Describe left and right panels at the bottom of the diff view

src/calibre/gui2/init.py

@@ -486,7 +486,7 @@ class LayoutMixin(object):  # {{{
         path1, path2 = db.format_abspath(book_id, ofmt), db.format_abspath(book_id, fmt)
         from calibre.gui2.tweak_book.diff.main import compare_books
         compare_books(path1, path2, parent=self, revert_msg=_('Restore %s') % ofmt, revert_callback=partial(
-            self.iactions['Remove Books'].restore_format, book_id, ofmt))
+            self.iactions['Remove Books'].restore_format, book_id, ofmt), names=(ofmt, fmt))
 
     def save_layout_state(self):
         for x in ('library', 'memory', 'card_a', 'card_b'):

src/calibre/gui2/tweak_book/boss.py

@@ -518,7 +518,9 @@ class Boss(QObject):
         self.commit_all_editors_to_container()
         d = self.create_diff_dialog()
         d.revert_requested.connect(partial(self.revert_requested, self.global_undo.previous_container))
-        d.container_diff(to_container or self.global_undo.previous_container, self.global_undo.current_container)
+        other = to_container or self.global_undo.previous_container
+        d.container_diff(other, self.global_undo.current_container,
+                         names=(self.global_undo.label_for_container(other), self.global_undo.label_for_container(self.global_undo.current_container)))
 
     def compare_book(self):
         self.commit_all_editors_to_container()
@@ -529,7 +531,8 @@ class Boss(QObject):
             with TemporaryDirectory('_compare') as tdir:
                 other = _gc(path[0], tdir=tdir, tweak_mode=True)
                 d = self.create_diff_dialog(revert_msg=None)
-                d.container_diff(other, c)
+                d.container_diff(other, c,
+                                 names=(_('Other book'), _('Current book')))
 
     def revert_requested(self, container):
         self.commit_all_editors_to_container()

src/calibre/gui2/tweak_book/diff/main.py

@@ -12,7 +12,7 @@ from functools import partial
 from PyQt4.Qt import (
     QGridLayout, QToolButton, QIcon, QRadioButton, QMenu, QApplication, Qt,
     QSize, QWidget, QLabel, QStackedLayout, QPainter, QRect, QVBoxLayout,
-    QCursor, QEventLoop, QKeySequence, pyqtSignal, QTimer)
+    QCursor, QEventLoop, QKeySequence, pyqtSignal, QTimer, QHBoxLayout)
 
 from calibre.ebooks.oeb.polish.container import Container
 from calibre.ebooks.oeb.polish.utils import guess_type
@@ -213,18 +213,18 @@ class Diff(Dialog):
         b.clicked.connect(partial(self.view.next_change, -1))
         b.setToolTip(_('Go to previous change') + ' [p]')
         b.setText(_('&Previous change')), b.setToolButtonStyle(Qt.ToolButtonTextBesideIcon)
-        l.addWidget(b, r, l.columnCount(), 1, 1)
+        l.addWidget(b, r, 0)
 
         self.bn = b = QToolButton(self)
         b.setIcon(QIcon(I('forward.png')))
         b.clicked.connect(partial(self.view.next_change, 1))
         b.setToolTip(_('Go to next change') + ' [n]')
         b.setText(_('&Next change')), b.setToolButtonStyle(Qt.ToolButtonTextBesideIcon)
-        l.addWidget(b, r, l.columnCount(), 1, 1)
+        l.addWidget(b, r, 1)
 
         self.search = s = HistoryLineEdit2(self)
         s.initialize('diff_search_history')
-        l.addWidget(s, r, l.columnCount(), 1, 1)
+        l.addWidget(s, r, 2)
         s.setPlaceholderText(_('Search for text'))
         s.returnPressed.connect(partial(self.do_search, False))
         self.sbn = b = QToolButton(self)
@@ -232,19 +232,19 @@ class Diff(Dialog):
         b.clicked.connect(partial(self.do_search, False))
         b.setToolTip(_('Find next match'))
         b.setText(_('Next &match')), b.setToolButtonStyle(Qt.ToolButtonTextBesideIcon)
-        l.addWidget(b, l.rowCount() - 1, l.columnCount(), 1, 1)
+        l.addWidget(b, r, 3)
         self.sbp = b = QToolButton(self)
         b.setIcon(QIcon(I('arrow-up.png')))
         b.clicked.connect(partial(self.do_search, True))
         b.setToolTip(_('Find previous match'))
         b.setText(_('P&revious match')), b.setToolButtonStyle(Qt.ToolButtonTextBesideIcon)
-        l.addWidget(b, l.rowCount() - 1, l.columnCount(), 1, 1)
+        l.addWidget(b, r, 4)
         self.lb = b = QRadioButton(_('Left panel'), self)
         b.setToolTip(_('Perform search in the left panel'))
-        l.addWidget(b, l.rowCount() - 1, l.columnCount(), 1, 1)
+        l.addWidget(b, r, 5)
         self.rb = b = QRadioButton(_('Right panel'), self)
         b.setToolTip(_('Perform search in the right panel'))
-        l.addWidget(b, l.rowCount() - 1, l.columnCount(), 1, 1)
+        l.addWidget(b, r, 6)
         b.setChecked(True)
         self.pb = b = QToolButton(self)
         b.setIcon(QIcon(I('config.png')))
@@ -259,7 +259,12 @@ class Diff(Dialog):
         cm.addAction(_('Show all text'), partial(self.change_context, None))
         m.addAction(_('Beautify files before comparing them'), partial(self.change_beautify, True))
         m.addMenu(cm)
-        l.addWidget(b, l.rowCount() - 1, l.columnCount(), 1, 1)
+        l.addWidget(b, r, 7)
+
+        self.hl = QHBoxLayout()
+        l.addLayout(self.hl, l.rowCount(), 0, 1, -1)
+        self.names = QLabel('')
+        self.hl.addWidget(self.names, r)
 
         self.bb.setStandardButtons(self.bb.Close)
         if self.revert_button_msg is not None:
@@ -267,7 +272,7 @@ class Diff(Dialog):
             b.setIcon(QIcon(I('edit-undo.png')))
             b.clicked.connect(self.revert_requested)
         self.bb.button(self.bb.Close).setDefault(True)
-        l.addWidget(self.bb, l.rowCount(), 0, 1, -1)
+        self.hl.addWidget(self.bb, r)
 
         self.view.setFocus(Qt.OtherFocusReason)
 
@@ -318,14 +323,22 @@ class Diff(Dialog):
         self.stacks.setCurrentIndex(1)
         QApplication.restoreOverrideCursor()
 
-    def ebook_diff(self, path1, path2):
+    def set_names(self, names):
+        if isinstance(names, tuple):
+            self.names.setText('%s <--> %s' % names)
+        else:
+            self.names.setText('')
+
+    def ebook_diff(self, path1, path2, names=None):
+        self.set_names(names)
         with self:
             identical = self.apply_diff(_('The books are identical'), *ebook_diff(path1, path2))
             self.view.finalize()
         if identical:
             self.reject()
 
-    def container_diff(self, left, right, identical_msg=None):
+    def container_diff(self, left, right, identical_msg=None, names=None):
+        self.set_names(names)
         with self:
             identical = self.apply_diff(identical_msg or _('No changes found'), *container_diff(left, right))
             self.view.finalize()
@@ -399,11 +412,11 @@ class Diff(Dialog):
                 return
             return Dialog.keyPressEvent(self, ev)
 
-def compare_books(path1, path2, revert_msg=None, revert_callback=None, parent=None):
+def compare_books(path1, path2, revert_msg=None, revert_callback=None, parent=None, names=None):
     d = Diff(parent=parent, revert_button_msg=revert_msg)
     if revert_msg is not None:
         d.revert_requested.connect(revert_callback)
-    QTimer.singleShot(0, partial(d.ebook_diff, path1, path2))
+    QTimer.singleShot(0, partial(d.ebook_diff, path1, path2, names=names))
     d.exec_()
     try:
         d.revert_requested.disconnect()

src/calibre/gui2/tweak_book/undo.py

@@ -43,15 +43,7 @@ class GlobalUndoHistory(QAbstractListModel):
 
     def data(self, index, role=Qt.DisplayRole):
         if role == Qt.DisplayRole:
-            row = index.row()
+            return QVariant(self.label_for_row(index.row()))
-            msg = self.states[row].message
-            if self.pos == row:
-                msg = _('Current state')
-            elif not msg:
-                msg = _('[Unnamed state]')
-            else:
-                msg = _('Before %s') % msg
-            return QVariant(msg)
         if role == Qt.FontRole and index.row() == self.pos:
             f = QApplication.instance().font()
             f.setBold(True)
@@ -60,6 +52,21 @@ class GlobalUndoHistory(QAbstractListModel):
             return QVariant(self.states[index.row()])
         return NONE
 
+    def label_for_row(self, row):
+        msg = self.states[row].message
+        if self.pos == row:
+            msg = _('Current state')
+        elif not msg:
+            msg = _('[Unnamed state]')
+        else:
+            msg = _('Before %s') % msg
+        return msg
+
+    def label_for_container(self, container):
+        for i, state in enumerate(self.states):
+            if state.container is container:
+                return self.label_for_row(i)
+
     @property
     def current_container(self):
         return self.states[self.pos].container