lib/tty/x11conn.c

   1 /*
   2    X11 support for the Midnight Commander.
   3
   4    Copyright (C) 2005, 2007 Free Software Foundation, Inc.
   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 /** \file x11conn.c
  25  *  \brief Source: X11 support
  26  *  \warning This code uses setjmp() and longjmp(). Before you modify _anything_ here,
  27  *  please read the relevant sections of the C standard.
  28  */
  29
  30 #include <config.h>
  31
  32 #ifndef HAVE_TEXTMODE_X11_SUPPORT
  33 typedef int dummy;              /* C99 forbids empty compilation unit */
  34 #else
  35
  36 #include <setjmp.h>
  37 #include <X11/Xlib.h>
  38 #ifdef HAVE_GMODULE
  39 #  include <gmodule.h>
  40 #endif
  41
  42 #include "lib/global.h"
  43 #include "x11conn.h"
  44
  45 /*** file scope type declarations **************************************/
  46
  47 typedef int (*mc_XErrorHandler_callback) (Display *, XErrorEvent *);
  48 typedef int (*mc_XIOErrorHandler_callback) (Display *);
  49
  50 /*** file scope variables **********************************************/
  51
  52 #ifdef HAVE_GMODULE
  53
  54 static Display *(*func_XOpenDisplay) (_Xconst char *);
  55 static int (*func_XCloseDisplay) (Display *);
  56 static mc_XErrorHandler_callback (*func_XSetErrorHandler)
  57   (mc_XErrorHandler_callback);
  58 static mc_XIOErrorHandler_callback (*func_XSetIOErrorHandler)
  59   (mc_XIOErrorHandler_callback);
  60 static Bool (*func_XQueryPointer) (Display *, Window, Window *, Window *,
  61                                    int *, int *, int *, int *, unsigned int *);
  62
  63 static GModule *x11_module;
  64
  65 #else
  66
  67 #define func_XOpenDisplay       XOpenDisplay
  68 #define func_XCloseDisplay      XCloseDisplay
  69 #define func_XSetErrorHandler   XSetErrorHandler
  70 #define func_XSetIOErrorHandler XSetIOErrorHandler
  71 #define func_XQueryPointer      XQueryPointer
  72
  73 #endif
  74
  75 static gboolean handlers_installed = FALSE;
  76
  77 /* This flag is set as soon as an X11 error is reported. Usually that
  78  * means that the DISPLAY is not available anymore. We do not try to
  79  * reconnect, as that would violate the X11 protocol. */
  80 static gboolean lost_connection = FALSE;
  81
  82 static jmp_buf x11_exception;   /* FIXME: get a better name */
  83 static gboolean longjmp_allowed = FALSE;
  84
  85 /*** file private functions ********************************************/
  86
  87 static int
  88 x_io_error_handler (Display * dpy)
  89 {
  90     (void) dpy;
  91
  92     lost_connection = TRUE;
  93     if (longjmp_allowed) {
  94         longjmp_allowed = FALSE;
  95         longjmp (x11_exception, 1);
  96     }
  97     return 0;
  98 }
  99
 100 static int
 101 x_error_handler (Display * dpy, XErrorEvent * ee)
 102 {
 103     (void) ee;
 104     (void) func_XCloseDisplay (dpy);
 105     return x_io_error_handler (dpy);
 106 }
 107
 108 static void
 109 install_error_handlers (void)
 110 {
 111     if (handlers_installed)
 112         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
 120 x11_available (void)
 121 {
 122 #ifdef HAVE_GMODULE
 123     gchar *x11_module_fname;
 124
 125     if (lost_connection)
 126         return FALSE;
 127
 128     if (x11_module != NULL)
 129         return TRUE;
 130
 131     x11_module_fname = g_module_build_path (NULL, "X11");
 132     x11_module = g_module_open (x11_module_fname, G_MODULE_BIND_LAZY);
 133     if (x11_module == NULL)
 134         x11_module = g_module_open ("libX11.so.6", G_MODULE_BIND_LAZY);
 135
 136     g_free (x11_module_fname);
 137
 138     if (x11_module == NULL)
 139         return FALSE;
 140
 141     if (!g_module_symbol (x11_module, "XOpenDisplay", (void *) &func_XOpenDisplay))
 142         goto cleanup;
 143     if (!g_module_symbol (x11_module, "XCloseDisplay", (void *) &func_XCloseDisplay))
 144         goto cleanup;
 145     if (!g_module_symbol (x11_module, "XQueryPointer", (void *) &func_XQueryPointer))
 146         goto cleanup;
 147     if (!g_module_symbol (x11_module, "XSetErrorHandler", (void *) &func_XSetErrorHandler))
 148         goto cleanup;
 149     if (!g_module_symbol (x11_module, "XSetIOErrorHandler", (void *) &func_XSetIOErrorHandler))
 150         goto cleanup;
 151
 152     install_error_handlers ();
 153     return TRUE;
 154
 155   cleanup:
 156     func_XOpenDisplay = 0;
 157     func_XCloseDisplay = 0;
 158     func_XQueryPointer = 0;
 159     func_XSetErrorHandler = 0;
 160     func_XSetIOErrorHandler = 0;
 161     g_module_close (x11_module);
 162     x11_module = NULL;
 163     return FALSE;
 164 #else
 165     install_error_handlers ();
 166     return !(lost_connection);
 167 #endif
 168 }
 169
 170 /*** public functions **************************************************/
 171
 172 Display *
 173 mc_XOpenDisplay (const char *displayname)
 174 {
 175     Display *retval;
 176
 177     if (x11_available ()) {
 178         if (setjmp (x11_exception) == 0) {
 179             longjmp_allowed = TRUE;
 180             retval = func_XOpenDisplay (displayname);
 181             longjmp_allowed = FALSE;
 182             return retval;
 183         }
 184     }
 185     return NULL;
 186 }
 187
 188 int
 189 mc_XCloseDisplay (Display * display)
 190 {
 191     int retval;
 192
 193     if (x11_available ()) {
 194         if (setjmp (x11_exception) == 0) {
 195             longjmp_allowed = TRUE;
 196             retval = func_XCloseDisplay (display);
 197             longjmp_allowed = FALSE;
 198             return retval;
 199         }
 200     }
 201     return 0;
 202 }
 203
 204 Bool
 205 mc_XQueryPointer (Display * display, Window win, Window * root_return,
 206                   Window * child_return, int *root_x_return, int *root_y_return,
 207                   int *win_x_return, int *win_y_return, unsigned int *mask_return)
 208 {
 209     Bool retval;
 210
 211     if (x11_available ()) {
 212         if (setjmp (x11_exception) == 0) {
 213             longjmp_allowed = TRUE;
 214             retval = func_XQueryPointer (display, win, root_return,
 215                                          child_return, root_x_return, root_y_return,
 216                                          win_x_return, win_y_return, mask_return);
 217             longjmp_allowed = FALSE;
 218             return retval;
 219         }
 220     }
 221     *root_return = None;
 222     *child_return = None;
 223     *root_x_return = 0;
 224     *root_y_return = 0;
 225     *win_x_return = 0;
 226     *win_y_return = 0;
 227     *mask_return = 0;
 228     return False;
 229 }
 230
 231 #endif /* HAVE_TEXTMODE_X11_SUPPORT */