medit/moo/mooedit/mootextbuffer.c

/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4; coding: utf-8 -*-
 *
 *   mootextbuffer.c
 *
 *   Copyright (C) 2004-2005 by Yevgen Muntyan <muntyan@math.tamu.edu>
 *
 *   This program 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 2 of the License, or
 *   (at your option) any later version.
 *
 *   See COPYING file that comes with this distribution.
 */

#define MOOEDIT_COMPILATION
#include "mooedit/moolinebuffer.h"
#include "mooedit/mootextiter.h"
#include "mooedit/moohighlighter.h"
#include "mooutils/moomarshals.h"
#include "mooutils/mooundomanager.h"
#include "mooutils/mooutils-gobject.h"
#include <string.h>


struct _MooTextBufferPrivate {
    gboolean has_selection;
    gboolean has_text;

    MooHighlighter *hl;
    MooLang *lang;
    gboolean may_apply_tag;
    gboolean do_highlight;

    gboolean check_brackets;
    guint num_brackets;
    gunichar *left_brackets, *right_brackets;
    GtkTextTag *correct_match_tag;
    GtkTextTag *incorrect_match_tag;
    GtkTextMark *bracket_mark[4];
    MooBracketMatchType bracket_found;

    LineBuffer *line_buf;

    guint interactive;
    guint non_interactive;
    int cursor_moved_frozen;
    gboolean cursor_moved;
    MooUndoMgr *undo_mgr;
    gpointer modifying_action;
    int move_cursor_to;
#if 0
    int cursor_was_at;
#endif
};


static void     moo_text_buffer_finalize            (GObject        *object);

static void     moo_text_buffer_set_property        (GObject        *object,
                                                     guint           prop_id,
                                                     const GValue   *value,
                                                     GParamSpec     *pspec);
static void     moo_text_buffer_get_property        (GObject        *object,
                                                     guint           prop_id,
                                                     GValue         *value,
                                                     GParamSpec     *pspec);

static void     moo_text_buffer_cursor_moved        (MooTextBuffer      *buffer,
                                                     const GtkTextIter  *iter);
static void     moo_text_buffer_mark_set            (GtkTextBuffer      *buffer,
                                                     const GtkTextIter  *iter,
                                                     GtkTextMark        *mark);
static void     moo_text_buffer_insert_text         (GtkTextBuffer      *buffer,
                                                     GtkTextIter        *pos,
                                                     const gchar        *text,
                                                     gint                length);
static void     moo_text_buffer_apply_tag           (GtkTextBuffer      *buffer,
                                                     GtkTextTag         *tag,
                                                     const GtkTextIter  *start,
                                                     const GtkTextIter  *end);
static void     moo_text_buffer_delete_range        (GtkTextBuffer      *buffer,
                                                     GtkTextIter        *start,
                                                     GtkTextIter        *end);
static void     moo_text_buffer_begin_user_action   (GtkTextBuffer      *buffer);
static void     moo_text_buffer_end_user_action     (GtkTextBuffer      *buffer);
static void     moo_text_buffer_modified_changed    (GtkTextBuffer      *buffer);

static void     moo_text_buffer_queue_highlight     (MooTextBuffer      *buffer);

static void     cursor_moved                        (MooTextBuffer      *buffer,
                                                     const GtkTextIter  *iter);
static void     freeze_cursor_moved                 (MooTextBuffer      *buffer);
static void     thaw_cursor_moved                   (MooTextBuffer      *buffer);


static guint    INSERT_ACTION_TYPE;
static guint    DELETE_ACTION_TYPE;
static void     init_undo_actions                   (void);
static MooUndoAction *insert_action_new             (GtkTextBuffer      *buffer,
                                                     GtkTextIter        *pos,
                                                     const char         *text,
                                                     int                 length);
static MooUndoAction *delete_action_new             (GtkTextBuffer      *buffer,
                                                     GtkTextIter        *start,
                                                     GtkTextIter        *end);
#if 0
static void     before_undo_redo                    (MooTextBuffer      *buffer);
#endif
static void     after_undo_redo                     (MooTextBuffer      *buffer);


enum {
    CURSOR_MOVED,
    SELECTION_CHANGED,
    HIGHLIGHTING_CHANGED,
    LAST_SIGNAL
};

static guint signals[LAST_SIGNAL];


enum {
    PROP_0,
    PROP_CHECK_BRACKETS,
    PROP_BRACKET_MATCH_STYLE,
    PROP_BRACKET_MISMATCH_STYLE,
    PROP_HAS_TEXT,
    PROP_HAS_SELECTION,
    PROP_LANG
};


/* MOO_TYPE_TEXT_BUFFER */
G_DEFINE_TYPE (MooTextBuffer, moo_text_buffer, GTK_TYPE_TEXT_BUFFER)


static void
moo_text_buffer_class_init (MooTextBufferClass *klass)
{
    GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
    GtkTextBufferClass *buffer_class = GTK_TEXT_BUFFER_CLASS (klass);

    init_undo_actions ();

    gobject_class->set_property = moo_text_buffer_set_property;
    gobject_class->get_property = moo_text_buffer_get_property;
    gobject_class->finalize = moo_text_buffer_finalize;

    buffer_class->mark_set = moo_text_buffer_mark_set;
    buffer_class->insert_text = moo_text_buffer_insert_text;
    buffer_class->delete_range = moo_text_buffer_delete_range;
    buffer_class->apply_tag = moo_text_buffer_apply_tag;
    buffer_class->begin_user_action = moo_text_buffer_begin_user_action;
    buffer_class->end_user_action = moo_text_buffer_end_user_action;
    buffer_class->modified_changed = moo_text_buffer_modified_changed;

    klass->cursor_moved = moo_text_buffer_cursor_moved;

    g_object_class_install_property (gobject_class,
                                     PROP_CHECK_BRACKETS,
                                     g_param_spec_boolean ("check-brackets",
                                             "check-brackets",
                                             "check-brackets",
                                             TRUE,
                                             G_PARAM_CONSTRUCT | G_PARAM_READWRITE));

    g_object_class_install_property (gobject_class,
                                     PROP_BRACKET_MATCH_STYLE,
                                     g_param_spec_boxed ("bracket-match-style",
                                             "bracket-match-style",
                                             "bracket-match-style",
                                             MOO_TYPE_TEXT_STYLE,
                                             G_PARAM_CONSTRUCT | G_PARAM_WRITABLE));

    g_object_class_install_property (gobject_class,
                                     PROP_BRACKET_MISMATCH_STYLE,
                                     g_param_spec_boxed ("bracket-mismatch-style",
                                             "bracket-mismatch-style",
                                             "bracket-mismatch-style",
                                             MOO_TYPE_TEXT_STYLE,
                                             G_PARAM_CONSTRUCT | G_PARAM_WRITABLE));

    g_object_class_install_property (gobject_class,
                                     PROP_HAS_TEXT,
                                     g_param_spec_boolean ("has-text",
                                             "has-text",
                                             "has-text",
                                             FALSE,
                                             G_PARAM_READABLE));

    g_object_class_install_property (gobject_class,
                                     PROP_HAS_SELECTION,
                                     g_param_spec_boolean ("has-selection",
                                             "has-selection",
                                             "has-selection",
                                             FALSE,
                                             G_PARAM_READABLE));

    g_object_class_install_property (gobject_class,
                                     PROP_LANG,
                                     g_param_spec_boxed ("lang",
                                             "lang",
                                             "lang",
                                             MOO_TYPE_LANG,
                                             G_PARAM_READWRITE));

    signals[CURSOR_MOVED] =
            g_signal_new ("cursor-moved",
                          G_OBJECT_CLASS_TYPE (klass),
                          G_SIGNAL_RUN_LAST,
                          G_STRUCT_OFFSET (MooTextBufferClass, cursor_moved),
                          NULL, NULL,
                          _moo_marshal_VOID__BOXED,
                          G_TYPE_NONE, 1,
                          GTK_TYPE_TEXT_ITER);

    signals[SELECTION_CHANGED] =
            g_signal_new ("selection-changed",
                          G_OBJECT_CLASS_TYPE (klass),
                          G_SIGNAL_RUN_LAST,
                          G_STRUCT_OFFSET (MooTextBufferClass, selection_changed),
                          NULL, NULL,
                          _moo_marshal_VOID__VOID,
                          G_TYPE_NONE, 0);

    signals[HIGHLIGHTING_CHANGED] =
            moo_signal_new_cb ("highlighting-changed",
                               G_OBJECT_CLASS_TYPE (klass),
                               G_SIGNAL_RUN_LAST,
                               NULL, NULL, NULL,
                               _moo_marshal_VOID__BOXED_BOXED,
                               G_TYPE_NONE, 2,
                               GTK_TYPE_TEXT_ITER | G_SIGNAL_TYPE_STATIC_SCOPE,
                               GTK_TYPE_TEXT_ITER | G_SIGNAL_TYPE_STATIC_SCOPE);
}


static void
moo_text_buffer_init (MooTextBuffer *buffer)
{
    buffer->priv = g_new0 (MooTextBufferPrivate, 1);
    buffer->priv->line_buf = moo_line_buffer_new ();
    buffer->priv->do_highlight = TRUE;
    buffer->priv->hl = moo_highlighter_new (GTK_TEXT_BUFFER (buffer),
                                            buffer->priv->line_buf, NULL);
    buffer->priv->bracket_found = MOO_BRACKET_MATCH_NONE;

    buffer->priv->undo_mgr = moo_undo_mgr_new (buffer);
    buffer->priv->move_cursor_to = -1;
#if 0
    g_signal_connect_swapped (buffer->priv->undo_mgr, "undo",
                              G_CALLBACK (before_undo_redo),
                              buffer);
    g_signal_connect_swapped (buffer->priv->undo_mgr, "redo",
                              G_CALLBACK (before_undo_redo),
                              buffer);
#endif
    g_signal_connect_data (buffer->priv->undo_mgr, "undo",
                           G_CALLBACK (after_undo_redo),
                           buffer, NULL,
                           G_CONNECT_AFTER | G_CONNECT_SWAPPED);
    g_signal_connect_data (buffer->priv->undo_mgr, "redo",
                           G_CALLBACK (after_undo_redo),
                           buffer, NULL,
                           G_CONNECT_AFTER | G_CONNECT_SWAPPED);
}


static void
moo_text_buffer_finalize (GObject *object)
{
    MooTextBuffer *buffer = MOO_TEXT_BUFFER (object);

    moo_highlighter_destroy (buffer->priv->hl, FALSE);
    moo_line_buffer_free (buffer->priv->line_buf);

    g_free (buffer->priv->left_brackets);
    g_free (buffer->priv->right_brackets);

#if 0
    g_signal_handlers_disconnect_by_func (buffer->priv->undo_mgr,
                                          (gpointer) before_undo_redo,
                                          buffer);
#endif
    g_signal_handlers_disconnect_by_func (buffer->priv->undo_mgr,
                                          (gpointer) after_undo_redo,
                                          buffer);
    g_object_unref (buffer->priv->undo_mgr);

    g_free (buffer->priv);
    buffer->priv = NULL;

    G_OBJECT_CLASS (moo_text_buffer_parent_class)->finalize (object);
}


GtkTextBuffer*
moo_text_buffer_new (GtkTextTagTable *table)
{
    return g_object_new (MOO_TYPE_TEXT_BUFFER,
                         "tag-table", table, NULL);
}


gpointer
moo_text_buffer_get_undo_mgr (MooTextBuffer *buffer)
{
    g_return_val_if_fail (MOO_IS_TEXT_BUFFER (buffer), NULL);
    return buffer->priv->undo_mgr;
}


static void
moo_text_buffer_begin_user_action (GtkTextBuffer *text_buffer)
{
    MooTextBuffer *buffer = MOO_TEXT_BUFFER (text_buffer);
    moo_text_buffer_freeze (buffer);
    moo_undo_mgr_start_group (buffer->priv->undo_mgr);
}


static void
moo_text_buffer_end_user_action (GtkTextBuffer *text_buffer)
{
    MooTextBuffer *buffer = MOO_TEXT_BUFFER (text_buffer);
    moo_text_buffer_thaw (buffer);
    moo_undo_mgr_end_group (buffer->priv->undo_mgr);
}


static void
moo_text_buffer_modified_changed (GtkTextBuffer *text_buffer)
{
    if (!gtk_text_buffer_get_modified (text_buffer))
        MOO_TEXT_BUFFER(text_buffer)->priv->modifying_action = NULL;
}


static void
update_selection (MooTextBuffer *buffer)
{
    GtkTextBuffer *text_buffer = GTK_TEXT_BUFFER (buffer);
    gboolean has_selection;
    gboolean selection_changed = TRUE;

    has_selection = gtk_text_buffer_get_selection_bounds (text_buffer, NULL, NULL) != 0;

    selection_changed = has_selection || buffer->priv->has_selection;

    if (has_selection != buffer->priv->has_selection)
    {
        buffer->priv->has_selection = has_selection;
        g_object_notify (G_OBJECT (buffer), "has-selection");
    }

    if (selection_changed)
        g_signal_emit (buffer, signals[SELECTION_CHANGED], 0);
}


static void
moo_text_buffer_mark_set (GtkTextBuffer      *text_buffer,
                          const GtkTextIter  *iter,
                          GtkTextMark        *mark)
{
    GtkTextMark *insert = gtk_text_buffer_get_insert (text_buffer);
    GtkTextMark *sel_bound = gtk_text_buffer_get_selection_bound (text_buffer);
    MooTextBuffer *buffer = MOO_TEXT_BUFFER (text_buffer);

    if (GTK_TEXT_BUFFER_CLASS(moo_text_buffer_parent_class)->mark_set)
        GTK_TEXT_BUFFER_CLASS(moo_text_buffer_parent_class)->mark_set (text_buffer, iter, mark);

    if (mark == insert || mark == sel_bound)
        update_selection (buffer);

    if (mark == insert)
        cursor_moved (buffer, iter);
}


static void
moo_text_buffer_insert_text (GtkTextBuffer      *text_buffer,
                             GtkTextIter        *pos,
                             const gchar        *text,
                             gint                length)
{
    MooTextBuffer *buffer = MOO_TEXT_BUFFER (text_buffer);
    GtkTextTag *tag;
    int first_line, last_line;
    gboolean starts_line, ins_line;

    if (!text[0])
        return;

    first_line = gtk_text_iter_get_line (pos);
    starts_line = gtk_text_iter_starts_line (pos);
    ins_line = (text[0] == '\n' || text[0] == '\r');

    if (!moo_undo_mgr_frozen (buffer->priv->undo_mgr))
    {
        MooUndoAction *action;
        action = insert_action_new (text_buffer, pos, text, length);
        moo_undo_mgr_add_action (buffer->priv->undo_mgr, INSERT_ACTION_TYPE, action);
    }

    if (((tag = buffer->priv->correct_match_tag) && gtk_text_iter_has_tag (pos, tag)) ||
        ((tag = buffer->priv->incorrect_match_tag) && gtk_text_iter_has_tag (pos, tag)))
    {
        if (!gtk_text_iter_begins_tag (pos, tag))
        {
            GtkTextIter next = *pos;
            gtk_text_iter_forward_char (&next);
            gtk_text_buffer_remove_tag (text_buffer, tag, pos, &next);
        }
    }

    GTK_TEXT_BUFFER_CLASS(moo_text_buffer_parent_class)->insert_text (text_buffer, pos, text, length);

    last_line = gtk_text_iter_get_line (pos);

    if (last_line == first_line)
        moo_line_buffer_invalidate (buffer->priv->line_buf, first_line);
    else
        moo_line_buffer_split_line (buffer->priv->line_buf,
                                    first_line, last_line - first_line);

    moo_text_buffer_queue_highlight (buffer);

    cursor_moved (buffer, pos);

    if (!buffer->priv->has_text)
    {
        buffer->priv->has_text = TRUE;
        g_object_notify (G_OBJECT (buffer), "has-text");
    }
}


static void
moo_text_buffer_delete_range (GtkTextBuffer      *text_buffer,
                              GtkTextIter        *start,
                              GtkTextIter        *end)
{
    MooTextBuffer *buffer = MOO_TEXT_BUFFER (text_buffer);
    int first_line, last_line;

    gtk_text_iter_order (start, end);

    first_line = gtk_text_iter_get_line (start);
    last_line = gtk_text_iter_get_line (end);

#define MANY_LINES 1000
    if (buffer->priv->lang && buffer->priv->do_highlight &&
        last_line - first_line > MANY_LINES)
    {
        gtk_text_buffer_remove_all_tags (text_buffer, start, end);
    }
#undef MANY_LINES

    if (!moo_undo_mgr_frozen (buffer->priv->undo_mgr))
    {
        MooUndoAction *action;
        action = delete_action_new (text_buffer, start, end);
        moo_undo_mgr_add_action (buffer->priv->undo_mgr, DELETE_ACTION_TYPE, action);
    }

    GTK_TEXT_BUFFER_CLASS(moo_text_buffer_parent_class)->delete_range (text_buffer, start, end);

    if (first_line < last_line)
        moo_line_buffer_delete (buffer->priv->line_buf,
                                first_line + 1,
                                last_line - first_line);
    else
        moo_line_buffer_invalidate (buffer->priv->line_buf,
                                    first_line);

    moo_text_buffer_queue_highlight (buffer);

    update_selection (buffer);
    cursor_moved (buffer, start);

    if (buffer->priv->has_text)
    {
        buffer->priv->has_text = moo_text_buffer_has_text (buffer);
        if (!buffer->priv->has_text)
            g_object_notify (G_OBJECT (buffer), "has-text");
    }
}


#if 0
static void
before_undo_redo (MooTextBuffer *buffer)
{
    GtkTextIter iter;
    gtk_text_buffer_get_iter_at_mark (GTK_TEXT_BUFFER (buffer), &iter,
                                      gtk_text_buffer_get_insert (GTK_TEXT_BUFFER (buffer)));
    buffer->priv->cursor_was_at = gtk_text_iter_get_offset (&iter);
}
#endif

static void
after_undo_redo (MooTextBuffer *buffer)
{
    GtkTextIter iter;
    int move_to = -1;

    if (buffer->priv->move_cursor_to >= 0)
        move_to = buffer->priv->move_cursor_to;
#if 0
    else
        move_to = buffer->priv->cursor_was_at;
#endif

    if (move_to >= 0)
    {
        gtk_text_buffer_get_iter_at_offset (GTK_TEXT_BUFFER (buffer), &iter, move_to);
        gtk_text_buffer_place_cursor (GTK_TEXT_BUFFER (buffer), &iter);
    }

    buffer->priv->move_cursor_to = -1;
#if 0
    buffer->priv->cursor_was_at = -1;
#endif
}


void
moo_text_buffer_set_lang (MooTextBuffer  *buffer,
                          MooLang        *lang)
{
    MooLang *old_lang;

    g_return_if_fail (MOO_IS_TEXT_BUFFER (buffer));

    if (buffer->priv->lang == lang)
        return;

    old_lang = buffer->priv->lang;

    if (old_lang)
        moo_lang_unref (old_lang);

    moo_highlighter_destroy (buffer->priv->hl, TRUE);

    buffer->priv->lang = lang;

    if (lang)
        moo_lang_ref (lang);

    buffer->priv->hl = moo_highlighter_new (GTK_TEXT_BUFFER (buffer),
                                            buffer->priv->line_buf, lang);

    if (old_lang)
        moo_line_buffer_invalidate_all (buffer->priv->line_buf);

    moo_text_buffer_queue_highlight (buffer);

    moo_text_buffer_set_brackets (buffer, lang ? lang->brackets : NULL);
}


MooLang*
moo_text_buffer_get_lang (MooTextBuffer  *buffer)
{
    g_return_val_if_fail (MOO_IS_TEXT_BUFFER (buffer), NULL);
    return buffer->priv->lang;
}


static void
moo_text_buffer_queue_highlight (MooTextBuffer *buffer)
{
    if (buffer->priv->lang && buffer->priv->do_highlight)
        moo_highlighter_queue_compute (buffer->priv->hl, FALSE);
}


void
moo_text_buffer_set_highlight (MooTextBuffer      *buffer,
                               gboolean            highlight)
{
    g_return_if_fail (MOO_IS_TEXT_BUFFER (buffer));

    highlight = highlight != 0;

    if (highlight == buffer->priv->do_highlight)
        return;

    if (buffer->priv->do_highlight && buffer->priv->lang)
        moo_highlighter_destroy (buffer->priv->hl, TRUE);
    else
        moo_highlighter_destroy (buffer->priv->hl, FALSE);

    buffer->priv->do_highlight = highlight;

    if (!highlight || !buffer->priv->lang)
    {
        buffer->priv->hl = moo_highlighter_new (GTK_TEXT_BUFFER (buffer),
                                                buffer->priv->line_buf, NULL);
    }
    else
    {
        buffer->priv->hl = moo_highlighter_new (GTK_TEXT_BUFFER (buffer),
                                                buffer->priv->line_buf,
                                                buffer->priv->lang);
        moo_line_buffer_invalidate_all (buffer->priv->line_buf);
        moo_text_buffer_queue_highlight (buffer);
    }
}


gboolean
moo_text_buffer_get_highlight (MooTextBuffer *buffer)
{
    g_return_val_if_fail (MOO_IS_TEXT_BUFFER (buffer), FALSE);
    return buffer->priv->do_highlight;
}


static void
moo_text_buffer_set_property (GObject        *object,
                              guint           prop_id,
                              const GValue   *value,
                              GParamSpec     *pspec)
{
    MooTextBuffer *buffer = MOO_TEXT_BUFFER (object);

    switch (prop_id)
    {
        case PROP_CHECK_BRACKETS:
            moo_text_buffer_set_check_brackets (buffer, g_value_get_boolean (value));
            break;

        case PROP_BRACKET_MATCH_STYLE:
            moo_text_buffer_set_bracket_match_style (buffer, g_value_get_boxed (value));
            break;

        case PROP_BRACKET_MISMATCH_STYLE:
            moo_text_buffer_set_bracket_mismatch_style (buffer, g_value_get_boxed (value));
            break;

        case PROP_LANG:
            moo_text_buffer_set_lang (buffer, g_value_get_boxed (value));
            break;

        default:
            G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
            break;
    }
}


static void
moo_text_buffer_get_property (GObject        *object,
                              guint           prop_id,
                              GValue         *value,
                              GParamSpec     *pspec)
{
    MooTextBuffer *buffer = MOO_TEXT_BUFFER (object);

    switch (prop_id)
    {
        case PROP_CHECK_BRACKETS:
            g_value_set_boolean (value, buffer->priv->check_brackets);
            break;

        case PROP_LANG:
            g_value_set_boxed (value, buffer->priv->lang);
            break;

        case PROP_HAS_TEXT:
            g_value_set_boolean (value, moo_text_buffer_has_text (buffer));
            break;

        case PROP_HAS_SELECTION:
            g_value_set_boolean (value, buffer->priv->has_selection);
            break;

        default:
            G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
            break;
    }
}


gboolean
moo_text_buffer_has_text (MooTextBuffer *buffer)
{
    GtkTextIter start, end;

    g_return_val_if_fail (MOO_IS_TEXT_BUFFER (buffer), TRUE);

    gtk_text_buffer_get_bounds (GTK_TEXT_BUFFER (buffer), &start, &end);
    return gtk_text_iter_compare (&start, &end) ? TRUE : FALSE;
}


gboolean
moo_text_buffer_has_selection (MooTextBuffer *buffer)
{
    g_return_val_if_fail (MOO_IS_TEXT_BUFFER (buffer), FALSE);
    return gtk_text_buffer_get_selection_bounds (GTK_TEXT_BUFFER (buffer), NULL, NULL);
}


void
_moo_text_buffer_ensure_highlight (MooTextBuffer      *buffer,
                                   int                 first_line,
                                   int                 last_line)
{
    g_return_if_fail (MOO_IS_TEXT_BUFFER (buffer));
    moo_highlighter_apply_tags (buffer->priv->hl, first_line, last_line);
}


void
_moo_text_buffer_highlighting_changed (MooTextBuffer *buffer,
                                       int            first,
                                       int            last)
{
    GtkTextIter start, end;

    g_assert (MOO_IS_TEXT_BUFFER (buffer));
    g_assert (first <= last && first >= 0);

    gtk_text_buffer_get_iter_at_line (GTK_TEXT_BUFFER (buffer), &start, first);

    if (first == last)
        end = start;
    else
        gtk_text_buffer_get_iter_at_line (GTK_TEXT_BUFFER (buffer), &end, last);

    g_signal_emit (buffer, signals[HIGHLIGHTING_CHANGED], 0, &start, &end);
}


static void
moo_text_buffer_apply_tag (GtkTextBuffer      *buffer,
                           GtkTextTag         *tag,
                           const GtkTextIter  *start,
                           const GtkTextIter  *end)
{
    if (MOO_IS_SYNTAX_TAG (tag) && !MOO_TEXT_BUFFER(buffer)->priv->may_apply_tag)
        return;

    GTK_TEXT_BUFFER_CLASS(moo_text_buffer_parent_class)->apply_tag (buffer, tag, start, end);
}


void
_moo_text_buffer_apply_syntax_tag (MooTextBuffer      *buffer,
                                   GtkTextTag         *tag,
                                   const GtkTextIter  *start,
                                   const GtkTextIter  *end)
{
    GtkTextBuffer *text_buffer = GTK_TEXT_BUFFER (buffer);
    buffer->priv->may_apply_tag = TRUE;
    gtk_text_buffer_apply_tag (text_buffer, tag, start, end);
    buffer->priv->may_apply_tag = FALSE;
}


void
moo_text_buffer_apply_scheme (MooTextBuffer      *buffer,
                              MooTextStyleScheme *scheme)
{
    g_return_if_fail (scheme != NULL);
    g_return_if_fail (MOO_IS_TEXT_BUFFER (buffer));

    moo_text_buffer_set_bracket_match_style (buffer, scheme->bracket_match);
    moo_text_buffer_set_bracket_mismatch_style (buffer, scheme->bracket_mismatch);
    moo_highlighter_apply_scheme (buffer->priv->hl, scheme);
}


void
moo_text_buffer_freeze (MooTextBuffer *buffer)
{
    g_return_if_fail (MOO_IS_TEXT_BUFFER (buffer));
    freeze_cursor_moved (buffer);
}


void
moo_text_buffer_thaw (MooTextBuffer *buffer)
{
    g_return_if_fail (MOO_IS_TEXT_BUFFER (buffer));
    thaw_cursor_moved (buffer);
}


void
moo_text_buffer_begin_interactive_action (MooTextBuffer *buffer)
{
    g_return_if_fail (MOO_IS_TEXT_BUFFER (buffer));
    buffer->priv->interactive++;
}


void
moo_text_buffer_end_interactive_action (MooTextBuffer *buffer)
{
    g_return_if_fail (MOO_IS_TEXT_BUFFER (buffer));
    g_return_if_fail (buffer->priv->interactive > 0);
    buffer->priv->interactive--;
}


void
moo_text_buffer_begin_non_interactive_action (MooTextBuffer *buffer)
{
    g_return_if_fail (MOO_IS_TEXT_BUFFER (buffer));
    buffer->priv->non_interactive++;
}


void
moo_text_buffer_end_non_interactive_action (MooTextBuffer *buffer)
{
    g_return_if_fail (MOO_IS_TEXT_BUFFER (buffer));
    g_return_if_fail (buffer->priv->non_interactive > 0);
    buffer->priv->non_interactive--;
}


/*****************************************************************************/
/* Matching brackets
 */

#define FIND_BRACKETS_LIMIT 10000

static void
cursor_moved (MooTextBuffer      *buffer,
              const GtkTextIter  *where)
{
    if (!buffer->priv->cursor_moved_frozen)
        g_signal_emit (buffer, signals[CURSOR_MOVED], 0, where);
    else
        buffer->priv->cursor_moved = TRUE;
}

static void
freeze_cursor_moved (MooTextBuffer *buffer)
{
    buffer->priv->cursor_moved_frozen++;
}

static void
thaw_cursor_moved (MooTextBuffer *buffer)
{
    g_return_if_fail (buffer->priv->cursor_moved_frozen > 0);

    /* XXX it should check cursor after text is rehighlighted */
    if (!--buffer->priv->cursor_moved_frozen && buffer->priv->cursor_moved)
    {
        GtkTextIter iter;
        GtkTextMark *insert = gtk_text_buffer_get_insert (GTK_TEXT_BUFFER (buffer));
        gtk_text_buffer_get_iter_at_mark (GTK_TEXT_BUFFER (buffer), &iter, insert);
        cursor_moved (buffer, &iter);
        buffer->priv->cursor_moved = FALSE;
    }
}


static void
moo_text_buffer_cursor_moved (MooTextBuffer      *buffer,
                              const GtkTextIter  *where)
{
    GtkTextIter iter[4];
    MooBracketMatchType bracket_match;
    GtkTextTag *tag;
    GtkTextBuffer *text_buffer = GTK_TEXT_BUFFER (buffer);
    int i;

    g_return_if_fail (where != NULL);

    switch (buffer->priv->bracket_found)
    {
        case MOO_BRACKET_MATCH_CORRECT:
            tag = buffer->priv->correct_match_tag;
            break;
        case MOO_BRACKET_MATCH_INCORRECT:
            tag = buffer->priv->incorrect_match_tag;
            break;
        default:
            tag = NULL;
    }

    if (tag)
    {
        for (i = 0; i < 4; ++i)
            gtk_text_buffer_get_iter_at_mark (text_buffer, &iter[i],
                                              buffer->priv->bracket_mark[i]);
        gtk_text_buffer_remove_tag (text_buffer, tag, &iter[0], &iter[1]);
        gtk_text_buffer_remove_tag (text_buffer, tag, &iter[2], &iter[3]);
    }

    if (!buffer->priv->check_brackets)
        return;

    iter[0] = *where;

    buffer->priv->bracket_found = MOO_BRACKET_MATCH_NONE;

    if (!moo_text_iter_at_bracket (&iter[0]))
        return;

    iter[2] = iter[0];
    bracket_match = moo_text_iter_find_matching_bracket (&iter[2], FIND_BRACKETS_LIMIT);

    buffer->priv->bracket_found = bracket_match;

    switch (bracket_match)
    {
        case MOO_BRACKET_MATCH_CORRECT:
            tag = buffer->priv->correct_match_tag;
            break;
        case MOO_BRACKET_MATCH_INCORRECT:
            tag = buffer->priv->incorrect_match_tag;
            break;
        default:
            tag = NULL;
    }

    if (tag != NULL)
    {
        iter[1] = iter[0];
        gtk_text_iter_forward_char (&iter[1]);
        iter[3] = iter[2];
        gtk_text_iter_forward_char (&iter[3]);

        if (!buffer->priv->bracket_mark[0])
            for (i = 0; i < 4; ++i)
                buffer->priv->bracket_mark[i] =
                        gtk_text_buffer_create_mark (text_buffer, NULL, &iter[i], FALSE);
        else
            for (i = 0; i < 4; ++i)
                gtk_text_buffer_move_mark (text_buffer, buffer->priv->bracket_mark[i], &iter[i]);

        gtk_text_buffer_apply_tag (text_buffer, tag, &iter[0], &iter[1]);
        gtk_text_buffer_apply_tag (text_buffer, tag, &iter[2], &iter[3]);
    }
}


void
moo_text_buffer_set_bracket_match_style (MooTextBuffer      *buffer,
                                         const MooTextStyle *style)
{
    static MooTextStyle empty;

    g_return_if_fail (MOO_IS_TEXT_BUFFER (buffer));

    if (!style)
        style = &empty;

    if (!buffer->priv->correct_match_tag)
        buffer->priv->correct_match_tag =
                gtk_text_buffer_create_tag (GTK_TEXT_BUFFER (buffer), NULL, NULL);

    _moo_style_set_tag_style (style, buffer->priv->correct_match_tag);
    g_object_notify (G_OBJECT (buffer), "bracket-match-style");
}


void
moo_text_buffer_set_bracket_mismatch_style (MooTextBuffer      *buffer,
                                            const MooTextStyle *style)
{
    static MooTextStyle empty;

    g_return_if_fail (MOO_IS_TEXT_BUFFER (buffer));

    if (!style)
        style = &empty;

    if (!buffer->priv->incorrect_match_tag)
        buffer->priv->incorrect_match_tag =
                gtk_text_buffer_create_tag (GTK_TEXT_BUFFER (buffer), NULL, NULL);

    _moo_style_set_tag_style (style, buffer->priv->incorrect_match_tag);
    g_object_notify (G_OBJECT (buffer), "bracket-mismatch-style");
}


static gboolean
parse_brackets (const char     *string,
                gunichar      **left_brackets,
                gunichar      **right_brackets,
                guint          *num)
{
    long len, i;
    const char *p;
    gunichar *left, *right;

    g_return_val_if_fail (g_utf8_validate (string, -1, NULL), FALSE);
    len = g_utf8_strlen (string, -1);
    g_return_val_if_fail (len > 0 && (len / 2) * 2 == len, FALSE);

    len /= 2;
    p = string;
    left = g_new (gunichar, len);
    right = g_new (gunichar, len);

    for (i = 0; i < len; ++i)
    {
        left[i] = g_utf8_get_char (p);
        p = g_utf8_next_char (p);
        right[i] = g_utf8_get_char (p);
        p = g_utf8_next_char (p);
    }

    *left_brackets = left;
    *right_brackets = right;
    *num = len;

    return TRUE;
}


void
moo_text_buffer_set_brackets (MooTextBuffer *buffer,
                              const gchar   *string)
{
    g_return_if_fail (MOO_IS_TEXT_BUFFER (buffer));

    buffer->priv->num_brackets = 0;
    g_free (buffer->priv->left_brackets);
    buffer->priv->left_brackets = NULL;
    g_free (buffer->priv->right_brackets);
    buffer->priv->right_brackets = NULL;

    if (!string)
    {
        buffer->priv->num_brackets = 3;
        buffer->priv->left_brackets = g_new (gunichar, 3);
        buffer->priv->right_brackets = g_new (gunichar, 3);
        buffer->priv->left_brackets[0] = '(';
        buffer->priv->left_brackets[1] = '{';
        buffer->priv->left_brackets[2] = '[';
        buffer->priv->right_brackets[0] = ')';
        buffer->priv->right_brackets[1] = '}';
        buffer->priv->right_brackets[2] = ']';
        return;
    }
    else if (!string[0])
    {
        return;
    }

    parse_brackets (string,
                    &(buffer->priv->left_brackets),
                    &(buffer->priv->right_brackets),
                    &(buffer->priv->num_brackets));
}


void
moo_text_buffer_set_check_brackets (MooTextBuffer  *buffer,
                                    gboolean        check)
{
    g_return_if_fail (MOO_IS_TEXT_BUFFER (buffer));
    buffer->priv->check_brackets = check ? TRUE : FALSE;
    g_object_notify (G_OBJECT (buffer), "check-brackets");
}


inline static gboolean
find (gunichar *vec, guint size, gunichar c)
{
    guint i;

    for (i = 0; i < size; ++i)
        if (c == vec[i])
            return TRUE;

    return FALSE;
}


gboolean
moo_text_iter_at_bracket (GtkTextIter *iter)
{
    gunichar c;
    GtkTextIter b;
    MooTextBuffer *buffer;

    buffer = MOO_TEXT_BUFFER (gtk_text_iter_get_buffer (iter));
    g_return_val_if_fail (MOO_IS_TEXT_BUFFER (buffer), FALSE);

    c = gtk_text_iter_get_char (iter);

    if (find (buffer->priv->left_brackets, buffer->priv->num_brackets, c) ||
        find (buffer->priv->right_brackets, buffer->priv->num_brackets, c))
    {
        return TRUE;
    }

    b = *iter;

    if (!gtk_text_iter_starts_line (&b) && gtk_text_iter_backward_char (&b))
    {
        c = gtk_text_iter_get_char (&b);

        if (find (buffer->priv->left_brackets, buffer->priv->num_brackets, c) ||
            find (buffer->priv->right_brackets, buffer->priv->num_brackets, c))
        {
            *iter = b;
            return TRUE;
        }
    }

    return FALSE;
}


MooBracketMatchType
moo_text_iter_find_matching_bracket (GtkTextIter *iter,
                                     int          limit)
{
    int addition = 0;
    int count;
    gunichar *same_direction = NULL, *inverse_direction = NULL;
    guint to_find;
    gunichar bracket = gtk_text_iter_get_char (iter);
    gunichar bracket_to_find = 0;
    MooContext *ctx;
    guint stack = 0;
    GtkTextIter b;
    MooTextBuffer *buffer;

    buffer = MOO_TEXT_BUFFER (gtk_text_iter_get_buffer (iter));
    g_return_val_if_fail (MOO_IS_TEXT_BUFFER (buffer), MOO_BRACKET_MATCH_NOT_AT_BRACKET);

    for (to_find = 0; to_find < buffer->priv->num_brackets; ++to_find)
    {
        if (bracket == buffer->priv->left_brackets[to_find])
        {
            bracket_to_find = buffer->priv->right_brackets[to_find];
            addition = 1;
            inverse_direction = buffer->priv->right_brackets;
            same_direction = buffer->priv->left_brackets;
            break;
        }
    }

    if (to_find == buffer->priv->num_brackets)
    {
        for (to_find = 0; to_find < buffer->priv->num_brackets; ++to_find)
        {
            if (bracket == buffer->priv->right_brackets[to_find])
            {
                bracket_to_find = buffer->priv->left_brackets[to_find];
                addition = -1;
                same_direction = buffer->priv->right_brackets;
                inverse_direction = buffer->priv->left_brackets;
                break;
            }
        }
    }

    if (to_find == buffer->priv->num_brackets)
        return MOO_BRACKET_MATCH_NOT_AT_BRACKET;

    ctx = _moo_text_iter_get_context (iter);
    stack = 0;
    b = *iter;

    if (limit < 0)
        limit = G_MAXINT;
    count = 0;

    while (gtk_text_iter_forward_chars (&b, addition) && count++ < limit)
    {
        if (ctx == _moo_text_iter_get_context (&b))
        {
            gunichar c = gtk_text_iter_get_char (&b);

            if (c == bracket_to_find && !stack)
            {
                *iter = b;
                return MOO_BRACKET_MATCH_CORRECT;
            }

            if (find (same_direction, buffer->priv->num_brackets, c))
            {
                ++stack;
            }
            else if (find (inverse_direction, buffer->priv->num_brackets, c))
            {
                if (stack)
                {
                    --stack;
                }
                else
                {
                    *iter = b;
                    return MOO_BRACKET_MATCH_INCORRECT;
                }
            }
        }
    }

    return MOO_BRACKET_MATCH_NONE;
}


/*****************************************************************************/
/* Undo/redo
 */

typedef enum {
    ACTION_INSERT,
    ACTION_DELETE
} ActionType;

typedef struct {
    char *text;
    guint interactive : 1;
    guint mergeable   : 1;
} EditAction;

typedef struct {
    EditAction edit;
    int pos;
    int length;
    int chars;
} InsertAction;

typedef struct {
    EditAction edit;
    int start;
    int end;
    guint forward : 1;
} DeleteAction;

#define EDIT_ACTION(action__)           ((EditAction*)action__)
#define ACTION_INTERACTIVE(action__)    (((EditAction*)action__)->interactive)

static void     edit_action_destroy     (EditAction     *action,
                                         MooTextBuffer  *buffer);

static void     insert_action_undo      (InsertAction   *action,
                                         GtkTextBuffer  *buffer);
static void     insert_action_redo      (InsertAction   *action,
                                         GtkTextBuffer  *buffer);
static gboolean insert_action_merge     (InsertAction   *action,
                                         InsertAction   *what,
                                         MooTextBuffer  *buffer);

static void     delete_action_undo      (DeleteAction   *action,
                                         GtkTextBuffer  *buffer);
static void     delete_action_redo      (DeleteAction   *action,
                                         GtkTextBuffer  *buffer);
static gboolean delete_action_merge     (DeleteAction   *action,
                                         DeleteAction   *what,
                                         MooTextBuffer  *buffer);

static MooUndoActionClass InsertActionClass = {
    (MooUndoActionUndo) insert_action_undo,
    (MooUndoActionRedo) insert_action_redo,
    (MooUndoActionMerge) insert_action_merge,
    (MooUndoActionDestroy) edit_action_destroy
};

static MooUndoActionClass DeleteActionClass = {
    (MooUndoActionUndo) delete_action_undo,
    (MooUndoActionRedo) delete_action_redo,
    (MooUndoActionMerge) delete_action_merge,
    (MooUndoActionDestroy) edit_action_destroy
};


static void
init_undo_actions (void)
{
    INSERT_ACTION_TYPE = moo_undo_action_register (&InsertActionClass);
    DELETE_ACTION_TYPE = moo_undo_action_register (&DeleteActionClass);
}


static EditAction *
action_new (ActionType     type,
            MooTextBuffer *buffer)
{
    EditAction *action;
    gsize size = 0;
    MooUndoActionClass *klass = NULL;
    GtkTextBuffer *text_buffer = GTK_TEXT_BUFFER (buffer);

    switch (type)
    {
        case ACTION_INSERT:
            size = sizeof (InsertAction);
            klass = &InsertActionClass;
            break;
        case ACTION_DELETE:
            size = sizeof (DeleteAction);
            klass = &DeleteActionClass;
            break;
    }

    action = g_malloc0 (size);
    action->interactive = !buffer->priv->non_interactive && buffer->priv->interactive ? TRUE : FALSE;

    if (!gtk_text_buffer_get_modified (text_buffer))
        buffer->priv->modifying_action = action;

    return action;
}


static MooUndoAction *
insert_action_new (GtkTextBuffer    *buffer,
                   GtkTextIter      *pos,
                   const char       *text,
                   int               length)
{
    InsertAction *action;
    EditAction *edit_action;

    if (length < 0)
        length = strlen (text);

    g_return_val_if_fail (length > 0, NULL);

    edit_action = action_new (ACTION_INSERT, MOO_TEXT_BUFFER (buffer));
    action = (InsertAction*) edit_action;

    action->pos = gtk_text_iter_get_offset (pos);
    action->edit.text = g_strndup (text, length);
    action->length = length;
    action->chars = g_utf8_strlen (text, length);

    if (action->chars > 1 || text[0] == '\n')
        edit_action->mergeable = FALSE;
    else
        edit_action->mergeable = TRUE;

    return (MooUndoAction*) action;
}


static MooUndoAction *
delete_action_new (GtkTextBuffer      *buffer,
                   GtkTextIter        *start,
                   GtkTextIter        *end)
{
    GtkTextIter iter;
    DeleteAction *action;
    EditAction *edit_action;
    int start_offset, end_offset;

    start_offset = gtk_text_iter_get_offset (start);
    end_offset = gtk_text_iter_get_offset (end);

    g_return_val_if_fail (start_offset < end_offset, NULL);

    edit_action = action_new (ACTION_DELETE, MOO_TEXT_BUFFER (buffer));
    action = (DeleteAction*) edit_action;

    action->start = start_offset;
    action->end = end_offset;
    action->edit.text = gtk_text_buffer_get_slice (buffer, start, end, TRUE);

    if (edit_action->interactive)
    {
        /* figure out if the user used the Delete or the Backspace key */
        gtk_text_buffer_get_iter_at_mark (buffer, &iter, gtk_text_buffer_get_insert (buffer));

        if (gtk_text_iter_get_offset (&iter) <= action->start)
            action->forward = TRUE;
        else
            action->forward = FALSE;
    }

    if (action->end - action->start > 1 || action->edit.text[0] == '\n')
        edit_action->mergeable = FALSE;
    else
        edit_action->mergeable = TRUE;

    return (MooUndoAction*) action;
}


static void
action_undo_or_redo (EditAction     *action,
                     GtkTextBuffer  *text_buffer,
                     gboolean        was_modified)
{
    MooTextBuffer *buffer = MOO_TEXT_BUFFER (text_buffer);

    if (!was_modified)
    {
        g_return_if_fail (gtk_text_buffer_get_modified (text_buffer));
        g_return_if_fail (buffer->priv->modifying_action == NULL);
        buffer->priv->modifying_action = action;
    }
    else if (buffer->priv->modifying_action == action)
    {
        gtk_text_buffer_set_modified (text_buffer, FALSE);
        buffer->priv->modifying_action = NULL;
    }
}


static void
insert_action_undo (InsertAction   *action,
                    GtkTextBuffer  *buffer)
{
    GtkTextIter start, end;
    gboolean was_modified;

    was_modified = gtk_text_buffer_get_modified (buffer);

    gtk_text_buffer_get_iter_at_offset (buffer, &start, action->pos);
    gtk_text_buffer_get_iter_at_offset (buffer, &end,
                                        action->pos + action->chars);
    gtk_text_buffer_delete (buffer, &start, &end);

    if (ACTION_INTERACTIVE (action))
        MOO_TEXT_BUFFER(buffer)->priv->move_cursor_to = action->pos;

    action_undo_or_redo (EDIT_ACTION (action), buffer, was_modified);
}


static void
delete_action_undo (DeleteAction   *action,
                    GtkTextBuffer  *buffer)
{
    GtkTextIter start;
    gboolean was_modified;

    was_modified = gtk_text_buffer_get_modified (buffer);

    gtk_text_buffer_get_iter_at_offset (buffer, &start, action->start);
    gtk_text_buffer_insert (buffer, &start, action->edit.text, -1);

    if (ACTION_INTERACTIVE (action))
    {
        if (action->forward)
            MOO_TEXT_BUFFER(buffer)->priv->move_cursor_to = action->start;
        else
            MOO_TEXT_BUFFER(buffer)->priv->move_cursor_to = action->end;
    }

    action_undo_or_redo (EDIT_ACTION (action), buffer, was_modified);
}


static void
insert_action_redo (InsertAction   *action,
                    GtkTextBuffer  *buffer)
{
    GtkTextIter start;
    gboolean was_modified;

    was_modified = gtk_text_buffer_get_modified (buffer);

    gtk_text_buffer_get_iter_at_offset (buffer, &start, action->pos);
    gtk_text_buffer_insert (buffer, &start, action->edit.text, action->length);

    if (ACTION_INTERACTIVE (action))
        MOO_TEXT_BUFFER(buffer)->priv->move_cursor_to = action->pos + action->length;

    action_undo_or_redo (EDIT_ACTION (action), buffer, was_modified);
}


static void
delete_action_redo (DeleteAction   *action,
                    GtkTextBuffer  *buffer)
{
    GtkTextIter start, end;
    gboolean was_modified;

    was_modified = gtk_text_buffer_get_modified (buffer);

    gtk_text_buffer_get_iter_at_offset (buffer, &start, action->start);
    gtk_text_buffer_get_iter_at_offset (buffer, &end, action->end);
    gtk_text_buffer_delete (buffer, &start, &end);

    if (ACTION_INTERACTIVE (action))
        MOO_TEXT_BUFFER(buffer)->priv->move_cursor_to = action->start;

    action_undo_or_redo (EDIT_ACTION (action), buffer, was_modified);
}


static void
edit_action_destroy (EditAction    *action,
                     MooTextBuffer *buffer)
{
    if (action)
    {
        if (buffer->priv->modifying_action == action)
            buffer->priv->modifying_action = NULL;
        g_free (action->text);
        g_free (action);
    }
}


static gboolean
action_merge (EditAction     *last_action,
              EditAction     *action,
              MooTextBuffer  *buffer)
{
    if (!last_action->mergeable)
        return FALSE;

    if (!action->mergeable ||
         buffer->priv->modifying_action == action ||
         action->interactive != last_action->interactive)
    {
        last_action->mergeable = FALSE;
        return FALSE;
    }

    return TRUE;
}


static gboolean
insert_action_merge (InsertAction   *last_action,
                     InsertAction   *action,
                     MooTextBuffer  *buffer)
{
    char *tmp;

    if (!action_merge (EDIT_ACTION (last_action), EDIT_ACTION (action), buffer))
        return FALSE;

    if (action->pos != (last_action->pos + last_action->chars) ||
        (action->edit.text[0] != ' ' && action->edit.text[0] != '\t' &&
         (last_action->edit.text[last_action->length-1] == ' ' ||
          last_action->edit.text[last_action->length-1] == '\t')))
    {
        EDIT_ACTION(last_action)->mergeable = FALSE;
        return FALSE;
    }

    tmp = g_strconcat (last_action->edit.text, action->edit.text, NULL);
    g_free (last_action->edit.text);
    last_action->length += action->length;
    last_action->edit.text = tmp;
    last_action->chars += action->chars;

    return TRUE;
}


static gboolean
delete_action_merge (DeleteAction   *last_action,
                     DeleteAction   *action,
                     MooTextBuffer  *buffer)
{
    char *tmp;

    if (!action_merge (EDIT_ACTION (last_action), EDIT_ACTION (action), buffer))
        return FALSE;

    if (last_action->forward != action->forward ||
        (last_action->start != action->start &&
         last_action->start != action->end))
    {
        EDIT_ACTION(last_action)->mergeable = FALSE;
        return FALSE;
    }

    if (last_action->start == action->start)
    {
        char *text_end = g_utf8_offset_to_pointer (last_action->edit.text,
                                                   last_action->end - last_action->start - 1);

        /* Deleted with the delete key */
        if (action->edit.text[0] != ' ' && action->edit.text[0] != '\t' &&
            (*text_end == ' ' || *text_end  == '\t'))
        {
            EDIT_ACTION(last_action)->mergeable = FALSE;
            return FALSE;
        }

        tmp = g_strconcat (last_action->edit.text, action->edit.text, NULL);
        g_free (last_action->edit.text);
        last_action->end += (action->end - action->start);
        last_action->edit.text = tmp;
    }
    else
    {
        /* Deleted with the backspace key */
        if (action->edit.text[0] != ' ' && action->edit.text[0] != '\t' &&
            (last_action->edit.text[0] == ' ' || last_action->edit.text[0] == '\t'))
        {
            EDIT_ACTION(last_action)->mergeable = FALSE;
            return FALSE;
        }

        tmp = g_strconcat (action->edit.text, last_action->edit.text, NULL);
        g_free (last_action->edit.text);
        last_action->start = action->start;
        last_action->edit.text = tmp;
    }

    return TRUE;
}