Show the view changes button only if there are some actual changes

src/calibre/ebooks/oeb/polish/css.py

@@ -147,3 +147,4 @@ def remove_unused_css(container, report):
         report(_('Removed %d unused CSS style rules') % num_of_removed_rules)
     else:
         report(_('No unused CSS style rules found'))
+    return num_of_removed_rules > 0

src/calibre/ebooks/oeb/polish/embed.py

@@ -116,7 +116,7 @@ def embed_all_fonts(container, stats, report):
 
     if not rules:
         report(_('No embeddable fonts found'))
-        return
+        return False
 
     # Write out CSS
     rules = [';\n\t'.join('%s: %s' % (
@@ -135,6 +135,7 @@ def embed_all_fonts(container, stats, report):
         href = container.name_to_href(name, spine_name)
         etree.SubElement(head, XHTML('link'), rel='stylesheet', type='text/css', href=href).tail = '\n'
         container.dirty(spine_name)
+    return True
 
 
 if __name__ == '__main__':

src/calibre/ebooks/oeb/polish/main.py

@@ -132,11 +132,13 @@ def update_metadata(ebook, new_opf):
 def polish_one(ebook, opts, report):
     rt = lambda x: report('\n### ' + x)
     jacket = None
+    changed = False
 
     if opts.subset or opts.embed:
         stats = StatsCollector(ebook, do_embed=opts.embed)
 
     if opts.opf:
+        changed = True
         rt(_('Updating metadata'))
         update_metadata(ebook, opts.opf)
         jacket = find_existing_jacket(ebook)
@@ -146,11 +148,13 @@ def polish_one(ebook, opts, report):
         report(_('Metadata updated\n'))
 
     if opts.cover:
+        changed = True
         rt(_('Setting cover'))
         set_cover(ebook, opts.cover, report)
         report('')
 
     if opts.jacket:
+        changed = True
         rt(_('Inserting metadata jacket'))
         if jacket is None:
             if add_or_replace_jacket(ebook):
@@ -165,30 +169,37 @@ def polish_one(ebook, opts, report):
         rt(_('Removing metadata jacket'))
         if remove_jacket(ebook):
             report(_('Metadata jacket removed'))
+            changed = True
         else:
             report(_('No metadata jacket found'))
         report('')
 
     if opts.smarten_punctuation:
         rt(_('Smartening punctuation'))
-        smarten_punctuation(ebook, report)
+        if smarten_punctuation(ebook, report):
+            changed = True
         report('')
 
     if opts.embed:
         rt(_('Embedding referenced fonts'))
-        embed_all_fonts(ebook, stats, report)
+        if embed_all_fonts(ebook, stats, report):
+            changed = True
         report('')
 
     if opts.subset:
         rt(_('Subsetting embedded fonts'))
-        subset_all_fonts(ebook, stats.font_stats, report)
+        if subset_all_fonts(ebook, stats.font_stats, report):
+            changed = True
         report('')
 
     if opts.remove_unused_css:
         rt(_('Removing unused CSS rules'))
-        remove_unused_css(ebook, report)
+        if remove_unused_css(ebook, report):
+            changed = True
         report('')
 
+    return changed
+
 
 def polish(file_map, opts, log, report):
     st = time.time()
@@ -228,8 +239,8 @@ def tweak_polish(container, actions):
     O = namedtuple('Options', ' '.join(ALL_OPTS.iterkeys()))
     opts = O(**opts)
     report = []
-    polish_one(container, opts, report.append)
+    changed = polish_one(container, opts, report.append)
-    return report
+    return report, changed
 
 def option_parser():
     from calibre.utils.config import OptionParser

src/calibre/ebooks/oeb/polish/replace.py

@@ -104,6 +104,7 @@ def smarten_punctuation(container, report):
             smartened = True
     if not smartened:
         report(_('No punctuation that could be smartened found'))
+    return smartened
 
 def rename_files(container, file_map):
     overlap = set(file_map).intersection(set(file_map.itervalues()))

src/calibre/ebooks/oeb/polish/subset.py

@@ -35,6 +35,7 @@ def remove_font_face_rules(container, sheet, remove_names, base):
 def subset_all_fonts(container, font_stats, report):
     remove = set()
     total_old = total_new = 0
+    changed = False
     for name, mt in container.mime_map.iteritems():
         if (mt in OEB_FONTS or name.rpartition('.')[-1].lower() in {'otf', 'ttf'}) and mt != guess_type('a.woff'):
             chars = font_stats.get(name, set())
@@ -69,10 +70,12 @@ def subset_all_fonts(container, font_stats, report):
                 else:
                     report('Decreased the font %s to %.1f%% of its original size'%
                        (font_name, nlen/olen * 100))
+                    changed = True
                 f.seek(0), f.truncate(), f.write(nraw)
 
     for name in remove:
         container.remove_item(name)
+        changed = True
 
     if remove:
         for name, mt in container.mime_map.iteritems():
@@ -92,6 +95,7 @@ def subset_all_fonts(container, font_stats, report):
             total_new/total_old*100))
     else:
         report('No embedded fonts found')
+    return changed
 
 if __name__ == '__main__':
     from calibre.ebooks.oeb.polish.container import get_container

src/calibre/gui2/tweak_book/boss.py

@@ -372,7 +372,7 @@ class Boss(QObject):
         with BusyCursor():
             self.add_savepoint(name)
             try:
-                report = tweak_polish(current_container(), {action:True})
+                report, changed = tweak_polish(current_container(), {action:True})
             except:
                 self.rewind_savepoint()
                 raise
@@ -386,9 +386,10 @@ 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)
+        if changed:
-        b.setIcon(QIcon(I('diff.png')))
+            b = d.b = d.bb.addButton(_('See what changed'), d.bb.AcceptRole)
-        b.clicked.connect(partial(self.show_current_diff, allow_revert=True))
+            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)