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1 | /* xscreensaver, Copyright (c) 1993-2017 Jamie Zawinski <jwz@jwz.org> |
2 | * | |
3 | * Permission to use, copy, modify, distribute, and sell this software and its | |
4 | * documentation for any purpose is hereby granted without fee, provided that | |
5 | * the above copyright notice appear in all copies and that both that | |
6 | * copyright notice and this permission notice appear in supporting | |
7 | * documentation. No representations are made about the suitability of this | |
8 | * software for any purpose. It is provided "as is" without express or | |
9 | * implied warranty. | |
10 | */ | |
11 | ||
12 | /* The MIT-SHM (Shared Memory) extension is pretty tricky to use. | |
13 | This file contains the common boiler-plate for creating a shared | |
14 | XImage structure, and for making sure that the shared memory segments | |
15 | get allocated and shut down cleanly. | |
16 | ||
17 | This code currently deals only with shared XImages, not with shared Pixmaps. | |
18 | It also doesn't use "completion events", but so far that doesn't seem to | |
19 | be a problem (and I'm not entirely clear on when they would actually be | |
20 | needed, anyway.) | |
21 | ||
22 | If you don't have man pages for this extension, see | |
23 | https://www.x.org/releases/current/doc/xextproto/shm.html | |
24 | ||
25 | (This document seems not to ever remain available on the web in one place | |
26 | for very long; you can search for it by the title, "MIT-SHM -- The MIT | |
27 | Shared Memory Extension".) | |
28 | ||
29 | To monitor the system's shared memory segments, run "ipcs -m". | |
30 | */ | |
31 | ||
32 | #include "utils.h" | |
33 | ||
34 | /* #define DEBUG */ | |
35 | ||
36 | #include <errno.h> /* for perror() */ | |
37 | ||
38 | #ifdef HAVE_JWXYZ | |
39 | # include "jwxyz.h" | |
40 | #else | |
41 | # include <X11/Xutil.h> /* for XDestroyImage() */ | |
42 | #endif | |
43 | ||
44 | #include "xshm.h" | |
45 | #include "resources.h" /* for get_string_resource() */ | |
46 | #include "thread_util.h" /* for thread_malloc() */ | |
47 | ||
48 | #ifdef DEBUG | |
49 | # include <X11/Xmu/Error.h> | |
50 | #endif | |
51 | ||
52 | extern char *progname; | |
53 | ||
54 | ||
55 | /* The documentation for the XSHM extension implies that if the server | |
56 | supports XSHM but is not the local machine, the XShm calls will return | |
57 | False; but this turns out not to be the case. Instead, the server | |
58 | throws a BadAccess error. So, we need to catch X errors around all | |
59 | of our XSHM calls, sigh. | |
60 | */ | |
61 | ||
62 | #ifdef HAVE_XSHM_EXTENSION | |
63 | ||
64 | static Bool shm_got_x_error = False; | |
65 | XErrorHandler old_handler = 0; | |
66 | static int | |
67 | shm_ehandler (Display *dpy, XErrorEvent *error) | |
68 | { | |
69 | shm_got_x_error = True; | |
70 | ||
71 | #ifdef DEBUG | |
72 | fprintf (stderr, "\n%s: ignoring X error from XSHM:\n", progname); | |
73 | XmuPrintDefaultErrorMessage (dpy, error, stderr); | |
74 | fprintf (stderr, "\n"); | |
75 | #endif | |
76 | ||
77 | return 0; | |
78 | } | |
79 | ||
80 | ||
81 | #define CATCH_X_ERROR(DPY) do { \ | |
82 | XSync((DPY), False); \ | |
83 | shm_got_x_error = False; \ | |
84 | if (old_handler != shm_ehandler) \ | |
85 | old_handler = XSetErrorHandler (shm_ehandler); \ | |
86 | } while(0) | |
87 | ||
88 | #define UNCATCH_X_ERROR(DPY) do { \ | |
89 | XSync((DPY), False); \ | |
90 | if (old_handler) \ | |
91 | XSetErrorHandler (old_handler); \ | |
92 | old_handler = 0; \ | |
93 | } while(0) | |
94 | ||
95 | #endif /* HAVE_XSHM_EXTENSION */ | |
96 | ||
97 | ||
98 | static void | |
99 | print_error (int err) | |
100 | { | |
101 | fprintf(stderr, "%s: %s\n", progname, strerror(err)); | |
102 | } | |
103 | ||
104 | static XImage * | |
105 | create_fallback (Display *dpy, Visual *visual, | |
106 | unsigned int depth, | |
107 | int format, XShmSegmentInfo *shm_info, | |
108 | unsigned int width, unsigned int height) | |
109 | { | |
110 | XImage *image = XCreateImage (dpy, visual, depth, format, 0, NULL, | |
111 | width, height, BitmapPad(dpy), 0); | |
112 | shm_info->shmid = -1; | |
113 | ||
114 | if (!image) { | |
115 | print_error (ENOMEM); | |
116 | } else { | |
117 | /* Sometimes the XImage data needs to be aligned, such as for SIMD (SSE2 | |
118 | in Fireworkx), or multithreading (AnalogTV). | |
119 | */ | |
120 | int error = thread_malloc ((void **)&image->data, dpy, | |
121 | image->height * image->bytes_per_line); | |
122 | if (error) { | |
123 | print_error (error); | |
124 | XDestroyImage (image); | |
125 | image = NULL; | |
126 | } else { | |
127 | memset (image->data, 0, image->height * image->bytes_per_line); | |
128 | } | |
129 | } | |
130 | ||
131 | return image; | |
132 | } | |
133 | ||
134 | ||
135 | XImage * | |
136 | create_xshm_image (Display *dpy, Visual *visual, | |
137 | unsigned int depth, | |
138 | int format, XShmSegmentInfo *shm_info, | |
139 | unsigned int width, unsigned int height) | |
140 | { | |
141 | #ifndef HAVE_XSHM_EXTENSION | |
142 | ||
143 | return create_fallback (dpy, visual, depth, format, shm_info, width, height); | |
144 | ||
145 | #else /* HAVE_XSHM_EXTENSION */ | |
146 | ||
147 | Status status; | |
148 | XImage *image = 0; | |
149 | if (!get_boolean_resource(dpy, "useSHM", "Boolean") || | |
150 | !XShmQueryExtension (dpy)) { | |
151 | return create_fallback (dpy, visual, depth, format, shm_info, | |
152 | width, height); | |
153 | } | |
154 | ||
155 | CATCH_X_ERROR(dpy); | |
156 | image = XShmCreateImage(dpy, visual, depth, | |
157 | format, NULL, shm_info, width, height); | |
158 | UNCATCH_X_ERROR(dpy); | |
159 | if (shm_got_x_error) | |
160 | return create_fallback (dpy, visual, depth, format, shm_info, | |
161 | width, height); | |
162 | ||
163 | #ifdef DEBUG | |
164 | fprintf(stderr, "\n%s: XShmCreateImage(... %d, %d)\n", progname, | |
165 | width, height); | |
166 | #endif | |
167 | ||
168 | shm_info->shmid = shmget(IPC_PRIVATE, | |
169 | image->bytes_per_line * image->height, | |
170 | IPC_CREAT | 0777); | |
171 | #ifdef DEBUG | |
172 | fprintf(stderr, "%s: shmget(IPC_PRIVATE, %d, IPC_CREAT | 0777) ==> %d\n", | |
173 | progname, image->bytes_per_line * image->height, shm_info->shmid); | |
174 | #endif | |
175 | ||
176 | if (shm_info->shmid == -1) | |
177 | { | |
178 | char buf[1024]; | |
179 | sprintf (buf, "%s: shmget failed", progname); | |
180 | perror(buf); | |
181 | XDestroyImage (image); | |
182 | image = 0; | |
183 | XSync(dpy, False); | |
184 | } | |
185 | else | |
186 | { | |
187 | shm_info->readOnly = False; | |
188 | image->data = shm_info->shmaddr = shmat(shm_info->shmid, 0, 0); | |
189 | ||
190 | #ifdef DEBUG | |
191 | fprintf(stderr, "%s: shmat(%d, 0, 0) ==> %d\n", progname, | |
192 | shm_info->shmid, (int) image->data); | |
193 | #endif | |
194 | ||
195 | CATCH_X_ERROR(dpy); | |
196 | status = XShmAttach(dpy, shm_info); | |
197 | UNCATCH_X_ERROR(dpy); | |
198 | if (shm_got_x_error) | |
199 | status = False; | |
200 | ||
201 | if (!status) | |
202 | { | |
203 | fprintf (stderr, "%s: XShmAttach failed!\n", progname); | |
204 | XDestroyImage (image); | |
205 | XSync(dpy, False); | |
206 | shmdt (shm_info->shmaddr); | |
207 | image = 0; | |
208 | } | |
209 | #ifdef DEBUG | |
210 | else | |
211 | fprintf(stderr, "%s: XShmAttach(dpy, shm_info) ==> True\n", progname); | |
212 | #endif | |
213 | ||
214 | XSync(dpy, False); | |
215 | ||
216 | /* Delete the shared segment right now; the segment won't actually | |
217 | go away until both the client and server have deleted it. The | |
218 | server will delete it as soon as the client disconnects, so we | |
219 | should delete our side early in case of abnormal termination. | |
220 | (And note that, in the context of xscreensaver, abnormal | |
221 | termination is the rule rather than the exception, so this would | |
222 | leak like a sieve if we didn't do this...) | |
223 | ||
224 | #### Are we leaking anyway? Perhaps because of the window of | |
225 | opportunity between here and the XShmAttach call above, during | |
226 | which we might be killed? Do we need to establish a signal | |
227 | handler for this case? | |
228 | */ | |
229 | shmctl (shm_info->shmid, IPC_RMID, 0); | |
230 | ||
231 | #ifdef DEBUG | |
232 | fprintf(stderr, "%s: shmctl(%d, IPC_RMID, 0)\n\n", progname, | |
233 | shm_info->shmid); | |
234 | #endif | |
235 | } | |
236 | ||
237 | if (!image) { | |
238 | return create_fallback (dpy, visual, depth, format, shm_info, | |
239 | width, height); | |
240 | } | |
241 | ||
242 | return image; | |
243 | ||
244 | #endif /* HAVE_XSHM_EXTENSION */ | |
245 | } | |
246 | ||
247 | ||
248 | Bool | |
249 | put_xshm_image (Display *dpy, Drawable d, GC gc, XImage *image, | |
250 | int src_x, int src_y, int dest_x, int dest_y, | |
251 | unsigned int width, unsigned int height, | |
252 | XShmSegmentInfo *shm_info) | |
253 | { | |
254 | #ifdef HAVE_XSHM_EXTENSION | |
255 | assert (shm_info); /* Don't just s/XShmPutImage/put_xshm_image/. */ | |
256 | if (shm_info->shmid != -1) { | |
257 | /* XShmPutImage is asynchronous; the contents of the XImage must not be | |
258 | modified until the server has placed the pixels on the screen and the | |
259 | client has received an XShmCompletionEvent. Breaking this rule can cause | |
260 | tearing. That said, put_xshm_image doesn't provide a send_event | |
261 | parameter, so we're always breaking this rule. Not that it seems to | |
262 | matter; everything (so far) looks fine without it. | |
263 | ||
264 | ####: Add a send_event parameter. And fake it for XPutImage. | |
265 | */ | |
266 | return XShmPutImage (dpy, d, gc, image, src_x, src_y, dest_x, dest_y, | |
267 | width, height, False); | |
268 | } | |
269 | #endif /* HAVE_XSHM_EXTENSION */ | |
270 | ||
271 | return XPutImage (dpy, d, gc, image, src_x, src_y, dest_x, dest_y, | |
272 | width, height); | |
273 | } | |
274 | ||
275 | ||
276 | Bool | |
277 | get_xshm_image (Display *dpy, Drawable d, XImage *image, int x, int y, | |
278 | unsigned long plane_mask, XShmSegmentInfo *shm_info) | |
279 | { | |
280 | #ifdef HAVE_XSHM_EXTENSION | |
281 | if (shm_info->shmid != -1) { | |
282 | return XShmGetImage (dpy, d, image, x, y, plane_mask); | |
283 | } | |
284 | #endif /* HAVE_XSHM_EXTENSION */ | |
285 | return XGetSubImage (dpy, d, x, y, image->width, image->height, plane_mask, | |
286 | image->format, image, 0, 0) != NULL; | |
287 | } | |
288 | ||
289 | ||
290 | void | |
291 | destroy_xshm_image (Display *dpy, XImage *image, XShmSegmentInfo *shm_info) | |
292 | { | |
293 | #ifdef HAVE_XSHM_EXTENSION | |
294 | Status status; | |
295 | ||
296 | if (shm_info->shmid == -1) { | |
297 | #endif /* HAVE_XSHM_EXTENSION */ | |
298 | ||
299 | /* Don't let XDestroyImage free image->data. */ | |
300 | thread_free (image->data); | |
301 | image->data = NULL; | |
302 | XDestroyImage (image); | |
303 | return; | |
304 | ||
305 | #ifdef HAVE_XSHM_EXTENSION | |
306 | } | |
307 | ||
308 | CATCH_X_ERROR(dpy); | |
309 | status = XShmDetach (dpy, shm_info); | |
310 | UNCATCH_X_ERROR(dpy); | |
311 | if (shm_got_x_error) | |
312 | status = False; | |
313 | if (!status) | |
314 | fprintf (stderr, "%s: XShmDetach failed!\n", progname); | |
315 | # ifdef DEBUG | |
316 | else | |
317 | fprintf (stderr, "%s: XShmDetach(dpy, shm_info) ==> True\n", progname); | |
318 | # endif | |
319 | ||
320 | XDestroyImage (image); | |
321 | XSync(dpy, False); | |
322 | ||
323 | status = shmdt (shm_info->shmaddr); | |
324 | ||
325 | if (status != 0) | |
326 | { | |
327 | char buf[1024]; | |
328 | sprintf (buf, "%s: shmdt(0x%lx) failed", progname, | |
329 | (unsigned long) shm_info->shmaddr); | |
330 | perror(buf); | |
331 | } | |
332 | # ifdef DEBUG | |
333 | else | |
334 | fprintf (stderr, "%s: shmdt(shm_info->shmaddr) ==> 0\n", progname); | |
335 | # endif | |
336 | ||
337 | XSync(dpy, False); | |
338 | ||
339 | #endif /* HAVE_XSHM_EXTENSION */ | |
340 | } |