Edit book: Allow customizing the base background/foreground and link colors for the preview window. Fixes #1889925 [[Enhancement] Editor Preview customise background colour](https://bugs.launchpad.net/calibre/+bug/1889925)

src/calibre/gui2/tweak_book/__init__.py

@@ -38,6 +38,9 @@ d['preview_standard_font_family'] = 'serif'
 d['preview_base_font_size'] = 18
 d['preview_mono_font_size'] = 14
 d['preview_minimum_font_size'] = 8
+d['preview_background'] = 'auto'
+d['preview_foreground'] = 'auto'
+d['preview_link_color'] = 'auto'
 d['remove_existing_links_when_linking_sheets'] = True
 d['charmap_favorites'] = list(map(ord, '\xa0\u2002\u2003\u2009\xad' '‘’“”‹›«»‚„' '—–§¶†‡©®™' '→⇒•·°±−×÷¼½½¾' '…µ¢£€¿¡¨´¸ˆ˜' 'ÀÁÂÃÄÅÆÇÈÉÊË' 'ÌÍÎÏÐÑÒÓÔÕÖØ' 'ŒŠÙÚÛÜÝŸÞßàá' 'âãäåæçèéêëìí' 'îïðñòóôõöøœš' 'ùúûüýÿþªºαΩ∞'))  # noqa
 d['folders_for_types'] = {'style':'styles', 'image':'images', 'font':'fonts', 'audio':'audio', 'video':'video'}

src/calibre/gui2/tweak_book/boss.py

@@ -207,6 +207,7 @@ class Boss(QObject):
             setup_css_parser_serialization()
             self.gui.apply_settings()
             self.refresh_file_list()
+            self.gui.preview.start_refresh_timer()
         if ret == p.Accepted or p.dictionaries_changed:
             for ed in itervalues(editors):
                 ed.apply_settings(dictionaries_changed=p.dictionaries_changed)

src/calibre/gui2/tweak_book/preferences.py

@@ -19,7 +19,7 @@ from PyQt5.Qt import (
     QListWidgetItem, QIcon, QWidget, QSize, QFormLayout, Qt, QSpinBox,
     QCheckBox, pyqtSignal, QDoubleSpinBox, QComboBox, QLabel, QFont, QApplication,
     QFontComboBox, QPushButton, QSizePolicy, QHBoxLayout, QGroupBox,
-    QToolButton, QVBoxLayout, QSpacerItem, QTimer)
+    QToolButton, QVBoxLayout, QSpacerItem, QTimer, QRadioButton)
 
 from calibre import prepare_string_for_xml
 from calibre.utils.localization import get_lang
@@ -30,6 +30,7 @@ from calibre.gui2.tweak_book.editor.themes import default_theme, all_theme_names
 from calibre.gui2.tweak_book.spell import ManageDictionaries
 from calibre.gui2.font_family_chooser import FontFamilyChooser
 from calibre.gui2.tweak_book.widgets import Dialog
+from calibre.gui2.widgets2 import ColorButton
 
 
 class BasicSettings(QWidget):  # {{{
@@ -154,7 +155,7 @@ class BasicSettings(QWidget):  # {{{
 # }}}
 
 
-class EditorSettings(BasicSettings):
+class EditorSettings(BasicSettings):  # {{{
 
     def __init__(self, parent=None):
         BasicSettings.__init__(self, parent)
@@ -269,9 +270,10 @@ class EditorSettings(BasicSettings):
         s.setter(s.widget, current_val)
         if d.theme_name:
             s.setter(s.widget, d.theme_name)
+# }}}
 
 
-class IntegrationSettings(BasicSettings):
+class IntegrationSettings(BasicSettings):  # {{{
 
     def __init__(self, parent=None):
         BasicSettings.__init__(self, parent)
@@ -293,9 +295,10 @@ class IntegrationSettings(BasicSettings):
         order.setToolTip(_('When auto-selecting the format to edit for a book with'
                            ' multiple formats, this is the preference order.'))
         l.addRow(_('Preferred format order (drag and drop to change)'), order)
+# }}}
 
 
-class MainWindowSettings(BasicSettings):
+class MainWindowSettings(BasicSettings):  # {{{
 
     def __init__(self, parent=None):
         BasicSettings.__init__(self, parent)
@@ -334,9 +337,10 @@ class MainWindowSettings(BasicSettings):
             ' multiple files with the same file name.'
         ))
         l.addRow(nd)
+# }}}
 
 
-class PreviewSettings(BasicSettings):
+class PreviewSettings(BasicSettings):  # {{{
 
     def __init__(self, parent=None):
         BasicSettings.__init__(self, parent)
@@ -377,6 +381,51 @@ class PreviewSettings(BasicSettings):
         w = self('preview_minimum_font_size')
         w.setMinimum(4), w.setMaximum(100), w.setSuffix(' px')
         l.addRow(_('Mi&nimum font size:'), w)
+        l.addRow(_('Background color:'), self.color_override('preview_background'))
+        l.addRow(_('Foreground color:'), self.color_override('preview_foreground'))
+        l.addRow(_('Link color:'), self.color_override('preview_link_color'))
+
+    def color_override(self, name):
+        w = QWidget(self)
+        l = QHBoxLayout(w)
+
+        def b(name, text, tt):
+            ans = QRadioButton(text, w)
+            l.addWidget(ans)
+            ans.setToolTip(tt)
+            setattr(w, name, ans)
+            ans.setObjectName(name)
+            return ans
+
+        b('unset', _('No change'), _('Use the colors from the book styles, defaulting to black-on-white'))
+        b('auto', _('Theme based'), _('When using a dark theme force dark colors, otherwise same as "No change"'))
+        b('manual', _('Custom'), _('Choose a custom color'))
+
+        c = w.color_button = ColorButton(parent=w)
+        l.addWidget(c)
+        connect_lambda(c.clicked, w, lambda w: w.manual.setChecked(True))
+
+        def getter(w):
+            if w.unset.isChecked():
+                return 'unset'
+            if w.auto.isChecked():
+                return 'auto'
+            return w.color_button.color or 'auto'
+
+        def setter(w, val):
+            val = val or 'auto'
+            if val == 'unset':
+                w.unset.setChecked(True)
+            elif val == 'auto':
+                w.auto.setChecked(True)
+            else:
+                w.manual.setChecked(True)
+                w.color_button.color = val
+        self(name, widget=w, getter=getter, setter=setter)
+        l.setContentsMargins(0, 0, 0, 0)
+        return w
+# }}}
+
 
 # ToolbarSettings  {{{
 

src/calibre/gui2/tweak_book/preview.py

@@ -26,7 +26,7 @@ from calibre.constants import (
 from calibre.ebooks.oeb.base import OEB_DOCS, XHTML_MIME, serialize
 from calibre.ebooks.oeb.polish.parsing import parse
 from calibre.gui2 import NO_URL_FORMATTING, error_dialog, is_dark_theme, open_url
-from calibre.gui2.palette import dark_color, dark_text_color
+from calibre.gui2.palette import dark_color, dark_link_color, dark_text_color
 from calibre.gui2.tweak_book import TOP, actions, current_container, editors, tprefs
 from calibre.gui2.tweak_book.file_list import OpenWithHandler
 from calibre.gui2.viewer.web_view import handle_mathjax_request, send_reply
@@ -251,30 +251,35 @@ def create_profile():
             create_script('csscolorparser.js', cparser),
             create_script('editor.js', js),
             create_script('dark-mode.js', '''
-            (function() {if (%s) {
+            (function() {
-                var dark_bg = "%s", dark_fg = "%s", css = %s;
+                var settings = JSON.parse(navigator.userAgent.split('|')[1]);
+                var dark_css = CSS;
+
+                function apply_body_colors(event) {
+                    if (document.documentElement) {
+                        if (settings.bg) document.documentElement.style.backgroundColor = settings.bg;
+                        if (settings.fg) document.documentElement.style.color = settings.fg;
+                    }
+                    if (document.body) {
+                        if (settings.bg) document.body.style.backgroundColor = settings.bg;
+                        if (settings.fg) document.body.style.color = settings.fg;
+                    }
+                }
+
                 function apply_css() {
+                    var css = '';
+                    if (settings.link) css += 'html > body :link, html > body :link * { color: ' + settings.link + ' !important; }';
+                    if (settings.is_dark_theme) { css += dark_css; }
                     var style = document.createElement('style');
                     style.textContent = css;
                     document.documentElement.appendChild(style);
+                    apply_body_colors();
                 }
 
-                function apply_dark_mode(event) {
+                apply_body_colors();
-                    if (document.documentElement) {
-                        document.documentElement.style.backgroundColor = dark_bg;
-                        document.documentElement.style.color = dark_fg;
-                    }
-                    if (document.body) {
-                        document.body.style.backgroundColor = dark_bg;
-                        document.body.style.color = dark_fg;
-                    }
-                }
-                apply_dark_mode();
                 document.addEventListener("DOMContentLoaded", apply_css);
-                document.addEventListener("DOMContentLoaded", apply_dark_mode);
+            })();
-            } })();
+            '''.replace('CSS', json.dumps(dark_mode_css), 1),
-            ''' % (
-            'true' if is_dark_theme() else 'false', dark_color.name(), dark_text_color.name(), json.dumps(dark_mode_css)),
             injection_point=QWebEngineScript.DocumentCreation)
         )
         url_handler = UrlSchemeHandler(ans)
@@ -392,10 +397,37 @@ class WebView(RestartingWebEngineView, OpenWithHandler):
     def sizeHint(self):
         return self._size_hint
 
+    def update_settings(self):
+        dark = is_dark_theme()
+
+        def get_color(name, dark_val):
+            ans = tprefs[name]
+            if ans == 'auto' and dark:
+                ans = dark_val.name()
+            if ans in ('auto', 'unset'):
+                return None
+            return ans
+
+        settings = {
+            'is_dark_theme': dark,
+            'bg': get_color('preview_background', dark_color),
+            'fg': get_color('preview_foreground', dark_text_color),
+            'link': get_color('preview_link_color', dark_link_color),
+        }
+        p = self._page.profile()
+        ua = p.httpUserAgent().split('|')[0] + '|' + json.dumps(settings)
+        p.setHttpUserAgent(ua)
+
     def refresh(self):
+        self.update_settings()
         self.pageAction(QWebEnginePage.ReloadAndBypassCache).trigger()
 
+    def set_url(self, qurl):
+        self.update_settings()
+        RestartingWebEngineView.setUrl(self, qurl)
+
     def clear(self):
+        self.update_settings()
         self.setHtml(_(
             '''
             <h3>Live preview</h3>
@@ -612,7 +644,7 @@ class Preview(QWidget):
             self.current_name = name
             self.report_worker_launch_error()
             parse_worker.add_request(name)
-            self.view.setUrl(self.name_to_qurl())
+            self.view.set_url(self.name_to_qurl())
             return True
 
     def refresh(self):
@@ -627,7 +659,7 @@ class Preview(QWidget):
             self.refresh_starting.emit()
             if current_url != self.view.url():
                 # The container was changed
-                self.view.setUrl(current_url)
+                self.view.set_url(current_url)
             else:
                 self.view.refresh()
             self.refreshed.emit()