Implement a metadata comparison/merging tool

src/calibre/gui2/comments_editor.py

@@ -66,6 +66,7 @@ class EditorWidget(QWebView): # {{{
 
     def __init__(self, parent=None):
         QWebView.__init__(self, parent)
+        self.readonly = False
 
         self.comments_pat = re.compile(r'<!--.*?-->', re.DOTALL)
 
@@ -163,7 +164,11 @@ class EditorWidget(QWebView): # {{{
         self.page().linkClicked.connect(self.link_clicked)
 
         self.setHtml('')
-        self.page().setContentEditable(True)
+        self.set_readonly(False)
+
+    def set_readonly(self, what):
+        self.readonly = what
+        self.page().setContentEditable(not self.readonly)
 
     def clear_text(self, *args):
         us = self.page().undoStack()
@@ -313,7 +318,7 @@ class EditorWidget(QWebView): # {{{
         # toList() is needed because PyQt on Debian is old/broken
         for body in self.page().mainFrame().documentElement().findAll('body').toList():
             body.setAttribute('style', style)
-        self.page().setContentEditable(True)
+        self.page().setContentEditable(not self.readonly)
 
     def keyPressEvent(self, ev):
         if ev.key() in (Qt.Key_Tab, Qt.Key_Escape, Qt.Key_Backtab):
@@ -585,6 +590,7 @@ class Editor(QWidget): # {{{
         self.tabs.addTab(self.code_edit, _('HTML Source'))
         self.tabs.currentChanged[int].connect(self.change_tab)
         self.highlighter = Highlighter(self.code_edit.document())
+        self.layout().setContentsMargins(0, 0, 0, 0)
 
         # toolbar1 {{{
         self.toolbar1.addAction(self.editor.action_undo)
@@ -666,6 +672,12 @@ class Editor(QWidget): # {{{
         self.toolbar2.setVisible(False)
         self.toolbar3.setVisible(False)
 
+    def set_readonly(self, what):
+        self.editor.set_readonly(what)
+
+    def hide_tabs(self):
+        self.tabs.tabBar().setVisible(False)
+
 # }}}
 
 if __name__ == '__main__':

src/calibre/gui2/metadata/basic_widgets.py

@@ -101,7 +101,7 @@ class TitleEdit(EnLineEdit):
                     getattr(db, 'set_'+ self.TITLE_ATTR)(id_, title, notify=False,
                             commit=False)
             except (IOError, OSError) as err:
-                if getattr(err, 'errno', None) == errno.EACCES: # Permission denied
+                if getattr(err, 'errno', None) == errno.EACCES:  # Permission denied
                     import traceback
                     fname = getattr(err, 'filename', None)
                     p = 'Locked file: %s\n\n'%fname if fname else ''
@@ -273,7 +273,7 @@ class AuthorsEdit(EditWithComplete):
                 self.books_to_refresh |= db.set_authors(id_, authors, notify=False,
                     allow_case_change=True)
             except (IOError, OSError) as err:
-                if getattr(err, 'errno', None) == errno.EACCES: # Permission denied
+                if getattr(err, 'errno', None) == errno.EACCES:  # Permission denied
                     import traceback
                     fname = getattr(err, 'filename', None)
                     p = 'Locked file: %s\n\n'%fname if fname else ''
@@ -485,7 +485,7 @@ class SeriesEdit(EditWithComplete):
     def initialize(self, db, id_):
         self.books_to_refresh = set([])
         all_series = db.all_series()
-        all_series.sort(key=lambda x : sort_key(x[1]))
+        all_series.sort(key=lambda x: sort_key(x[1]))
         self.update_items_cache([x[1] for x in all_series])
         series_id = db.series_id(id_, index_is_id=True)
         inval = ''
@@ -586,7 +586,7 @@ class SeriesIndexEdit(QDoubleSpinBox):
 
 # }}}
 
-class BuddyLabel(QLabel): # {{{
+class BuddyLabel(QLabel):  # {{{
 
     def __init__(self, buddy):
         QLabel.__init__(self, buddy.LABEL)
@@ -698,11 +698,11 @@ class FormatsManager(QWidget):
         self.formats.setIconSize(QSize(32, 32))
         self.formats.setMaximumWidth(200)
 
-        l.addWidget(self.cover_from_format_button,    0, 0, 1, 1)
+        l.addWidget(self.cover_from_format_button, 0, 0, 1, 1)
         l.addWidget(self.metadata_from_format_button, 2, 0, 1, 1)
-        l.addWidget(self.add_format_button,           0, 2, 1, 1)
+        l.addWidget(self.add_format_button, 0, 2, 1, 1)
-        l.addWidget(self.remove_format_button,        2, 2, 1, 1)
+        l.addWidget(self.remove_format_button, 2, 2, 1, 1)
-        l.addWidget(self.formats,                     0, 1, 3, 1)
+        l.addWidget(self.formats, 0, 1, 3, 1)
 
         self.temp_files = []
 
@@ -882,7 +882,7 @@ class FormatsManager(QWidget):
         self.temp_files = []
 # }}}
 
-class Cover(ImageView): # {{{
+class Cover(ImageView):  # {{{
 
     download_cover = pyqtSignal()
 
@@ -1052,7 +1052,7 @@ class Cover(ImageView): # {{{
 
 # }}}
 
-class CommentsEdit(Editor): # {{{
+class CommentsEdit(Editor):  # {{{
 
     @dynamic_property
     def current_val(self):
@@ -1076,7 +1076,7 @@ class CommentsEdit(Editor): # {{{
         return True
 # }}}
 
-class RatingEdit(QSpinBox): # {{{
+class RatingEdit(QSpinBox):  # {{{
     LABEL = _('&Rating:')
     TOOLTIP = _('Rating of this book. 0-5 stars')
 
@@ -1120,7 +1120,7 @@ class RatingEdit(QSpinBox): # {{{
 
 # }}}
 
-class TagsEdit(EditWithComplete): # {{{
+class TagsEdit(EditWithComplete):  # {{{
     LABEL = _('Ta&gs:')
     TOOLTIP = '<p>'+_('Tags categorize the book. This is particularly '
             'useful while searching. <br><br>They can be any words '
@@ -1174,7 +1174,6 @@ class TagsEdit(EditWithComplete): # {{{
             self.current_val = d.tags
             self.all_items = db.all_tags()
 
-
     def commit(self, db, id_):
         self.books_to_refresh |= db.set_tags(
                 id_, self.current_val, notify=False, commit=False,
@@ -1183,7 +1182,7 @@ class TagsEdit(EditWithComplete): # {{{
 
 # }}}
 
-class LanguagesEdit(LE): # {{{
+class LanguagesEdit(LE):  # {{{
 
     LABEL = _('&Languages:')
     TOOLTIP = _('A comma separated list of languages for this book')
@@ -1194,8 +1193,10 @@ class LanguagesEdit(LE): # {{{
 
     @dynamic_property
     def current_val(self):
-        def fget(self): return self.lang_codes
+        def fget(self):
-        def fset(self, val): self.lang_codes = val
+            return self.lang_codes
+        def fset(self, val):
+            self.lang_codes = val
         return property(fget=fget, fset=fset)
 
     def initialize(self, db, id_):
@@ -1221,7 +1222,7 @@ class LanguagesEdit(LE): # {{{
         return True
 # }}}
 
-class IdentifiersEdit(QLineEdit): # {{{
+class IdentifiersEdit(QLineEdit):  # {{{
     LABEL = _('I&ds:')
     BASE_TT = _('Edit the identifiers for this book. '
             'For example: \n\n%s')%(
@@ -1309,7 +1310,7 @@ class IdentifiersEdit(QLineEdit): # {{{
 
 # }}}
 
-class ISBNDialog(QDialog) : # {{{
+class ISBNDialog(QDialog):  # {{{
 
     def __init__(self, parent, txt):
         QDialog.__init__(self, parent)
@@ -1320,7 +1321,7 @@ class ISBNDialog(QDialog) : # {{{
         l.addWidget(w, 0, 0, 1, 2)
         w = QLabel(_('ISBN:'))
         l.addWidget(w, 1, 0, 1, 1)
-        self.line_edit = w = QLineEdit();
+        self.line_edit = w = QLineEdit()
         w.setText(txt)
         w.selectAll()
         w.textChanged.connect(self.checkText)
@@ -1361,7 +1362,7 @@ class ISBNDialog(QDialog) : # {{{
 
 # }}}
 
-class PublisherEdit(EditWithComplete): # {{{
+class PublisherEdit(EditWithComplete):  # {{{
     LABEL = _('&Publisher:')
 
     def __init__(self, parent):
@@ -1388,7 +1389,7 @@ class PublisherEdit(EditWithComplete): # {{{
     def initialize(self, db, id_):
         self.books_to_refresh = set([])
         all_publishers = db.all_publishers()
-        all_publishers.sort(key=lambda x : sort_key(x[1]))
+        all_publishers.sort(key=lambda x: sort_key(x[1]))
         self.update_items_cache([x[1] for x in all_publishers])
         publisher_id = db.publisher_id(id_, index_is_id=True)
         inval = ''
@@ -1421,7 +1422,7 @@ class DateEdit(QDateTimeEdit):
     ATTR = 'timestamp'
     TWEAK = 'gui_timestamp_display_format'
 
-    def __init__(self, parent):
+    def __init__(self, parent, create_clear_button=True):
         QDateTimeEdit.__init__(self, parent)
         self.setToolTip(self.TOOLTIP)
         self.setWhatsThis(self.TOOLTIP)
@@ -1435,10 +1436,11 @@ class DateEdit(QDateTimeEdit):
         self.setCalendarWidget(self.cw)
         self.setMinimumDateTime(UNDEFINED_QDATETIME)
         self.setSpecialValueText(_('Undefined'))
-        self.clear_button = QToolButton(parent)
+        if create_clear_button:
-        self.clear_button.setIcon(QIcon(I('trash.png')))
+            self.clear_button = QToolButton(parent)
-        self.clear_button.setToolTip(_('Clear date'))
+            self.clear_button.setIcon(QIcon(I('trash.png')))
-        self.clear_button.clicked.connect(self.reset_date)
+            self.clear_button.setToolTip(_('Clear date'))
+            self.clear_button.clicked.connect(self.reset_date)
 
     def reset_date(self, *args):
         self.current_val = None

src/calibre/gui2/metadata/diff.py

@@ -6,5 +6,477 @@ from __future__ import (unicode_literals, division, absolute_import,
 __license__ = 'GPL v3'
 __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 
+import os
+from collections import OrderedDict, namedtuple
+from functools import partial
 
+from PyQt4.Qt import (
+    QDialog, QWidget, QGridLayout, QLineEdit, QLabel, QToolButton, QIcon,
+    QVBoxLayout, QDialogButtonBox, QApplication, pyqtSignal, QFont, QPixmap,
+    QSize, QPainter, Qt, QColor, QPen, QSizePolicy, QScrollArea, QFrame)
+
+from calibre import fit_image
+from calibre.ebooks.metadata import title_sort, authors_to_sort_string
+from calibre.gui2 import pixmap_to_data, gprefs
+from calibre.gui2.comments_editor import Editor
+from calibre.gui2.metadata.basic_widgets import PubdateEdit, RatingEdit
+from calibre.ptempfile import PersistentTemporaryFile
+from calibre.utils.date import UNDEFINED_DATE
+
+Widgets = namedtuple('Widgets', 'new old label button')
+
+# Widgets {{{
+
+class LineEdit(QLineEdit):
+
+    changed = pyqtSignal()
+
+    def __init__(self, field, is_new, parent, metadata, extra):
+        QLineEdit.__init__(self, parent)
+        self.is_new = is_new
+        self.field = field
+        self.metadata = metadata
+        if not is_new:
+            self.setReadOnly(True)
+        self.textChanged.connect(self.changed)
+
+    def from_mi(self, mi):
+        val = mi.get(self.field, default='') or ''
+        ism = self.metadata['is_multiple']
+        if ism:
+            if not val:
+                val = ''
+            else:
+                val = ism['list_to_ui'].join(val)
+        self.setText(val)
+        self.setCursorPosition(0)
+
+    def to_mi(self, mi):
+        val = unicode(self.text()).strip()
+        ism = self.metadata['is_multiple']
+        if ism:
+            if not val:
+                val = []
+            else:
+                val = [x.strip() for x in val.split(ism['list_to_ui']) if x.strip()]
+        mi.set(self.field, val)
+        if self.field == 'title':
+            mi.set('title_sort', title_sort(val, lang=mi.language))
+        elif self.field == 'authors':
+            mi.set('author_sort', authors_to_sort_string(val))
+
+    @dynamic_property
+    def current_val(self):
+        def fget(self):
+            return unicode(self.text())
+        def fset(self, val):
+            self.setText(val)
+            self.setCursorPosition(0)
+        return property(fget=fget, fset=fset)
+
+    @property
+    def is_blank(self):
+        return not self.current_val.strip()
+
+class RatingsEdit(RatingEdit):
+
+    changed = pyqtSignal()
+
+    def __init__(self, field, is_new, parent, metadata, extra):
+        RatingEdit.__init__(self, parent)
+        self.is_new = is_new
+        self.field = field
+        self.metadata = metadata
+        self.valueChanged.connect(self.changed)
+        if not is_new:
+            self.setReadOnly(True)
+
+    def from_mi(self, mi):
+        val = (mi.get(self.field, default=0) or 0)/2
+        self.setValue(val)
+
+    def to_mi(self, mi):
+        mi.set(self.field, self.value() * 2)
+
+    @property
+    def is_blank(self):
+        return self.value() == 0
+
+class DateEdit(PubdateEdit):
+
+    changed = pyqtSignal()
+
+    def __init__(self, field, is_new, parent, metadata, extra):
+        PubdateEdit.__init__(self, parent, create_clear_button=False)
+        self.is_new = is_new
+        self.field = field
+        self.metadata = metadata
+        self.setDisplayFormat(extra)
+        self.dateTimeChanged.connect(self.changed)
+        if not is_new:
+            self.setReadOnly(True)
+
+    def from_mi(self, mi):
+        self.current_val = mi.get(self.field, default=None)
+
+    def to_mi(self, mi):
+        mi.set(self.field, self.current_val)
+
+    @property
+    def is_blank(self):
+        return self.current_val == UNDEFINED_DATE
+
+class SeriesEdit(LineEdit):
+
+    def from_mi(self, mi):
+        series = mi.get(self.field, default='')
+        series_index = mi.get(self.field + '_index', default=1.0)
+        val = ''
+        if series:
+            val = '%s [%s]' % (series, mi.format_series_index(series_index))
+        self.setText(val)
+        self.setCursorPosition(0)
+
+    def to_mi(self, mi):
+        val = unicode(self.text()).strip()
+        try:
+            series_index = float(val.rpartition('[')[-1].rstrip(']').strip())
+        except:
+            series_index = 1.0
+        series = val.rpartition('[')[0].strip() or None
+        mi.set(self.field, series)
+        mi.set(self.field + '_index', series_index)
+
+class IdentifiersEdit(LineEdit):
+
+    def from_mi(self, mi):
+        val = ('%s:%s' % (k, v) for k, v in mi.identifiers.iteritems())
+        self.setText(', '.join(val))
+
+    def to_mi(self, mi):
+        parts = (x.strip() for x in self.current_val.split(',') if x.strip())
+        val = {x.partition(':')[0].strip():x.partition(':')[-1].strip() for x in parts}
+        mi.set_identifiers({k:v for k, v in val.iteritems() if k and v})
+
+class CommentsEdit(Editor):
+
+    changed = pyqtSignal()
+
+    def __init__(self, field, is_new, parent, metadata, extra):
+        Editor.__init__(self, parent, one_line_toolbar=False)
+        self.is_new = is_new
+        self.field = field
+        self.metadata = metadata
+        self.hide_tabs()
+        if not is_new:
+            self.hide_toolbars()
+            self.set_readonly(True)
+
+    @dynamic_property
+    def current_val(self):
+        def fget(self):
+            return self.html
+        def fset(self, val):
+            self.html = val or ''
+            self.changed.emit()
+        return property(fget=fget, fset=fset)
+
+    def from_mi(self, mi):
+        val = mi.get(self.field, default='')
+        self.current_val = val
+
+    def to_mi(self, mi):
+        mi.set(self.field, self.current_val)
+
+    def sizeHint(self):
+        return QSize(450, 200)
+
+    @property
+    def is_blank(self):
+        return not self.current_val.strip()
+
+class CoverView(QWidget):
+
+    changed = pyqtSignal()
+
+    def __init__(self, field, is_new, parent, metadata, extra):
+        QWidget.__init__(self, parent)
+        self.is_new = is_new
+        self.field = field
+        self.metadata = metadata
+        self.pixmap = None
+        self.blank = QPixmap(I('blank.png'))
+        self.setSizePolicy(QSizePolicy.Preferred, QSizePolicy.GrowFlag|QSizePolicy.ExpandFlag)
+        self.sizePolicy().setHeightForWidth(True)
+
+    @property
+    def is_blank(self):
+        return self.pixmap is None
+
+    @dynamic_property
+    def current_val(self):
+        def fget(self):
+            return self.pixmap
+        def fset(self, val):
+            self.pixmap = val
+            self.changed.emit()
+            self.update()
+        return property(fget=fget, fset=fset)
+
+    def from_mi(self, mi):
+        p = getattr(mi, 'cover', None)
+        if p and os.path.exists(p):
+            pmap = QPixmap()
+            with open(p, 'rb') as f:
+                pmap.loadFromData(f.read())
+            if not pmap.isNull():
+                self.pixmap = pmap
+                self.update()
+                self.changed.emit()
+                return
+        cd = getattr(mi, 'cover_data', (None, None))
+        if cd and cd[1]:
+            pmap = QPixmap()
+            pmap.loadFromData(cd[1])
+            if not pmap.isNull():
+                self.pixmap = pmap
+                self.update()
+                self.changed.emit()
+                return
+        self.pixmap = None
+        self.update()
+        self.changed.emit()
+
+    def to_mi(self, mi):
+        mi.cover, mi.cover_data = None, (None, None)
+        if self.pixmap is not None and not self.pixmap.isNull():
+            with PersistentTemporaryFile('.jpg') as pt:
+                pt.write(pixmap_to_data(self.pixmap))
+                mi.cover = pt.name
+
+    def sizeHint(self):
+        return QSize(225, 300)
+
+    def paintEvent(self, event):
+        pmap = self.blank if self.pixmap is None or self.pixmap.isNull() else self.pixmap
+        target = self.rect()
+        scaled, width, height = fit_image(pmap.width(), pmap.height(), target.width(), target.height())
+        target.setRect(target.x(), target.y(), width, height)
+        p = QPainter(self)
+        p.setRenderHints(QPainter.Antialiasing | QPainter.SmoothPixmapTransform)
+        p.drawPixmap(target, pmap)
+
+        if self.pixmap is not None and not self.pixmap.isNull():
+            sztgt = target.adjusted(0, 0, 0, -4)
+            f = p.font()
+            f.setBold(True)
+            p.setFont(f)
+            sz = u'\u00a0%d x %d\u00a0'%(self.pixmap.width(), self.pixmap.height())
+            flags = Qt.AlignBottom|Qt.AlignRight|Qt.TextSingleLine
+            szrect = p.boundingRect(sztgt, flags, sz)
+            p.fillRect(szrect.adjusted(0, 0, 0, 4), QColor(0, 0, 0, 200))
+            p.setPen(QPen(QColor(255,255,255)))
+            p.drawText(sztgt, flags, sz)
+        p.end()
+# }}}
+
+class CompareSingle(QWidget):
+
+    def __init__(
+            self, field_metadata, parent=None, revert_tooltip=None,
+            datetime_fmt='MMMM yyyy', blank_as_equal=True,
+            fields=('title', 'authors', 'series', 'tags', 'rating', 'publisher', 'pubdate', 'identifiers', 'comments', 'cover')):
+        QWidget.__init__(self, parent)
+        self.l = l = QGridLayout()
+        l.setContentsMargins(0, 0, 0, 0)
+        self.setLayout(l)
+        revert_tooltip = revert_tooltip or _('Revert %s')
+        self.current_mi = None
+        self.changed_font = QFont(QApplication.font())
+        self.changed_font.setBold(True)
+        self.changed_font.setItalic(True)
+        self.blank_as_equal = blank_as_equal
+
+        self.widgets = OrderedDict()
+        row = 0
+
+        for field in fields:
+            m = field_metadata[field]
+            dt = m['datatype']
+            extra = None
+            if 'series' in {field, dt}:
+                cls = SeriesEdit
+            elif field == 'identifiers':
+                cls = IdentifiersEdit
+            elif 'comments' in {field, dt}:
+                cls = CommentsEdit
+            elif 'rating' in {field, dt}:
+                cls = RatingsEdit
+            elif dt == 'datetime':
+                extra = datetime_fmt
+                cls = DateEdit
+            elif field == 'cover':
+                cls = CoverView
+            elif dt in {'text', 'enum'}:
+                cls = LineEdit
+            else:
+                continue
+            neww = cls(field, True, self, m, extra)
+            neww.changed.connect(partial(self.changed, field))
+            oldw = cls(field, False, self, m, extra)
+            newl = QLabel('&%s:' % m['name'])
+            newl.setBuddy(neww)
+            button = QToolButton(self)
+            button.setIcon(QIcon(I('back.png')))
+            button.clicked.connect(partial(self.revert, field))
+            button.setToolTip(revert_tooltip % m['name'])
+            self.widgets[field] = Widgets(neww, oldw, newl, button)
+            for i, w in enumerate((newl, neww, button, oldw)):
+                c = i if i < 2 else i + 1
+                if w is oldw:
+                    c += 1
+                l.addWidget(w, row, c)
+            row += 1
+
+        self.sep = f = QFrame(self)
+        f.setFrameShape(f.VLine)
+        l.addWidget(f, 0, 2, row, 1)
+        self.sep2 = f = QFrame(self)
+        f.setFrameShape(f.VLine)
+        l.addWidget(f, 0, 4, row, 1)
+
+    def changed(self, field):
+        w = self.widgets[field]
+        if w.new.current_val != w.old.current_val and (not self.blank_as_equal or not w.new.is_blank):
+            w.label.setFont(self.changed_font)
+        else:
+            w.label.setFont(QApplication.font())
+
+    def revert(self, field):
+        widgets = self.widgets[field]
+        neww, oldw = widgets[:2]
+        neww.current_val = oldw.current_val
+
+    def __call__(self, oldmi, newmi):
+        self.current_mi = newmi
+        self.initial_vals = {}
+        for field, widgets in self.widgets.iteritems():
+            widgets.old.from_mi(oldmi)
+            widgets.new.from_mi(newmi)
+            self.initial_vals[field] = widgets.new.current_val
+
+    def apply_changes(self):
+        changed = False
+        for field, widgets in self.widgets.iteritems():
+            val = widgets.new.current_val
+            if val != self.initial_vals[field]:
+                widgets.new.to_mi(self.current_mi)
+                changed = True
+        return changed
+
+class CompareMany(QDialog):
+
+    def __init__(self, ids, get_metadata, field_metadata, parent=None, window_title=None, skip_button_tooltip=None,
+                 accept_all_tooltip=None, reject_all_tooltip=None, **kwargs):
+        QDialog.__init__(self, parent)
+        self.l = l = QVBoxLayout()
+        self.setLayout(l)
+        self.setWindowIcon(QIcon(I('auto_author_sort.png')))
+        self.get_metadata = get_metadata
+        self.ids = list(ids)
+        self.total = len(self.ids)
+        self.accepted = OrderedDict()
+        self.window_title = window_title or _('Compare metadata')
+
+        self.compare_widget = CompareSingle(field_metadata, parent=parent, **kwargs)
+        self.sa = sa = QScrollArea()
+        l.addWidget(sa)
+        sa.setWidget(self.compare_widget)
+        sa.setWidgetResizable(True)
+
+        self.bb = bb = QDialogButtonBox(QDialogButtonBox.Cancel)
+        bb.rejected.connect(self.reject)
+        self.aarb = b = bb.addButton(_('&Accept all remaining'), bb.YesRole)
+        if accept_all_tooltip:
+            b.setToolTip(accept_all_tooltip)
+        b.clicked.connect(self.accept_all_remaining)
+        self.rarb = b = bb.addButton(_('Re&ject all remaining'), bb.NoRole)
+        if reject_all_tooltip:
+            b.setToolTip(reject_all_tooltip)
+        b.clicked.connect(self.reject_all_remaining)
+        self.sb = b = bb.addButton(_('&Reject'), bb.ActionRole)
+        b.clicked.connect(partial(self.next_item, False))
+        if skip_button_tooltip:
+            b.setToolTip(skip_button_tooltip)
+        self.nb = b = bb.addButton(_('&Next'), bb.ActionRole)
+        b.setIcon(QIcon(I('forward.png')))
+        b.clicked.connect(partial(self.next_item, True))
+        b.setDefault(True)
+        l.addWidget(bb)
+
+        self.next_item(True)
+
+        desktop = QApplication.instance().desktop()
+        geom = desktop.availableGeometry(parent or self)
+        width = max(700, min(950, geom.width()-50))
+        height = max(650, min(1000, geom.height()-100))
+        self.resize(QSize(width, height))
+        geom = gprefs.get('diff_dialog_geom', None)
+        if geom is not None:
+            self.restoreGeometry(geom)
+
+    def accept(self):
+        gprefs.set('diff_dialog_geom', bytearray(self.saveGeometry()))
+        super(CompareMany, self).accept()
+
+    def reject(self):
+        gprefs.set('diff_dialog_geom', bytearray(self.saveGeometry()))
+        super(CompareMany, self).reject()
+
+    @property
+    def current_mi(self):
+        return self.compare_widget.current_mi
+
+    def next_item(self, accept):
+        if not self.ids:
+            return self.accept()
+        if self.current_mi is not None:
+            changed = self.compare_widget.apply_changes()
+        self.setWindowTitle(self.window_title + _(' [%(num)d of %(tot)d]') % dict(
+            num=(self.total - len(self.ids) + 1), tot=self.total))
+        oldmi, newmi = self.get_metadata(self.ids[0])
+        old_id = self.ids.pop(0)
+        if self.current_mi is not None:
+            self.accepted[old_id] = (changed, self.current_mi) if accept else (False, None)
+        self.compare_widget(oldmi, newmi)
+
+    def accept_all_remaining(self):
+        self.next_item(True)
+        for id_ in self.ids:
+            oldmi, newmi = self.get_metadata(id_)
+            self.accepted[id_] = (False, newmi)
+        self.ids = []
+        self.accept()
+
+    def reject_all_remaining(self):
+        self.next_item(False)
+        for id_ in self.ids:
+            oldmi, newmi = self.get_metadata(id_)
+            self.accepted[id_] = (False, None)
+        self.ids = []
+        self.accept()
+
+if __name__ == '__main__':
+    app = QApplication([])
+    from calibre.library import db
+    db = db()
+    ids = sorted(db.all_ids(), reverse=True)
+    ids = [(x, ids[i+1]) for i, x in enumerate(ids[0::2])]
+    gm = partial(db.get_metadata, index_is_id=True, get_cover=True, cover_as_data=True)
+    get_metadata = lambda x:map(gm, ids[x])
+    d = CompareMany(list(xrange(len(ids))), get_metadata, db.field_metadata)
+    if d.exec_() == d.Accepted:
+        for changed, mi in d.accepted.itervalues():
+            if changed and mi is not None:
+                print (mi)
 

src/calibre/library/field_metadata.py

@@ -252,7 +252,7 @@ class FieldMetadata(dict):
                            'datatype':'int',
                            'is_multiple':{},
                            'kind':'field',
-                           'name':None,
+                           'name':_('Cover'),
                            'search_terms':['cover'],
                            'is_custom':False,
                            'is_category':False,