[gtksourceview] vim: implement rudimentary search through previous commands

[Christian Hergert <chergert src gnome org>]

commit 559032fbe2d88973bde1caea4a87b1ef0efbb474
Author: Christian Hergert <chergert redhat com>
Date:   Wed Oct 5 13:43:04 2022 -0700

    vim: implement rudimentary search through previous commands
    
    This allows using arrow keys to find other commands in the history which
    match the currently typed prefix.

 gtksourceview/vim/gtksourcevimcommandbar.c | 57 +++++++++++++++++++++++-------
 1 file changed, 45 insertions(+), 12 deletions(-)
---
diff --git a/gtksourceview/vim/gtksourcevimcommandbar.c b/gtksourceview/vim/gtksourcevimcommandbar.c
index f558a702..32d24eaa 100644
--- a/gtksourceview/vim/gtksourcevimcommandbar.c
+++ b/gtksourceview/vim/gtksourcevimcommandbar.c
@@ -1,7 +1,7 @@
 /*
  * This file is part of GtkSourceView
  *
- * Copyright 2021 Christian Hergert <chergert redhat com>
+ * Copyright 2021-2022 Christian Hergert <chergert redhat com>
  *
  * GtkSourceView is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -32,6 +32,7 @@ struct _GtkSourceVimCommandBar
        GtkSourceVimState parent_instance;
        GtkSourceVimCommand *command;
        GString *buffer;
+       char *typed;
        int history_pos;
 };
 
@@ -58,6 +59,8 @@ gtk_source_vim_command_bar_dispose (GObject *object)
 {
        GtkSourceVimCommandBar *self = (GtkSourceVimCommandBar *)object;
 
+       g_clear_pointer (&self->typed, g_free);
+
        if (self->buffer == NULL)
        {
                g_string_free (self->buffer, TRUE);
@@ -86,23 +89,45 @@ static void
 move_history (GtkSourceVimCommandBar *self,
               int                     direction)
 {
+       int position;
+
        g_assert (GTK_SOURCE_IS_VIM_COMMAND_BAR (self));
 
        if (history->len == 0)
+       {
                return;
+       }
+
+       if (self->typed == NULL && self->buffer->len > 0)
+       {
+               self->typed = g_strdup (self->buffer->str);
+       }
 
-       if (direction < 0)
-               self->history_pos--;
-       else
-               self->history_pos++;
+       direction = direction < 0 ? -1 : 1;
+       position = self->history_pos + direction;
 
-       if (self->history_pos < 0)
-               self->history_pos = history->len - 1;
-       else if (self->history_pos >= history->len)
-               self->history_pos = 0;
+       while (position >= 0 && position < history->len)
+       {
+               const char *item = g_ptr_array_index (history, position);
 
-       g_string_truncate (self->buffer, 0);
-       g_string_append (self->buffer, g_ptr_array_index (history, self->history_pos));
+               if (self->typed == NULL || g_str_has_prefix (item, self->typed))
+               {
+                       self->history_pos = position;
+                       g_string_truncate (self->buffer, 0);
+                       g_string_append (self->buffer, item);
+                       return;
+               }
+
+               position += direction;
+       }
+
+       /* Reset to typed text if we exhausted the tail of history */
+       if (position >= history->len && self->typed != NULL)
+       {
+               self->history_pos = history->len;
+               g_string_truncate (self->buffer, 0);
+               g_string_append (self->buffer, self->typed);
+       }
 }
 
 static void
@@ -191,6 +216,8 @@ gtk_source_vim_command_bar_handle_keypress (GtkSourceVimState *state,
                {
                        gsize len = g_utf8_strlen (self->buffer->str, -1);
 
+                       g_clear_pointer (&self->typed, g_free);
+
                        if (len > 1)
                        {
                                char *s = g_utf8_offset_to_pointer (self->buffer->str, len-1);
@@ -219,6 +246,7 @@ gtk_source_vim_command_bar_handle_keypress (GtkSourceVimState *state,
                case GDK_KEY_Return:
                case GDK_KEY_KP_Enter:
                case GDK_KEY_ISO_Enter:
+                       g_clear_pointer (&self->typed, g_free);
                        do_execute (self, self->buffer->str);
                        g_string_truncate (self->buffer, 0);
                        do_notify (self);
@@ -228,6 +256,7 @@ gtk_source_vim_command_bar_handle_keypress (GtkSourceVimState *state,
                case GDK_KEY_u:
                        if (mods & GDK_CONTROL_MASK)
                        {
+                               g_clear_pointer (&self->typed, g_free);
                                g_string_truncate (self->buffer, 1);
                                do_notify (self);
                                return TRUE;
@@ -242,6 +271,7 @@ gtk_source_vim_command_bar_handle_keypress (GtkSourceVimState *state,
        if (str[0])
        {
                g_string_append (self->buffer, str);
+               g_clear_pointer (&self->typed, g_free);
                do_notify (self);
        }
 
@@ -256,7 +286,7 @@ gtk_source_vim_command_bar_enter (GtkSourceVimState *state)
 
        g_assert (GTK_SOURCE_VIM_STATE (self));
 
-       self->history_pos = 0;
+       self->history_pos = history->len;
 
        if (self->buffer->len == 0)
        {
@@ -276,6 +306,9 @@ gtk_source_vim_command_bar_leave (GtkSourceVimState *state)
 
        g_assert (GTK_SOURCE_VIM_STATE (self));
 
+       self->history_pos = 0;
+
+       g_clear_pointer (&self->typed, g_free);
        g_string_truncate (self->buffer, 0);
        do_notify (self);