Attempt to fix bug#65068

* src/xterm.c (handle_one_xevent) <KeyPress>: Prevent calls to
XkbTranslateKeysym with a modified keysym if overflow happens.
<XI_KeyPress>: Expound upon the different forms of key event
lookup and the chaotic code beneath within the commentary.
Discontinue separating keycode lookup from key translation.
Supply the effective group within the modifier mask provided
to both XKB translation functions.  (bug#65068)

1 files changed, 186 insertions, 61 deletions

diff --git a/src/xterm.c b/src/xterm.c
index 6a1642ff56e..01b9e3f1c1f 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -20198,15 +20198,24 @@ handle_one_xevent (struct x_display_info *dpyinfo,
 #ifdef HAVE_XKB
               int overflow;
               unsigned int consumed;
+              KeySym sym;
 
               if (dpyinfo->xkb_desc)
                 {
+                  /* Translate the keycode into the keysym it
+                     represents, using STATE.  CONSUMED is set to the
+                     modifier bits consumed while undertaking this
+                     translation and should be subsequently ignored
+                     during keysym translation.  */
+
                   if (!XkbTranslateKeyCode (dpyinfo->xkb_desc,
                                             xkey.keycode, xkey.state,
                                             &consumed, &keysym))
                     goto done_keysym;
 
-                  overflow = 0;
+                  /* Save the original keysym in case
+                     XkbTranslateKeysym overflows.  */
+                  sym = keysym, overflow = 0;
 
                   nbytes = XkbTranslateKeySym (dpyinfo->display, &keysym,
                                                xkey.state & ~consumed,
@@ -20218,7 +20227,11 @@ handle_one_xevent (struct x_display_info *dpyinfo,
                       copy_bufptr = SAFE_ALLOCA ((copy_bufsiz += overflow)
                                                  * sizeof *copy_bufptr);
                       overflow = 0;
-                      nbytes = XkbTranslateKeySym (dpyinfo->display, &keysym,
+
+                      /* Use the original keysym derived from the
+                         keycode translation in this second call to
+                         XkbTranslateKeysym.  */
+                      nbytes = XkbTranslateKeySym (dpyinfo->display, &sym,
                                                    xkey.state & ~consumed,
                                                    (char *) copy_bufptr,
                                                    copy_bufsiz, &overflow);
@@ -23725,7 +23738,7 @@ handle_one_xevent (struct x_display_info *dpyinfo,
               Lisp_Object c;
 #ifdef HAVE_XKB
               unsigned int mods_rtrn;
-#endif
+#endif /* HAVE_XKB */
               int keycode = xev->detail;
               KeySym keysym;
               char copy_buffer[81];
@@ -23734,15 +23747,122 @@ handle_one_xevent (struct x_display_info *dpyinfo,
               ptrdiff_t i;
               unsigned int old_state;
               struct xi_device_t *device, *source;
+              XKeyPressedEvent xkey;
 
               coding = Qlatin_1;
 
+              /* The code under this label is quite desultory.  There
+                 are also several important discrepancies with the
+                 core KeyPress code to mind.
+
+                 There are three principal objectives:
+
+                 The first is to produce a core or GDK translation of
+                 this XI_KeyPress event, which is relayed to the
+                 toolkit.  This transpires by setting `copy' to a
+                 close copy of XEV, which is later copied or
+                 dispatched to the toolkit by the code beneath the
+                 OTHER label.
+
+                 The second objective is to filter the event through
+                 an input method, by generating a second copy of the
+                 event expressly tailored for such a purpose.  The
+                 core KeyPress code does not endeavor to do so;
+                 instead, this action is taken prior to calling
+                 handle_one_xevent.  Calls to `x_filter_event' or
+                 `xg_filter_key' serve to implement this objective.
+
+                 If the event is not removed by the input method's
+                 filter, the third objective is to establish either a
+                 keysym or a sequence of characters to insert, using
+                 the information supplied within the key event.
+
+                 When an input method connection is available, this
+                 responsibility is vested in the hands of the input
+                 method -- yet another copy of XEV as a core event is
+                 produced, and the input method is responsible for
+                 deriving a keysym or text to insert.
+
+                 Otherwise, if the XKB extension is available, calls
+                 are made to XkbLookupKeycode and XkbTranslateKeysym.
+
+                 And if all else fails, XEV is transformed into a core
+                 event and provided to XLookupString, in a manner
+                 analogous to the core event processing under the
+                 KeyPress label.
+
+                 A wide number of variables are employed during this
+                 translation process.  The most pertinent ones are:
+
+                 `copy'
+
+                   This variable is defined when an X toolkit
+                   incognizant of input extension events is being
+                   employed.  If a popup is active, Emacs copies
+                   fields of interest from the extension event to
+                   COPY, sets the `use_copy' flag, and jumps to the
+                   XI_OTHER label.  `copy' is then relayed to the
+                   toolkit.
+
+                 `xkey'
+
+                   This variable is defined to a copy of the event
+                   used by input methods or XLookupString at various
+                   points during the execution of this label.
+
+                 `coding'
+
+                   This variable is consulted at the conclusion of
+                   event generation, and holds the coding system
+                   for any generated string.
+
+                 `keysym'
+
+                   This variable is eventually set to the keysym tied
+                   to the event, which may be directly provided within
+                   a generated struct input_event, should it bear a
+                   direct relation to an ASCII or Unicode character,
+                   or if it is a control key.
+
+                 `copy_buffer', `copy_bufptr', `copy_bufsiz'
+
+                   These variables hold the buffer that incorporates
+                   characters generated during the keycode-to-keysym
+                   conversion process.
+
+                 `nbytes'
+
+                   Holds the number of characters within that buffer,
+                   in bytes.  These characters are encoded using the
+                   coding system in `coding'.
+
+                   If greater than 0 and KEYSYM does not immediately
+                   relate to a function key, control key or character,
+                   it is provided as the string to insert within a
+                   MULTIBYTE_CHAR_KEYSTROKE_EVENT.
+
+                 `state'
+
+                   Holds the keyboard and group (but not button)
+                   state.  After event filtering concludes, modifier
+                   bits within `extra_keyboard_modifiers' are also
+                   introduced.
+
+                 This illustration may reflect the treatment taken
+                 towards core key events to some degree.  */
+
               device = xi_device_from_id (dpyinfo, xev->deviceid);
               source = xi_device_from_id (dpyinfo, xev->sourceid);
 
               if (!device)
                 goto XI_OTHER;
 
+              /* Convert the keyboard state within XEV to a core
+                 modifier mask, later supplied as arguments to XKB and
+                 core functions.  This encompasses the keyboard group
+                 and effective modifiers but not the button state.  */
+              state = xi_convert_event_keyboard_state (xev);
+
 #if defined (USE_X_TOOLKIT) || defined (USE_GTK)
               /* Dispatch XI_KeyPress events when in menu.  */
               if (popup_activated ())
@@ -23758,7 +23878,7 @@ handle_one_xevent (struct x_display_info *dpyinfo,
                   copy.xkey.root = xev->root;
                   copy.xkey.subwindow = xev->child;
                   copy.xkey.time = xev->time;
-                  copy.xkey.state = xi_convert_event_keyboard_state (xev);
+                  copy.xkey.state = state;
                   xi_convert_button_state (&xev->buttons, &copy.xkey.state);
 
                   copy.xkey.x = lrint (xev->event_x);
@@ -23767,10 +23887,10 @@ handle_one_xevent (struct x_display_info *dpyinfo,
                   copy.xkey.y_root = lrint (xev->root_y);
                   copy.xkey.keycode = xev->detail;
                   copy.xkey.same_screen = True;
-#endif
+#endif /* USE_LUCID */
                   goto XI_OTHER;
                 }
-#endif
+#endif /* USE_X_TOOLKIT || USE_GTK */
 
               x_display_set_last_user_time (dpyinfo, xev->time,
                                             xev->send_event, true);
@@ -23790,7 +23910,7 @@ handle_one_xevent (struct x_display_info *dpyinfo,
 #ifdef USE_GTK
               if (f)
                 x_set_gtk_user_time (f, xev->time);
-#endif
+#endif /* USE_GTK */
 
               if (f)
                 {
@@ -23802,7 +23922,9 @@ handle_one_xevent (struct x_display_info *dpyinfo,
                                            xev->time);
                 }
 
-              XKeyPressedEvent xkey;
+              /* Convert the XI event into a core event structure
+                 provided to old Xlib functions and input method
+                 filter functions.  */
 
               memset (&xkey, 0, sizeof xkey);
 
@@ -23814,8 +23936,7 @@ handle_one_xevent (struct x_display_info *dpyinfo,
               xkey.root = xev->root;
               xkey.subwindow = xev->child;
               xkey.time = xev->time;
-              xkey.state = xi_convert_event_keyboard_state (xev);
-
+              xkey.state = state;
               xkey.x = lrint (xev->event_x);
               xkey.y = lrint (xev->event_y);
               xkey.x_root = lrint (xev->root_x);
@@ -23844,7 +23965,7 @@ handle_one_xevent (struct x_display_info *dpyinfo,
                   *finish = X_EVENT_DROP;
                   goto XI_OTHER;
                 }
-#else
+#else /* !USE_GTK */
               if (x_filter_event (dpyinfo, (XEvent *) &xkey))
                 {
                   /* Try to attribute core key events from the input
@@ -23856,8 +23977,8 @@ handle_one_xevent (struct x_display_info *dpyinfo,
                   *finish = X_EVENT_DROP;
                   goto XI_OTHER;
                 }
-#endif
-#elif USE_GTK
+#endif /* HAVE_X_I18N */
+#elif USE_GTK /* && !HAVE_X_I18N */
               if ((x_gtk_use_native_input
                    || dpyinfo->prefer_native_input)
                   && xg_filter_key (any, event))
@@ -23871,48 +23992,17 @@ handle_one_xevent (struct x_display_info *dpyinfo,
                   *finish = X_EVENT_DROP;
                   goto XI_OTHER;
                 }
-#endif
+#endif /* HAVE_X_I18N || USE_GTK */
 
               state |= x_emacs_to_x_modifiers (dpyinfo, extra_keyboard_modifiers);
 
-#ifdef HAVE_XKB
-              if (dpyinfo->xkb_desc)
-                {
-                  unsigned int xkb_state;
-
-                  xkb_state = state & ~(1 << 13 | 1 << 14);
-                  xkb_state |= xev->group.effective << 13;
-
-                  if (!XkbTranslateKeyCode (dpyinfo->xkb_desc, keycode,
-                                            xkb_state, &mods_rtrn, &keysym))
-                    goto XI_OTHER;
-                }
-              else
-                {
-#endif
-                  int keysyms_per_keycode_return;
-                  KeySym *ksms = XGetKeyboardMapping (dpyinfo->display, keycode, 1,
-                                                      &keysyms_per_keycode_return);
-                  if (!(keysym = ksms[0]))
-                    {
-                      XFree (ksms);
-                      goto XI_OTHER;
-                    }
-                  XFree (ksms);
-#ifdef HAVE_XKB
-                }
-#endif
-
-              if (keysym == NoSymbol)
-                goto XI_OTHER;
-
               /* If mouse-highlight is an integer, input clears out
                  mouse highlighting.  */
               if (!hlinfo->mouse_face_hidden && FIXNUMP (Vmouse_highlight)
                   && (f == 0
 #if ! defined (USE_GTK)
                       || !EQ (f->tool_bar_window, hlinfo->mouse_face_window)
-#endif
+#endif /* !USE_GTK */
                       || !EQ (f->tab_bar_window, hlinfo->mouse_face_window))
                   )
                 {
@@ -23933,7 +24023,7 @@ handle_one_xevent (struct x_display_info *dpyinfo,
                      dialogs because in that case popup_activated is nonzero
                      (see above).  */
                   *finish = X_EVENT_DROP;
-#endif
+#endif /* USE_GTK */
 
                   XSETFRAME (inev.ie.frame_or_window, f);
                   inev.ie.timestamp = xev->time;
@@ -23970,25 +24060,54 @@ handle_one_xevent (struct x_display_info *dpyinfo,
                         emacs_abort ();
                     }
                   else
-#endif
+#endif /* HAVE_X_I18N */
                     {
 #ifdef HAVE_XKB
-                      int overflow = 0;
-                      KeySym sym = keysym;
-
                       if (dpyinfo->xkb_desc)
                         {
-                          nbytes = XkbTranslateKeySym (dpyinfo->display, &sym,
-                                                       state & ~mods_rtrn, copy_bufptr,
-                                                       copy_bufsiz, &overflow);
+                          KeySym sym;
+                          int overflow;
+
+                          /* Translate the keycode into the keysym it
+                             represents, using STATE.  MODS_RTRN is
+                             set to the modifier bits consumed while
+                             undertaking this translation and should
+                             be subsequently ignored during keysym
+                             translation.  */
+
+                          if (!XkbTranslateKeyCode (dpyinfo->xkb_desc,
+                                                    keycode, state,
+                                                    &mods_rtrn, &keysym))
+                            goto xi_done_keysym;
+
+                          /* Save the original keysym in case
+                             XkbTranslateKeysym overflows.  */
+                          sym = keysym, overflow = 0;
+
+                          /* Translate this keysym and its modifier
+                             state into the actual symbol and string
+                             it represents.  */
+                          nbytes = XkbTranslateKeySym (dpyinfo->display,
+                                                       &keysym,
+                                                       state & ~mods_rtrn,
+                                                       copy_bufptr,
+                                                       copy_bufsiz,
+                                                       &overflow);
                           if (overflow)
                             {
-                              copy_bufptr = SAFE_ALLOCA ((copy_bufsiz += overflow)
-                                                         * sizeof *copy_bufptr);
+                              copy_bufptr
+                                = SAFE_ALLOCA ((copy_bufsiz += overflow)
+                                               * sizeof *copy_bufptr);
                               overflow = 0;
-                              nbytes = XkbTranslateKeySym (dpyinfo->display, &sym,
-                                                           state & ~mods_rtrn, copy_bufptr,
-                                                           copy_bufsiz, &overflow);
+
+                              /* Use the original keysym derived from
+                                 the keycode translation.  */
+                              nbytes = XkbTranslateKeySym (dpyinfo->display,
+                                                           &sym,
+                                                           state & ~mods_rtrn,
+                                                           copy_bufptr,
+                                                           copy_bufsiz,
+                                                           &overflow);
 
                               if (overflow)
                                 nbytes = 0;
@@ -23997,8 +24116,14 @@ handle_one_xevent (struct x_display_info *dpyinfo,
                           coding = Qnil;
                         }
                       else
-#endif
+#endif /* HAVE_XKB */
                         {
+                          /* Save the state within XKEY, then remove
+                             all modifier keys Emacs understands from
+                             it, forestalling any attempt by
+                             XLookupString to introduce control
+                             characters.  */
+
                           old_state = xkey.state;
                           xkey.state &= ~ControlMask;
                           xkey.state &= ~(dpyinfo->meta_mod_mask
@@ -24024,7 +24149,7 @@ handle_one_xevent (struct x_display_info *dpyinfo,
                       x_dnd_xm_use_help = true;
                       goto xi_done_keysym;
                     }
-#endif
+#endif /* XK_F1 */
 
                   /* See if keysym should make Emacs quit.  */