src/x11conn.c

   1 /*
   2    X11 support for the Midnight Commander.
   3
   4    Copyright (C) 2005 The Free Software Foundation
   5
   6    Written by:
   7    Roland Illig <roland.illig@gmx.de>, 2005.
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 2 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program; if not, write to the Free Software
  21    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  22  */
  23
  24 /*
  25    !!! WARNING !!!
  26
  27    This code uses setjmp() and longjmp(). Before you modify _anything_
  28    here, please read the relevant sections of the C standard.
  29 */
  30
  31 #include <config.h>
  32
  33 #ifndef HAVE_TEXTMODE_X11_SUPPORT
  34 typedef int dummy;              /* C99 forbids empty compilation unit */
  35 #else
  36
  37 #include <setjmp.h>
  38
  39 #include <X11/Xlib.h>
  40
  41 #include "../src/global.h"
  42
  43 #ifdef HAVE_GMODULE
  44 #  include <gmodule.h>
  45 #endif
  46
  47 #include "x11conn.h"
  48
  49 /*** file scope type declarations **************************************/
  50
  51 typedef int (*mc_XErrorHandler_callback) (Display *, XErrorEvent *);
  52 typedef int (*mc_XIOErrorHandler_callback) (Display *);
  53
  54 /*** file scope variables **********************************************/
  55
  56 #ifdef HAVE_GMODULE
  57
  58 static Display * (*func_XOpenDisplay) (_Xconst char *);
  59 static int (*func_XCloseDisplay) (Display *);
  60 static mc_XErrorHandler_callback (*func_XSetErrorHandler)
  61         (mc_XErrorHandler_callback);
  62 static mc_XIOErrorHandler_callback (*func_XSetIOErrorHandler)
  63         (mc_XIOErrorHandler_callback);
  64 static Bool (*func_XQueryPointer) (Display *, Window, Window *, Window *,
  65         int *, int *, int *, int *, unsigned int *);
  66
  67 static GModule *x11_module;
  68
  69 #else
  70
  71 #define func_XOpenDisplay       XOpenDisplay
  72 #define func_XCloseDisplay      XCloseDisplay
  73 #define func_XSetErrorHandler   XSetErrorHandler
  74 #define func_XSetIOErrorHandler XSetIOErrorHandler
  75 #define func_XQueryPointer      XQueryPointer
  76
  77 #endif
  78
  79 static gboolean handlers_installed = FALSE;
  80
  81 /* This flag is set as soon as an X11 error is reported. Usually that
  82  * means that the DISPLAY is not available anymore. We do not try to
  83  * reconnect, as that would violate the X11 protocol. */
  84 static gboolean lost_connection = FALSE;
  85
  86 static jmp_buf x11_exception; /* FIXME: get a better name */
  87 static gboolean longjmp_allowed = FALSE;
  88
  89 /*** file private functions ********************************************/
  90
  91 static int x_io_error_handler (Display *dpy)
  92 {
  93     (void) dpy;
  94
  95     lost_connection = TRUE;
  96     if (longjmp_allowed) {
  97         longjmp_allowed = FALSE;
  98         longjmp(x11_exception, 1);
  99     }
 100     return 0;
 101 }
 102
 103 static int x_error_handler (Display *dpy, XErrorEvent *ee)
 104 {
 105     (void) ee;
 106     (void) func_XCloseDisplay (dpy);
 107     return x_io_error_handler (dpy);
 108 }
 109
 110 static void install_error_handlers(void)
 111 {
 112     if (handlers_installed) return;
 113
 114     (void) func_XSetErrorHandler (x_error_handler);
 115     (void) func_XSetIOErrorHandler (x_io_error_handler);
 116     handlers_installed = TRUE;
 117 }
 118
 119 static gboolean x11_available(void)
 120 {
 121 #ifdef HAVE_GMODULE
 122     gchar *x11_module_fname;
 123
 124     if (lost_connection)
 125         return FALSE;
 126
 127     if (x11_module != NULL)
 128         return TRUE;
 129
 130     x11_module_fname = g_module_build_path (NULL, "X11");
 131
 132     if (x11_module_fname == NULL)
 133         return FALSE;
 134
 135     x11_module = g_module_open (x11_module_fname, G_MODULE_BIND_LAZY);
 136     g_free (x11_module_fname);
 137
 138     if (x11_module == NULL)
 139         return FALSE;
 140
 141     if (!g_module_symbol (x11_module, "XOpenDisplay",
 142                         (void *) &func_XOpenDisplay))
 143         goto cleanup;
 144     if (!g_module_symbol (x11_module, "XCloseDisplay",
 145                         (void *) &func_XCloseDisplay))
 146         goto cleanup;
 147     if (!g_module_symbol (x11_module, "XQueryPointer",
 148                         (void *) &func_XQueryPointer))
 149         goto cleanup;
 150     if (!g_module_symbol (x11_module, "XSetErrorHandler",
 151                         (void *) &func_XSetErrorHandler))
 152         goto cleanup;
 153     if (!g_module_symbol (x11_module, "XSetIOErrorHandler",
 154                         (void *) &func_XSetIOErrorHandler))
 155         goto cleanup;
 156
 157     install_error_handlers();
 158     return TRUE;
 159
 160 cleanup:
 161     func_XOpenDisplay = 0;
 162     func_XCloseDisplay = 0;
 163     func_XQueryPointer = 0;
 164     func_XSetErrorHandler = 0;
 165     func_XSetIOErrorHandler = 0;
 166     g_module_close (x11_module);
 167     x11_module = NULL;
 168     return FALSE;
 169 #else
 170     install_error_handlers();
 171     return !(lost_connection);
 172 #endif
 173 }
 174
 175 /*** public functions **************************************************/
 176
 177 Display *mc_XOpenDisplay (const char *displayname)
 178 {
 179     Display *retval;
 180
 181     if (x11_available()) {
 182         if (setjmp(x11_exception) == 0) {
 183             longjmp_allowed = TRUE;
 184             retval = func_XOpenDisplay (displayname);
 185             longjmp_allowed = FALSE;
 186             return retval;
 187         }
 188     }
 189     return NULL;
 190 }
 191
 192 int mc_XCloseDisplay (Display *display)
 193 {
 194     int retval;
 195
 196     if (x11_available()) {
 197         if (setjmp(x11_exception) == 0) {
 198             longjmp_allowed = TRUE;
 199             retval = func_XCloseDisplay (display);
 200             longjmp_allowed = FALSE;
 201             return retval;
 202         }
 203     }
 204     return 0;
 205 }
 206
 207 Bool mc_XQueryPointer (Display *display, Window win, Window *root_return,
 208         Window *child_return, int *root_x_return, int *root_y_return,
 209         int *win_x_return, int *win_y_return, unsigned int *mask_return)
 210 {
 211     Bool retval;
 212
 213     if (x11_available()) {
 214         if (setjmp(x11_exception) == 0) {
 215             longjmp_allowed = TRUE;
 216             retval = func_XQueryPointer (display, win, root_return,
 217                 child_return, root_x_return, root_y_return,
 218                 win_x_return, win_y_return, mask_return);
 219             longjmp_allowed = FALSE;
 220             return retval;
 221         }
 222     }
 223     *root_return = None;
 224     *child_return = None;
 225     *root_x_return = 0;
 226     *root_y_return = 0;
 227     *win_x_return = 0;
 228     *win_y_return = 0;
 229     *mask_return = 0;
 230     return False;
 231 }
 232
 233 #endif /* HAVE_TEXTMODE_X11_SUPPORT */