Fix #1503910 [Cmd+T doesn't toggle TOC back off when in window mode](https://bugs.launchpad.net/calibre/+bug/1503910)

src/calibre/gui2/viewer/main.py

@@ -138,6 +138,17 @@ class EbookViewer(MainWindow):
         self.search.focus_to_library.connect(lambda: self.view.setFocus(Qt.OtherFocusReason))
         self.toc.pressed[QModelIndex].connect(self.toc_clicked)
         self.toc.searched.connect(partial(self.toc_clicked, force=True))
+        def toggle_toc(ev):
+            try:
+                key = self.view.shortcuts.get_match(ev)
+            except AttributeError:
+                pass
+            if key == 'Table of Contents':
+                ev.accept()
+                self.action_table_of_contents.trigger()
+                return True
+            return False
+        self.toc.handle_shortcuts = toggle_toc
         self.reference.goto.connect(self.goto)
         self.bookmarks.edited.connect(self.bookmarks_edited)
         self.bookmarks.activated.connect(self.goto_bookmark)

src/calibre/gui2/viewer/toc.py

@@ -95,6 +95,14 @@ class TOCView(QTreeView):
         m.addAction(_('Collapse all items'), self.collapseAll)
         m.exec_(self.mapToGlobal(pos))
 
+    def keyPressEvent(self, event):
+        try:
+            if self.handle_shortcuts(event):
+                return
+        except AttributeError:
+            pass
+        return QTreeView.keyPressEvent(self, event)
+
 class TOCSearch(QWidget):
 
     def __init__(self, toc_view, parent=None):