Viewer: Add a setting under Preferences->Colors to control when the viewer will override all book colors or not.

src/pyj/read_book/prefs/colors.pyj

@@ -185,6 +185,7 @@ def set_action_button_visibility():
 def create_colors_panel(container, apply_func, cancel_func):
     container.appendChild(E.div(id=CONTAINER))
     container = container.lastChild
+    sd = get_session_data()
     cs = resolve_color_scheme()
     container.dataset.bg = cs.background
     container.dataset.fg = cs.foreground
@@ -192,6 +193,19 @@ def create_colors_panel(container, apply_func, cancel_func):
     container.appendChild(E.p(_('Choose a color scheme below'), style='margin:1ex 1em; padding: 1ex 0'))
     ul = E.ul(id=COLOR_LIST)
     container.appendChild(ul)
+    container.appendChild(E.div(
+        E.span(_('Override all book colors:') + '\xa0'),
+        E.label(E.input(type='radio', name='override_book_colors', value='never'), _('Never')),
+        '  ',
+        E.label(E.input(type='radio', name='override_book_colors', value='dark'), _('In dark mode')),
+        '  ',
+        E.label(E.input(type='radio', name='override_book_colors', value='always'), _('Always')),
+        style='margin:1ex 1em; padding: 1ex 0; white-space: pre-wrap'
+    ))
+    try:
+        container.lastChild.querySelector(f'[name=override_book_colors][value={sd.get("override_book_colors")}]').checked = True
+    except:
+        container.lastChild.querySelector('[name=override_book_colors][value=never]').checked = True
     create_color_buttons()
 
     container.appendChild(E.div(
@@ -229,7 +243,11 @@ def commit_colors(onchange):
     rcs = resolve_color_scheme(ccs)
     c = get_container()
     sd = get_session_data()
+    prev_obc = sd.get('override_book_colors')
+    cur_obc = c.querySelector('[name=override_book_colors]:checked').value
     sd.set('current_color_scheme', ccs)
-    if rcs.foreground is not c.dataset.fg or rcs.background is not c.dataset.bg or c.dataset.link is not rcs.link:
+    if cur_obc is not prev_obc:
+        sd.set('override_book_colors', cur_obc)
+    if rcs.foreground is not c.dataset.fg or rcs.background is not c.dataset.bg or c.dataset.link is not rcs.link or cur_obc is not prev_obc:
         ui_operations.update_color_scheme()
         onchange()

src/pyj/read_book/settings.pyj

@@ -20,6 +20,7 @@ def update_settings(settings):
     opts.bg_image_fade = settings.bg_image_fade or 'transparent'
     opts.paged_wheel_scrolls_by_screen = v'!!settings.paged_wheel_scrolls_by_screen'
     opts.is_dark_theme = v'!!settings.is_dark_theme'
+    opts.override_book_colors = settings.override_book_colors or 'never'
 
 update_settings()
 
@@ -40,11 +41,17 @@ def apply_colors():
     if not ss:
         ss = E.style(id='calibre-color-scheme-style-overrides', type='text/css')
         document.documentElement.appendChild(ss)
+    text = ''
+    if opts.override_book_colors is not 'never':
+        text = 'body'
+        if opts.override_book_colors is 'dark':
+            text += '.calibre-viewer-dark-colors'
+        text += f' * {{ color: {opts.color_scheme.foreground} !important; background-color: {opts.color_scheme.background} !important }}'
     if opts.color_scheme.link:
         c = opts.color_scheme.link
-        text = f':link, :link * {{ color: {c} !important }} :visited, :visited * {{ color: {c} !important }}'
-    else:
-        text = ''
+        # we use the html > body form so that these selectors have higher
+        # priority than the override all selectors above
+        text += f'\nhtml > body :link, html > body :link * {{ color: {c} !important }} html > body :visited, html > body :visited * {{ color: {c} !important }}'
 
     ss.textContent = text
 

src/pyj/read_book/view.pyj

@@ -691,6 +691,7 @@ class View:
             'read_mode': sd.get('read_mode'),
             'columns_per_screen': sd.get('columns_per_screen'),
             'color_scheme': cs,
+            'override_book_colors': sd.get('override_book_colors'),
             'is_dark_theme': is_dark_theme,
             'bg_image_fade': bg_image_fade,
             'base_font_size': sd.get('base_font_size'),

src/pyj/session.pyj

@@ -39,6 +39,7 @@ defaults = {
     'background_image_fade': 0,
     'current_color_scheme': 'system',
     'user_color_schemes': {},
+    'override_book_colors': 'never',
     'base_font_size': 16,
     'controls_help_shown_count': 0,
     'header': {},
@@ -68,6 +69,7 @@ is_local_setting = {
     'background_image_style': True,
     'background_image_fade': True,
     'current_color_scheme': True,
+    'override_book_colors': True,
     'base_font_size': True,
     'controls_help_shown_count': True,
     'standalone_font_settings': True,