Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!mailrus!purdue!decwrl!hplabs!hp-pcd!hpcvlx!fred From: fred@hpcvlx.HP.COM (Fred Taft) Newsgroups: comp.windows.x Subject: Re: HP's Xtk Fixes (as Context Diffs) Message-ID: <1610052@hpcvlx.HP.COM> Date: 19 Aug 88 19:53:12 GMT References: <1610043@hpcvlx.HP.COM> Organization: Hewlett-Packard Co., Corvallis, OR, USA Lines: 159 ### bug number: 518 ### area: Xt ### severity: low ### comments: VERSION: Xtk release 2 SYNOPSIS: Under certain conditions, it is possible for a widget to have more than one keyboard focus entry on the grablist, when in fact only one should have been present. DESCRIPTION: The current implementation of the input focus for Xtk enforces the rule that if a widget has a non-focus entry on the grab list, then a focus entry for that widget will always be placed after the non-focus entry. Unfortunately, there are bugs in the current implementation, which may cause this rule to be broken. Additionally, the current implementation looks on the grab list for an existing focus entry before adding a new one; if an existing one is found, then it is replaced - you don't end up with duplicate focus entries for a widget; again, there is a bug which causes duplicate entries to be placed on the grablist. When a focus grab is to be added to the grablist, the current implementation searches the grab list to see if there is already a grab entry for this widget. If there is, and the current entry is a non-focus entry, then it simply adds the focus entry after the non-focus entry; unfortunately, if there was already a focus entry after the non-focus entry, you now end up with 2 (or more) focus entries on the grab list. At this point, the grablist has suffered irreparable damage. An additional problem can occur if a widget has multiple non-focus entries on the grab list. To guarantee that the focus entry is always after the non-focus entries, the grablist must be searched until all non-focus grab list entries have been found for this widget; the focus entry must then be placed after the last non-focus entry. FIX: /* Patch to Event.c */ /* add a grab record to the list, or replace the focus widget in an existing grab record. Returns True if the action was not a no-op. */ static Boolean InsertKeyboardGrab(widget, keyboard_focus) Widget widget; Widget keyboard_focus; { register GrabRec *gl; register Widget w; GrabRec* ge; Boolean found = False; GrabRec * lastMatch = NULL; if (grabList == NULL) { AddGrab( widget, False, False, keyboard_focus ); return True; } /* look for a keyboard grab entry for the same parent; if none, reposition this entry after any other entries for the same tree */ for (w = widget; (w != NULL) && !((w != widget) && (lastMatch != NULL)); w = w->core.parent) { for (gl = grabList; gl != NULL; gl = gl->next) { if (gl->widget == w) { if (gl->widget == widget) { /* * Because we know that focus entries always appear * after a normal grab entry for the same widget, we * can't stop when we encounter the normal grab entry; * we must continue checking until we either find a * matching focus entry, or we find no more entries for * this widget. */ if (gl->keyboard_focus != NULL) { /* * Since the widget in the grab entry matches the * passed-in widget, and since we know that a non-focus * entry always appears after a normal grab list entry, * we are assured that this is the only focus entry for * this widget, so we can update it and then return. */ if (gl->keyboard_focus == keyboard_focus) { return False; } else { SendFocusNotify(gl->keyboard_focus, FocusOut); gl->keyboard_focus = keyboard_focus; return True; } } else { /* * Keep going, in case there is a focus entry * following this one. */ lastMatch = gl; found = True; } } else { /* * One of our parent widgets has an entry on the * grab list; add our entry after its entry. */ AddGrab( widget, False, False, keyboard_focus ); ge = grabList; grabList = grabList->next; ge->next = gl->next; gl->next = ge; return True; } } } } if (found) { /* * The specified widget had a non-focus entry on the grab * list, but currently no focus grab. Therefore, add the * focus entry after the non-focus entry. */ AddGrab( widget, False, False, keyboard_focus ); ge = grabList; grabList = grabList->next; ge->next = lastMatch->next; lastMatch->next = ge; } else { /* insert a new grab at end of list */ AddGrab( widget, False, False, keyboard_focus ); if (grabList->next != NULL) { ge = grabList; grabList = grabList->next; ge->next = NULL; for (gl = grabList; gl->next != NULL; gl = gl->next); gl->next = ge; } } return True; }