Try restarting the render process on crash

Also only load the link reports web view on demand

src/calibre/gui2/tweak_book/boss.py

@@ -146,6 +146,7 @@ class Boss(QObject):
         self.gui.preview.split_start_requested.connect(self.split_start_requested)
         self.gui.preview.split_requested.connect(self.split_requested)
         self.gui.preview.link_clicked.connect(self.link_clicked)
+        self.gui.preview.render_process_restarted.connect(self.report_render_process_restart)
         self.gui.check_book.item_activated.connect(self.check_item_activated)
         self.gui.check_book.check_requested.connect(self.check_requested)
         self.gui.check_book.fix_requested.connect(self.fix_requested)
@@ -170,6 +171,9 @@ class Boss(QObject):
         self.gui.reports.refresh_starting.connect(self.commit_all_editors_to_container)
         self.gui.reports.delete_requested.connect(self.delete_requested)
 
+    def report_render_process_restart(self):
+        self.gui.show_status_message(_('The Qt WebEngine Render process crashed and has been restarted'))
+
     @property
     def currently_editing(self):
         ' Return the name of the file being edited currently or None if no file is being edited '

src/calibre/gui2/tweak_book/preview.py

@@ -14,8 +14,8 @@ from functools import partial
 from threading import Thread
 
 from PyQt5.Qt import (
-    QApplication, QBuffer, QByteArray, QIcon, QMenu, QSize, QTimer,
+    QApplication, QBuffer, QByteArray, QIcon, QMenu, QSize, QTimer, QToolBar, QUrl,
-    QToolBar, QUrl, QVBoxLayout, QWidget, pyqtSignal
+    QVBoxLayout, QWidget, pyqtSignal
 )
 from PyQt5.QtWebEngineCore import QWebEngineUrlSchemeHandler
 from PyQt5.QtWebEngineWidgets import (
@@ -30,7 +30,10 @@ 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, open_url
 from calibre.gui2.tweak_book import TOP, actions, current_container, editors, tprefs
-from calibre.gui2.webengine import create_script, insert_scripts, secure_webengine, Bridge, from_js, to_js
+from calibre.gui2.webengine import (
+    Bridge, RestartingWebEngineView, create_script, from_js, insert_scripts,
+    secure_webengine, to_js
+)
 from calibre.gui2.widgets2 import HistoryLineEdit2
 from calibre.utils.ipc.simple_worker import offload_worker
 from polyglot.builtins import unicode_type
@@ -325,10 +328,10 @@ class WebPage(QWebEnginePage):
             self.bridge.set_split_mode.emit(1 if enabled else 0)
 
 
-class WebView(QWebEngineView):
+class WebView(RestartingWebEngineView):
 
     def __init__(self, parent=None):
-        QWebEngineView.__init__(self, parent)
+        RestartingWebEngineView.__init__(self, parent)
         self.inspector = QWebEngineView(self)
         w = QApplication.instance().desktop().availableGeometry(self).width()
         self._size_hint = QSize(int(w/3), int(w/2))
@@ -337,12 +340,13 @@ class WebView(QWebEngineView):
         self.setPage(self._page)
         self.clear()
         self.setAcceptDrops(False)
-        self.renderProcessTerminated.connect(self.render_process_terminated)
+        self.render_process_failed.connect(self.render_process_died)
 
-    def render_process_terminated(self):
+    def render_process_died(self):
         error_dialog(self, _('Render process crashed'), _(
-            'The Qt WebEngine Render process has crashed so Preview/Live css'
+            'The Qt WebEngine Render process has crashed so Preview/Live css will not work.'
-            ' will not work. You should try restarting the editor.'), show=True)
+            ' You should try restarting the editor.')
+, show=True)
 
     def sizeHint(self):
         return self._size_hint
@@ -393,6 +397,7 @@ class Preview(QWidget):
     link_clicked = pyqtSignal(object, object)
     refresh_starting = pyqtSignal()
     refreshed = pyqtSignal()
+    render_process_restarted = pyqtSignal()
 
     def __init__(self, parent=None):
         QWidget.__init__(self, parent)
@@ -403,6 +408,7 @@ class Preview(QWidget):
         self.view._page.bridge.request_sync.connect(self.request_sync)
         self.view._page.bridge.request_split.connect(self.request_split)
         self.view._page.loadFinished.connect(self.load_finished)
+        self.view.render_process_restarted.connect(self.render_process_restarted)
         self.pending_go_to_anchor = None
         self.inspector = self.view.inspector
         l.addWidget(self.view)

src/calibre/gui2/tweak_book/reports.py

@@ -21,7 +21,6 @@ from PyQt5.Qt import (
     QStyledItemDelegate, QModelIndex, QRect, QStyle, QPalette, QTimer, QMenu,
     QAbstractItemModel, QTreeView, QFont, QRadioButton, QHBoxLayout,
     QFontDatabase, QComboBox, QUrl)
-from PyQt5.QtWebEngineWidgets import QWebEngineView
 
 from calibre import human_readable, fit_image
 from calibre.constants import DEBUG
@@ -29,7 +28,7 @@ from calibre.ebooks.oeb.polish.report import (
     gather_data, CSSEntry, CSSFileMatch, MatchLocation, ClassEntry,
     ClassFileMatch, ClassElement, CSSRule, LinkLocation)
 from calibre.gui2 import error_dialog, question_dialog, choose_save_file, open_url
-from calibre.gui2.webengine import secure_webengine
+from calibre.gui2.webengine import secure_webengine, RestartingWebEngineView
 from calibre.gui2.tweak_book import current_container, tprefs, dictionaries
 from calibre.gui2.tweak_book.widgets import Dialog
 from calibre.gui2.progress_indicator import ProgressIndicator
@@ -578,7 +577,7 @@ class LinksModel(FileCollection):
                 pass
 
 
-class WebView(QWebEngineView):
+class WebView(RestartingWebEngineView):
 
     def sizeHint(self):
         return QSize(600, 200)
@@ -604,11 +603,8 @@ class LinksWidget(QWidget):
         e.textChanged.connect(f.proxy.filter_text)
         s.addWidget(f)
         self.links.restore_table('links-table', sort_column=1)
-        self.view = WebView(self)
+        self.view = None
-        secure_webengine(self.view)
         self.setContextMenuPolicy(Qt.NoContextMenu)
-        self.view.setContextMenuPolicy(Qt.NoContextMenu)
-        s.addWidget(self.view)
         self.ignore_current_change = False
         self.current_url = None
         f.current_changed.connect(self.current_changed)
@@ -616,10 +612,16 @@ class LinksWidget(QWidget):
             s.restoreState(read_state('links-view-splitter'))
         except TypeError:
             pass
-        s.setCollapsible(0, False), s.setCollapsible(1, True)
+        s.setCollapsible(0, False)
         s.setStretchFactor(0, 10)
 
     def __call__(self, data):
+        if self.view is None:
+            self.view = WebView(self)
+            secure_webengine(self.view)
+            self.view.setContextMenuPolicy(Qt.NoContextMenu)
+            self.splitter.addWidget(self.view)
+            self.splitter.setCollapsible(1, True)
         self.ignore_current_change = True
         self.model(data)
         self.filter_edit.clear()
@@ -644,10 +646,12 @@ class LinksWidget(QWidget):
                 if link.anchor.id:
                     url.setFragment(link.anchor.id)
         if url is None:
+            if self.view:
                 self.view.setHtml('<p>' + _('No destination found for this link'))
             self.current_url = url
         elif url != self.current_url:
             self.current_url = url
+            if self.view:
                 self.view.setUrl(url)
 
     def double_clicked(self, index):

src/calibre/gui2/webengine.py

@@ -6,10 +6,11 @@ from __future__ import absolute_import, division, print_function, unicode_litera
 
 import json
 
-from PyQt5.Qt import QObject, pyqtSignal
+from PyQt5.Qt import QObject, Qt, pyqtSignal
 from PyQt5.QtWebEngineWidgets import QWebEngineScript, QWebEngineView
 
 from calibre import prints
+from calibre.utils.monotonic import monotonic
 from calibre.utils.rapydscript import special_title
 
 
@@ -125,6 +126,27 @@ class Bridge(QObject):
             traceback.print_exc()
 
 
+class RestartingWebEngineView(QWebEngineView):
+
+    render_process_restarted = pyqtSignal()
+    render_process_failed = pyqtSignal()
+
+    def __init__(self, parent=None):
+        QWebEngineView.__init__(self, parent)
+        self._last_reload_at = None
+        self.renderProcessTerminated.connect(self.render_process_terminated)
+        self.render_process_restarted.connect(self.reload, type=Qt.QueuedConnection)
+
+    def render_process_terminated(self):
+        if self._last_reload_at is not None and monotonic() - self._last_reload_at < 2:
+            self.render_process_failed.emit()
+            print('The Qt WebEngine Render process crashed too often')
+        else:
+            self._last_reload_at = monotonic()
+            self.render_process_restarted.emit()
+            prints('The Qt WebEngine Render process crashed, restarting it')
+
+
 if __name__ == '__main__':
     from calibre.gui2 import Application
     from calibre.gui2.tweak_book.preview import WebPage