Fix a crash when running with assertions turned on in Qt. Fixes #1652685 [Calibre startup crash (assert in QStyledItemDelegate)](https://bugs.launchpad.net/calibre/+bug/1652685)

src/calibre/gui2/__init__.py

@@ -9,7 +9,7 @@ from PyQt5.QtWidgets import QStyle  # Gives a nicer error message than import fr
 from PyQt5.Qt import (
     QFileInfo, QObject, QBuffer, Qt, QByteArray, QTranslator, QSocketNotifier,
     QCoreApplication, QThread, QEvent, QTimer, pyqtSignal, QDateTime, QFontMetrics,
-    QDesktopServices, QFileDialog, QFileIconProvider, QSettings, QIcon,
+    QDesktopServices, QFileDialog, QFileIconProvider, QSettings, QIcon, QStringListModel,
     QApplication, QDialog, QUrl, QFont, QFontDatabase, QLocale, QFontInfo)
 
 from calibre import prints
@@ -1414,3 +1414,7 @@ def secure_web_page(qwebpage_or_qwebsettings):
     settings.setAttribute(QWebSettings.NotificationsEnabled, False)
     settings.setThirdPartyCookiePolicy(QWebSettings.AlwaysBlockThirdPartyCookies)
     return settings
+
+
+empty_model = QStringListModel([''])
+empty_index = empty_model.index(0)

src/calibre/gui2/font_family_chooser.py

@@ -13,10 +13,10 @@ from PyQt5.Qt import (QFontInfo, QFontMetrics, Qt, QFont, QFontDatabase, QPen,
         QStyledItemDelegate, QSize, QStyle, QStringListModel, pyqtSignal,
         QDialog, QVBoxLayout, QApplication, QFontComboBox, QPushButton,
         QToolButton, QGridLayout, QListView, QWidget, QDialogButtonBox, QIcon,
-        QHBoxLayout, QLabel, QModelIndex, QLineEdit, QSizePolicy)
+        QHBoxLayout, QLabel, QLineEdit, QSizePolicy)
 
 from calibre.constants import config_dir
-from calibre.gui2 import choose_files, error_dialog, info_dialog
+from calibre.gui2 import choose_files, error_dialog, info_dialog, empty_index
 
 
 def add_fonts(parent):
@@ -103,7 +103,7 @@ class FontFamilyDelegate(QStyledItemDelegate):
         return QSize(m.width(text), m.height())
 
     def paint(self, painter, option, index):
-        QStyledItemDelegate.paint(self, painter, option, QModelIndex())
+        QStyledItemDelegate.paint(self, painter, option, empty_index)
         painter.save()
         try:
             self.do_paint(painter, option, index)
@@ -380,6 +380,6 @@ def test():
     d.layout().addWidget(QFontComboBox(d))
     d.exec_()
 
+
 if __name__ == '__main__':
     test()
-

src/calibre/gui2/icon_theme.py

@@ -18,14 +18,14 @@ from PyQt5.Qt import (
     QImageReader, QFormLayout, QVBoxLayout, QSplitter, QGroupBox, QListWidget,
     QLineEdit, QSpinBox, QTextEdit, QSize, QListWidgetItem, QIcon, QImage,
     pyqtSignal, QStackedLayout, QWidget, QLabel, Qt, QComboBox, QPixmap,
-    QGridLayout, QStyledItemDelegate, QModelIndex, QApplication, QStaticText,
+    QGridLayout, QStyledItemDelegate, QApplication, QStaticText,
     QStyle, QPen, QProgressDialog
 )
 
 from calibre import walk, fit_image, human_readable, detect_ncpus as cpu_count
 from calibre.constants import cache_dir, config_dir
 from calibre.customize.ui import interface_actions
-from calibre.gui2 import must_use_qt, gprefs, choose_dir, error_dialog, choose_save_file, question_dialog
+from calibre.gui2 import must_use_qt, gprefs, choose_dir, error_dialog, choose_save_file, question_dialog, empty_index
 from calibre.gui2.dialogs.progress import ProgressDialog
 from calibre.gui2.progress_indicator import ProgressIndicator
 from calibre.gui2.widgets2 import Dialog
@@ -508,7 +508,7 @@ class Delegate(QStyledItemDelegate):
         return QSize(COVER_SIZE[0] * 2, COVER_SIZE[1] + 2 * self.SPACING)
 
     def paint(self, painter, option, index):
-        QStyledItemDelegate.paint(self, painter, option, QModelIndex())
+        QStyledItemDelegate.paint(self, painter, option, empty_index)
         theme = index.data(Qt.UserRole)
         if not theme:
             return
@@ -840,6 +840,7 @@ def install_icon_theme(theme, f):
     buf.seek(0)
     safe_copy(buf, metadata_file)
 
+
 if __name__ == '__main__':
     from calibre.gui2 import Application
     app = Application([])

src/calibre/gui2/library/alternate_views.py

@@ -25,7 +25,7 @@ from calibre import fit_image, prints, prepare_string_for_xml, human_readable
 from calibre.constants import DEBUG, config_dir, islinux
 from calibre.ebooks.metadata import fmt_sidx, rating_to_stars
 from calibre.utils import join_with_timeout
-from calibre.gui2 import gprefs, config, rating_font
+from calibre.gui2 import gprefs, config, rating_font, empty_index
 from calibre.gui2.library.caches import CoverCache, ThumbnailCache
 from calibre.utils.config import prefs, tweaks
 
@@ -451,7 +451,7 @@ class CoverDelegate(QStyledItemDelegate):
         return ans
 
     def paint(self, painter, option, index):
-        QStyledItemDelegate.paint(self, painter, option, QModelIndex())  # draw the hover and selection highlights
+        QStyledItemDelegate.paint(self, painter, option, empty_index)  # draw the hover and selection highlights
         m = index.model()
         db = m.db
         try:

src/calibre/gui2/store/search/results_view.py

@@ -9,9 +9,10 @@ __docformat__ = 'restructuredtext en'
 from functools import partial
 
 from PyQt5.Qt import (
-    pyqtSignal, QMenu, QTreeView, QStyledItemDelegate, QModelIndex, Qt, QIcon)
+    pyqtSignal, QMenu, QTreeView, QStyledItemDelegate, Qt, QIcon)
 
 from calibre import fit_image
+from calibre.gui2 import empty_index
 from calibre.gui2.metadata.single_download import RichTextDelegate
 from calibre.gui2.store.search.models import Matches
 
@@ -19,7 +20,7 @@ from calibre.gui2.store.search.models import Matches
 class ImageDelegate(QStyledItemDelegate):
 
     def paint(self, painter, option, index):
-        QStyledItemDelegate.paint(self, painter, option, QModelIndex())
+        QStyledItemDelegate.paint(self, painter, option, empty_index)
         img = index.data(Qt.DecorationRole)
         if img:
             h = option.rect.height() - 4

src/calibre/gui2/tag_browser/view.py

@@ -22,7 +22,7 @@ from calibre.constants import config_dir
 from calibre.ebooks.metadata import rating_to_stars
 from calibre.gui2.tag_browser.model import (TagTreeItem, TAG_SEARCH_STATES,
         TagsModel, DRAG_IMAGE_ROLE, COUNT_ROLE)
-from calibre.gui2 import config, gprefs, choose_files, pixmap_to_data, rating_font
+from calibre.gui2 import config, gprefs, choose_files, pixmap_to_data, rating_font, empty_index
 from calibre.utils.icu import sort_key
 
 
@@ -91,7 +91,7 @@ class TagDelegate(QStyledItemDelegate):  # {{{
         painter.drawText(tr, flags, text)
 
     def paint(self, painter, option, index):
-        QStyledItemDelegate.paint(self, painter, option, QModelIndex())
+        QStyledItemDelegate.paint(self, painter, option, empty_index)
         widget = self.parent()
         style = QApplication.style() if widget is None else widget.style()
         self.initStyleOption(option, index)

src/calibre/gui2/tweak_book/editor/insert_resource.py

@@ -12,7 +12,7 @@ from functools import partial
 from PyQt5.Qt import (
     QGridLayout, QSize, QListView, QStyledItemDelegate, QLabel, QPixmap,
     QApplication, QSizePolicy, QAbstractListModel, Qt, QRect, QCheckBox,
-    QPainter, QModelIndex, QSortFilterProxyModel, QLineEdit, QToolButton,
+    QPainter, QSortFilterProxyModel, QLineEdit, QToolButton,
     QIcon, QFormLayout, pyqtSignal, QTreeWidget, QTreeWidgetItem, QVBoxLayout,
     QMenu, QInputDialog, QHBoxLayout)
 
@@ -20,7 +20,7 @@ from calibre import fit_image
 from calibre.constants import plugins
 from calibre.ebooks.metadata import string_to_authors
 from calibre.ebooks.metadata.book.base import Metadata
-from calibre.gui2 import choose_files, error_dialog, pixmap_to_data
+from calibre.gui2 import choose_files, error_dialog, pixmap_to_data, empty_index
 from calibre.gui2.languages import LanguagesEdit
 from calibre.gui2.tweak_book import current_container, tprefs
 from calibre.gui2.tweak_book.widgets import Dialog
@@ -101,7 +101,7 @@ class ImageDelegate(QStyledItemDelegate):
         return self.item_size
 
     def paint(self, painter, option, index):
-        QStyledItemDelegate.paint(self, painter, option, QModelIndex())  # draw the hover and selection highlights
+        QStyledItemDelegate.paint(self, painter, option, empty_index)  # draw the hover and selection highlights
         name = unicode(index.data(Qt.DisplayRole) or '')
         cover = self.cover_cache.get(name, None)
         if cover is None:
@@ -462,6 +462,7 @@ class NewBook(Dialog):  # {{{
 
 # }}}
 
+
 if __name__ == '__main__':
     app = QApplication([])  # noqa
     from calibre.gui2.tweak_book import set_current_container

src/calibre/gui2/tweak_book/polish.py

@@ -11,12 +11,13 @@ from threading import Thread
 from PyQt5.Qt import (
     QTextBrowser, QVBoxLayout, QDialog, QDialogButtonBox, QIcon, QLabel,
     QCheckBox, Qt, QListWidgetItem, QHBoxLayout, QListWidget, QPixmap,
-    QSpinBox, QStyledItemDelegate, QSize, QModelIndex, QStyle, QPen,
+    QSpinBox, QStyledItemDelegate, QSize, QStyle, QPen,
     QProgressBar, pyqtSignal
 )
 
 from calibre import human_readable, fit_image, force_unicode
 from calibre.ebooks.oeb.polish.main import CUSTOMIZATION
+from calibre.gui2 import empty_index
 from calibre.gui2.tweak_book import tprefs, current_container, set_current_container
 from calibre.gui2.tweak_book.widgets import Dialog
 from calibre.utils.icu import numeric_sort_key
@@ -122,7 +123,7 @@ class ImageItemDelegate(QStyledItemDelegate):
             index.model().setData(index, pmap, Qt.UserRole+1)
         x, y = (irect.width() - pmap.width())//2, (irect.height() - pmap.height())//2
         r = irect.adjusted(x, y, -x, -y)
-        QStyledItemDelegate.paint(self, painter, option, QModelIndex())
+        QStyledItemDelegate.paint(self, painter, option, empty_index)
         painter.drawPixmap(r, pmap)
         trect = irect.adjusted(irect.width() + 10, 0, 0, 0)
         trect.setRight(option.rect.right())
@@ -253,6 +254,7 @@ class CompressImagesProgress(Dialog):
 
 # }}}
 
+
 if __name__ == '__main__':
     from calibre.gui2 import Application
     app = Application([])