#!/usr/bin/env python


__license__   = 'GPL v3'
__copyright__ = '2011, Kovid Goyal <kovid@kovidgoyal.net>'
__docformat__ = 'restructuredtext en'

import errno
import os
from datetime import datetime
from functools import partial
from qt.core import (
    QDialog, QDialogButtonBox, QFrame, QGridLayout, QGroupBox, QHBoxLayout, QIcon,
    QInputDialog, QKeySequence, QMenu, QPushButton, QScrollArea, QShortcut, QSize,
    QSizePolicy, QSpacerItem, QSplitter, Qt, QTabWidget, QToolButton, QVBoxLayout,
    QWidget, pyqtSignal,
)

from calibre.constants import ismacos
from calibre.ebooks.metadata import authors_to_string, string_to_authors
from calibre.ebooks.metadata.book.base import Metadata
from calibre.gui2 import error_dialog, gprefs, pixmap_to_data
from calibre.gui2.custom_column_widgets import Comments, populate_metadata_page
from calibre.gui2.dialogs.confirm_delete import confirm
from calibre.gui2.metadata.basic_widgets import (
    AuthorsEdit, AuthorSortEdit, BuddyLabel, CommentsEdit, Cover, DateEdit,
    FormatsManager, IdentifiersEdit, LanguagesEdit, PubdateEdit, PublisherEdit,
    RatingEdit, RightClickButton, SeriesEdit, SeriesIndexEdit, TagsEdit, TitleEdit,
    TitleSortEdit, show_locked_file_error,
)
from calibre.gui2.metadata.single_download import FullFetch
from calibre.gui2.widgets2 import CenteredToolButton
from calibre.library.comments import merge_comments as merge_two_comments
from calibre.utils.date import local_tz
from calibre.utils.localization import canonicalize_lang, ngettext
from polyglot.builtins import iteritems

BASE_TITLE = _('Edit metadata')
fetched_fields = ('title', 'title_sort', 'authors', 'author_sort', 'series',
                  'series_index', 'languages', 'publisher', 'tags', 'rating',
                  'comments', 'pubdate')


class ScrollArea(QScrollArea):

    def __init__(self, widget=None, parent=None):
        QScrollArea.__init__(self, parent)
        self.setFrameShape(QFrame.Shape.NoFrame)
        self.setWidgetResizable(True)
        if widget is not None:
            self.setWidget(widget)


class MetadataSingleDialogBase(QDialog):

    view_format = pyqtSignal(object, object)
    edit_format = pyqtSignal(object, object)
    one_line_comments_toolbar = False
    use_toolbutton_for_config_metadata = True

    def __init__(self, db, parent=None, editing_multiple=False):
        self.db = db
        self.was_data_edited = False
        self.changed = set()
        self.books_to_refresh = set()
        self.rows_to_refresh = set()
        self.metadata_before_fetch = None
        self.editing_multiple = editing_multiple
        self.comments_edit_state_at_apply = {}
        QDialog.__init__(self, parent)
        self.setupUi()

    def setupUi(self, *args):  # {{{
        self.download_shortcut = QShortcut(self)
        self.download_shortcut.setKey(QKeySequence('Ctrl+D',
            QKeySequence.SequenceFormat.PortableText))
        p = self.parent()
        if hasattr(p, 'keyboard'):
            kname = 'Interface Action: Edit Metadata (Edit Metadata) : menu action : download'
            sc = p.keyboard.keys_map.get(kname, None)
            if sc:
                self.download_shortcut.setKey(sc[0])
        self.swap_title_author_shortcut = s = QShortcut(self)
        s.setKey(QKeySequence('Alt+Down', QKeySequence.SequenceFormat.PortableText))

        self.button_box = bb = QDialogButtonBox(self)
        self.button_box.accepted.connect(self.accept)
        self.button_box.rejected.connect(self.reject)
        self.next_button = QPushButton(QIcon.ic('forward.png'), _('Next'),
                self)
        self.next_button.setShortcut(QKeySequence('Alt+Right'))
        self.next_button.clicked.connect(self.next_clicked)
        self.prev_button = QPushButton(QIcon.ic('back.png'), _('Previous'),
                self)
        self.prev_button.setShortcut(QKeySequence('Alt+Left'))

        self.button_box.addButton(self.prev_button, QDialogButtonBox.ButtonRole.ActionRole)
        self.button_box.addButton(self.next_button, QDialogButtonBox.ButtonRole.ActionRole)
        self.prev_button.clicked.connect(self.prev_clicked)
        bb.setStandardButtons(QDialogButtonBox.StandardButton.Ok|QDialogButtonBox.StandardButton.Cancel)
        bb.button(QDialogButtonBox.StandardButton.Ok).setDefault(True)

        self.central_widget = QTabWidget(self)

        self.l = QVBoxLayout(self)
        self.setLayout(self.l)
        self.l.addWidget(self.central_widget)
        ll = self.button_box_layout = QHBoxLayout()
        self.l.addLayout(ll)
        ll.addSpacing(10)
        ll.addWidget(self.button_box)

        self.setWindowIcon(QIcon.ic('edit_input.png'))
        self.setWindowTitle(BASE_TITLE)

        self.create_basic_metadata_widgets()

        if len(self.db.custom_column_label_map):
            self.create_custom_metadata_widgets()
        self.comments_edit_state_at_apply = {self.comments:None}

        self.do_layout()
        self.restore_geometry(gprefs, 'metasingle_window_geometry3')
        self.restore_widget_settings()
    # }}}

    def sizeHint(self):
        geom = self.screen().availableSize()
        nh, nw = max(300, geom.height()-50), max(400, geom.width()-70)
        return QSize(nw, nh)

    def create_basic_metadata_widgets(self):  # {{{
        self.basic_metadata_widgets = []

        self.languages = LanguagesEdit(self)
        self.basic_metadata_widgets.append(self.languages)

        self.title = TitleEdit(self)
        self.title.textChanged.connect(self.update_window_title)
        self.deduce_title_sort_button = QToolButton(self)
        self.deduce_title_sort_button.setToolTip(
            _('Automatically create the title sort entry based on the current '
                'title entry.\nUsing this button to create title sort will '
                'change title sort from red to green.'))
        self.deduce_title_sort_button.setWhatsThis(
                self.deduce_title_sort_button.toolTip())
        self.title_sort = TitleSortEdit(self, self.title,
                self.deduce_title_sort_button, self.languages)
        self.basic_metadata_widgets.extend([self.title, self.title_sort])

        self.deduce_author_sort_button = b = RightClickButton(self)
        b.setToolTip('<p>' +
            _('Automatically create the author sort entry based on the current '
              'author entry. Using this button to create author sort will '
              'change author sort from red to green.  There is a menu of '
              'functions available under this button. Click and hold '
              'on the button to see it.') + '</p>')
        if ismacos:
            # Workaround for https://bugreports.qt-project.org/browse/QTBUG-41017
            class Menu(QMenu):

                def mouseReleaseEvent(self, ev):
                    ac = self.actionAt(ev.pos())
                    if ac is not None:
                        ac.trigger()
                    return QMenu.mouseReleaseEvent(self, ev)
            b.m = m = Menu(b)
        else:
            b.m = m = QMenu(b)
        ac = m.addAction(QIcon.ic('forward.png'), _('Set author sort from author'))
        ac2 = m.addAction(QIcon.ic('back.png'), _('Set author from author sort'))
        ac3 = m.addAction(QIcon.ic('user_profile.png'), _('Manage authors'))
        ac4 = m.addAction(QIcon.ic('next.png'),
                _('Copy author to author sort'))
        ac5 = m.addAction(QIcon.ic('previous.png'),
                _('Copy author sort to author'))

        b.setMenu(m)
        self.authors = AuthorsEdit(self, ac3)
        self.author_sort = AuthorSortEdit(self, self.authors, b, self.db, ac,
                ac2, ac4, ac5)
        self.basic_metadata_widgets.extend([self.authors, self.author_sort])

        self.swap_title_author_button = QToolButton(self)
        self.swap_title_author_button.setIcon(QIcon.ic('swap.png'))
        self.swap_title_author_button.setToolTip(_(
            'Swap the author and title') + ' [%s]' % self.swap_title_author_shortcut.key().toString(QKeySequence.SequenceFormat.NativeText))
        self.swap_title_author_button.clicked.connect(self.swap_title_author)
        self.swap_title_author_shortcut.activated.connect(self.swap_title_author_button.click)

        self.manage_authors_button = QToolButton(self)
        self.manage_authors_button.setIcon(QIcon.ic('user_profile.png'))
        self.manage_authors_button.setToolTip('<p>' + _(
            'Open the Authors Category editor. Use to rename authors and correct '
            'individual author\'s sort values') + '</p>')
        self.manage_authors_button.clicked.connect(self.authors.manage_authors)

        self.series_editor_button = QToolButton(self)
        self.series_editor_button.setToolTip(_('Open the Series Category editor'))
        self.series_editor_button.setIcon(QIcon.ic('chapters.png'))
        self.series_editor_button.clicked.connect(self.series_editor)
        self.series = SeriesEdit(self)
        self.series.editor_requested.connect(self.series_editor)
        self.clear_series_button = QToolButton(self)
        self.clear_series_button.setToolTip(_('Clear series'))
        self.clear_series_button.clicked.connect(self.series.clear)
        self.series_index = SeriesIndexEdit(self, self.series)
        self.basic_metadata_widgets.extend([self.series, self.series_index])

        self.formats_manager = FormatsManager(self, self.copy_fmt)
        # We want formats changes to be committed before title/author, as
        # otherwise we could have data loss if the title/author changed and the
        # user was trying to add an extra file from the old books directory.
        self.basic_metadata_widgets.insert(0, self.formats_manager)
        self.formats_manager.metadata_from_format_button.clicked.connect(
                self.metadata_from_format)
        self.formats_manager.cover_from_format_button.clicked.connect(
                self.cover_from_format)
        self.cover = Cover(self)
        self.cover.download_cover.connect(self.download_cover)
        self.basic_metadata_widgets.append(self.cover)

        self.comments = CommentsEdit(self, self.one_line_comments_toolbar)
        self.basic_metadata_widgets.append(self.comments)

        self.rating = RatingEdit(self)
        self.clear_ratings_button = QToolButton(self)
        self.clear_ratings_button.setToolTip(_('Clear rating'))
        self.clear_ratings_button.setIcon(QIcon.ic('trash.png'))
        self.clear_ratings_button.clicked.connect(self.rating.zero)

        self.basic_metadata_widgets.append(self.rating)

        self.tags = TagsEdit(self)
        self.tags_editor_button = QToolButton(self)
        self.tags_editor_button.setToolTip(_('Open the Tag editor. If Ctrl or Shift is pressed, open the Tags Category editor'))
        self.tags_editor_button.setIcon(QIcon.ic('chapters.png'))
        self.tags_editor_button.clicked.connect(self.tags_editor)
        self.tags.tag_editor_requested.connect(self.tags_editor)
        self.clear_tags_button = QToolButton(self)
        self.clear_tags_button.setToolTip(_('Clear all tags'))
        self.clear_tags_button.setIcon(QIcon.ic('trash.png'))
        self.clear_tags_button.clicked.connect(self.tags.clear)
        self.basic_metadata_widgets.append(self.tags)

        self.identifiers = IdentifiersEdit(self)
        self.basic_metadata_widgets.append(self.identifiers)
        self.clear_identifiers_button = QToolButton(self)
        self.clear_identifiers_button.setIcon(QIcon.ic('trash.png'))
        self.clear_identifiers_button.setToolTip(_('Clear Ids'))
        self.clear_identifiers_button.clicked.connect(self.identifiers.clear)
        self.paste_isbn_button = b = RightClickButton(self)
        b.setToolTip('<p>' +
                    _('Paste the contents of the clipboard into the '
                      'identifiers prefixed with isbn: or url:. Or right click, '
                      'to choose a different prefix.') + '</p>')
        b.setIcon(QIcon.ic('edit-paste.png'))
        b.clicked.connect(self.identifiers.paste_identifier)
        b.setPopupMode(QToolButton.ToolButtonPopupMode.DelayedPopup)
        b.setMenu(QMenu(b))
        self.update_paste_identifiers_menu()

        self.publisher_editor_button = QToolButton(self)
        self.publisher_editor_button.setToolTip(_('Open the Publishers Category editor'))
        self.publisher_editor_button.setIcon(QIcon.ic('chapters.png'))
        self.publisher_editor_button.clicked.connect(self.publisher_editor)
        self.publisher = PublisherEdit(self)
        self.publisher.editor_requested.connect(self.publisher_editor)
        self.basic_metadata_widgets.append(self.publisher)

        self.timestamp = DateEdit(self)
        self.pubdate = PubdateEdit(self)
        self.basic_metadata_widgets.extend([self.timestamp, self.pubdate])

        self.fetch_metadata_button = b = CenteredToolButton(QIcon.ic('download-metadata.png'), _('&Download metadata'), self)
        b.setPopupMode(QToolButton.ToolButtonPopupMode.DelayedPopup)
        b.setToolTip(_('Download metadata for this book [%s]') % self.download_shortcut.key().toString(QKeySequence.SequenceFormat.NativeText))
        self.fetch_metadata_button.clicked.connect(self.fetch_metadata)
        self.fetch_metadata_menu = m = QMenu(self.fetch_metadata_button)
        m.addAction(QIcon.ic('edit-undo.png'), _('Undo last metadata download'), self.undo_fetch_metadata)
        self.fetch_metadata_button.setMenu(m)
        self.download_shortcut.activated.connect(self.fetch_metadata_button.click)

        if self.use_toolbutton_for_config_metadata:
            self.config_metadata_button = QToolButton(self)
            self.config_metadata_button.setIcon(QIcon.ic('config.png'))
        else:
            self.config_metadata_button = QPushButton(self)
            self.config_metadata_button.setText(_('Configure download metadata'))
        self.config_metadata_button.setIcon(QIcon.ic('config.png'))
        self.config_metadata_button.clicked.connect(self.configure_metadata)
        self.config_metadata_button.setToolTip(
            _('Change how calibre downloads metadata'))
        for w in self.basic_metadata_widgets:
            w.data_changed.connect(self.data_changed)

    # }}}

    def update_paste_identifiers_menu(self):
        m = self.paste_isbn_button.menu()
        m.clear()
        m.addAction(_('Edit list of prefixes'), self.edit_prefix_list)
        m.addSeparator()
        for prefix in gprefs['paste_isbn_prefixes'][1:]:
            m.addAction(prefix, partial(self.identifiers.paste_prefix, prefix))

    def edit_prefix_list(self):
        prefixes, ok = QInputDialog.getMultiLineText(
            self, _('Edit prefixes'), _('Enter prefixes, one on a line. The first prefix becomes the default.'),
            '\n'.join(list(map(str, gprefs['paste_isbn_prefixes']))))
        if ok:
            gprefs['paste_isbn_prefixes'] = list(filter(None, (x.strip() for x in prefixes.splitlines()))) or gprefs.defaults['paste_isbn_prefixes']
            self.update_paste_identifiers_menu()

    def use_two_columns_for_custom_metadata(self):
        raise NotImplementedError

    def create_custom_metadata_widgets(self):  # {{{
        self.custom_metadata_widgets_parent = w = QWidget(self)
        layout = QGridLayout()
        w.setLayout(layout)
        self.custom_metadata_widgets, self.__cc_spacers = \
            populate_metadata_page(layout, self.db, None, parent=w, bulk=False,
                two_column=self.use_two_columns_for_custom_metadata())
        self.__custom_col_layouts = [layout]
        for widget in self.custom_metadata_widgets:
            widget.connect_data_changed(self.data_changed)
            if isinstance(widget, Comments):
                self.comments_edit_state_at_apply[widget] = None
    # }}}

    def set_custom_metadata_tab_order(self, before=None, after=None):  # {{{
        sto = QWidget.setTabOrder
        if getattr(self, 'custom_metadata_widgets', []):
            ans = self.custom_metadata_widgets
            for i in range(len(ans)-1):
                if before is not None and i == 0:
                    pass
                if len(ans[i+1].widgets) == 2:
                    sto(ans[i].widgets[-1], ans[i+1].widgets[1])
                else:
                    sto(ans[i].widgets[-1], ans[i+1].widgets[0])
                for c in range(2, len(ans[i].widgets), 2):
                    sto(ans[i].widgets[c-1], ans[i].widgets[c+1])
            if after is not None:
                pass
    # }}}

    def do_view_format(self, path, fmt):
        if path:
            self.view_format.emit(None, path)
        else:
            self.view_format.emit(self.book_id, fmt)

    def do_edit_format(self, path, fmt):
        if self.was_data_edited:
            from calibre.gui2.tweak_book import tprefs
            tprefs.refresh()  # In case they were changed in a Tweak Book process
            from calibre.gui2 import question_dialog
            if tprefs['update_metadata_from_calibre'] and question_dialog(
                    self, _('Save changed metadata?'),
                    _("You've changed the metadata for this book."
                      " Edit book is set to update embedded metadata when opened."
                      " You need to save your changes for them to be included."),
                    yes_text=_('&Save'), no_text=_("&Don't save"),
                    yes_icon='dot_green.png', no_icon='dot_red.png',
                    default_yes=True, skip_dialog_name='edit-metadata-save-before-edit-format'):
                if self.apply_changes():
                    self.was_data_edited = False
        self.edit_format.emit(self.book_id, fmt)

    def copy_fmt(self, fmt, f):
        self.db.copy_format_to(self.book_id, fmt, f, index_is_id=True)

    def do_layout(self):
        raise NotImplementedError()

    def save_widget_settings(self):
        pass

    def restore_widget_settings(self):
        pass

    def data_changed(self):
        self.was_data_edited = True

    def __call__(self, id_):
        self.book_id = id_
        self.books_to_refresh = set()
        self.metadata_before_fetch = None
        for widget in self.basic_metadata_widgets:
            widget.initialize(self.db, id_)
        for widget in getattr(self, 'custom_metadata_widgets', []):
            widget.initialize(id_)
        if callable(self.set_current_callback):
            self.set_current_callback(id_)
        self.was_data_edited = False
        # Commented out as it doesn't play nice with Next, Prev buttons
        # self.fetch_metadata_button.setFocus(Qt.FocusReason.OtherFocusReason)

    # Miscellaneous interaction methods {{{
    def update_window_title(self, *args):
        title = self.title.current_val
        if len(title) > 50:
            title = title[:50] + '\u2026'
        self.setWindowTitle(BASE_TITLE + ' - ' +
                title + ' - ' +
                _(' [%(num)d of %(tot)d]')%dict(num=self.current_row+1,
                tot=len(self.row_list)))

    def swap_title_author(self, *args):
        title = self.title.current_val
        self.title.current_val = authors_to_string(self.authors.current_val)
        self.authors.current_val = string_to_authors(title)
        self.title_sort.auto_generate()
        self.author_sort.auto_generate()

    def tags_editor(self, *args):
        self.tags.edit(self.db, self.book_id)

    def publisher_editor(self, *args):
        self.publisher.edit(self.db, self.book_id)

    def series_editor(self, *args):
        self.series.edit(self.db, self.book_id)

    def metadata_from_format(self, *args):
        mi, ext = self.formats_manager.get_selected_format_metadata(self.db,
                self.book_id)
        if mi is not None:
            self.update_from_mi(mi)

    def choose_cover_from_pages(self, ext):
        path = self.formats_manager.get_format_path(self.db, self.book_id, ext.lower())
        from calibre.gui2.metadata.pdf_covers import PDFCovers
        d = PDFCovers(path, parent=self)
        if d.exec() == QDialog.DialogCode.Accepted:
            cpath = d.cover_path
            if cpath:
                with open(cpath, 'rb') as f:
                    self.update_cover(f.read(), ext.upper())
        d.cleanup()

    def cover_from_format(self, *args):
        ext = self.formats_manager.get_selected_format()
        if ext is None:
            return
        if ext in ('pdf', 'cbz', 'cbr'):
            return self.choose_cover_from_pages(ext)
        try:
            mi, ext = self.formats_manager.get_selected_format_metadata(self.db,
                    self.book_id)
        except OSError as err:
            if getattr(err, 'errno', None) == errno.EACCES:  # Permission denied
                import traceback
                fname = err.filename if err.filename else 'file'
                error_dialog(self, _('Permission denied'),
                        _('Could not open %s. Is it being used by another'
                        ' program?')%fname, det_msg=traceback.format_exc(),
                        show=True)
                return
            raise
        if mi is None:
            return
        cdata = None
        if mi.cover and os.access(mi.cover, os.R_OK):
            with open(mi.cover, 'rb') as f:
                cdata = f.read()
        elif mi.cover_data[1] is not None:
            cdata = mi.cover_data[1]
        if cdata is None:
            error_dialog(self, _('Could not read cover'),
                         _('Could not read cover from %s format')%ext.upper()).exec()
            return
        self.update_cover(cdata, ext)

    def update_cover(self, cdata, fmt):
        orig = self.cover.current_val
        self.cover.current_val = cdata
        if self.cover.current_val is None:
            self.cover.current_val = orig
            return error_dialog(self, _('Could not read cover'),
                         _('The cover in the %s format is invalid')%fmt,
                         show=True)
            return

    def update_from_mi(self, mi, update_sorts=True, merge_tags=True, merge_comments=False):
        fw = self.focusWidget()
        if not mi.is_null('title'):
            self.title.set_value(mi.title)
            if update_sorts:
                self.title_sort.auto_generate()
        if not mi.is_null('authors'):
            self.authors.set_value(mi.authors)
        if not mi.is_null('author_sort'):
            self.author_sort.set_value(mi.author_sort)
        elif update_sorts and not mi.is_null('authors'):
            self.author_sort.auto_generate()
        if not mi.is_null('rating'):
            self.rating.set_value(mi.rating * 2)
        if not mi.is_null('publisher'):
            self.publisher.set_value(mi.publisher)
        if not mi.is_null('tags'):
            old_tags = self.tags.current_val
            tags = mi.tags if mi.tags else []
            if old_tags and merge_tags:
                ltags, lotags = {t.lower() for t in tags}, {t.lower() for t in
                        old_tags}
                tags = [t for t in tags if t.lower() in ltags-lotags] + old_tags
            self.tags.set_value(tags)
        if not mi.is_null('identifiers'):
            current = self.identifiers.current_val
            current.update(mi.identifiers)
            self.identifiers.set_value(current)
        if not mi.is_null('pubdate'):
            self.pubdate.set_value(mi.pubdate)
        if not mi.is_null('series') and mi.series.strip():
            self.series.set_value(mi.series)
            if mi.series_index is not None:
                self.series_index.reset_original()
                self.series_index.set_value(float(mi.series_index))
        if not mi.is_null('languages'):
            langs = [canonicalize_lang(x) for x in mi.languages]
            langs = [x for x in langs if x is not None]
            if langs:
                self.languages.set_value(langs)
        if mi.comments and mi.comments.strip():
            val = mi.comments
            if val and merge_comments:
                cval = self.comments.current_val
                if cval:
                    val = merge_two_comments(cval, val)
            self.comments.set_value(val)
        if fw is not None:
            fw.setFocus(Qt.FocusReason.OtherFocusReason)

    def fetch_metadata(self, *args):
        from calibre.ebooks.metadata.sources.update import update_sources
        update_sources()
        d = FullFetch(self.cover.pixmap(), self)
        ret = d.start(title=self.title.current_val, authors=self.authors.current_val,
                identifiers=self.identifiers.current_val)
        if ret == QDialog.DialogCode.Accepted:
            self.metadata_before_fetch = {f:getattr(self, f).current_val for f in fetched_fields}
            from calibre.ebooks.metadata.sources.prefs import msprefs
            mi = d.book
            dummy = Metadata(_('Unknown'))
            for f in msprefs['ignore_fields']:
                if ':' not in f:
                    setattr(mi, f, getattr(dummy, f))
            if mi is not None:
                pd = mi.pubdate
                if pd is not None:
                    # Put the downloaded published date into the local timezone
                    # as we discard time info and the date is timezone
                    # invariant. This prevents the as_local_timezone() call in
                    # update_from_mi from changing the pubdate
                    mi.pubdate = datetime(pd.year, pd.month, pd.day,
                            tzinfo=local_tz)
                self.update_from_mi(mi, merge_comments=msprefs['append_comments'])
            if d.cover_pixmap is not None:
                self.metadata_before_fetch['cover'] = self.cover.current_val
                self.cover.current_val = pixmap_to_data(d.cover_pixmap)

    def undo_fetch_metadata(self):
        if self.metadata_before_fetch is None:
            return error_dialog(self, _('No downloaded metadata'), _(
                'There is no downloaded metadata to undo'), show=True)
        for field, val in iteritems(self.metadata_before_fetch):
            getattr(self, field).current_val = val
        self.metadata_before_fetch = None

    def configure_metadata(self):
        from calibre.gui2.preferences import show_config_widget
        gui = self.parent()
        show_config_widget('Sharing', 'Metadata download', parent=self,
                gui=gui, never_shutdown=True)

    def download_cover(self, *args):
        from calibre.ebooks.metadata.sources.update import update_sources
        update_sources()
        from calibre.gui2.metadata.single_download import CoverFetch
        d = CoverFetch(self.cover.pixmap(), self)
        ret = d.start(self.title.current_val, self.authors.current_val,
                self.identifiers.current_val)
        if ret == QDialog.DialogCode.Accepted:
            if d.cover_pixmap is not None:
                self.cover.current_val = pixmap_to_data(d.cover_pixmap)

    # }}}

    def to_book_metadata(self):
        mi = Metadata(_('Unknown'))
        if self.db is None:
            return mi
        mi.set_all_user_metadata(self.db.field_metadata.custom_field_metadata())
        for widget in self.basic_metadata_widgets:
            widget.apply_to_metadata(mi)
        for widget in getattr(self, 'custom_metadata_widgets', []):
            widget.apply_to_metadata(mi)
        return mi

    def apply_changes(self):
        self.changed.add(self.book_id)
        if self.db is None:
            # break_cycles has already been called, don't know why this should
            # happen but a user reported it
            return True
        self.comments_edit_state_at_apply = {w:w.tab for w in self.comments_edit_state_at_apply}
        for widget in self.basic_metadata_widgets:
            try:
                if hasattr(widget, 'validate_for_commit'):
                    title, msg, det_msg = widget.validate_for_commit()
                    if title is not None:
                        error_dialog(self, title, msg, det_msg=det_msg, show=True)
                        return False
                widget.commit(self.db, self.book_id)
                self.books_to_refresh |= getattr(widget, 'books_to_refresh', set())
            except OSError as err:
                if getattr(err, 'errno', None) == errno.EACCES:  # Permission denied
                    show_locked_file_error(self, err)
                    return False
                raise
        for widget in getattr(self, 'custom_metadata_widgets', []):
            self.books_to_refresh |= widget.commit(self.book_id)

        self.db.commit()
        rows = self.db.refresh_ids(list(self.books_to_refresh))
        if rows:
            self.rows_to_refresh |= set(rows)

        return True

    def accept(self):
        self.save_state()
        if not self.apply_changes():
            return
        if self.editing_multiple and self.current_row != len(self.row_list) - 1:
            num = len(self.row_list) - 1 - self.current_row
            from calibre.gui2 import question_dialog
            pm = ngettext('There is another book to edit in this set.',
                          'There are still {} more books to edit in this set.', num).format(num)
            if not question_dialog(
                    self, _('Are you sure?'), pm + ' ' + _(
                      'Are you sure you want to stop? Use the "Next" button'
                      ' instead of the "OK" button to move through books in the set.'),
                    yes_text=_('&Stop editing'), no_text=_('&Continue editing'),
                    yes_icon='dot_red.png', no_icon='dot_green.png',
                    default_yes=False, skip_dialog_name='edit-metadata-single-confirm-ok-on-multiple'):
                return self.do_one(delta=1, apply_changes=False)
        QDialog.accept(self)

    def reject(self):
        self.save_state()
        if self.was_data_edited and not confirm(
                title=_('Are you sure?'), name='confirm-cancel-edit-single-metadata', msg=_(
                    'You will lose all unsaved changes. Are you sure?'), parent=self):
            return
        QDialog.reject(self)

    def save_state(self):
        try:
            self.save_geometry(gprefs, 'metasingle_window_geometry3')
            self.save_widget_settings()
        except:
            # Weird failure, see https://bugs.launchpad.net/bugs/995271
            import traceback
            traceback.print_exc()

    # Dialog use methods {{{
    def start(self, row_list, current_row, view_slot=None, edit_slot=None,
            set_current_callback=None):
        self.row_list = row_list
        self.current_row = current_row
        if view_slot is not None:
            self.view_format.connect(view_slot)
        if edit_slot is not None:
            self.edit_format.connect(edit_slot)
        self.set_current_callback = set_current_callback
        self.do_one(apply_changes=False)
        ret = self.exec()
        self.break_cycles()
        return ret

    def next_clicked(self):
        if not self.apply_changes():
            return
        self.do_one(delta=1, apply_changes=False)

    def prev_clicked(self):
        if not self.apply_changes():
            return
        self.do_one(delta=-1, apply_changes=False)

    def do_one(self, delta=0, apply_changes=True):
        if apply_changes:
            self.apply_changes()
        self.current_row += delta
        self.update_window_title()
        prev = next_ = None
        if self.current_row > 0:
            prev = self.db.title(self.row_list[self.current_row-1])
        if self.current_row < len(self.row_list) - 1:
            next_ = self.db.title(self.row_list[self.current_row+1])

        if next_ is not None:
            tip = _('Save changes and edit the metadata of {} [Alt+Right]').format(next_)
            self.next_button.setToolTip(tip)
        self.next_button.setEnabled(next_ is not None)
        if prev is not None:
            tip = _('Save changes and edit the metadata of {} [Alt+Left]').format(prev)
            self.prev_button.setToolTip(tip)
        self.prev_button.setEnabled(prev is not None)
        self.button_box.button(QDialogButtonBox.StandardButton.Ok).setDefault(True)
        self.button_box.button(QDialogButtonBox.StandardButton.Ok).setFocus(Qt.FocusReason.OtherFocusReason)
        self(self.db.id(self.row_list[self.current_row]))
        for w, state in iteritems(self.comments_edit_state_at_apply):
            if state == 'code':
                w.tab = 'code'

    def break_cycles(self):
        # Break any reference cycles that could prevent python
        # from garbage collecting this dialog
        self.set_current_callback = self.db = None
        self.metadata_before_fetch = None

        def disconnect(signal):
            try:
                signal.disconnect()
            except:
                pass  # Fails if view format was never connected
        disconnect(self.view_format)
        disconnect(self.edit_format)
        for b in ('next_button', 'prev_button'):
            x = getattr(self, b, None)
            if x is not None:
                disconnect(x.clicked)
        for widget in self.basic_metadata_widgets:
            bc = getattr(widget, 'break_cycles', None)
            if bc is not None and callable(bc):
                bc()
        for widget in getattr(self, 'custom_metadata_widgets', []):
            widget.break_cycles()

    # }}}


class Splitter(QSplitter):

    frame_resized = pyqtSignal(object)

    def resizeEvent(self, ev):
        self.frame_resized.emit(ev)
        return super().resizeEvent(ev)


class MetadataSingleDialog(MetadataSingleDialogBase):  # {{{

    def use_two_columns_for_custom_metadata(self):
        return gprefs['edit_metadata_single_use_2_cols_for_custom_fields']

    def do_layout(self):
        if len(self.db.custom_column_label_map) == 0:
            self.central_widget.tabBar().setVisible(False)
        self.central_widget.clear()
        self.tabs = []
        self.labels = []
        self.tabs.append(QWidget(self))
        self.central_widget.addTab(ScrollArea(self.tabs[0], self), _("&Basic metadata"))
        self.tabs[0].l = l = QVBoxLayout()
        self.tabs[0].tl = tl = QGridLayout()
        self.tabs[0].setLayout(l)
        w = getattr(self, 'custom_metadata_widgets_parent', None)
        if w is not None:
            self.tabs.append(w)
            self.central_widget.addTab(ScrollArea(w, self), _('&Custom metadata'))
        l.addLayout(tl)
        l.addItem(QSpacerItem(10, 15, QSizePolicy.Policy.Expanding,
            QSizePolicy.Policy.Fixed))

        sto = QWidget.setTabOrder
        sto(self.button_box, self.fetch_metadata_button)
        sto(self.fetch_metadata_button, self.config_metadata_button)
        sto(self.config_metadata_button, self.title)

        def create_row(row, one, two, three, col=1, icon='forward.png'):
            ql = BuddyLabel(one)
            tl.addWidget(ql, row, col+0, 1, 1)
            self.labels.append(ql)
            tl.addWidget(one, row, col+1, 1, 1)
            if two is not None:
                tl.addWidget(two, row, col+2, 1, 1)
                two.setIcon(QIcon.ic(icon))
            ql = BuddyLabel(three)
            tl.addWidget(ql, row, col+3, 1, 1)
            self.labels.append(ql)
            tl.addWidget(three, row, col+4, 1, 1)
            sto(one, two)
            sto(two, three)

        tl.addWidget(self.swap_title_author_button, 0, 0, 1, 1)
        tl.addWidget(self.manage_authors_button, 1, 0, 1, 1)

        sto(self.swap_title_author_button, self.title)
        create_row(0, self.title, self.deduce_title_sort_button, self.title_sort)
        sto(self.title_sort, self.manage_authors_button)
        sto(self.manage_authors_button, self.authors)
        create_row(1, self.authors, self.deduce_author_sort_button, self.author_sort)
        tl.addWidget(self.series_editor_button, 2, 0, 1, 1)
        sto(self.author_sort, self.series_editor_button)
        sto(self.series_editor_button, self.series)
        create_row(2, self.series, self.clear_series_button,
                self.series_index, icon='trash.png')

        tl.addWidget(self.formats_manager, 0, 6, 3, 1)

        self.splitter = Splitter(Qt.Orientation.Horizontal, self)
        self.splitter.addWidget(self.cover)
        self.splitter.frame_resized.connect(self.cover.frame_resized)
        l.addWidget(self.splitter)
        self.tabs[0].gb = gb = QGroupBox(_('Change cover'), self)
        gb.l = l = QGridLayout()
        gb.setLayout(l)
        for i, b in enumerate(self.cover.buttons[:3]):
            l.addWidget(b, 0, i, 1, 1)
            sto(b, self.cover.buttons[i+1])
        gb.hl = QHBoxLayout()
        for b in self.cover.buttons[3:]:
            gb.hl.addWidget(b)
        sto(self.cover.buttons[-2], self.cover.buttons[-1])
        l.addLayout(gb.hl, 1, 0, 1, 3)
        self.tabs[0].middle = w = QWidget(self)
        w.l = l = QGridLayout()
        w.setLayout(w.l)
        self.splitter.addWidget(w)

        def create_row2(row, widget, button=None, front_button=None):
            row += 1
            ql = BuddyLabel(widget)
            if front_button:
                ltl = QHBoxLayout()
                ltl.addWidget(front_button)
                ltl.addWidget(ql)
                l.addLayout(ltl, row, 0, 1, 1)
            else:
                l.addWidget(ql, row, 0, 1, 1)
            l.addWidget(widget, row, 1, 1, 2 if button is None else 1)
            if button is not None:
                l.addWidget(button, row, 2, 1, 1)
            if button is not None:
                sto(widget, button)

        l.addWidget(gb, 0, 0, 1, 3)
        self.tabs[0].spc_one = QSpacerItem(10, 10, QSizePolicy.Policy.Expanding,
                QSizePolicy.Policy.Expanding)
        l.addItem(self.tabs[0].spc_one, 1, 0, 1, 3)
        sto(self.cover.buttons[-1], self.rating)
        create_row2(1, self.rating, self.clear_ratings_button)
        sto(self.rating, self.clear_ratings_button)
        sto(self.clear_ratings_button, self.tags_editor_button)
        sto(self.tags_editor_button, self.tags)
        create_row2(2, self.tags, self.clear_tags_button, front_button=self.tags_editor_button)
        sto(self.clear_tags_button, self.paste_isbn_button)
        sto(self.paste_isbn_button, self.identifiers)
        create_row2(3, self.identifiers, self.clear_identifiers_button,
                                        front_button=self.paste_isbn_button)
        sto(self.clear_identifiers_button, self.timestamp)
        create_row2(4, self.timestamp, self.timestamp.clear_button)
        sto(self.timestamp.clear_button, self.pubdate)
        create_row2(5, self.pubdate, self.pubdate.clear_button)
        sto(self.pubdate.clear_button, self.publisher_editor_button)
        sto(self.publisher_editor_button, self.publisher)
        create_row2(6, self.publisher, self.publisher.clear_button, front_button=self.publisher_editor_button)
        sto(self.publisher.clear_button, self.languages)
        create_row2(7, self.languages)
        self.tabs[0].spc_two = QSpacerItem(10, 10, QSizePolicy.Policy.Expanding,
                QSizePolicy.Policy.Expanding)
        l.addItem(self.tabs[0].spc_two, 9, 0, 1, 3)
        l.addWidget(self.fetch_metadata_button, 10, 0, 1, 2)
        l.addWidget(self.config_metadata_button, 10, 2, 1, 1)

        self.tabs[0].gb2 = gb = QGroupBox(_('Co&mments'), self)
        gb.l = l = QVBoxLayout()
        l.setContentsMargins(0, 0, 0, 0)
        gb.setLayout(l)
        l.addWidget(self.comments)
        self.splitter.addWidget(gb)

        self.set_custom_metadata_tab_order()

    def save_widget_settings(self):
        gprefs['basic_metadata_widget_splitter_state'] = bytearray(self.splitter.saveState())

    def restore_widget_settings(self):
        s = gprefs.get('basic_metadata_widget_splitter_state')
        if s is not None:
            self.splitter.restoreState(s)

# }}}


class DragTrackingWidget(QWidget):  # {{{

    def __init__(self, parent, on_drag_enter):
        QWidget.__init__(self, parent)
        self.on_drag_enter = on_drag_enter

    def dragEnterEvent(self, ev):
        self.on_drag_enter.emit()

# }}}


class MetadataSingleDialogAlt1(MetadataSingleDialogBase):  # {{{

    one_line_comments_toolbar = True
    use_toolbutton_for_config_metadata = False
    on_drag_enter = pyqtSignal()

    def handle_drag_enter(self):
        self.central_widget.setCurrentIndex(1)

    def use_two_columns_for_custom_metadata(self):
        return False

    def do_layout(self):
        self.central_widget.clear()
        self.tabs = []
        self.labels = []
        sto = QWidget.setTabOrder

        self.on_drag_enter.connect(self.handle_drag_enter)
        self.tabs.append(DragTrackingWidget(self, self.on_drag_enter))
        self.central_widget.addTab(ScrollArea(self.tabs[0], self), _("&Metadata"))
        self.tabs[0].l = QGridLayout()
        self.tabs[0].setLayout(self.tabs[0].l)

        self.tabs.append(QWidget(self))
        self.central_widget.addTab(ScrollArea(self.tabs[1], self), _("&Cover and formats"))
        self.tabs[1].l = QGridLayout()
        self.tabs[1].setLayout(self.tabs[1].l)

        # accept drop events so we can automatically switch to the second tab to
        # drop covers and formats
        self.tabs[0].setAcceptDrops(True)

        # Tab 0
        tab0 = self.tabs[0]

        tl = QGridLayout()
        gb = QGroupBox(_('&Basic metadata'), self.tabs[0])
        self.tabs[0].l.addWidget(gb, 0, 0, 1, 1)
        gb.setLayout(tl)

        self.button_box_layout.insertWidget(1, self.fetch_metadata_button)
        self.button_box_layout.insertWidget(2, self.config_metadata_button)
        sto(self.button_box, self.fetch_metadata_button)
        sto(self.fetch_metadata_button, self.config_metadata_button)
        sto(self.config_metadata_button, self.title)

        def create_row(row, widget, tab_to, button=None, icon=None, span=1):
            ql = BuddyLabel(widget)
            tl.addWidget(ql, row, 1, 1, 1)
            tl.addWidget(widget, row, 2, 1, 1)
            if button is not None:
                tl.addWidget(button, row, 3, span, 1)
                if icon is not None:
                    button.setIcon(QIcon.ic(icon))
            if tab_to is not None:
                if button is not None:
                    sto(widget, button)
                    sto(button, tab_to)
                else:
                    sto(widget, tab_to)

        tl.addWidget(self.swap_title_author_button, 0, 0, 2, 1)
        tl.addWidget(self.manage_authors_button, 2, 0, 1, 1)
        tl.addWidget(self.series_editor_button, 6, 0, 1, 1)
        tl.addWidget(self.tags_editor_button, 6, 0, 1, 1)
        tl.addWidget(self.publisher_editor_button, 9, 0, 1, 1)
        tl.addWidget(self.paste_isbn_button, 12, 0, 1, 1)

        create_row(0, self.title, self.title_sort,
                   button=self.deduce_title_sort_button, span=2,
                   icon='auto_author_sort.png')
        create_row(1, self.title_sort, self.authors)
        create_row(2, self.authors, self.author_sort,
                   button=self.deduce_author_sort_button,
                   span=2, icon='auto_author_sort.png')
        create_row(3, self.author_sort, self.series)
        create_row(4, self.series, self.series_index,
                   button=self.clear_series_button, icon='trash.png')
        create_row(5, self.series_index, self.tags)
        create_row(6, self.tags, self.rating, button=self.clear_tags_button)
        create_row(7, self.rating, self.pubdate, button=self.clear_ratings_button)
        create_row(8, self.pubdate, self.publisher,
                   button=self.pubdate.clear_button, icon='trash.png')
        create_row(9, self.publisher, self.languages, button=self.publisher.clear_button, icon='trash.png')
        create_row(10, self.languages, self.timestamp)
        create_row(11, self.timestamp, self.identifiers,
                   button=self.timestamp.clear_button, icon='trash.png')
        create_row(12, self.identifiers, self.comments,
                   button=self.clear_identifiers_button, icon='trash.png')
        sto(self.clear_identifiers_button, self.swap_title_author_button)
        sto(self.swap_title_author_button, self.manage_authors_button)
        sto(self.manage_authors_button, self.series_editor_button)
        sto(self.series_editor_button, self.tags_editor_button)
        sto(self.tags_editor_button, self.publisher_editor_button)
        sto(self.publisher_editor_button, self.paste_isbn_button)
        tl.addItem(QSpacerItem(1, 1, QSizePolicy.Policy.Fixed, QSizePolicy.Policy.Expanding),
                   13, 1, 1 ,1)

        w = getattr(self, 'custom_metadata_widgets_parent', None)
        if w is not None:
            gb = QGroupBox(_('C&ustom metadata'), tab0)
            gbl = QVBoxLayout()
            gb.setLayout(gbl)
            sr = QScrollArea(tab0)
            sr.setWidgetResizable(True)
            sr.setFrameStyle(QFrame.Shape.NoFrame)
            sr.setWidget(w)
            gbl.addWidget(sr)
            self.tabs[0].l.addWidget(gb, 0, 1, 1, 1)
            sto(self.identifiers, gb)

        w = QGroupBox(_('&Comments'), tab0)
        sp = QSizePolicy()
        sp.setVerticalStretch(10)
        sp.setHorizontalPolicy(QSizePolicy.Policy.Expanding)
        sp.setVerticalPolicy(QSizePolicy.Policy.Expanding)
        w.setSizePolicy(sp)
        l = QHBoxLayout()
        w.setLayout(l)
        l.addWidget(self.comments)
        tab0.l.addWidget(w, 1, 0, 1, 2)

        # Tab 1
        tab1 = self.tabs[1]

        wsp = QWidget(tab1)
        wgl = QVBoxLayout()
        wsp.setLayout(wgl)

        # right-hand side of splitter
        gb = QGroupBox(_('Change cover'), tab1)
        l = QGridLayout()
        gb.setLayout(l)
        for i, b in enumerate(self.cover.buttons[:3]):
            l.addWidget(b, 0, i, 1, 1)
            sto(b, self.cover.buttons[i+1])
        hl = QHBoxLayout()
        for b in self.cover.buttons[3:]:
            hl.addWidget(b)
        sto(self.cover.buttons[-2], self.cover.buttons[-1])
        l.addLayout(hl, 1, 0, 1, 3)
        wgl.addWidget(gb)
        wgl.addItem(QSpacerItem(10, 10, QSizePolicy.Policy.Expanding,
            QSizePolicy.Policy.Expanding))
        wgl.addItem(QSpacerItem(10, 10, QSizePolicy.Policy.Expanding,
            QSizePolicy.Policy.Expanding))
        wgl.addWidget(self.formats_manager)

        self.splitter = Splitter(Qt.Orientation.Horizontal, tab1)
        tab1.l.addWidget(self.splitter)
        self.splitter.addWidget(self.cover)
        self.splitter.addWidget(wsp)

        self.formats_manager.formats.setMaximumWidth(10000)
        self.formats_manager.formats.setIconSize(QSize(64, 64))

# }}}


class MetadataSingleDialogAlt2(MetadataSingleDialogBase):  # {{{

    one_line_comments_toolbar = True
    use_toolbutton_for_config_metadata = False

    def use_two_columns_for_custom_metadata(self):
        return False

    def do_layout(self):
        self.central_widget.clear()
        self.labels = []
        sto = QWidget.setTabOrder

        # The dialog is in three main parts. Basic and custom metadata in one
        # panel on the left over another panel containing comments, separated
        # by a splitter. The cover and format information is in a panel on the
        # right, separated by another splitter.

        main_splitter = self.main_splitter = Splitter(Qt.Orientation.Horizontal, self)
        self.central_widget.tabBar().setVisible(False)
        self.central_widget.addTab(ScrollArea(main_splitter, self), _("&Metadata"))

        # Left side (metadata & comments)
        # basic and custom split from comments
        metadata_splitter = self.metadata_splitter = Splitter(Qt.Orientation.Vertical, self)
        main_splitter.addWidget(metadata_splitter)
        metadata_widget = QWidget()
        metadata_layout = QHBoxLayout()
        metadata_layout.setContentsMargins(3, 0, 0, 0)
        metadata_widget.setLayout(metadata_layout)
        metadata_splitter.addWidget(metadata_widget)

        gb = QGroupBox(_('Basic metadata'), metadata_splitter)
        metadata_layout.addWidget(gb)

        # Basic metadata in col 0, custom in col 1
        tl = QGridLayout()
        gb.setLayout(tl)

        self.button_box_layout.insertWidget(1, self.fetch_metadata_button)
        self.button_box_layout.insertWidget(2, self.config_metadata_button)
        sto(self.button_box, self.fetch_metadata_button)
        sto(self.fetch_metadata_button, self.config_metadata_button)
        sto(self.config_metadata_button, self.title)

        def create_row(row, widget, tab_to, button=None, icon=None, span=1):
            ql = BuddyLabel(widget)
            tl.addWidget(ql, row, 1, 1, 1)
            tl.addWidget(widget, row, 2, 1, 1)
            if button is not None:
                tl.addWidget(button, row, 3, span, 1)
                if icon is not None:
                    button.setIcon(QIcon.ic(icon))
            if tab_to is not None:
                if button is not None:
                    sto(widget, button)
                    sto(button, tab_to)
                else:
                    sto(widget, tab_to)

        tl.addWidget(self.swap_title_author_button, 0, 0, 2, 1)
        tl.addWidget(self.manage_authors_button, 2, 0, 2, 1)
        tl.addWidget(self.series_editor_button, 4, 0, 1, 1)
        tl.addWidget(self.tags_editor_button, 6, 0, 1, 1)
        tl.addWidget(self.publisher_editor_button, 9, 0, 1, 1)
        tl.addWidget(self.paste_isbn_button, 12, 0, 1, 1)

        create_row(0, self.title, self.title_sort,
                   button=self.deduce_title_sort_button, span=2,
                   icon='auto_author_sort.png')
        create_row(1, self.title_sort, self.authors)
        create_row(2, self.authors, self.author_sort,
                   button=self.deduce_author_sort_button,
                   span=2, icon='auto_author_sort.png')
        create_row(3, self.author_sort, self.series)
        create_row(4, self.series, self.series_index,
                   button=self.clear_series_button, icon='trash.png')
        create_row(5, self.series_index, self.tags)
        create_row(6, self.tags, self.rating, button=self.clear_tags_button)
        create_row(7, self.rating, self.pubdate, button=self.clear_ratings_button)
        create_row(8, self.pubdate, self.publisher,
                   button=self.pubdate.clear_button, icon='trash.png')
        create_row(9, self.publisher, self.languages,
                   button=self.publisher.clear_button, icon='trash.png')
        create_row(10, self.languages, self.timestamp)
        create_row(11, self.timestamp, self.identifiers,
                   button=self.timestamp.clear_button, icon='trash.png')
        create_row(12, self.identifiers, self.comments,
                   button=self.clear_identifiers_button, icon='trash.png')
        sto(self.clear_identifiers_button, self.swap_title_author_button)
        sto(self.swap_title_author_button, self.manage_authors_button)
        sto(self.manage_authors_button, self.series_editor_button)
        sto(self.series_editor_button, self.tags_editor_button)
        sto(self.tags_editor_button, self.publisher_editor_button)
        sto(self.publisher_editor_button, self.paste_isbn_button)
        tl.addItem(QSpacerItem(1, 1, QSizePolicy.Policy.Fixed, QSizePolicy.Policy.Expanding),
                   13, 1, 1 ,1)

        # Custom metadata in col 1
        w = getattr(self, 'custom_metadata_widgets_parent', None)
        if w is not None:
            gb = QGroupBox(_('Custom metadata'), metadata_splitter)
            gbl = QVBoxLayout()
            gb.setLayout(gbl)
            sr = QScrollArea(gb)
            sr.setHorizontalScrollBarPolicy(Qt.ScrollBarPolicy.ScrollBarAlwaysOff)
            sr.setWidgetResizable(True)
            sr.setFrameStyle(QFrame.Shape.NoFrame)
            sr.setWidget(w)
            gbl.addWidget(sr)
            metadata_layout.addWidget(gb)
            sp = QSizePolicy()
            sp.setVerticalStretch(10)
            sp.setHorizontalPolicy(QSizePolicy.Policy.Minimum)
            sp.setVerticalPolicy(QSizePolicy.Policy.Expanding)
            gb.setSizePolicy(sp)
            self.set_custom_metadata_tab_order()

        # comments below metadata splitter. The mess of widgets is to get the
        # contents margins right so things line up
        cw = QWidget()
        cl = QHBoxLayout()
        cw.setLayout(cl)
        cl.setContentsMargins(3, 0, 0, 0)
        metadata_splitter.addWidget(cw)
        # Now the real stuff
        sp = QSizePolicy()
        sp.setVerticalStretch(10)
        sp.setHorizontalPolicy(QSizePolicy.Policy.Expanding)
        sp.setVerticalPolicy(QSizePolicy.Policy.Expanding)
        cw.setSizePolicy(sp)
        gb = QGroupBox(_('Comments'), metadata_splitter)
        gbl = QHBoxLayout()
        gbl.setContentsMargins(0, 0, 0, 0)
        gb.setLayout(gbl)
        cl.addWidget(gb)
        gbl.addWidget(self.comments)

        # Cover & formats on right side
        # First the cover & buttons
        cover_group_box = QGroupBox(_('Cover'), main_splitter)
        cover_layout = QVBoxLayout()
        cover_layout.setContentsMargins(0, 0, 0, 0)
        cover_group_box.setLayout(cover_layout)
        cover_layout.addWidget(self.cover)
        sto(self.manage_authors_button, self.cover.buttons[0])
        # First row of cover buttons
        hl = QHBoxLayout()
        hl.setContentsMargins(0, 0, 0, 0)
        for i, b in enumerate(self.cover.buttons[:3]):
            hl.addWidget(b)
            sto(b, self.cover.buttons[i+1])
        cover_layout.addLayout(hl)
        # Second row of cover buttons
        hl = QHBoxLayout()
        hl.setContentsMargins(0, 0, 0, 0)
        for b in self.cover.buttons[3:]:
            hl.addWidget(b)
        cover_layout.addLayout(hl)
        sto(self.cover.buttons[-2], self.cover.buttons[-1])
        # Splitter for both cover & formats boxes
        self.cover_and_formats = cover_and_formats = Splitter(Qt.Orientation.Vertical)
        # Put a very small margin on the left so that the word "Cover" doesn't
        # touch the splitter
        cover_and_formats.setContentsMargins(1, 0, 0, 0)
        cover_and_formats.addWidget(cover_group_box)
        # Add the formats manager box
        cover_and_formats.addWidget(self.formats_manager)
        sto(self.cover.buttons[-1], self.formats_manager)
        self.formats_manager.formats.setMaximumWidth(10000)
        self.formats_manager.formats.setIconSize(QSize(32, 32))
        main_splitter.addWidget(cover_and_formats)

    def save_widget_settings(self):
        gprefs['all_on_one_metadata_splitter_1_state'] = bytearray(self.metadata_splitter.saveState())
        gprefs['all_on_one_metadata_splitter_2_state'] = bytearray(self.main_splitter.saveState())
        gprefs['all_on_one_metadata_splitter_3_state'] = bytearray(self.cover_and_formats.saveState())

    def restore_widget_settings(self):
        s = gprefs.get('all_on_one_metadata_splitter_1_state')
        if s is not None:
            self.metadata_splitter.restoreState(s)
        s = gprefs.get('all_on_one_metadata_splitter_2_state')
        if s is not None:
            self.main_splitter.restoreState(s)
        s = gprefs.get('all_on_one_metadata_splitter_3_state')
        if s is not None:
            self.cover_and_formats.restoreState(s)
# }}}


editors = {'default': MetadataSingleDialog, 'alt1': MetadataSingleDialogAlt1,
           'alt2': MetadataSingleDialogAlt2}


def edit_metadata(db, row_list, current_row, parent=None, view_slot=None, edit_slot=None,
        set_current_callback=None, editing_multiple=False):
    cls = gprefs.get('edit_metadata_single_layout', '')
    if cls not in editors:
        cls = 'default'
    d = editors[cls](db, parent, editing_multiple=editing_multiple)
    try:
        d.start(row_list, current_row, view_slot=view_slot, edit_slot=edit_slot,
                set_current_callback=set_current_callback)
        return d.changed, d.rows_to_refresh
    finally:
        # possible workaround for bug reports of occasional ghost edit metadata dialog on windows
        d.deleteLater()


if __name__ == '__main__':
    from calibre.gui2 import Application
    app = Application([])
    from calibre.library import db
    db = db()
    row_list = list(range(len(db.data)))
    edit_metadata(db, row_list, 0)
