lib/tty/x11conn.c

   1 /*
   2    X11 support for the Midnight Commander.
   3
   4    Copyright (C) 2005-2019
   5    Free Software Foundation, Inc.
   6
   7    Written by:
   8    Roland Illig <roland.illig@gmx.de>, 2005.
   9
  10    This file is part of the Midnight Commander.
  11
  12    The Midnight Commander is free software: you can redistribute it
  13    and/or modify it under the terms of the GNU General Public License as
  14    published by the Free Software Foundation, either version 3 of the License,
  15    or (at your option) any later version.
  16
  17    The Midnight Commander is distributed in the hope that it will be useful,
  18    but WITHOUT ANY WARRANTY; without even the implied warranty of
  19    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20    GNU General Public License for more details.
  21
  22    You should have received a copy of the GNU General Public License
  23    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  24  */
  25
  26 /** \file x11conn.c
  27  *  \brief Source: X11 support
  28  *  \warning This code uses setjmp() and longjmp(). Before you modify _anything_ here,
  29  *  please read the relevant sections of the C standard.
  30  */
  31
  32 #include <config.h>
  33
  34 #include <setjmp.h>
  35 #include <X11/Xlib.h>
  36 #ifdef HAVE_GMODULE
  37 #include <gmodule.h>
  38 #endif
  39
  40 #include "lib/global.h"
  41 #include "x11conn.h"
  42
  43 /*** global variables ****************************************************************************/
  44
  45 /*** file scope macro definitions ****************************************************************/
  46
  47 #ifndef HAVE_GMODULE
  48 #define func_XOpenDisplay       XOpenDisplay
  49 #define func_XCloseDisplay      XCloseDisplay
  50 #define func_XSetErrorHandler   XSetErrorHandler
  51 #define func_XSetIOErrorHandler XSetIOErrorHandler
  52 #define func_XQueryPointer      XQueryPointer
  53 #endif
  54
  55 /*** file scope type declarations ****************************************************************/
  56
  57 typedef int (*mc_XErrorHandler_callback) (Display *, XErrorEvent *);
  58 typedef int (*mc_XIOErrorHandler_callback) (Display *);
  59
  60 /*** file scope variables ************************************************************************/
  61
  62 #ifdef HAVE_GMODULE
  63 static Display *(*func_XOpenDisplay) (_Xconst char *);
  64 static int (*func_XCloseDisplay) (Display *);
  65 static mc_XErrorHandler_callback (*func_XSetErrorHandler) (mc_XErrorHandler_callback);
  66 static mc_XIOErrorHandler_callback (*func_XSetIOErrorHandler) (mc_XIOErrorHandler_callback);
  67 static Bool (*func_XQueryPointer) (Display *, Window, Window *, Window *,
  68                                    int *, int *, int *, int *, unsigned int *);
  69 static GModule *x11_module;
  70 #endif
  71
  72 static gboolean handlers_installed = FALSE;
  73
  74 /* This flag is set as soon as an X11 error is reported. Usually that
  75  * means that the DISPLAY is not available anymore. We do not try to
  76  * reconnect, as that would violate the X11 protocol. */
  77 static gboolean lost_connection = FALSE;
  78
  79 static jmp_buf x11_exception;   /* FIXME: get a better name */
  80 static gboolean longjmp_allowed = FALSE;
  81
  82 /*** file scope functions ************************************************************************/
  83 /* --------------------------------------------------------------------------------------------- */
  84
  85 static int
  86 x_io_error_handler (Display * dpy)
  87 {
  88     (void) dpy;
  89
  90     lost_connection = TRUE;
  91     if (longjmp_allowed)
  92     {
  93         longjmp_allowed = FALSE;
  94         longjmp (x11_exception, 1);
  95     }
  96     return 0;
  97 }
  98
  99 /* --------------------------------------------------------------------------------------------- */
 100
 101 static int
 102 x_error_handler (Display * dpy, XErrorEvent * ee)
 103 {
 104     (void) ee;
 105     (void) func_XCloseDisplay (dpy);
 106     return x_io_error_handler (dpy);
 107 }
 108
 109 /* --------------------------------------------------------------------------------------------- */
 110
 111 static void
 112 install_error_handlers (void)
 113 {
 114     if (handlers_installed)
 115         return;
 116
 117     (void) func_XSetErrorHandler (x_error_handler);
 118     (void) func_XSetIOErrorHandler (x_io_error_handler);
 119     handlers_installed = TRUE;
 120 }
 121
 122 /* --------------------------------------------------------------------------------------------- */
 123
 124 static gboolean
 125 x11_available (void)
 126 {
 127 #ifdef HAVE_GMODULE
 128     gchar *x11_module_fname;
 129
 130     if (lost_connection)
 131         return FALSE;
 132
 133     if (x11_module != NULL)
 134         return TRUE;
 135
 136     x11_module_fname = g_module_build_path (NULL, "X11");
 137     x11_module = g_module_open (x11_module_fname, G_MODULE_BIND_LAZY);
 138     if (x11_module == NULL)
 139         x11_module = g_module_open ("libX11.so.6", G_MODULE_BIND_LAZY);
 140
 141     g_free (x11_module_fname);
 142
 143     if (x11_module == NULL)
 144         return FALSE;
 145
 146     if (!g_module_symbol (x11_module, "XOpenDisplay", (void *) &func_XOpenDisplay))
 147         goto cleanup;
 148     if (!g_module_symbol (x11_module, "XCloseDisplay", (void *) &func_XCloseDisplay))
 149         goto cleanup;
 150     if (!g_module_symbol (x11_module, "XQueryPointer", (void *) &func_XQueryPointer))
 151         goto cleanup;
 152     if (!g_module_symbol (x11_module, "XSetErrorHandler", (void *) &func_XSetErrorHandler))
 153         goto cleanup;
 154     if (!g_module_symbol (x11_module, "XSetIOErrorHandler", (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 /* --------------------------------------------------------------------------------------------- */
 176 /*** public functions ****************************************************************************/
 177 /* --------------------------------------------------------------------------------------------- */
 178
 179 Display *
 180 mc_XOpenDisplay (const char *displayname)
 181 {
 182     if (x11_available ())
 183     {
 184         if (setjmp (x11_exception) == 0)
 185         {
 186             Display *retval;
 187
 188             /* cppcheck-suppress redundantAssignment */
 189             longjmp_allowed = TRUE;
 190
 191             retval = func_XOpenDisplay (displayname);
 192
 193             /* cppcheck-suppress redundantAssignment */
 194             longjmp_allowed = FALSE;
 195             return retval;
 196         }
 197     }
 198     return NULL;
 199 }
 200
 201 /* --------------------------------------------------------------------------------------------- */
 202
 203 int
 204 mc_XCloseDisplay (Display * display)
 205 {
 206     if (x11_available ())
 207     {
 208         if (setjmp (x11_exception) == 0)
 209         {
 210             int retval;
 211
 212             /* cppcheck-suppress redundantAssignment */
 213             longjmp_allowed = TRUE;
 214
 215             retval = func_XCloseDisplay (display);
 216
 217             /* cppcheck-suppress redundantAssignment */
 218             longjmp_allowed = FALSE;
 219
 220             return retval;
 221         }
 222     }
 223     return 0;
 224 }
 225
 226 /* --------------------------------------------------------------------------------------------- */
 227
 228 Bool
 229 mc_XQueryPointer (Display * display, Window win, Window * root_return,
 230                   Window * child_return, int *root_x_return, int *root_y_return,
 231                   int *win_x_return, int *win_y_return, unsigned int *mask_return)
 232 {
 233     Bool retval;
 234
 235     if (x11_available ())
 236     {
 237         if (setjmp (x11_exception) == 0)
 238         {
 239             /* cppcheck-suppress redundantAssignment */
 240             longjmp_allowed = TRUE;
 241
 242             retval = func_XQueryPointer (display, win, root_return,
 243                                          child_return, root_x_return, root_y_return,
 244                                          win_x_return, win_y_return, mask_return);
 245
 246             /* cppcheck-suppress redundantAssignment */
 247             longjmp_allowed = FALSE;
 248
 249             return retval;
 250         }
 251     }
 252     *root_return = None;
 253     *child_return = None;
 254     *root_x_return = 0;
 255     *root_y_return = 0;
 256     *win_x_return = 0;
 257     *win_y_return = 0;
 258     *mask_return = 0;
 259     return False;
 260 }
 261
 262 /* --------------------------------------------------------------------------------------------- */