E-book viewer: Fix indication of current section in Table of Contents sometimes wrong after changing font size. Fixes #2033205 [E-book viewer: incorrect ToC highligting after changing font size](https://bugs.launchpad.net/calibre/+bug/2033205)

src/pyj/read_book/iframe.pyj

@@ -402,7 +402,7 @@ class IframeBoss:
                 if cfi:
                     self.jump_to_cfi('/' + cfi)
             self.update_cfi()
-            self.update_toc_position()
+        self.update_toc_position(True)
 
     def number_of_columns_changed(self, data):
         opts.columns_per_screen = data.columns_per_screen
@@ -548,8 +548,8 @@ class IframeBoss:
                     self.send_message(
                         'update_progress_frac', progress_frac=pf, file_progress_frac=fpf, page_counts=page_counts())
 
-    def update_toc_position(self):
+    def update_toc_position(self, recalculate_toc_anchor_positions):
-        visible_anchors = update_visible_toc_anchors(self.book.manifest.toc_anchor_map, self.anchor_funcs)
+        visible_anchors = update_visible_toc_anchors(self.book.manifest.toc_anchor_map, self.anchor_funcs, bool(recalculate_toc_anchor_positions))
         self.send_message('update_toc_position', visible_anchors=visible_anchors)
 
     def onscroll(self):

src/pyj/read_book/toc.pyj

@@ -198,32 +198,38 @@ def create_toc_panel(book, container, onclick):
     toc_panel.style.flexShrink = '1'
     toc_panel.style.overflow = 'auto'
 
+def recalculate_toc_anchor_positions(tam, anchor_funcs):
+    name = current_spine_item().name
+    am = {}
+    anchors = v'[]'
+    pos_map = {}
+    for i, anchor in enumerate(tam[name] or v'[]'):
+        val = anchor_funcs.pos_for_elem()
+        if anchor.frag:
+            elem = document.getElementById(anchor.frag)
+            if elem:
+                val = anchor_funcs.pos_for_elem(elem)
+        am[anchor.id] = val
+        anchors.push(anchor.id)
+        pos_map[anchor.id] = i
+    # stable sort by position in document
+    anchors.sort(def (a, b): return anchor_funcs.cmp(am[a], am[b]) or (pos_map[a] - pos_map[b]);)
+
+    current_map = {'layout_mode': current_layout_mode(), 'width': scroll_viewport.width(), 'height': scroll_viewport.height(), 'pos_map': am, 'sorted_anchors':anchors}
+    set_toc_anchor_map(current_map)
+    return current_map
+
 
 def current_toc_anchor_map(tam, anchor_funcs):
     current_map = toc_anchor_map()
     if not (current_map and current_map.layout_mode is current_layout_mode() and current_map.width is scroll_viewport.width() and current_map.height is scroll_viewport.height()):
-        name = current_spine_item().name
+        current_map = recalculate_toc_anchor_positions(tam, anchor_funcs)
-        am = {}
-        anchors = v'[]'
-        pos_map = {}
-        for i, anchor in enumerate(tam[name] or v'[]'):
-            val = anchor_funcs.pos_for_elem()
-            if anchor.frag:
-                elem = document.getElementById(anchor.frag)
-                if elem:
-                    val = anchor_funcs.pos_for_elem(elem)
-            am[anchor.id] = val
-            anchors.push(anchor.id)
-            pos_map[anchor.id] = i
-        # stable sort by position in document
-        anchors.sort(def (a, b): return anchor_funcs.cmp(am[a], am[b]) or (pos_map[a] - pos_map[b]);)
-
-        current_map = {'layout_mode': current_layout_mode(), 'width': scroll_viewport.width(), 'height': scroll_viewport.height(), 'pos_map': am, 'sorted_anchors':anchors}
-        set_toc_anchor_map(current_map)
     return current_map
 
 
-def update_visible_toc_anchors(toc_anchor_map, anchor_funcs):
+def update_visible_toc_anchors(toc_anchor_map, anchor_funcs, recalculate):
+    if recalculate:
+        recalculate_toc_anchor_positions(toc_anchor_map, anchor_funcs)
     tam = current_toc_anchor_map(toc_anchor_map, anchor_funcs)
     before = after = None
     visible_anchors = {}