| 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 | } |