64 *  - \c EINVAL Dirty rectangles were not disabled.
65 *
66 *  \param cv A libcaca canvas.
67 *  \return 0 in case of success, -1 if an error occurred.
68 */
69int caca_enable_dirty_rect(caca_canvas_t *cv)
70{
71    if(cv->dirty_disabled <= 0)
72    {
73        seterrno(EINVAL);
74        return -1;
75    }
76
77    cv->dirty_disabled--;
78
79    return 0;
80}
81
82/** \brief Get the number of dirty rectangles in the canvas.
83 *
84 *  Get the number of dirty rectangles in a canvas. Dirty rectangles are
85 *  areas that contain cells that have changed since the last reset.
86 *
87 *  The dirty rectangles are used internally by display drivers to optimise
88 *  rendering by avoiding to redraw the whole screen. Once the display driver
89 *  has rendered the canvas, it resets the dirty rectangle list.
90 *
91 *  Dirty rectangles are guaranteed not to overlap.
92 *
93 *  This function never fails.
94 *
95 *  \param cv A libcaca canvas.
96 *  \return The number of dirty rectangles in the given canvas.
97 */
98int caca_get_dirty_rect_count(caca_canvas_t *cv)
99{
100    return cv->ndirty;
101}
102
103/** \brief Get a canvas's dirty rectangle.
104 *
105 *  Get the canvas's given dirty rectangle coordinates. The index must be
106 *  within the dirty rectangle count. See caca_get_dirty_rect_count()
107 *  for how to compute this count.
108 *
109 *  If an error occurs, no coordinates are written in the pointer arguments,
110 *  -1 is returned and \b errno is set accordingly:
111 *  - \c EINVAL Specified rectangle index is out of bounds.
112 *
113 *  \param cv A libcaca canvas.
114 *  \param r The requested rectangle index.
115 *  \param x A pointer to an integer where the leftmost edge of the
116 *           dirty rectangle will be stored.
117 *  \param y A pointer to an integer where the topmost edge of the
118 *           dirty rectangle will be stored.
119 *  \param width A pointer to an integer where the width of the
120 *               dirty rectangle will be stored.
121 *  \param height A pointer to an integer where the height of the
122 *                dirty rectangle will be stored.
123 *  \return 0 in case of success, -1 if an error occurred.
124 */
125int caca_get_dirty_rect(caca_canvas_t *cv, int r,
126                        int *x, int *y, int *width, int *height)
127{
128    if(r < 0 || r >= cv->ndirty)
129    {
130        seterrno(EINVAL);
131        return -1;
132    }
133
134    *x = cv->dirty[r].xmin;
135    *y = cv->dirty[r].ymin;
136    *width = cv->dirty[r].xmax - cv->dirty[r].xmin + 1;
137    *height = cv->dirty[r].ymax - cv->dirty[r].ymin + 1;
138
139    debug("dirty #%i: %ix%i at (%i,%i)", r, *width, *height, *x, *y);
140
141    return 0;
142}
143
144/** \brief Add an area to the canvas's dirty rectangle list.
145 *
146 *  Add an invalidating zone to the canvas's dirty rectangle list. For more
147 *  information about the dirty rectangles, see caca_get_dirty_rect().
148 *
149 *  This function may be useful to force refresh of a given zone of the
150 *  canvas even if the dirty rectangle tracking indicates that it is
151 *  unchanged. This may happen if the canvas contents were somewhat
152 *  directly modified.
153 *
154 *  If an error occurs, -1 is returned and \b errno is set accordingly:
155 *  - \c EINVAL Specified rectangle coordinates are out of bounds.
156 *
157 *  \param cv A libcaca canvas.
158 *  \param x The leftmost edge of the additional dirty rectangle.
159 *  \param y The topmost edge of the additional dirty rectangle.
160 *  \param width The width of the additional dirty rectangle.
161 *  \param height The height of the additional dirty rectangle.
162 *  \return 0 in case of success, -1 if an error occurred.
163 */
164int caca_add_dirty_rect(caca_canvas_t *cv, int x, int y, int width, int height)
165{
166    debug("new dirty: %ix%i at (%i,%i)", width, height, x, y);
167
168    /* Clip arguments to canvas */
169    if(x < 0) { width += x; x = 0; }
170
171    if(x + width > cv->width)
172        width = cv->width - x;
173
174    if(y < 0) { height += y; y = 0; }
175
176    if(y + height > cv->height)
177        height = cv->height - y;
178
179    /* Ignore empty and out-of-canvas rectangles */
180    if(width <= 0 || height <= 0)
181    {
182        seterrno(EINVAL);
183        return -1;
184    }
185
186    /* Add the new rectangle to the list; it works even if cv->ndirty
187     * is MAX_DIRTY_COUNT because there's an extra cell in the array. */
188    cv->dirty[cv->ndirty].xmin = x;
189    cv->dirty[cv->ndirty].ymin = y;
190    cv->dirty[cv->ndirty].xmax = x + width - 1;
191    cv->dirty[cv->ndirty].ymax = y + height - 1;
192    cv->ndirty++;
193
194    /* Try to merge the new rectangle with existing ones. This also ensures
195     * that cv->ndirty is brought back below MAX_DIRTY_COUNT. */
196    merge_new_rect(cv, cv->ndirty - 1);
197
198    return 0;
199}
200
201/** \brief Remove an area from the dirty rectangle list.
202 *
203 *  Mark a cell area in the canvas as not dirty. For more information about
204 *  the dirty rectangles, see caca_get_dirty_rect().
205 *
206 *  Values such that \b xmin > \b xmax or \b ymin > \b ymax indicate that
207 *  the dirty rectangle is empty. They will be silently ignored.
208 *
209 *  If an error occurs, -1 is returned and \b errno is set accordingly:
210 *  - \c EINVAL Specified rectangle coordinates are out of bounds.
211 *
212 *  \param cv A libcaca canvas.
213 *  \param x The leftmost edge of the clean rectangle.
214 *  \param y The topmost edge of the clean rectangle.
215 *  \param width The width of the clean rectangle.
216 *  \param height The height of the clean rectangle.
217 *  \return 0 in case of success, -1 if an error occurred.
218 */
219int caca_remove_dirty_rect(caca_canvas_t *cv, int x, int y,
220                           int width, int height)
221{
222    /* Clip arguments to canvas size */
223    if(x < 0) { width += x; x = 0; }
224
225    if(x + width > cv->width)
226        width = cv->width - x;
227
228    if(y < 0) { height += y; y = 0; }
229
230    if(y + height > cv->height)
231        height = cv->height - y;
232
233    /* Ignore empty and out-of-canvas rectangles */
234    if(width <= 0 || height <= 0)
235    {
236        seterrno(EINVAL);
237        return -1;
238    }
239
240    /* FIXME: implement this function. It's OK to have it do nothing,
241     * since we take a conservative approach in dirty rectangle handling,
242     * but we ought to help the rendering eventually. */
243
244    return 0;
245}
246
247/** \brief Clear a canvas's dirty rectangle list.
248 *
249 *  Empty the canvas's dirty rectangle list.
250 *
251 *  This function never fails.
252 *
253 *  \param cv A libcaca canvas.
254 *  \return This function always returns 0.
255 */
256int caca_clear_dirty_rect_list(caca_canvas_t *cv)
257{
258    cv->ndirty = 0;
259
260    return 0;
261}
262
263/*
264 * XXX: the following functions are local.
265 */
266
267static inline int int_min(int a, int b) { return a < b ? a : b; }
268static inline int int_max(int a, int b) { return a > b ? a : b; }
269
270/* Merge a newly added rectangle, if necessary. */
271static void merge_new_rect(caca_canvas_t *cv, int n)
272{
273    int wasted[MAX_DIRTY_COUNT + 1];
274    int i, sn, best, best_score;
275
276    best = -1;
277    best_score = cv->width * cv->height;
278
279    sn = (cv->dirty[n].xmax - cv->dirty[n].xmin + 1)
280           * (cv->dirty[n].ymax - cv->dirty[n].ymin + 1);
281
282    /* Check whether the new rectangle can be merged with an existing one. */
283    for(i = 0; i < cv->ndirty; i++)
284    {
285        int si, sf, xmin, ymin, xmax, ymax;
286
287        if(i == n)
288            continue;
289
290        xmin = int_min(cv->dirty[i].xmin, cv->dirty[n].xmin);
291        ymin = int_min(cv->dirty[i].ymin, cv->dirty[n].ymin);
292        xmax = int_max(cv->dirty[i].xmax, cv->dirty[n].xmax);
293        ymax = int_max(cv->dirty[i].ymax, cv->dirty[n].ymax);
294
295        sf = (xmax - xmin + 1) * (ymax - ymin + 1);
296
297        /* Shortcut: if the current rectangle is inside the new rectangle,
298         * we remove the current rectangle and continue trying merges. */
299        if(sf == sn)
300        {
301            memmove(&cv->dirty[i], &cv->dirty[i + 1],
302                    (cv->ndirty - i) * sizeof(cv->dirty[0]));
303            cv->ndirty--;
304
305            if(i < n)
306                n--;
307            else
308                i--;
309
310            continue;
311        }
312
313        si = (cv->dirty[i].xmax - cv->dirty[i].xmin + 1)
314               * (cv->dirty[i].ymax - cv->dirty[i].ymin + 1);
315
316        /* Shortcut: if the new rectangle is inside the current rectangle,
317         * we get rid of the new rectangle and bail out. */
318        if(sf == si)
319        {
320            cv->ndirty--;
321            memmove(&cv->dirty[n], &cv->dirty[n + 1],
322                    (cv->ndirty - n) * sizeof(cv->dirty[0]));
323            return;
324        }
325
326        /* We store approximately how many bytes were wasted. FIXME: this is
327         * not an exact computation, we need to be more precise. */
328        wasted[i] = sf - si - sn;
329
330        if(wasted[i] < best_score)
331        {
332             best = i;
333             best_score = wasted[i];
334        }
335    }
336
337    /* FIXME: we only try to merge the current rectangle, ignoring
338     * potentially better merges. */
339
340    /* If no acceptable score was found and the dirty rectangle list is
341     * not full, we bail out. */
342    if(best_score > 0 && cv->ndirty < MAX_DIRTY_COUNT)
343        return;
344
345    /* Otherwise, merge the rectangle with the best candidate */
346    cv->dirty[best].xmin = int_min(cv->dirty[best].xmin, cv->dirty[n].xmin);
347    cv->dirty[best].ymin = int_min(cv->dirty[best].ymin, cv->dirty[n].ymin);
348    cv->dirty[best].xmax = int_max(cv->dirty[best].xmax, cv->dirty[n].xmax);
349    cv->dirty[best].ymax = int_max(cv->dirty[best].ymax, cv->dirty[n].ymax);
350
351    memmove(&cv->dirty[n], &cv->dirty[n + 1],
352            (cv->ndirty - n) * sizeof(cv->dirty[0]));
353    cv->ndirty--;
354
355    if(best < n)
356        merge_new_rect(cv, best);
357    else
358        merge_new_rect(cv, best - 1);
359}
360
361/* Clip all dirty rectangles in case they're larger than the canvas */
362void _caca_clip_dirty_rect_list(caca_canvas_t *cv)
363{
364    int i;
365
366    for(i = 0; i < cv->ndirty; i++)
367    {
368        if(cv->dirty[i].xmin < 0)
369            cv->dirty[i].xmin = 0;
370
371        if(cv->dirty[i].ymin < 0)
372            cv->dirty[i].ymin = 0;
373
374        if(cv->dirty[i].xmax >= cv->width)
375            cv->dirty[i].xmax = cv->width - 1;
376
377        if(cv->dirty[i].ymax >= cv->height)
378            cv->dirty[i].ymax = cv->height - 1;
379    }
380}
381
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