Loading of footnote link data works

src/calibre/gui2/viewer/footnote.py

@@ -7,29 +7,52 @@ __license__ = 'GPL v3'
 __copyright__ = '2014, Kovid Goyal <kovid at kovidgoyal.net>'
 
 import json
+from collections import defaultdict
 
 from PyQt5.Qt import QUrl
 
+from calibre import prints
+
 class Footnotes(object):
 
-    def __init__(self, document):
-        self.document = document
+    def __init__(self, view):
+        self.view = view
         self.clear()
 
     def clear(self):
         self.footnote_data_cache = {}
+        self.known_footnote_targets = defaultdict(set)
 
-    def get_footnote_data(self, url):
-        current_url = unicode(self.document.mainFrame().baseUrl().toLocalFile())
+    def spine_index(self, path):
+        try:
+            return self.view.manager.iterator.spine.index(path)
+        except (AttributeError, ValueError):
+            return -1
+
+    def load_footnote_data(self, current_url):
+        fd = self.footnote_data_cache[current_url] = {}
+        try:
+            raw = self.view.document.javascript('window.calibre_extract.get_footnote_data()', typ='string')
+            for x in json.loads(raw):
+                if x not in fd:
+                    qu = QUrl(x)
+                    path = qu.toLocalFile()
+                    si = self.spine_index(path)
+                    if si > -1:
+                        target = qu.fragment(QUrl.FullyDecoded)
+                        fd[qu.toString()] = (path, target)
+                        self.known_footnote_targets[path].add(target)
+        except Exception:
+            prints('Failed to get footnote data, with error:')
+            import traceback
+            traceback.print_exc()
+        return fd
+
+    def get_footnote_data(self, qurl):
+        current_url = unicode(self.view.document.mainFrame().baseUrl().toLocalFile())
         if not current_url:
             return  # Not viewing a local file
-        fd = self.footnote_data_cache.get(current_url, None)
+        fd = self.footnote_data_cache.get(current_url)
         if fd is None:
-            raw = self.document.javascript('window.calibre_extract.get_footnote_data()', typ='string')
-            try:
-                fd = frozenset(QUrl(x).toLocalFile() for x in json.loads(raw))
-            except Exception:
-                fd = frozenset()
-            self.footnote_data_cache[current_url] = fd
-
-
+            fd = self.load_footnote_data(current_url)
+        return fd.get(qurl.toString())