Viewer toolbar: Add a button to easily change color schemes

Fixes #1859547 [[Enhancement] Toggle between color schemes](https://bugs.launchpad.net/calibre/+bug/1859547)

src/calibre/gui2/viewer/toolbars.py

@@ -40,6 +40,7 @@ class Actions(object):
 def all_actions():
     if not hasattr(all_actions, 'ans'):
         all_actions.ans = Actions({
+            'color_scheme': Action('format-fill-color.png', _('Switch color scheme')),
             'back': Action('back.png', _('Back')),
             'forward': Action('forward.png', _('Forward')),
             'open': Action('document_open.png', _('Open e-book')),
@@ -67,7 +68,7 @@ def all_actions():
 
 
 DEFAULT_ACTIONS = (
-        'back', 'forward', None, 'open', 'copy', 'increase_font_size', 'decrease_font_size', 'fullscreen',
+        'back', 'forward', None, 'open', 'copy', 'increase_font_size', 'decrease_font_size', 'fullscreen', 'color_scheme',
         None, 'previous', 'next', None, 'toc', 'bookmarks', 'lookup', 'reference', 'chrome', None, 'mode', 'print', 'preferences',
         'metadata', 'inspector'
 )
@@ -131,6 +132,7 @@ class ActionsToolBar(ToolBar):
         web_view.standalone_misc_settings_changed.connect(self.update_visibility)
         web_view.autoscroll_state_changed.connect(self.update_autoscroll_action)
         web_view.customize_toolbar.connect(self.customize, type=Qt.QueuedConnection)
+        web_view.view_created.connect(self.on_view_created)
 
         self.back_action = page.action(QWebEnginePage.Back)
         self.back_action.setIcon(aa.back.icon)
@@ -176,6 +178,11 @@ class ActionsToolBar(ToolBar):
         self.preferences_action = shortcut_action('preferences')
         self.metadata_action = shortcut_action('metadata')
         self.update_mode_action()
+        self.color_scheme_action = a = QAction(aa.color_scheme.icon, aa.color_scheme.text, self)
+        self.color_scheme_menu = m = QMenu(self)
+        a.setMenu(m)
+        m.aboutToShow.connect(self.populate_color_scheme_menu)
+
         self.add_actions()
 
     def add_actions(self):
@@ -189,6 +196,9 @@ class ActionsToolBar(ToolBar):
                     self.addAction(getattr(self, '{}_action'.format(x)))
                 except AttributeError:
                     pass
+        w = self.widgetForAction(self.color_scheme_action)
+        if w:
+            w.setPopupMode(w.InstantPopup)
 
     def update_mode_action(self):
         mode = get_session_pref('read_mode', default='paged', group=None)
@@ -244,6 +254,33 @@ class ActionsToolBar(ToolBar):
                     elided_text(os.path.basename(path), width=250))).triggered.connect(partial(
                     self.open_book_at_path.emit, path))
 
+    def on_view_created(self, data):
+        self.default_color_schemes = data['default_color_schemes']
+
+    def populate_color_scheme_menu(self):
+        m = self.color_scheme_menu
+        m.clear()
+        ccs = get_session_pref('current_color_scheme', group=None) or ''
+        ucs = get_session_pref('user_color_schemes', group=None) or {}
+
+        def add_action(key, defns):
+            a = m.addAction(defns[key]['name'])
+            a.setCheckable(True)
+            a.setObjectName('color-switch-action:{}'.format(key))
+            a.triggered.connect(self.color_switch_triggerred)
+            if key == ccs:
+                a.setChecked(True)
+
+        for key in sorted(ucs, key=lambda x: primary_sort_key(ucs[x]['name'])):
+            add_action(key, ucs)
+        m.addSeparator()
+        for key in sorted(self.default_color_schemes, key=lambda x: primary_sort_key(self.default_color_schemes[x]['name'])):
+            add_action(key, self.default_color_schemes)
+
+    def color_switch_triggerred(self):
+        key = self.sender().objectName().partition(':')[-1]
+        self.action_triggered.emit('switch_color_scheme:' + key)
+
     def update_visibility(self):
         self.setVisible(bool(get_session_pref('show_actions_toolbar', default=False)))
 

src/calibre/gui2/viewer/web_view.py

@@ -234,6 +234,7 @@ def create_profile():
 
 class ViewerBridge(Bridge):
 
+    view_created = from_js(object)
     set_session_data = from_js(object, object)
     set_local_storage = from_js(object, object)
     reload_book = from_js()
@@ -430,6 +431,7 @@ class WebView(RestartingWebEngineView):
     shortcuts_changed = pyqtSignal(object)
     paged_mode_changed = pyqtSignal()
     standalone_misc_settings_changed = pyqtSignal(object)
+    view_created = pyqtSignal(object)
 
     def __init__(self, parent=None):
         self._host_widget = None
@@ -445,6 +447,7 @@ class WebView(RestartingWebEngineView):
         self._size_hint = QSize(int(w/3), int(w/2))
         self._page = WebPage(self)
         self.bridge.bridge_ready.connect(self.on_bridge_ready)
+        self.bridge.view_created.connect(self.on_view_created)
         self.bridge.set_session_data.connect(self.set_session_data)
         self.bridge.set_local_storage.connect(self.set_local_storage)
         self.bridge.reload_book.connect(self.reload_book)
@@ -550,6 +553,9 @@ class WebView(RestartingWebEngineView):
         for func, args in iteritems(self.pending_bridge_ready_actions):
             getattr(self.bridge, func)(*args)
 
+    def on_view_created(self, data):
+        self.view_created.emit(data)
+
     def start_book_load(self, initial_position=None):
         key = (set_book_path.path,)
         self.execute_when_ready('start_book_load', key, initial_position, set_book_path.pathtoebook)

src/pyj/read_book/view.pyj

@@ -437,12 +437,18 @@ class View:
             self.update_scroll_speed(-SCROLL_SPEED_STEP)
         elif data.name is 'toggle_autoscroll':
             self.toggle_autoscroll()
+        elif data.name.startsWith('switch_color_scheme:'):
+            self.switch_color_scheme(data.name.partition(':')[-1])
 
     def on_selection_change(self, data):
         self.currently_showing.selected_text = data.text
         if ui_operations.selection_changed:
             ui_operations.selection_changed(data.text)
 
+    def switch_color_scheme(self, name):
+        get_session_data().set('current_color_scheme', name)
+        ui_operations.redisplay_book()
+
     def toggle_paged_mode(self):
         sd = get_session_data()
         mode = sd.get('read_mode')

src/pyj/viewer-main.pyj

@@ -16,7 +16,7 @@ from modals import create_modal_container
 from qt import from_python, to_python
 from read_book.db import new_book
 from read_book.footnotes import main as footnotes_main
-from read_book.globals import runtime, set_system_colors, ui_operations
+from read_book.globals import runtime, set_system_colors, ui_operations, default_color_schemes
 from read_book.iframe import main as iframe_main
 from read_book.shortcuts import add_standalone_viewer_shortcuts
 from read_book.view import View
@@ -225,6 +225,7 @@ def create_view(prefs, local_storage, field_metadata, ui_data):
         create_session_data(prefs, local_storage)
         view = View(document.getElementById('view'))
         window.addEventListener('resize', debounce(view.on_resize.bind(self), 250))
+        to_python.view_created({'default_color_schemes': default_color_schemes})
         if ui_data.show_home_page_on_ready:
             view.overlay.open_book(False)