Fix popup footnotes not working in viewer

src/pyj/iframe_comm.pyj

@@ -58,13 +58,14 @@ class Messenger:
 
 class IframeWrapper:
 
-    def __init__(self, handlers, iframe, entry_point, bootstrap_text):
+    def __init__(self, handlers, iframe, entry_point, bootstrap_text, srcdoc):
         self.messenger = Messenger()
         self.iframe_id = ensure_id(iframe, 'content-iframe')
         self.needs_init = True
         self.ready = False
         self.encrypted_communications = False
         self.srcdoc_created = False
+        self.constructor_srcdoc = srcdoc
         self.entry_point = entry_point
         self.bootstrap_text = bootstrap_text
         self.handlers = {k: handlers[k] for k in handlers}
@@ -90,7 +91,7 @@ class IframeWrapper:
             }
             self.iframe.srcdoc = LOADING_DOC.replace(r, def(match, field): return data[field];)
         else:
-            self.iframe.srcdoc = '<div>\xa0</div>'
+            self.iframe.srcdoc = self.constructor_srcdoc or '<div>\xa0</div>'
         self.srcdoc_created = True
 
     def init(self):

src/pyj/read_book/content_popup.pyj

@@ -7,6 +7,7 @@ from gettext import gettext as _
 
 from dom import add_extra_css, build_rule, clear, svgicon
 from iframe_comm import IframeWrapper
+from read_book.globals import runtime
 from read_book.resources import load_resources
 
 CLASS_NAME = 'book-content-popup-container'
@@ -56,7 +57,10 @@ class ContentPopupOverlay:
             'error': self.view.on_iframe_error,
             'content_loaded': self.on_content_loaded,
         }
-        self.iframe_wrapper = IframeWrapper(handlers, iframe, 'read_book.footnotes', _('Loading data, please wait...'))
+        entry_point = None if runtime.is_standalone_viewer else 'read_book.footnotes'
+        self.iframe_wrapper = IframeWrapper(
+            handlers, iframe, entry_point, _('Loading data, please wait...'),
+            '<div id="calibre-viewer-footnote-iframe">\xa0</div>')
         self.pending_load = None
 
     @property
@@ -106,7 +110,7 @@ class ContentPopupOverlay:
         def cb(resource_data):
             self.loaded_resources = resource_data
             done_callback(resource_data)
-        load_resources(self.view.ui.db, self.view.book, name, self.loaded_resources, cb)
+        load_resources(self.view.book, name, self.loaded_resources, cb)
 
     def show_footnote(self, data):
         self.current_footnote_data = data

src/pyj/viewer-main.pyj

@@ -17,6 +17,7 @@ from read_book.db import new_book
 from read_book.globals import runtime, ui_operations
 from read_book.iframe import main as iframe_main
 from read_book.view import View
+from read_book.footnotes import main as footnotes_main
 from session import session_defaults
 from utils import encode_query_with_path
 from viewer.constants import FAKE_HOST, FAKE_PROTOCOL
@@ -250,5 +251,9 @@ if window is window.top:
     set_css(document.body, background_color=get_color('window-background'), color=get_color('window-foreground'))
 else:
     # iframe
-    iframe_main()
+    div = document.getElementById('calibre-viewer-footnote-iframe')
+    if div:
+        footnotes_main()
+    else:
+        iframe_main()
 window.calibre_translations_data = v'undefined'