Ticket #4165: MultiSearch_v5.7.patch

lib/keybind.c

@@ -93 +93 @@
     ADD_KEYMAP_NAME (SearchContinue),
     ADD_KEYMAP_NAME (Replace),
     ADD_KEYMAP_NAME (ReplaceContinue),
+    ADD_KEYMAP_NAME (MultiSearch),
     ADD_KEYMAP_NAME (Help),
     ADD_KEYMAP_NAME (Shell),
     ADD_KEYMAP_NAME (Edit),

lib/keybind.h

@@ -82 +82 @@
     CK_SearchContinue,
     CK_Replace,
     CK_ReplaceContinue,
+    CK_MultiSearch,
     CK_SearchStop,
     CK_Help,
     CK_Edit,

lib/widget.h

@@ -30 +30 @@
 #include "lib/widget/groupbox.h"
 #include "lib/widget/label.h"
 #include "lib/widget/listbox.h"
+#include "lib/widget/filtering_listbox.h"
 #include "lib/widget/menu.h"
 #include "lib/widget/radio.h"
 #include "lib/widget/input.h"
+#include "lib/widget/forwarding_input.h"
 #include "lib/widget/listbox-window.h"
 #include "lib/widget/quick.h"
 #include "lib/widget/wtools.h"

lib/widget/Makefile.am

@@ -16 +16 @@
         history.c history.h \
         input.c input.h \
         input_complete.c \
+        forwarding_input.c forwarding_input.h \
         listbox-window.c listbox-window.h \
         listbox.c listbox.h \
+        filtering_listbox.c filtering_listbox.h \
         label.c label.h \
         menu.c menu.h \
         mouse.c mouse.h \

lib/widget/dialog-switch.c

@@ -241 +241 @@
         else
             title = g_strdup ("");
 
-        listbox_add_item (listbox->list, LISTBOX_APPEND_BEFORE, get_hotkey (i++), title, h, FALSE);
+        listbox_add_item (LISTBOX (listbox->list), LISTBOX_APPEND_BEFORE, get_hotkey (i++), title,
+                          h, FALSE);
 
         g_free (title);
     }

lib/widget/dialog.c

@@ -87 +87 @@
     return CONST_DIALOG (w)->colors;
 }
 
-/* --------------------------------------------------------------------------------------------- */
-/**
-  * Read histories from the ${XDG_CACHE_HOME}/mc/history file
-  */
-static void
-dlg_read_history (WDialog * h)
-{
-    char *profile;
-    ev_history_load_save_t event_data;
-
-    if (num_history_items_recorded == 0)        /* this is how to disable */
-        return;
-
-    profile = mc_config_get_full_path (MC_HISTORY_FILE);
-    event_data.cfg = mc_config_init (profile, TRUE);
-    event_data.receiver = NULL;
-
-    /* create all histories in dialog */
-    mc_event_raise (h->event_group, MCEVENT_HISTORY_LOAD, &event_data);
-
-    mc_config_deinit (event_data.cfg);
-    g_free (profile);
-}
-
 /* --------------------------------------------------------------------------------------------- */
 
 static void
@@ -473 +449 @@
 
 /* --------------------------------------------------------------------------------------------- */
 
+/**
+  * Read histories from the ${XDG_CACHE_HOME}/mc/history file
+  */
+void
+dlg_read_history (WDialog * h)
+{
+    char *profile;
+    ev_history_load_save_t event_data;
+
+    if (num_history_items_recorded == 0)        /* this is how to disable */
+        return;
+
+    profile = mc_config_get_full_path (MC_HISTORY_FILE);
+    event_data.cfg = mc_config_init (profile, TRUE);
+    event_data.receiver = NULL;
+
+    /* create all histories in dialog */
+    mc_event_raise (h->event_group, MCEVENT_HISTORY_LOAD, &event_data);
+
+    mc_config_deinit (event_data.cfg);
+    g_free (profile);
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
 void
 dlg_stop (WDialog * h)
 {

lib/widget/dialog.h

@@ -109 +109 @@
 void dlg_destroy (WDialog * h);
 
 void dlg_run_done (WDialog * h);
+void dlg_read_history (WDialog * h);
 void dlg_save_history (WDialog * h);
 void dlg_process_event (WDialog * h, int key, Gpm_Event * event);
 

new file lib/widget/filtering_listbox.c

@@ +1 @@
+/*
+   A class extending WListbox with dynamic filtering (i.e.: removal) of entries.
+
+   Copyright (C) <2021>
+   Free Software Foundation, Inc.
+
+   Written by:
+   Sebastian Gniazdowski <sgniazdowski@gmail.com>, 2021.
+
+   This file is part of the Midnight Commander.
+
+   The Midnight Commander is free software: you can redistribute it
+   and/or modify it under the terms of the GNU General Public License as
+   published by the Free Software Foundation, either version 3 of the License,
+   or (at your option) any later version.
+
+   The Midnight Commander is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** \file filtering_listbox.c
+ *  \brief A WListbox inheriting class that adds dynamic filtering of entries.
+ *  \author Sebastian Gniazdowski
+ *  \date 2021
+ *
+ * In order to enable/disable (i.e.: toggle) MultiSearch on an listbox you can send a message:
+ *      send_message (listbox, NULL, MSG_ACTION, CK_MultiSearch, NULL);
+ *
+ * It'll extend owning dialog with a new MultiSearch input and pair it up with the listbox, so that
+ * some of keys (basically all that aren't in input's keymap) are forwarded to listbox.
+ */
+
+#include <config.h>
+
+#include "lib/global.h"
+#include "src/setup.h"
+#include "lib/widget.h"
+#include "lib/tty/tty.h"
+
+/*** global variables ****************************************************************************/
+
+/*** file scope macro definitions ****************************************************************/
+
+/*** file scope type declarations ****************************************************************/
+
+/*** file scope variables ************************************************************************/
+
+/*** file scope functions ************************************************************************/
+/* --------------------------------------------------------------------------------------------- */
+
+static WLEntry *
+filt_listbox_shallow_copy_entry (WLEntry * src, gboolean take_ownership)
+{
+    WLEntry *copy;
+    copy = g_new (WLEntry, 1);
+    *copy = *src;
+
+    /* Who has the ownership of the data? */
+    src->free_text = src->free_text && !take_ownership;
+    src->free_data = src->free_data && !take_ownership;
+    copy->free_text = copy->free_text && take_ownership;
+    copy->free_data = copy->free_data && take_ownership;
+
+    return copy;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+static void
+filt_listbox_make_one_line_room (WFilteringListbox * sl, gboolean should_add_free_room)
+{
+    WListbox *l = LISTBOX (sl);
+    Widget *w = WIDGET (l), *owner = WIDGET (WIDGET (w)->owner);
+    WRect r_dialog, r_listbox;
+    int new_dialog_height, new_dialog_ypos, new_listbox_height, take_give_from_to_owner = 1;
+
+    /*
+     * IF the enlarged dialog won't fit the screen, don't resize it but the listbox instead.
+     * Do it also when requested if the listbox is large (for small listboxes always try to
+     * enlarge the dialog).
+     */
+    if ((sl->resize_strategy == FILT_LIST_DIALOG_AUTO_RESIZE && LINES <= owner->lines + 2) ||
+        (sl->resize_strategy == FILT_LIST_KEEP_DIALOG_SIZE && owner->lines > 7))
+        take_give_from_to_owner = 0;
+
+    /* Increase the height of the dialog by 1, so that the new input fits. */
+    if (should_add_free_room)
+    {
+        new_dialog_height = owner->lines + take_give_from_to_owner;
+        new_listbox_height = w->lines + (-1 + take_give_from_to_owner);
+        new_dialog_ypos = owner->y - take_give_from_to_owner;
+    }
+    else
+    {
+        new_dialog_height = owner->lines - take_give_from_to_owner;
+        new_listbox_height = w->lines - (-1 + take_give_from_to_owner);
+        new_dialog_ypos = owner->y + take_give_from_to_owner;
+    }
+    rect_init (&r_dialog, new_dialog_ypos, owner->x, new_dialog_height, owner->cols);
+    rect_init (&r_listbox, w->y, w->x, new_listbox_height, w->cols);
+
+    /*
+     * Doing widget_set_size_rect(w, &r_listbox) causes problems as it invokes
+     * drawing of the widget owner.
+     */
+    send_message (w, NULL, MSG_RESIZE, 0, &r_listbox);
+    send_message (owner, NULL, MSG_RESIZE, 0, &r_dialog);
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+static void
+filt_listbox_show_multi_search_widget (WFilteringListbox * sl)
+{
+    WListbox *l = LISTBOX (sl);
+    Widget *w = WIDGET (l), *owner = WIDGET (WIDGET (l)->owner);
+    WForwardingInput *multi_search_in;
+    int distance_y = owner->y + owner->lines - (w->y + w->lines) + 1;
+    int distance_x = w->cols > 40 ? 5 : 1, small = w->cols <= 15 ? 1 : 0;
+
+    filt_listbox_make_one_line_room (sl, 1);
+
+    /* Adjust active display. */
+    if (l->pos < 0)
+        l->pos = 0;
+    if (l->pos < l->top || l->pos >= l->top + w->lines)
+        l->top = l->pos - w->lines/2 + 1;
+    if (l->top < 0)
+        l->top = 0;
+
+    multi_search_in = forwarding_input_new (owner->lines - distance_y, distance_x,
+                                            input_colors, w->cols - 2 - distance_x + small, "",
+                                            "multi_search", INPUT_COMPLETE_NONE, w);
+    group_add_widget_autopos (GROUP (owner), multi_search_in, WPOS_KEEP_TOP | WPOS_CENTER_HORZ,
+                              NULL);
+    /* Initialize input widget. */
+    send_message (WIDGET (multi_search_in), w, MSG_INIT, 0, NULL);
+    dlg_read_history (DIALOG (w->owner));
+
+    /* Draw dialog and listbox, and then input. */
+    widget_draw (WIDGET (w->owner));
+    widget_draw (w);
+    widget_draw (WIDGET (multi_search_in));
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+static void
+filt_listbox_hide_multi_search_widget (WFilteringListbox * sl)
+{
+    WListbox *l = LISTBOX (sl);
+    Widget *w = WIDGET (sl);
+    Widget *in;
+    in = widget_find_by_type (WIDGET (WIDGET (l)->owner), forw_input_callback);
+    if (in != NULL)
+    {
+        group_remove_widget (in);
+        filt_listbox_make_one_line_room (sl, 0);
+        group_select_next_widget (WIDGET (l)->owner);
+
+        /*
+         * Repainting is needed because some part of the resized dialog can be left on the
+         * background.
+         */
+        if (sl->resize_strategy != FILT_LIST_KEEP_DIALOG_SIZE || w->lines <= 7)
+            repaint_screen ();
+
+        widget_draw (WIDGET (w->owner));
+        widget_draw (w);
+        widget_destroy (in);
+    }
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+/* Return TRUE if given listbox is in WST_FILTER state. */
+static gboolean
+filt_listbox_is_filter_state (WFilteringListbox * sl)
+{
+    return widget_get_state (WIDGET (sl), WST_FILTER);
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+static void
+filt_listbox_filter_list (WFilteringListbox * sl, const char *text)
+{
+    WListbox *l = LISTBOX (sl);
+    int i, size;
+    GList *le;
+    char **query_terms;
+    gboolean has_c_files = FALSE, has_header_files = FALSE;
+    /*
+     * Remove the list and allocate a new one. The elements are only shallowly freed because the
+     * internal data is still used (and kept in list_keep field).
+     */
+    if (l->list != NULL)
+        g_queue_free_full (l->list, g_free);
+    l->list = g_queue_new ();
+
+    /* Split the query into space delimeted strings. */
+    query_terms = g_strsplit (text, " ", 10);
+
+
+    size = g_queue_get_length (sl->list_keep);
+    le = g_queue_peek_head_link (sl->list_keep);
+    for (i = 0; i < size; i++, le = g_list_next (le))
+    {
+        WLEntry *e = LENTRY (le->data);
+        size_t e_len;
+
+        /* Compute lenght once, then use it. */
+        e_len = e->text ? strlen (e->text) : 0;
+
+        if (g_strrstr (e->text, ".c") == e->text + e_len - 2 ||
+            g_strrstr (e->text, ".c~") == e->text + e_len - 3)
+            has_c_files = TRUE;
+        if (g_strrstr (e->text, ".cpp") == e->text + e_len - 4 ||
+            g_strrstr (e->text, ".cpp~") == e->text + e_len - 5)
+            has_c_files = TRUE;
+        if (g_strrstr (e->text, ".h") == e->text + e_len - 2 ||
+            g_strrstr (e->text, ".h~") == e->text + e_len - 3)
+            has_header_files = TRUE;
+        if (has_c_files && has_header_files)
+            break;
+    }
+
+    /*
+     * Get the size of the listbox and iterate over it testing each element against «all» words in
+     * query_terms.
+     */
+    le = g_queue_peek_head_link (sl->list_keep);
+    for (i = 0; i < size; i++, le = g_list_next (le))
+    {
+        WLEntry *e = LENTRY (le->data);
+        size_t e_len;
+        gboolean match = TRUE;
+
+        e_len = e->text ? strlen (e->text) : 0;
+
+        /* Test the query against the list entry. */
+        for (gchar ** p = query_terms; *p != NULL; p++)
+        {
+
+            gboolean is_p_special;
+
+            /* Is it a special, shorthand query ("c" or "h") ? */
+            is_p_special = g_strcmp0 (*p, "h") == 0 || g_strcmp0 (*p, "c") == 0;
+
+            /* Use special meaning of c/h queries only, when files seem to include such files. */
+            if (is_p_special && (has_c_files || has_header_files))
+            {
+                if (has_header_files && **p == 'h' && (g_strrstr (e->text, ".h") ==
+                                                       e->text + e_len - 2
+                                                       || g_strrstr (e->text,
+                                                                     ".h~") == e->text + e_len - 3))
+                {
+                    /* The file name (...apparently) matches -> do nothing. */
+                }
+                else if (has_c_files && **p == 'c' && (g_strrstr (e->text, ".c") ==
+                                                       e->text + e_len - 2
+                                                       || g_strrstr (e->text,
+                                                                     ".c~") == e->text + e_len - 3
+                                                       || g_strrstr (e->text,
+                                                                     ".cpp") == e->text + e_len - 4
+                                                       || g_strrstr (e->text,
+                                                                     ".cpp~") ==
+                                                       e->text + e_len - 5))
+                {
+                    /* The file name (...apparently) matches -> do nothing. */
+                }
+                else
+                {
+                    /* No matching of a special query -> filter element out. */
+                    match = FALSE;
+                    break;
+                }
+            }
+            else if (**p != '\0' && !strcasestr (e->text, *p))
+            {
+                /*
+                 * No match -> filter out this entry. */
+                match = FALSE;
+                break;
+            }
+        }
+
+        /* If all the terms matched, then add the element to the list. */
+        if (match)
+            g_queue_push_tail (l->list, filt_listbox_shallow_copy_entry (e, FALSE));
+    }
+    if (listbox_is_empty (l))
+    {
+        listbox_add_item (l, LISTBOX_APPEND_AT_END, 0, "<no search results>", NULL, FALSE);
+        LENTRY (g_queue_peek_head_link (l->list)->data)->index = -2;
+    }
+    size = g_queue_get_length (l->list);
+    if (l->pos >= size)
+        listbox_select_entry (l, size - 1);
+    else
+        listbox_select_entry (l, l->pos);
+
+    g_strfreev (query_terms);
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+/* Restores original elements of the list (from sl->list_keep) and turns off the WST_FILTER state. */
+static gboolean
+filt_listbox_set_to_normal_state (WFilteringListbox * sl)
+{
+    WListbox *l = LISTBOX (sl);
+    /* The listbox is already in non-filter state? */
+    if (!widget_get_state (WIDGET (l), WST_FILTER))
+    {
+        /* Return doing no change, just signal the error. */
+        return FALSE;
+    }
+
+    /* The keep-list must be allocated (even if it's empty). */
+    g_assert (sl->list_keep != NULL);
+
+    /* Mark the new state. */
+    widget_set_state (WIDGET (l), WST_FILTER, FALSE);
+
+    /* Release the filtered list and replace it with the original, complete list (it owns the
+     * internal data, hence the release is a shallow one). */
+    g_queue_free_full (l->list, g_free);
+    l->list = sl->list_keep;
+    sl->list_keep = NULL;
+    return TRUE;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+/*
+ * Sets the listbox into «filter» state. In this state, there's a separate copy of all list
+ * entries, while the original (and displayed) field ->list is being a filtered version of the
+ * full copy.
+ */
+static gboolean
+filt_listbox_set_to_filter_state (WFilteringListbox * sl)
+{
+    WListbox *l = LISTBOX (sl);
+    GList *le;
+
+    /* The listbox is already in filter state? */
+    if (widget_get_state (WIDGET (l), WST_FILTER))
+    {
+        /* Return doing no change, just signal the error. */
+        return FALSE;
+    }
+
+    /* Mark the new state. */
+    widget_set_state (WIDGET (l), WST_FILTER, TRUE);
+
+    /* No list copy when entering filter mode. */
+    g_assert (sl->list_keep == NULL);
+    sl->list_keep = g_queue_new ();
+
+    /* Skip empty lists. */
+    if (listbox_is_empty (l))
+        return TRUE;
+
+    /*
+     * Remember the original position in the list in the field. It'll be used to determine the
+     * virtual_pos field.
+     */
+    listbox_init_indices (l);
+
+    /* Perform a shallow copy of the original list. */
+    for (le = g_queue_peek_head_link (l->list); le != NULL; le = g_list_next (le))
+    {
+        WLEntry *copy;
+        copy = filt_listbox_shallow_copy_entry (LENTRY (le->data), TRUE);
+        g_queue_push_tail (sl->list_keep, copy);
+    }
+
+    return TRUE;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+/*
+ * If the list is filtered it replaces from the back list (list_keep). It returns whether such
+ * change occurred – FALSE means that the list was already unfiltered.
+ */
+gboolean
+filt_listbox_ensure_unfiltered_state (WFilteringListbox * sl)
+{
+    gboolean ret = FALSE;
+    if (filt_listbox_is_filter_state (sl))
+        ret = filt_listbox_set_to_normal_state (sl);
+    return ret;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+gboolean
+filt_listbox_conditionally_enable_multi_search_init (WFilteringListbox * sl)
+{
+    gboolean start_with_multi_search_active;
+
+    /* Option of starting the listbox with MultiSearch pre-activated. */
+    start_with_multi_search_active = option_multisearch;
+
+    /* CK_MultiSearch toggles the state. */
+    if (start_with_multi_search_active)
+        send_message (WIDGET (sl), NULL, MSG_ACTION, CK_MultiSearch, NULL);
+    else
+        /* Only init embedded position indices. */
+        listbox_init_indices (LISTBOX (sl));
+
+    /* Return if did enable MultiSearch. */
+    return start_with_multi_search_active;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+/*** public functions ****************************************************************************/
+/* --------------------------------------------------------------------------------------------- */
+
+WFilteringListbox *
+filtering_listbox_new (int y, int x, int height, int width,
+                       gboolean deletable, lcback_fn callback,
+                       filt_listbox_resize_strategy_t resize)
+{
+    WFilteringListbox *object;
+    Widget *w_ref;
+
+    /* Allocate memory for the object body. */
+    object = g_new (WFilteringListbox, 1);
+
+    /* Forward the call to construct the inherited object. */
+    listbox_init (&object->base, y, x, height, width, deletable, callback);
+
+    /* Alter fields of base class. */
+    w_ref = WIDGET (object);
+    w_ref->callback = filt_listbox_callback;    /* Set custom callback handler */
+
+    /* Set extending fields of this class. */
+    object->list_keep = NULL;   /* No back buffer at startup */
+    object->resize_strategy = resize;   /* Save resize strategy */
+    object->initialized = FALSE;
+
+    return object;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+cb_ret_t
+filt_listbox_callback (Widget * w, Widget * sender, widget_msg_t msg, int parm, void *data)
+{
+    WFilteringListbox *sl = FILT_LISTBOX (w);   /* s* - from `screen`, a "screened" listbox */
+    cb_ret_t ret = MSG_NOT_HANDLED;
+    long activity;
+
+    switch (msg)
+    {
+    case MSG_INIT:
+        if (!sl->initialized)
+        {
+            filt_listbox_conditionally_enable_multi_search_init (sl);
+            sl->initialized = TRUE;
+        }
+        /* WListbox doesn't have MSG_INIT, so don't forward. */
+        ret = MSG_HANDLED;
+        break;
+    case MSG_ACTION:
+        if (parm == CK_MultiSearch)
+        {
+            gboolean retval;
+            /* Toggle the multi term searching of any listbox. */
+            if (filt_listbox_is_filter_state (sl))
+            {
+                /* Remove the input widget from the dialog. */
+                filt_listbox_hide_multi_search_widget (sl);
+                /* Restore original (unfiltered) listbox contents. */
+                retval = filt_listbox_set_to_normal_state (sl);
+            }
+            else
+            {
+                /* Add input widget for the filter query at the bottom of the dialog window. */
+                filt_listbox_show_multi_search_widget (sl);
+                /* ... and then turn on the filter state. */
+                retval = filt_listbox_set_to_filter_state (sl);
+            }
+            if (!retval)
+                message (D_ERROR | D_CENTER, MSG_ERROR,
+                         "An internal error #3 occurred (filtered listbox support).");
+
+            ret = MSG_HANDLED;
+        }
+        break;
+
+    case MSG_KEY:
+        activity = widget_lookup_key (WIDGET (sl), parm);
+        if (activity == CK_MultiSearch)
+            ret = send_message (w, NULL, MSG_ACTION, CK_MultiSearch, NULL);
+        break;
+
+    case MSG_NOTIFY:
+        if (widget_get_state (w, WST_FILTER))
+        {
+            filt_listbox_filter_list (sl, (char *) data);
+            ret = MSG_HANDLED;
+        }
+        widget_draw (w);
+        /* Protect against normal, non ForwardingInput messages, which might not have sender set. */
+        if (sender)
+            widget_draw (sender);
+        break;
+
+    case MSG_DESTROY:
+        filt_listbox_ensure_unfiltered_state (sl);
+        /* ret is unhandled -> the message will be forwarded to base class. */
+        break;
+    default:
+        break;
+    }
+
+    /* Forward action to base class in case it's not yet handled. */
+    if (ret == MSG_NOT_HANDLED)
+        ret = listbox_callback (w, sender, msg, parm, data);
+
+    return ret;
+}
+
+/* --------------------------------------------------------------------------------------------- */

new file lib/widget/filtering_listbox.h

@@ +1 @@
+#ifndef MC__FILTERING_LISTBOX_H
+#define MC__FILTERING_LISTBOX_H
+
+/*** typedefs(not structures) and defined constants **********************************************/
+
+/* Casting macros. */
+#define FILT_LISTBOX(x) ((WFilteringListbox *)(x))
+#define CONST_FILT_LISTBOX(x) ((const WFilteringListbox *)(x))
+
+/*** enums ***************************************************************************************/
+
+typedef enum filt_listbox_resize_strategy_e
+{
+    FILT_LIST_EXTEND_DIALOG = 0,
+    FILT_LIST_KEEP_DIALOG_SIZE,
+    FILT_LIST_DIALOG_AUTO_RESIZE
+} filt_listbox_resize_strategy_t;
+
+/*** structures declarations (and typedefs of structures)*****************************************/
+
+typedef struct WFilteringListbox_s
+{
+    WListbox base;
+    gboolean initialized;       /* Whether MSG_INIT has been received. */
+
+    /* Fields for new logic. */
+    GQueue *list_keep;          /* Unfiltered list (used in  WST_FILTER state). */
+    filt_listbox_resize_strategy_t resize_strategy;
+} WFilteringListbox;
+
+/*** global variables defined in .c file *********************************************************/
+
+/*** declarations of public functions ************************************************************/
+
+WFilteringListbox *filtering_listbox_new (int y, int x, int height, int width,
+                                          gboolean deletable, lcback_fn callback,
+                                          filt_listbox_resize_strategy_t resize);
+gboolean filt_listbox_ensure_unfiltered_state (WFilteringListbox * l);
+gboolean filt_listbox_conditionally_enable_multi_search_init (WFilteringListbox * l);
+void filt_listbox_select_entry (WFilteringListbox * sl, int dest);
+cb_ret_t filt_listbox_callback (Widget * w, Widget * sender, widget_msg_t msg, int parm,
+                                void *data);
+
+/*** inline functions ****************************************************************************/
+
+#endif /* MC__FILTERING_LISTBOX_H */

new file lib/widget/forwarding_input.c

@@ +1 @@
+/*
+   A key forwarding extended input class.
+
+   Copyright (C) 2021
+   Free Software Foundation, Inc.
+
+   Written by:
+   Sebastian Gniazdowski <sgniazdowski@gmail.com>, 2021.
+
+   This file is part of the Midnight Commander.
+
+   The Midnight Commander is free software: you can redistribute it
+   and/or modify it under the terms of the GNU General Public License as
+   published by the Free Software Foundation, either version 3 of the License,
+   or (at your option) any later version.
+
+   The Midnight Commander is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** \file forwarding-input.c
+ *  \brief This input class has a feature of forwarding unrecognized keys to a widget passed at
+ *         creation.
+ *  \author Sebastian Gniazdowski
+ *  \date 2021
+ *
+ *  It's being used by MultiSearch to allow moving across listbox while typing to the input.
+ */
+
+#include <config.h>
+
+#include "lib/global.h"
+#include "lib/widget.h"
+
+/*** global variables ****************************************************************************/
+
+/*** file scope macro definitions ****************************************************************/
+
+/*** file scope type declarations ****************************************************************/
+
+/*** file scope variables ************************************************************************/
+
+/*** file scope functions ************************************************************************/
+/* --------------------------------------------------------------------------------------------- */
+
+/* --------------------------------------------------------------------------------------------- */
+/*** public functions ****************************************************************************/
+/* --------------------------------------------------------------------------------------------- */
+
+WForwardingInput *
+forwarding_input_new (int y, int x, const int *colors,
+                      int len, const char *text, const char *histname,
+                      input_complete_t completion_flags, Widget * forward_to_widget)
+{
+    WForwardingInput *object;
+    Widget *w_ref;
+
+    /* Allocate memory for the object body. */
+    object = g_new (WForwardingInput, 1);
+
+    /* Call upper constructor to initialize the inherited object. */
+    input_init (&object->base, y, x, colors, len, text, histname, completion_flags);
+
+    /* Alter fields of base class. */
+    w_ref = WIDGET (object);
+    w_ref->callback = forw_input_callback;      /* Set custom callback handler */
+
+    /* Set  extending fields of this class. */
+    object->forward_to_widget = forward_to_widget;
+    return object;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+cb_ret_t
+forw_input_callback (Widget * w, Widget * sender, widget_msg_t msg, int parm, void *data)
+{
+    WForwardingInput *in = FORW_INPUT (w);
+    gboolean key_message = FALSE;
+    cb_ret_t ret;
+
+    switch (msg)
+    {
+    case MSG_KEY:
+        ret = forw_input_handle_char (in, parm);
+        key_message = TRUE;
+        break;
+    default:
+        break;
+    }
+
+    /*
+     * Simply pass on all messages to the base class (except for MSG_KEY, which might have
+     * been possibly already sent from forw_input_handle_char() function).
+     */
+
+    if (!key_message)
+        ret = input_callback (WIDGET (in), sender, msg, parm, data);
+
+    return ret;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+cb_ret_t
+forw_input_handle_char (WForwardingInput * in, int key)
+{
+    cb_ret_t ret = MSG_NOT_HANDLED;
+    gboolean sent_to_base = FALSE;
+    long activity;
+    char *str_cp;
+
+    /* Save to detect if a change happened. */
+    str_cp = g_strdup (in->base.buffer);
+
+    /* Is this key recognized by the base object? */
+    activity = widget_lookup_key (WIDGET (in), key);
+    if (activity != CK_IgnoreKey && activity != CK_Complete)
+    {
+        /* Yes -> send the key to the upper class. */
+        ret = input_callback (WIDGET (in), WIDGET (in), MSG_KEY, key, NULL);
+        sent_to_base = TRUE;
+    }
+    /* Should we try to forward the key to any paired widget? */
+    if (in->forward_to_widget != NULL && ret == MSG_NOT_HANDLED)
+    {
+        /* Is it maybe recognized by forward_to_widget paired object? */
+        activity = widget_lookup_key (WIDGET (in->forward_to_widget), key);
+        if (activity != CK_IgnoreKey)
+        {
+            /* Yes - forward the key to the paired widget (most probably WListbox). */
+            ret = send_message (WIDGET (in->forward_to_widget), NULL, MSG_KEY, key, NULL);
+        }
+        /* Abort as this widget is probably released */
+        if (activity == CK_MultiSearch && ret == MSG_HANDLED)
+            return ret;
+    }
+
+    /*
+     * If not handled yet, then send the key to the base object for general recognition (if
+     * not already done that).
+     */
+
+    if (!sent_to_base && ret == MSG_NOT_HANDLED)
+    {
+        ret = input_callback (WIDGET (in), WIDGET (in), MSG_KEY, key, NULL);
+        sent_to_base = TRUE;    /* currently unused */
+    }
+
+    /* Send update signal to paired widget «iff» input's text has changed. */
+    if (in->forward_to_widget != NULL && g_strcmp0 (str_cp, in->base.buffer) != 0)
+        send_message (WIDGET (in->forward_to_widget), NULL, MSG_NOTIFY, key, in->base.buffer);
+    g_free (str_cp);
+
+    return ret;
+}
+
+/* --------------------------------------------------------------------------------------------- */

new file lib/widget/forwarding_input.h

@@ +1 @@
+#ifndef MC__FORWARDING_INPUT_H
+#define MC__FORWARDING_INPUT_H
+
+/*** typedefs(not structures) and defined constants **********************************************/
+
+/* Casting macros. */
+#define FORW_INPUT(x) ((WForwardingInput *)(x))
+#define CONST_FORW_INPUT(x) ((const WForwardingInput *)(x))
+
+typedef struct
+{
+    WInput base;
+
+    /* Fields for new logic. */
+    Widget *forward_to_widget;  /* The paired widget to receive unhandled keys */
+} WForwardingInput;
+
+/*** enums ***************************************************************************************/
+
+/*** structures declarations (and typedefs of structures)*****************************************/
+
+/*** global variables defined in .c file *********************************************************/
+
+/*** declarations of public functions ************************************************************/
+
+WForwardingInput *forwarding_input_new (int y, int x, const int *colors,
+                                        int len, const char *text, const char *histname,
+                                        input_complete_t completion_flags,
+                                        Widget * forward_to_widget);
+
+cb_ret_t forw_input_callback (Widget * w, Widget * sender, widget_msg_t msg, int parm, void *data);
+cb_ret_t forw_input_handle_char (WForwardingInput * in, int key);
+
+/*** inline functions ****************************************************************************/
+
+#endif /* MC__FORWARDING_INPUT_H */

lib/widget/group.c

@@ -749 +749 @@
  * @param w Widget object
  */
 void
-group_remove_widget (void *w)
+group_remove_widget (void *wid)
 {
+    Widget *w = WIDGET (wid);
     WGroup *g;
     GList *d;
 
     /* Don't accept NULL widget. This shouldn't happen */
     assert (w != NULL);
 
-    g = WIDGET (w)->owner;
+    /* Invoke widget's pre unlink callback. */
+    if (w->pre_unlink_func != NULL)
+        w->pre_unlink_func (w);
+
+    g = w->owner;
 
     d = g_list_find (g->widgets, w);
     if (d == g->current)
@@ -774 +779 @@
         group_select_current_widget (g);
     }
 
-    WIDGET (w)->owner = NULL;
+    w->owner = NULL;
 }
 
 /* --------------------------------------------------------------------------------------------- */

lib/widget/history.c

@@ -66 +66 @@
 /*** file scope functions ************************************************************************/
 
 static cb_ret_t
-history_dlg_reposition (WDialog * dlg_head)
+history_dlg_reposition (WDialog * dlg_head, WRect * resize)
 {
-    history_dlg_data *data;
-    int x = 0, y, he, wi;
     WRect r;
 
-    /* guard checks */
-    if ((dlg_head == NULL) || (dlg_head->data == NULL))
-        return MSG_NOT_HANDLED;
-
-    data = (history_dlg_data *) dlg_head->data;
-
-    y = data->y;
-    he = data->count + 2;
-
-    if (he <= y || y > (LINES - 6))
+    if (resize == NULL)
     {
-        he = MIN (he, y - 1);
-        y -= he;
+        history_dlg_data *data;
+        int x = 0, y, he, wi;
+
+        /* guard checks */
+        if ((dlg_head == NULL) || (dlg_head->data == NULL))
+            return MSG_NOT_HANDLED;
+
+        data = (history_dlg_data *) dlg_head->data;
+
+        y = data->y;
+        he = data->count + 2;
+
+        if (he <= y || y > (LINES - 6))
+        {
+            he = MIN (he, y - 1);
+            y -= he;
+        }
+        else
+        {
+            y++;
+            he = MIN (he, LINES - y);
+        }
+
+        if (data->x > 2)
+            x = data->x - 2;
+
+        wi = data->max_width + 4;
+
+        if ((wi + x) > COLS)
+        {
+            wi = MIN (wi, COLS);
+            x = COLS - wi;
+        }
+        rect_init (&r, y, x, he, wi);
     }
     else
     {
-        y++;
-        he = MIN (he, LINES - y);
+        /* A resize from some other code (currently from the listbox filter). */
+        r = *resize;
     }
 
-    if (data->x > 2)
-        x = data->x - 2;
-
-    wi = data->max_width + 4;
-
-    if ((wi + x) > COLS)
-    {
-        wi = MIN (wi, COLS);
-        x = COLS - wi;
-    }
-
-    rect_init (&r, y, x, he, wi);
 
     return dlg_default_callback (WIDGET (dlg_head), NULL, MSG_RESIZE, 0, &r);
 }
@@ -116 +125 @@
     switch (msg)
     {
     case MSG_RESIZE:
-        return history_dlg_reposition (DIALOG (w));
+        return history_dlg_reposition (DIALOG (w), data);
 
     case MSG_NOTIFY:
         {
@@ -158 +167 @@
     width = str_term_width1 (text);
     hd->max_width = MAX (width, hd->max_width);
 
-    listbox_add_item (hd->listbox, LISTBOX_APPEND_AT_END, 0, text, NULL, TRUE);
+    listbox_add_item (LISTBOX (hd->listbox), LISTBOX_APPEND_AT_END, 0, text, NULL, TRUE);
 }
 
 /* --------------------------------------------------------------------------------------------- */
@@ -190 +199 @@
     hd->action = CK_IgnoreKey;
     hd->text = NULL;
     hd->max_width = 0;
-    hd->listbox = listbox_new (1, 1, 2, 2, TRUE, NULL);
+    hd->listbox = filtering_listbox_new (1, 1, 2, 2, TRUE, NULL, FILT_LIST_KEEP_DIALOG_SIZE);
     /* in most cases history list contains string only and no any other data */
     hd->create = history_create_item;
     hd->release = history_release_item;
@@ -205 +214 @@
     GList *z, *hi;
     size_t count;
     WDialog *query_dlg;
+    WListbox *lw;
     history_dlg_data hist_data;
     int dlg_ret;
 
@@ -217 +227 @@
         hd->create (hd, z->data);
     /* after this, the order of history items is following: recent at begin, oldest at end */
 
-    count = listbox_get_length (hd->listbox);
+    /* Get the WListbox pointer for convenience. */
+    lw = LISTBOX (hd->listbox);
+    count = listbox_get_length (lw);
 
     hist_data.y = hd->y;
     hist_data.x = hd->x;
@@ -244 +256 @@
     {
         /* history is above base widget -- revert order to place recent item at bottom */
         /* revert history direction */
-        g_queue_reverse (hd->listbox->list);
+        g_queue_reverse (lw->list);
         if (hd->current < 0 || (size_t) hd->current >= count)
-            listbox_select_last (hd->listbox);
+            listbox_select_last (lw);
         else
-            listbox_select_entry (hd->listbox, count - 1 - (size_t) hd->current);
+            listbox_select_entry (lw, count - 1 - (size_t) hd->current);
     }
     else
     {
         /* history is below base widget -- keep order to place recent item on top  */
         if (hd->current > 0)
-            listbox_select_entry (hd->listbox, hd->current);
+            listbox_select_entry (lw, hd->current);
     }
 
     dlg_ret = dlg_run (query_dlg);
@@ -274 +286 @@
             hd->action = CK_Enter;
         }
 
-        listbox_get_current (hd->listbox, &q, NULL);
-        hd->text = g_strdup (q);
+        listbox_get_current (lw, &q, NULL);
+        /* Can still be 0 if special entry "<no search results>" will be selected. */
+        if (q != NULL)
+            hd->text = g_strdup (q);
     }
 
+    /* If needed, restore normal listbox state, with no backlist (list_keep). */
+    filt_listbox_ensure_unfiltered_state (hd->listbox);
+
     /* get modified history from dialog */
     z = NULL;
-    for (hi = listbox_get_first_link (hd->listbox); hi != NULL; hi = g_list_next (hi))
+    for (hi = listbox_get_first_link (lw); hi != NULL; hi = g_list_next (hi))
         /* history is being reverted here again */
         z = g_list_prepend (z, hd->release (hd, LENTRY (hi->data)));
 

lib/widget/history.h

@@ -11 +11 @@
 /* forward declarations */
 struct history_descriptor_t;
 struct WLEntry;
-struct WListbox;
+typedef struct WFilteringListbox_s WFilteringListbox;
 
 typedef void (*history_create_item_func) (struct history_descriptor_t * hd, void *data);
 typedef void *(*history_release_item_func) (struct history_descriptor_t * hd, struct WLEntry * le);
@@ -30 +30 @@
     char *text;                 /**< return text of selected item */
 
     size_t max_width;           /**< maximum width of sring in history */
-    struct WListbox *listbox;   /**< listbox widget to draw history */
+    WFilteringListbox *listbox;   /**< listbox widget to draw history */
 
     history_create_item_func create;    /**< function to create item of @list */
     history_release_item_func release;  /**< function to release item of @list */

lib/widget/input.c

@@ -871 +871 @@
     (void) event_group_name;
     (void) event_name;
 
-    if (!in->is_password && (DIALOG (WIDGET (in)->owner)->ret_value != B_CANCEL))
+    if (!in->is_password && WIDGET (in)->owner != NULL
+        && (DIALOG (WIDGET (in)->owner)->ret_value != B_CANCEL))
     {
         ev_history_load_save_t *ev = (ev_history_load_save_t *) data;
 
@@ -970 +971 @@
     }
 }
 
+/* --------------------------------------------------------------------------------------------- */
+/* a callback used when removing the widget from its WGroup */
+
+static void
+input_unregister_history_events_cb (Widget * wid_ptr)
+{
+    WDialog *h = DIALOG (wid_ptr->owner);
+
+    /* unsubscribe from "history_load" event */
+    mc_event_del (h->event_group, MCEVENT_HISTORY_LOAD, input_load_history, wid_ptr);
+    /* unsubscribe from "history_save" event */
+    mc_event_del (h->event_group, MCEVENT_HISTORY_SAVE, input_save_history, wid_ptr);
+}
+
 /* --------------------------------------------------------------------------------------------- */
 /*** public functions ****************************************************************************/
 /* --------------------------------------------------------------------------------------------- */
 
+WInput *
+input_new (int y, int x, const int *colors, int width, const char *def_text,
+           const char *histname, input_complete_t completion_flags)
+{
+    WInput *in;
+
+    in = g_new (WInput, 1);
+    input_init (in, y, x, colors, width, def_text, histname, completion_flags);
+    return in;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
 /** Create new instance of WInput object.
   * @param y                    Y coordinate
   * @param x                    X coordinate
@@ -984 +1012 @@
   * @param completion_flags     Flags for specify type of completions
   * @return                     WInput object
   */
-WInput *
-input_new (int y, int x, const int *colors, int width, const char *def_text,
-           const char *histname, input_complete_t completion_flags)
+void
+input_init (WInput * in, int y, int x, const int *colors, int width, const char *def_text,
+            const char *histname, input_complete_t completion_flags)
 {
-    WInput *in;
-    Widget *w;
+    Widget *w = WIDGET (in);
 
-    in = g_new (WInput, 1);
-    w = WIDGET (in);
     widget_init (w, y, x, 1, width, input_callback, input_mouse_callback);
     w->options |= WOP_SELECTABLE | WOP_IS_INPUT | WOP_WANT_CURSOR;
     w->keymap = input_map;
@@ -1028 +1053 @@
     if ((histname != NULL) && (*histname != '\0'))
         in->history.name = g_strdup (histname);
     /* history will be loaded later */
-
     in->label = NULL;
-
-    return in;
 }
 
 /* --------------------------------------------------------------------------------------------- */
@@ -1050 +1072 @@
         mc_event_add (h->event_group, MCEVENT_HISTORY_LOAD, input_load_history, w, NULL);
         /* subscribe to "history_save" event */
         mc_event_add (h->event_group, MCEVENT_HISTORY_SAVE, input_save_history, w, NULL);
+        /* unregister (via the func) above events in case of removal from dialog */
+        w->pre_unlink_func = input_unregister_history_events_cb;
         if (in->label != NULL)
             widget_set_state (WIDGET (in->label), WST_DISABLED, widget_get_state (w, WST_DISABLED));
         return MSG_HANDLED;
@@ -1063 +1087 @@
             return v;
         }
 
-        /* Keys we want others to handle */
+        /* Keys we want others to handle. */
         if (parm == KEY_UP || parm == KEY_DOWN || parm == ESC_CHAR
             || parm == KEY_F (10) || parm == '\n')
             return MSG_NOT_HANDLED;
@@ -1097 +1121 @@
         return MSG_HANDLED;
 
     case MSG_DESTROY:
-        /* unsubscribe from "history_load" event */
-        mc_event_del (h->event_group, MCEVENT_HISTORY_LOAD, input_load_history, w);
-        /* unsubscribe from "history_save" event */
-        mc_event_del (h->event_group, MCEVENT_HISTORY_SAVE, input_save_history, w);
+        /* Only, if there is an owner WGroup. */
+        if (h != NULL)
+        {
+            /* unsubscribe from "history_load" event */
+            mc_event_del (h->event_group, MCEVENT_HISTORY_LOAD, input_load_history, w);
+            /* unsubscribe from "history_save" event */
+            mc_event_del (h->event_group, MCEVENT_HISTORY_SAVE, input_save_history, w);
+        }
         input_destroy (in);
         return MSG_HANDLED;
 

lib/widget/input.h

@@ -83 +83 @@
 
 /*** declarations of public functions ************************************************************/
 
+void input_init (WInput * in, int y, int x, const int *colors, int width, const char *def_text,
+                 const char *histname, input_complete_t completion_flags);
 WInput *input_new (int y, int x, const int *colors,
                    int len, const char *text, const char *histname,
                    input_complete_t completion_flags);

lib/widget/input_complete.c

@@ -1017 +1017 @@
 {
     static int bl = 0;
 
-    WGroup *g = GROUP (w);
     WDialog *h = DIALOG (w);
+    WFilteringListbox *slw;
+    cb_ret_t ret = MSG_NOT_HANDLED;
+
+    /* Find the listbox in dialog's group. */
+    slw = FILT_LISTBOX (WIDGET (h)->find_by_type (WIDGET (h), filt_listbox_callback));
 
     switch (msg)
     {
@@ -1027 +1031 @@
         {
         case KEY_LEFT:
         case KEY_RIGHT:
+            /* MultiSearch (list filtering) is allowing for left/right movement in query input. */
+            if (widget_get_state (WIDGET (slw), WST_FILTER))
+                break;
             bl = 0;
             h->ret_value = 0;
             dlg_stop (h);
-            return MSG_HANDLED;
+            ret = MSG_HANDLED;
+            break;
 
         case KEY_BACKSPACE:
+            /* MultiSearch is exclusive with completion widening. */
+            if (widget_get_state (WIDGET (slw), WST_FILTER))
+                break;
             bl = 0;
             /* exit from completion list if input line is empty */
             if (end == 0)
@@ -1056 +1067 @@
 
                 new_end = str_get_prev_char (&input->buffer[end]) - input->buffer;
 
-                for (i = 0, e = listbox_get_first_link (LISTBOX (g->current->data));
+                for (i = 0, e = listbox_get_first_link (LISTBOX (slw));
                      e != NULL; i++, e = g_list_next (e))
                 {
                     WLEntry *le = LENTRY (e->data);
 
                     if (strncmp (input->buffer + start, le->text, new_end - start) == 0)
                     {
-                        listbox_select_entry (LISTBOX (g->current->data), i);
+                        listbox_select_entry (LISTBOX (slw), i);
                         end = new_end;
                         input_handle_char (input, parm);
-                        widget_draw (WIDGET (g->current->data));
+                        widget_draw (WIDGET (slw));
                         break;
                     }
                 }
             }
-            return MSG_HANDLED;
+            ret = MSG_HANDLED;
+            break;
 
         default:
             if (parm < 32 || parm > 255)
             {
                 bl = 0;
-                if (widget_lookup_key (WIDGET (input), parm) != CK_Complete)
-                    return MSG_NOT_HANDLED;
-
-                if (end == min_end)
-                    return MSG_HANDLED;
-
-                /* This means we want to refill the list box and start again */
-                h->ret_value = B_USER;
-                dlg_stop (h);
+                /* CK_Complete -> Is completion up to date? */
+                if ((widget_lookup_key (WIDGET (input), parm) == CK_Complete) && (end != min_end))
+                {
+                    /* This means we want to refill the list box and start again. */
+                    h->ret_value = B_USER;
+                    dlg_stop (h);
+                }
+                /*
+                 * else - key will be ignored by this function, so leave ret unchanged - allow other
+                 * widgets to process it.
+                 */
             }
-            else
+
+            /*
+             * Do standard live entry lookup only when not filtering list via MultiSearch – it is
+             * a feature that to a great extent replaces old engine. It can be still used as MultiSearch
+             * can be dynamically enabled and disabled (by default with: Alt-space and Ctrl-space).
+             */
+            else if (!widget_get_state (WIDGET (slw), WST_FILTER))
             {
                 static char buff[MB_LEN_MAX] = "";
                 GList *e;
@@ -1110 +1130 @@
                     break;
                 }
 
-                for (i = 0, e = listbox_get_first_link (LISTBOX (g->current->data));
+                for (i = 0, e = listbox_get_first_link (LISTBOX (slw));
                      e != NULL; i++, e = g_list_next (e))
                 {
                     WLEntry *le = LENTRY (e->data);
@@ -1121 +1141 @@
                         if (need_redraw == 0)
                         {
                             need_redraw = 1;
-                            listbox_select_entry (LISTBOX (g->current->data), i);
+                            listbox_select_entry (LISTBOX (slw), i);
                             last_text = le->text;
                         }
                         else
@@ -1172 +1192 @@
                 if (need_redraw == 2)
                 {
                     insert_text (input, last_text, low);
-                    widget_draw (WIDGET (g->current->data));
+                    widget_draw (WIDGET (slw));
                 }
                 else if (need_redraw == 1)
                 {
@@ -1180 +1200 @@
                     dlg_stop (h);
                 }
                 bl = 0;
+                ret = MSG_HANDLED;
             }
         }
-        return MSG_HANDLED;
+        break;
 
     default:
         return dlg_default_callback (w, sender, msg, parm, data);
     }
+    return ret;
 }
 
 /* --------------------------------------------------------------------------------------------- */
@@ -1223 +1245 @@
             int start_x, start_y;
             char **p, *q;
             WDialog *complete_dlg;
-            WListbox *complete_list;
+            WFilteringListbox *complete_list;
 
             for (p = in->completions + 1; *p != NULL; count++, p++)
             {
@@ -1266 +1288 @@
             complete_dlg =
                 dlg_create (TRUE, y, x, complete_height, complete_width, WPOS_KEEP_DEFAULT, TRUE,
                             dialog_colors, complete_callback, NULL, "[Completion]", NULL);
-            complete_list = listbox_new (1, 1, h - 2, w - 2, FALSE, NULL);
+            complete_list = filtering_listbox_new (1, 1, h - 2, w - 2, FALSE, NULL,
+                                                   FILT_LIST_KEEP_DIALOG_SIZE);
             group_add_widget (GROUP (complete_dlg), complete_list);
 
             for (p = in->completions + 1; *p != NULL; p++)
-                listbox_add_item (complete_list, LISTBOX_APPEND_AT_END, 0, *p, NULL, FALSE);
+                listbox_add_item (LISTBOX (complete_list), LISTBOX_APPEND_AT_END, 0, *p, NULL,
+                                  FALSE);
 
             i = dlg_run (complete_dlg);
             q = NULL;
             if (i == B_ENTER)
             {
-                listbox_get_current (complete_list, &q, NULL);
+                listbox_get_current (LISTBOX (complete_list), &q, NULL);
                 if (q != NULL)
                     insert_text (in, q, strlen (q));
             }
             if (q != NULL || end != min_end)
                 input_complete_free (in);
+
             dlg_destroy (complete_dlg);
 
             /* B_USER if user wants to start over again */

lib/widget/listbox-window.c

@@ -108 +108 @@
         dlg_create (TRUE, ypos, xpos, lines + space, cols + space, pos_flags, FALSE, listbox_colors,
                     NULL, NULL, help, title);
 
-    listbox->list = listbox_new (2, 2, lines, cols, FALSE, NULL);
-    group_add_widget (GROUP (listbox->dlg), listbox->list);
+    listbox->list =
+        filtering_listbox_new (2, 2, lines, cols, FALSE, NULL, FILT_LIST_DIALOG_AUTO_RESIZE);
+    group_add_widget (GROUP (listbox->dlg), WIDGET (listbox->list));
 
     return listbox;
 }
@@ -128 +129 @@
 int
 run_listbox (Listbox * l)
 {
+    WListbox *lw = LISTBOX (l->list);
     int val = -1;
 
     if (dlg_run (l->dlg) != B_CANCEL)
-        val = l->list->pos;
+    {
+        /* Get the virtual index first, to support filtered listboxes. */
+        val = lw->virtual_pos;
+
+        /* No virtual position -> get pos. */
+        if (val == -1)
+            val = lw->pos;
+    }
+
     dlg_destroy (l->dlg);
     g_free (l);
     return val;
@@ -149 +159 @@
 void *
 run_listbox_with_data (Listbox * l, const void *select)
 {
+    WListbox *lw = LISTBOX (l->list);
     void *val = NULL;
 
     if (select != NULL)
-        listbox_select_entry (l->list, listbox_search_data (l->list, select));
+        listbox_select_entry (lw, listbox_search_data (lw, select));
 
     if (dlg_run (l->dlg) != B_CANCEL)
     {
         WLEntry *e;
-        e = listbox_get_nth_item (l->list, l->list->pos);
-        if (e != NULL)
+        e = listbox_get_nth_item (lw, lw->pos);
+        /* -2 means that "<no search results>" has been selected. */
+        if (e != NULL && e->index != -2)
         {
             /* The assert guards against returning a soon-to-be deallocated
              * pointer (as in listbox_add_item(..., TRUE)). */

lib/widget/listbox-window.h

@@ -8 +8 @@
 /*** typedefs(not structures) and defined constants **********************************************/
 
 #define LISTBOX_APPEND_TEXT(l,h,t,d,f) \
-    listbox_add_item (l->list, LISTBOX_APPEND_AT_END, h, t, d, f)
+    listbox_add_item (LISTBOX(l->list), LISTBOX_APPEND_AT_END, h, t, d, f)
 
 /*** enums ***************************************************************************************/
 
@@ -17 +17 @@
 typedef struct
 {
     WDialog *dlg;
-    WListbox *list;
+    WFilteringListbox *list;
 } Listbox;
 
 /*** global variables defined in .c file *********************************************************/

lib/widget/listbox.c

@@ -77 +77 @@
 {
     WLEntry *e = data;
 
-    g_free (e->text);
+    if (e->free_text)
+        g_free (e->text);
     if (e->free_data)
         g_free (e->data);
     g_free (e);
@@ -358 +359 @@
 
 /* --------------------------------------------------------------------------------------------- */
 
+/* When called via g_queue_foreach it assigns the index field with an incremented int. */
+static void
+listbox_foreach_apply_index (gpointer data, gpointer user_data)
+{
+    WLEntry *e = data;
+    int *cur_idx = user_data;
+
+    /* Set the index and increment it. */
+    e->index = *cur_idx;
+    *cur_idx = *cur_idx + 1;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
 /* Listbox item adding function */
 static inline void
 listbox_append_item (WListbox * l, WLEntry * e, listbox_append_t pos)
@@ -445 +460 @@
 
 /* --------------------------------------------------------------------------------------------- */
 
-static cb_ret_t
+cb_ret_t
 listbox_callback (Widget * w, Widget * sender, widget_msg_t msg, int parm, void *data)
 {
     WListbox *l = LISTBOX (w);
@@ -544 +559 @@
 /*** public functions ****************************************************************************/
 /* --------------------------------------------------------------------------------------------- */
 
-WListbox *
-listbox_new (int y, int x, int height, int width, gboolean deletable, lcback_fn callback)
+void
+listbox_init (WListbox * l, int y, int x, int height, int width, gboolean deletable,
+              lcback_fn callback)
 {
-    WListbox *l;
-    Widget *w;
+    Widget *w = WIDGET (l);
 
     if (height <= 0)
         height = 1;
 
-    l = g_new (WListbox, 1);
-    w = WIDGET (l);
     widget_init (w, y, x, height, width, listbox_callback, listbox_mouse_callback);
-    w->options |= WOP_SELECTABLE | WOP_WANT_HOTKEY;
+    w->options |= WOP_SELECTABLE;
     w->keymap = listbox_map;
 
     l->list = NULL;
-    l->top = l->pos = 0;
+    l->top = l->pos = l->virtual_pos = 0;
     l->deletable = deletable;
     l->callback = callback;
     l->allow_duplicates = TRUE;
     l->scrollbar = !mc_global.tty.slow_terminal;
+}
 
+/* --------------------------------------------------------------------------------------------- */
+
+WListbox *
+listbox_new (int y, int x, int height, int width, gboolean deletable, lcback_fn callback)
+{
+    WListbox *l;
+
+    l = g_new (WListbox, 1);
+    listbox_init (l, y, x, height, width, deletable, callback);
     return l;
 }
 
@@ -648 +671 @@
 void
 listbox_select_entry (WListbox * l, int dest)
 {
+    WLEntry *e;
     GList *le;
     int pos;
     gboolean top_seen = FALSE;
 
     if (listbox_is_empty (l) || dest < 0)
+    {
+        /* Reset position to a minimal one. */
+        l->pos = 0;
+        l->virtual_pos = 0;
         return;
+    }
 
     /* Special case */
     for (pos = 0, le = g_queue_peek_head_link (l->list); le != NULL; pos++, le = g_list_next (le))
@@ -673 +702 @@
                 if (l->pos - l->top >= lines)
                     l->top = l->pos - lines + 1;
             }
+            /*
+             * Set the virtual position, i.e.: a position in the initial, unfiltered list if the
+             * same element would be selected.
+             */
+            e = LENTRY (le->data);
+            l->virtual_pos = e->index;
             return;
         }
     }
@@ -701 +736 @@
     if (l != NULL)
         e = listbox_get_nth_item (l, l->pos);
 
-    ok = (e != NULL);
+    ok = (e != NULL && e->index != -2);
 
     if (string != NULL)
         *string = ok ? e->text : NULL;
@@ -720 +755 @@
         GList *item;
 
         item = g_queue_peek_nth_link (l->list, (guint) pos);
-        if (item != NULL)
+        if (item != NULL && LENTRY (item->data)->index != -2)
             return LENTRY (item->data);
     }
 
@@ -802 +837 @@
 
 /* --------------------------------------------------------------------------------------------- */
 
+/*
+ * Initializes the listbox elements with their position index. This allows to alter (filter, in
+ * particular) the listbox elements order and still get the original index (when selecting an
+ * element).
+ */
+void
+listbox_init_indices (WListbox * l)
+{
+    int index = 0;
+    g_queue_foreach (l->list, listbox_foreach_apply_index, &index);
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
 char *
 listbox_add_item (WListbox * l, listbox_append_t pos, int hotkey, const char *text, void *data,
                   gboolean free_data)
@@ -815 +864 @@
         return NULL;
 
     entry = g_new (WLEntry, 1);
+    entry->index = -1;          /* Will be initialized when switching to the filter state */
     entry->text = g_strdup (text);
+    entry->free_text = 1;
     entry->data = data;
     entry->free_data = free_data;
     entry->hotkey = hotkey;

lib/widget/listbox.h

@@ -35 +35 @@
 
 typedef struct WLEntry
 {
+    int index;                  /* The location in the list (used when it's filtered) */
     char *text;                 /* Text to display */
+    gboolean free_text;         /* Whether to free the text on entry's removal */
     int hotkey;
     void *data;                 /* Client information */
     gboolean free_data;         /* Whether to free the data on entry's removal */
@@ -46 +48 @@
     Widget widget;
     GQueue *list;               /* Pointer to the list of WLEntry */
     int pos;                    /* The current element displayed */
+    int virtual_pos;            /* The initial index of the current element, works also for filtered listbox */
     int top;                    /* The first element displayed */
     gboolean allow_duplicates;  /* Do we allow duplicates on the list? */
     gboolean scrollbar;         /* Draw a scrollbar? */
@@ -60 +63 @@
 
 /*** declarations of public functions ************************************************************/
 
+void listbox_init (WListbox * l, int y, int x, int height, int width, gboolean deletable,
+                   lcback_fn callback);
 WListbox *listbox_new (int y, int x, int height, int width, gboolean deletable, lcback_fn callback);
+cb_ret_t listbox_callback (Widget * w, Widget * sender, widget_msg_t msg, int parm, void *data);
+
 int listbox_search_text (WListbox * l, const char *text);
 int listbox_search_data (WListbox * l, const void *data);
 void listbox_select_first (WListbox * l);
@@ -74 +81 @@
 gboolean listbox_is_empty (const WListbox * l);
 void listbox_set_list (WListbox * l, GQueue * list);
 void listbox_remove_list (WListbox * l);
+void listbox_init_indices (WListbox * l);
 char *listbox_add_item (WListbox * l, listbox_append_t pos, int hotkey, const char *text,
                         void *data, gboolean free_data);
 

lib/widget/widget-common.c

@@ -338 +338 @@
     w->find_by_type = widget_default_find_by_type;
     w->find_by_id = widget_default_find_by_id;
 
+    w->pre_unlink_func = NULL;
+
     w->set_state = widget_default_set_state;
     w->get_colors = widget_default_get_colors;
 }

lib/widget/widget-common.h

@@ -42 +42 @@
     MSG_POST_KEY,               /* The key has been handled */
     MSG_ACTION,                 /* Send to widget to handle command */
     MSG_NOTIFY,                 /* Typically sent to dialog to inform it of state-change
-                                 * of listboxes, check- and radiobuttons. */
+                                 * of listboxes, check- and radiobuttons. Also from input
+                                 * to paired listbox when query of MultiSearch changes. */
     MSG_CURSOR,                 /* Sent to widget to position the cursor */
     MSG_IDLE,                   /* The idle state is active */
     MSG_RESIZE,                 /* Screen size has changed */
@@ -88 +89 @@
     WST_CONSTRUCT = (1 << 15),  /* Widget has been constructed but not run yet */
     WST_ACTIVE = (1 << 16),     /* Dialog is visible and active */
     WST_SUSPENDED = (1 << 17),  /* Dialog is suspended */
-    WST_CLOSED = (1 << 18)      /* Dialog is closed */
+    WST_CLOSED = (1 << 18),     /* Dialog is closed */
+
+    WST_FILTER = (1 << 19)      /* Listbox is filtering its contents */
 } widget_state_t;
 
 /* Flags for widget repositioning on dialog resize */
@@ -125 +128 @@
 typedef void (*widget_mouse_cb_fn) (Widget * w, mouse_msg_t msg, mouse_event_t * event);
 /* translate mouse event and process it */
 typedef int (*widget_mouse_handle_fn) (Widget * w, Gpm_Event * event);
+/* Pre unlinking (removing from a WGroup) callback. */
+typedef void (*pre_widget_unlink_cb) (Widget * w);
 
 /* Every Widget must have this as its first element */
 struct Widget
@@ -165 +170 @@
     cb_ret_t (*set_state) (Widget * w, widget_state_t state, gboolean enable);
     /* *INDENT-ON* */
 
+    pre_widget_unlink_cb pre_unlink_func;       /* a function invoked right before removing from a WGroup by
+                                                 * group_remove_widget; it can unregister any events, which
+                                                 * is an operation that depends on the `event_group` field of
+                                                 * the group, so it cannot be done «after» widget has been
+                                                 * removed from it (i.e.: when w.owner has been set to 0) */
+
     const int *(*get_colors) (const Widget * w);
 };
 

src/editor/choosesyntax.c

@@ -84 +84 @@
         name = g_ptr_array_index (names, i);
         LISTBOX_APPEND_TEXT (syntaxlist, 0, name, NULL, FALSE);
         if (current_syntax != NULL && strcmp (name, current_syntax) == 0)
-            listbox_select_entry (syntaxlist->list, i + N_DFLT_ENTRIES);
+            listbox_select_entry (LISTBOX (syntaxlist->list), i + N_DFLT_ENTRIES);
     }
 
     return run_listbox (syntaxlist);

src/editor/editcmd_dialogs.c

@@ -351 +351 @@
     int start_x, start_y, offset, i;
     char *curr = NULL;
     WDialog *compl_dlg;
-    WListbox *compl_list;
+    WFilteringListbox *compl_list;
+    WListbox *lw;
     int compl_dlg_h;            /* completion dialog height */
     int compl_dlg_w;            /* completion dialog width */
 
@@ -384 +385 @@
                     dialog_colors, NULL, NULL, "[Completion]", NULL);
 
     /* create the listbox */
-    compl_list = listbox_new (1, 1, compl_dlg_h - 2, compl_dlg_w - 2, FALSE, NULL);
+    compl_list = filtering_listbox_new (1, 1, compl_dlg_h - 2, compl_dlg_w - 2, FALSE, NULL,
+                                        FILT_LIST_DIALOG_AUTO_RESIZE);
+
+    /* Save WListbox pointer for convenience. */
+    lw = LISTBOX (compl_list);
 
     /* add the dialog */
     group_add_widget (GROUP (compl_dlg), compl_list);
 
     /* fill the listbox with the completions */
     for (i = num_compl - 1; i >= 0; i--)        /* reverse order */
-        listbox_add_item (compl_list, LISTBOX_APPEND_AT_END, 0, (char *) compl[i]->str, NULL,
-                          FALSE);
+        listbox_add_item (lw, LISTBOX_APPEND_AT_END, 0, (char *) compl[i]->str, NULL, FALSE);
 
     /* pop up the dialog and apply the chosen completion */
     if (dlg_run (compl_dlg) == B_ENTER)
     {
-        listbox_get_current (compl_list, &curr, NULL);
+        listbox_get_current (lw, &curr, NULL);
         curr = g_strdup (curr);
     }
 

src/editor/editoptions.c

@@ -175 +175 @@
                     QUICK_CHECKBOX (N_("Cursor be&yond end of line"), &option_cursor_beyond_eol,
                                      NULL),
                     QUICK_CHECKBOX (N_("&Group undo"), &option_group_undo, NULL),
+                    QUICK_CHECKBOX (N_("Default use MultiS&earch"), &option_multisearch,
+                                     NULL),
                     QUICK_LABELED_INPUT (N_("Word wrap line length:"), input_label_left, wrap_length,
                                          "edit-word-wrap", &p, NULL, FALSE, FALSE, INPUT_COMPLETE_NONE),
                 QUICK_STOP_GROUPBOX,

src/editor/editwidget.c

@@ -302 +302 @@
     Listbox *listbox;
     GList *w;
     WEdit *selected;
+    WListbox *lw;
     int i = 0;
 
     lines = MIN ((size_t) (LINES * 2 / 3), dlg_num);
@@ -309 +310 @@
 
     listbox = create_listbox_window (lines, cols, _("Open files"), "[Open files]");
 
+    /* Convenience variable. */
+    lw = LISTBOX (listbox->list);
+
     for (w = g->widgets; w != NULL; w = g_list_next (w))
         if (edit_widget_is_editor (CONST_WIDGET (w->data)))
         {
@@ -322 +326 @@
                     g_strdup_printf ("%c%s", e->modified ? '*' : ' ',
                                      vfs_path_as_str (e->filename_vpath));
 
-            listbox_add_item (listbox->list, LISTBOX_APPEND_AT_END, get_hotkey (i++),
-                              str_term_trim (fname, WIDGET (listbox->list)->cols - 2), e, FALSE);
+            listbox_add_item (lw, LISTBOX_APPEND_AT_END, get_hotkey (i++),
+                              str_term_trim (fname, WIDGET (lw)->cols - 2), e, FALSE);
             g_free (fname);
         }
 

src/file_history.c

@@ -155 +155 @@
     width = str_term_width1 (fhd->file_name);
     hd->max_width = MAX (width, hd->max_width);
 
-    listbox_add_item (hd->listbox, LISTBOX_APPEND_AT_END, 0, fhd->file_name, fhd->file_pos, TRUE);
+    listbox_add_item (LISTBOX (hd->listbox), LISTBOX_APPEND_AT_END, 0, fhd->file_name,
+                      fhd->file_pos, TRUE);
     /* fhd->file_pos is not copied, NULLize it to prevent double free */
     fhd->file_pos = NULL;
 }

src/filemanager/boxes.c

@@ -571 +571 @@
                 QUICK_START_GROUPBOX (N_("Other options")),
                     QUICK_CHECKBOX (N_("Use internal edi&t"), &use_internal_edit, NULL),
                     QUICK_CHECKBOX (N_("Use internal vie&w"), &use_internal_view, NULL),
+                    QUICK_CHECKBOX (N_("Default use MultiSearch"), &option_multisearch, NULL),
                     QUICK_CHECKBOX (N_("A&sk new file name"),
                                     &editor_ask_filename_before_edit, NULL),
                     QUICK_CHECKBOX (N_("Auto m&enus"), &auto_menu, NULL),

src/keybind-defaults.c

@@ -293 +293 @@
     {"Bottom", "end; alt-gt; c1"},
     {"PageUp", "pgup; alt-v"},
     {"PageDown", "pgdn; ctrl-v"},
-    {"Delete", "delete; d"},
-    {"Clear", "shift-delete; shift-d"},
+    {"Delete", "delete"},
+    {"Clear", "shift-delete"},
     {"View", "f3"},
     {"Edit", "f4"},
+    {"MultiSearch", "alt-space; ctrl-space"},
     {"Enter", "enter"},
     {NULL, NULL}
 };

src/selcodepage.c

@@ -107 +107 @@
         ? ((current_charset < 0) ? codepages->len : (size_t) current_charset)
         : ((size_t) current_charset + 1);
 
-    listbox_select_entry (listbox->list, i);
+    listbox_select_entry (LISTBOX (listbox->list), i);
 
     listbox_result = run_listbox (listbox);
 

src/setup.c

@@ -113 +113 @@
    are tagged files */
 gboolean confirm_view_dir = FALSE;
 
+/* Should MultiSearch listbox grepping be enabled by default on all lists */
+gboolean option_multisearch = FALSE;
+
 /* Ask file name before start the editor */
 gboolean editor_ask_filename_before_edit = FALSE;
 
@@ -295 +298 @@
     { "use_internal_view", &use_internal_view },
     { "use_internal_edit", &use_internal_edit },
     { "clear_before_exec", &clear_before_exec },
+    { "multi_search_active_by_default", &option_multisearch },
     { "confirm_delete", &confirm_delete },
     { "confirm_overwrite", &confirm_overwrite },
     { "confirm_execute", &confirm_execute },

src/setup.h

@@ -98 +98 @@
 extern gboolean output_starts_shell;
 extern gboolean use_file_to_check_type;
 extern gboolean file_op_compute_totals;
+extern gboolean option_multisearch;
 extern gboolean editor_ask_filename_before_edit;
 
 extern panels_options_t panels_options;

src/usermenu.c

@@ -1122 +1122 @@
                                      extract_line (p, p + MAX_ENTRY_LEN), p, FALSE);
             }
             /* Select the default entry */
-            listbox_select_entry (listbox->list, selected);
+            listbox_select_entry (LISTBOX (listbox->list), selected);
 
             selected = run_listbox (listbox);
         }