Viewer: The --open-at command line argument now allows matching on ToC hrefs as well as titles

src/calibre/gui2/viewer/main.py

@@ -166,7 +166,9 @@ View an e-book.
         'a location or position you can get by using the Go to->Location action in the viewer controls. '
         'Alternately, you can use the form toc:something and it will open '
         'at the location of the first Table of Contents entry that contains '
-        'the string "something".'))
+        'the string "something". The form toc-href:something will match the '
+        'href (internal link destination) of toc nodes. The matching is exact, '
+        'If you want to match a substring, use the form toc-href-contains:something. '))
     a('--continue', default=False, action='store_true', dest='continue_reading',
         help=_('Continue reading at the previously opened book'))
 
@@ -187,8 +189,10 @@ def main(args=sys.argv):
 
     parser = option_parser()
     opts, args = parser.parse_args(args)
-
-    if opts.open_at and not (opts.open_at.startswith('toc:') or opts.open_at.startswith('epubcfi(/') or is_float(opts.open_at)):
+    oat = opts.open_at
+    if oat and not (
+            oat.startswith('toc:') or oat.startswith('toc-href:') or oat.startswith('toc-href-contains:') or
+            oat.startswith('epubcfi(/') or is_float(oat)):
         raise SystemExit('Not a valid --open-at value: {}'.format(opts.open_at))
 
     listener = None

src/calibre/gui2/viewer/toc.py

@@ -144,6 +144,9 @@ class TOCItem(QStandardItem):
 
     def __init__(self, toc, depth, all_items, normal_font, emphasis_font, parent=None):
         text = toc.get('title') or ''
+        self.href = (toc.get('dest') or '')
+        if toc.get('frag'):
+            self.href += '#' + toc['frag']
         if text:
             text = re.sub(r'\s', ' ', text)
         self.title = text
@@ -214,6 +217,12 @@ class TOC(QStandardItemModel):
         for item in self.find_items(query):
             return item.node_id
 
+    def node_id_for_href(self, query, exact=False):
+        for item in self.all_items:
+            href = item.href
+            if (exact and query == href) or (not exact and query in href):
+                return item.node_id
+
     def search(self, query):
         cq = self.current_query
         if cq['items'] and -1 < cq['index'] < len(cq['items']):

src/calibre/gui2/viewer/ui.py

@@ -407,6 +407,10 @@ class EbookViewer(MainWindow):
         if open_at:
             if open_at.startswith('toc:'):
                 initial_toc_node = self.toc_model.node_id_for_text(open_at[len('toc:'):])
+            elif open_at.startswith('toc-href:'):
+                initial_toc_node = self.toc_model.node_id_for_href(open_at[len('toc-href:'):], exact=True)
+            elif open_at.startswith('toc-href-contains:'):
+                initial_toc_node = self.toc_model.node_id_for_href(open_at[len('toc-href-contains:'):], exact=False)
             elif open_at.startswith('epubcfi(/'):
                 initial_cfi = open_at
             elif is_float(open_at):