Viewer: Fix number of columns not auto-adjusting when font size is changed until a subsequent chapter change occurs

src/calibre/gui2/viewer/web_view.py

@@ -288,6 +288,7 @@ class ViewerBridge(Bridge):
     set_system_palette = to_js()
     show_search_result = to_js()
     prepare_for_close = to_js()
+    viewer_font_size_changed = to_js()
 
 
 def apply_font_settings(page_or_view):
@@ -309,6 +310,8 @@ def apply_font_settings(page_or_view):
     sf = fs.get('standard_font') or 'serif'
     sf = getattr(s, {'serif': 'SerifFont', 'sans': 'SansSerifFont', 'mono': 'FixedFont'}[sf])
     s.setFontFamily(s.StandardFont, s.fontFamily(sf))
+    old_minimum = s.fontSize(s.MinimumFontSize)
+    old_base = s.fontSize(s.DefaultFontSize)
     mfs = fs.get('minimum_font_size')
     if mfs is None:
         s.resetFontSize(s.MinimumFontSize)
@@ -318,6 +321,10 @@ def apply_font_settings(page_or_view):
     if bfs is not None:
         s.setFontSize(s.DefaultFontSize, bfs)
 
+    font_size_changed = old_minimum != s.fontSize(s.MinimumFontSize) or old_base != s.fontSize(s.DefaultFontSize)
+    if font_size_changed and hasattr(page_or_view, 'execute_when_ready'):
+        page_or_view.execute_when_ready('viewer_font_size_changed')
+
     return s
 
 
@@ -610,7 +617,7 @@ class WebView(RestartingWebEngineView):
     def set_session_data(self, key, val):
         if key == '*' and val is None:
             vprefs['session_data'] = {}
-            apply_font_settings(self._page)
+            apply_font_settings(self)
             self.paged_mode_changed.emit()
             self.standalone_misc_settings_changed.emit()
         elif key != '*':
@@ -618,7 +625,7 @@ class WebView(RestartingWebEngineView):
             sd[key] = val
             vprefs['session_data'] = sd
             if key in ('standalone_font_settings', 'base_font_size'):
-                apply_font_settings(self._page)
+                apply_font_settings(self)
             elif key == 'read_mode':
                 self.paged_mode_changed.emit()
             elif key == 'standalone_misc_settings':

src/pyj/read_book/iframe.pyj

@@ -24,11 +24,11 @@ from read_book.mathjax import apply_mathjax
 from read_book.paged_mode import (
     anchor_funcs as paged_anchor_funcs,
     auto_scroll_action as paged_auto_scroll_action, calc_columns_per_screen,
-    current_cfi, handle_gesture as paged_handle_gesture,
+    will_columns_per_screen_change, current_cfi,
-    handle_shortcut as paged_handle_shortcut, jump_to_cfi as paged_jump_to_cfi,
+    handle_gesture as paged_handle_gesture, handle_shortcut as paged_handle_shortcut,
-    layout as paged_layout, onwheel as paged_onwheel,
+    jump_to_cfi as paged_jump_to_cfi, layout as paged_layout,
-    prepare_for_resize as paged_prepare_for_resize, progress_frac,
+    onwheel as paged_onwheel, prepare_for_resize as paged_prepare_for_resize,
-    reset_paged_mode_globals, resize_done as paged_resize_done,
+    progress_frac, reset_paged_mode_globals, resize_done as paged_resize_done,
     scroll_by_page as paged_scroll_by_page, scroll_to_elem,
     scroll_to_fraction as paged_scroll_to_fraction, snap_to_selection
 )
@@ -44,8 +44,9 @@ from read_book.shortcuts import (
     create_shortcut_map, keyevent_as_shortcut, shortcut_for_key_event
 )
 from read_book.toc import update_visible_toc_anchors
-from read_book.touch import (create_handlers as create_touch_handlers,
+from read_book.touch import (
-                             reset_handlers as reset_touch_handlers)
+    create_handlers as create_touch_handlers, reset_handlers as reset_touch_handlers
+)
 from read_book.viewport import scroll_viewport
 from utils import (
     apply_cloned_selection, clone_selection, debounce, html_escape, is_ios
@@ -99,6 +100,7 @@ class IframeBoss:
         handlers = {
             'change_color_scheme': self.change_color_scheme,
             'change_font_size': self.change_font_size,
+            'viewer_font_size_changed': self.viewer_font_size_changed,
             'change_scroll_speed': self.change_scroll_speed,
             'display': self.display,
             'find': self.find,
@@ -264,10 +266,29 @@ class IframeBoss:
         else:
             paged_scroll_by_page(backwards, data.all_pages_on_screen)
 
+
     def change_font_size(self, data):
         if data.base_font_size? and data.base_font_size != opts.base_font_size:
             opts.base_font_size = data.base_font_size
             apply_font_size()
+            if not runtime.is_standalone_viewer:
+                # in the standalone viewer this is a separate event as
+                # apply_font_size() is a no-op
+                self.relayout_on_font_size_change()
+
+    def viewer_font_size_changed(self, data):
+        opts.base_font_size = data.base_font_size
+        self.relayout_on_font_size_change()
+
+    def relayout_on_font_size_change(self):
+        if current_layout_mode() is not 'flow' and will_columns_per_screen_change():
+            self.do_layout(self.is_titlepage)
+            if self.last_cfi:
+                cfi = self.last_cfi[len('epubcfi(/'):-1].partition('/')[2]
+                if cfi:
+                    paged_jump_to_cfi('/' + cfi)
+            self.update_cfi()
+            self.update_toc_position()
 
     def change_scroll_speed(self, data):
         if data.lines_per_sec_auto?:

src/pyj/read_book/paged_mode.pyj

@@ -152,6 +152,10 @@ def calc_columns_per_screen():
     return cps
 
 
+def will_columns_per_screen_change():
+    return calc_columns_per_screen() != cols_per_screen
+
+
 def layout(is_single_page, on_resize):
     nonlocal _in_paged_mode, col_width, col_and_gap, screen_height, gap, screen_width, is_full_screen_layout, cols_per_screen, number_of_cols
     body_style = window.getComputedStyle(document.body)

src/pyj/read_book/view.pyj

@@ -1066,6 +1066,9 @@ class View:
     def update_font_size(self):
         self.iframe_wrapper.send_message('change_font_size', base_font_size=get_session_data().get('base_font_size'))
 
+    def viewer_font_size_changed(self):
+        self.iframe_wrapper.send_message('viewer_font_size_changed', base_font_size=get_session_data().get('base_font_size'))
+
     def update_scroll_speed(self, amt):
         self.iframe_wrapper.send_message('change_scroll_speed', lines_per_sec_auto=change_scroll_speed(amt))
 

src/pyj/viewer-main.pyj

@@ -300,6 +300,13 @@ def prepare_for_close():
     else:
         ui_operations.close_prep_finished(None)
 
+
+@from_python
+def viewer_font_size_changed():
+    if view:
+        view.viewer_font_size_changed()
+
+
 def onerror(msg, script_url, line_number, column_number, error_object):
     if not error_object:
         # cross domain error