private void button_entity_copy_to_marked_Click(object sender, EventArgs e)
        {
            Editor editor = ActiveDocument;
            Level  level  = editor.m_level;

            if (level.selected_entity > -1 && level.entity[level.selected_entity].alive)
            {
                editor.SaveStateForUndo("Copy entity properties");
                int num = level.CopyEntityPropertiesToMarked(level.entity[level.selected_entity], true);
                ActiveDocument.AddOutputText("Copied properties to " + num + " entities.");
                editor.RefreshGeometry();
            }
        }
        private void button_entity_mark_type_Click(object sender, EventArgs e)
        {
            Editor editor = ActiveDocument;
            Level  level  = editor.m_level;

            Entity entity = level.GetSelectedEntity();

            if (entity != null)
            {
                editor.SaveStateForUndo("Mark entities of same type");
                int num = level.MarkEntitiesOfType(entity.Type);
                ActiveDocument.AddOutputText("Marked " + num + " " + entity.Type.ToString() + " entities.");
                editor.RefreshGeometry();
            }
        }
        private void button_entity_copy_subtype_Click(object sender, EventArgs e)
        {
            Editor editor = ActiveDocument;
            Level  level  = editor.m_level;

            Entity entity = level.GetSelectedEntity();

            if (entity != null)
            {
                editor.SaveStateForUndo("Copy entity subtype");
                int num = level.CopyEntityPropertiesToMarked(entity, false);
                editor.RefreshGeometry();
                ActiveDocument.AddOutputText("Copied subtype to " + num + " entities.");
            }
        }
        private void button_entity_marked_reset_rotation_Click(object sender, EventArgs e)
        {
            int num = ActiveDocument.EntityMarkedResetRotation();

            ActiveDocument.AddOutputText("Rotation reset for " + num + " marked entities.");
        }
        private void button_entity_marked_face_selected_side_Click(object sender, EventArgs e)
        {
            int num = ActiveDocument.EntityMarkedFaceSelectedSide();

            ActiveDocument.AddOutputText(num + "marked entities turned to face selected side.");
        }
        private void button_entity_duplicate_Click(object sender, EventArgs e)
        {
            int num = ActiveDocument.DuplicateMarkedEntities();

            ActiveDocument.AddOutputText("Duplicated " + num + " entities.");
        }