Edit Book: Add a button to show diffs after any Polish action

src/calibre/gui2/tweak_book/boss.py

@@ -38,6 +38,8 @@ from calibre.gui2.tweak_book.editor.insert_resource import get_resource_data, Ne
 from calibre.gui2.tweak_book.preferences import Preferences
 from calibre.gui2.tweak_book.widgets import RationalizeFolders, MultiSplit
 
+_diff_dialogs = []
+
 def get_container(*args, **kwargs):
     kwargs['tweak_mode'] = True
     container = _gc(*args, **kwargs)
@@ -384,12 +386,35 @@ class Boss(QObject):
         d.l.addWidget(d.e)
         d.e.setHtml(report)
         d.bb = QDialogButtonBox(QDialogButtonBox.Close)
+        b = d.b = d.bb.addButton(_('See what changed'), d.bb.AcceptRole)
+        b.setIcon(QIcon(I('diff.png')))
+        b.clicked.connect(partial(self.show_current_diff, allow_revert=True))
         d.l.addWidget(d.bb)
         d.bb.rejected.connect(d.reject)
         d.bb.accepted.connect(d.accept)
         d.resize(600, 400)
         d.exec_()
 
+    def create_diff_dialog(self, revert_msg=_('&Revert changes')):
+        global _diff_dialogs
+        from calibre.gui2.tweak_book.diff.main import Diff
+        d = Diff(revert_button_msg=revert_msg, parent=self.gui)
+        [x.break_cycles() for x in _diff_dialogs if not x.isVisible()]
+        _diff_dialogs = [x for x in _diff_dialogs if x.isVisible()] + [d]
+        d.show(), d.raise_(), d.setFocus(Qt.OtherFocusReason)
+        return d
+
+    def show_current_diff(self, allow_revert=True):
+        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(self.global_undo.previous_container, self.global_undo.current_container)
+
+    def revert_requested(self, container):
+        nc = self.global_undo.revert_to(container)
+        set_current_container(nc)
+        self.apply_container_update_to_gui()
+
     # Renaming {{{
 
     def rationalize_folders(self):

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

@@ -11,7 +11,7 @@ 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)
+    QCursor, QEventLoop, QKeySequence, pyqtSignal)
 
 from calibre.ebooks.oeb.polish.container import Container
 from calibre.gui2 import info_dialog
@@ -128,9 +128,12 @@ def ebook_diff(path1, path2):
 
 class Diff(Dialog):
 
-    def __init__(self, parent=None):
+    revert_requested = pyqtSignal()
+
+    def __init__(self, revert_button_msg=None, parent=None):
         self.context = 3
         self.apply_diff_calls = []
+        self.revert_button_msg = revert_button_msg
         Dialog.__init__(self, _('Differences between books'), 'diff-dialog', parent=parent)
 
     def sizeHint(self):
@@ -187,10 +190,23 @@ class Diff(Dialog):
         l.addWidget(b, l.rowCount() - 1, l.columnCount(), 1, 1)
 
         self.bb.setStandardButtons(self.bb.Close)
+        if self.revert_button_msg is not None:
+            self.rvb = b = self.bb.addButton(self.revert_button_msg, self.bb.RejectRole)
+            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.view.setFocus(Qt.OtherFocusReason)
 
+    def break_cycles(self):
+        self.view = None
+        for x in ('revert_requested',):
+            try:
+                getattr(self, x).disconnect()
+            except:
+                pass
+
     def do_search(self, reverse):
         text = unicode(self.search.text())
         if not text.strip():

src/calibre/gui2/tweak_book/undo.py

@@ -33,6 +33,10 @@ class GlobalUndoHistory(object):
     def current_container(self):
         return self.states[self.pos].container
 
+    @property
+    def previous_container(self):
+        return self.states[self.pos - 1].container
+
     def open_book(self, container):
         self.states = [State(container)]
         self.pos = 0
@@ -76,6 +80,12 @@ class GlobalUndoHistory(object):
             self.pos += 1
             return self.current_container
 
+    def revert_to(self, container):
+        for i, state in enumerate(self.states):
+            if state.container is container:
+                self.pos = i
+                return container
+
     @property
     def can_undo(self):
         return self.pos > 0