Make WebKit support optional again

QtWebKit has been deprecated upstream, and is no longer part of e.g.
the official PyQt Windows installers.

ReText/tab.py

@@ -22,7 +22,6 @@
 from ReText import app_version, globalSettings, converterprocess
 from ReText.editor import ReTextEdit
 from ReText.highlighter import ReTextHighlighter
-from ReText.syncscroll import SyncScroll
 
 try:
 	from ReText.fakevimeditor import ReTextFakeVimHandler
@@ -37,8 +36,11 @@
 from PyQt5.QtCore import pyqtSignal, Qt, QDir, QFile, QFileInfo, QPoint, QTextStream, QTimer, QUrl
 from PyQt5.QtGui import QDesktopServices, QTextCursor, QTextDocument
 from PyQt5.QtWidgets import QTextBrowser, QTextEdit, QSplitter
-from PyQt5.QtWebKit import QWebSettings
-from PyQt5.QtWebKitWidgets import QWebPage, QWebView
+
+try:
+	from ReText.webkitpreview import ReTextWebPreview
+except ImportError:
+	ReTextWebPreview = None
 
 PreviewDisabled, PreviewLive, PreviewNormal = range(3)
 
@@ -248,11 +250,7 @@ def updatePreviewBox(self):
 				newValue = scrollbar.maximum() - distToBottom
 				scrollbar.setValue(newValue)
 		else:
-			settings = self.previewBox.settings()
-			settings.setFontFamily(QWebSettings.StandardFont,
-			                       globalSettings.font.family())
-			settings.setFontSize(QWebSettings.DefaultFontSize,
-			                     globalSettings.font.pointSize())
+			self.previewBox.updateFontSettings()
 
 			# Always provide a baseUrl otherwise QWebView will
 			# refuse to show images or other external objects
@@ -355,63 +353,6 @@ def find(self, text, flags):
 			return True
 		return False
 
-class ReTextWebPreview(QWebView):
-
-	def __init__(self, editBox,
-	             editorPositionToSourceLineFunc,
-	             sourceLineToEditorPositionFunc):
-
-		QWebView.__init__(self)
-
-		self.editBox = editBox
-
-		if not globalSettings.handleWebLinks:
-			self.page().setLinkDelegationPolicy(QWebPage.DelegateExternalLinks)
-			self.page().linkClicked.connect(QDesktopServices.openUrl)
-		self.settings().setAttribute(QWebSettings.LocalContentCanAccessFileUrls, False)
-		self.settings().setDefaultTextEncoding('utf-8')
-		# Avoid caching of CSS
-		self.settings().setObjectCacheCapacities(0,0,0)
-
-		self.syncscroll = SyncScroll(self.page().mainFrame(),
-					     editorPositionToSourceLineFunc,
-					     sourceLineToEditorPositionFunc)
-
-		# Events relevant to sync scrolling
-		self.editBox.cursorPositionChanged.connect(self._handleCursorPositionChanged)
-		self.editBox.verticalScrollBar().valueChanged.connect(self.syncscroll.handleEditorScrolled)
-		self.editBox.resized.connect(self._handleEditorResized)
-
-		# Scroll the preview when the mouse wheel is used to scroll
-		# beyond the beginning/end of the editor
-		self.editBox.scrollLimitReached.connect(self._handleWheelEvent)
-
-	def disconnectExternalSignals(self):
-		self.editBox.cursorPositionChanged.disconnect(self._handleCursorPositionChanged)
-		self.editBox.verticalScrollBar().valueChanged.disconnect(self.syncscroll.handleEditorScrolled)
-		self.editBox.resized.disconnect(self._handleEditorResized)
-
-		self.editBox.scrollLimitReached.disconnect(self._handleWheelEvent)
-
-	def _handleWheelEvent(self, event):
-		"""
-		Use this intermediate function because it is not possible to
-		disconnect a built-in method. It would generate the following error:
-		  TypeError: 'builtin_function_or_method' object is not connected
-		"""
-		# Only pass wheelEvents on to the preview if syncscroll is
-		# controlling the position of the preview
-		if self.syncscroll.isActive():
-			self.wheelEvent(event)
-
-	def _handleCursorPositionChanged(self):
-		editorCursorPosition = self.editBox.verticalScrollBar().value() + \
-				       self.editBox.cursorRect().top()
-		self.syncscroll.handleCursorPositionChanged(editorCursorPosition)
-
-	def _handleEditorResized(self, rect):
-		self.syncscroll.handleEditorResized(rect.height())
-
 
 class ReTextPreview(QTextBrowser):
 	"""

ReText/webkitpreview.py

@@ -0,0 +1,90 @@
+# vim: ts=8:sts=8:sw=8:noexpandtab
+#
+# This file is part of ReText
+# Copyright: 2015-2016 Dmitry Shachnev
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+from ReText import globalSettings
+from ReText.syncscroll import SyncScroll
+
+from PyQt5.QtGui import QDesktopServices
+from PyQt5.QtWebKit import QWebSettings
+from PyQt5.QtWebKitWidgets import QWebPage, QWebView
+
+
+class ReTextWebPreview(QWebView):
+
+	def __init__(self, editBox,
+	             editorPositionToSourceLineFunc,
+	             sourceLineToEditorPositionFunc):
+
+		QWebView.__init__(self)
+
+		self.editBox = editBox
+
+		if not globalSettings.handleWebLinks:
+			self.page().setLinkDelegationPolicy(QWebPage.DelegateExternalLinks)
+			self.page().linkClicked.connect(QDesktopServices.openUrl)
+		self.settings().setAttribute(QWebSettings.LocalContentCanAccessFileUrls, False)
+		self.settings().setDefaultTextEncoding('utf-8')
+		# Avoid caching of CSS
+		self.settings().setObjectCacheCapacities(0,0,0)
+
+		self.syncscroll = SyncScroll(self.page().mainFrame(),
+					     editorPositionToSourceLineFunc,
+					     sourceLineToEditorPositionFunc)
+
+		# Events relevant to sync scrolling
+		self.editBox.cursorPositionChanged.connect(self._handleCursorPositionChanged)
+		self.editBox.verticalScrollBar().valueChanged.connect(self.syncscroll.handleEditorScrolled)
+		self.editBox.resized.connect(self._handleEditorResized)
+
+		# Scroll the preview when the mouse wheel is used to scroll
+		# beyond the beginning/end of the editor
+		self.editBox.scrollLimitReached.connect(self._handleWheelEvent)
+
+	def disconnectExternalSignals(self):
+		self.editBox.cursorPositionChanged.disconnect(self._handleCursorPositionChanged)
+		self.editBox.verticalScrollBar().valueChanged.disconnect(self.syncscroll.handleEditorScrolled)
+		self.editBox.resized.disconnect(self._handleEditorResized)
+
+		self.editBox.scrollLimitReached.disconnect(self._handleWheelEvent)
+
+	def _handleWheelEvent(self, event):
+		"""
+		Use this intermediate function because it is not possible to
+		disconnect a built-in method. It would generate the following error:
+		  TypeError: 'builtin_function_or_method' object is not connected
+		"""
+		# Only pass wheelEvents on to the preview if syncscroll is
+		# controlling the position of the preview
+		if self.syncscroll.isActive():
+			self.wheelEvent(event)
+
+	def _handleCursorPositionChanged(self):
+		editorCursorPosition = self.editBox.verticalScrollBar().value() + \
+				       self.editBox.cursorRect().top()
+		self.syncscroll.handleCursorPositionChanged(editorCursorPosition)
+
+	def _handleEditorResized(self, rect):
+		self.syncscroll.handleEditorResized(rect.height())
+
+	def updateFontSettings(self):
+		settings = self.settings()
+		settings.setFontFamily(QWebSettings.StandardFont,
+		                       globalSettings.font.family())
+		settings.setFontSize(QWebSettings.DefaultFontSize,
+		                     globalSettings.font.pointSize())

ReText/window.py

@@ -21,7 +21,7 @@
 from subprocess import Popen
 from ReText import icon_path, app_version, globalSettings, readListFromSettings, \
  writeListToSettings, writeToSettings, datadirs
-from ReText.tab import ReTextTab, PreviewNormal, PreviewLive
+from ReText.tab import ReTextTab, ReTextWebPreview, PreviewNormal, PreviewLive
 from ReText.dialogs import HtmlDialog, LocaleDialog
 from ReText.config import ConfigDialog
 from ReText.icontheme import get_icon_theme
@@ -179,6 +179,9 @@ def __init__(self, parent=None):
 			self.actionEnableSC = self.act(self.tr('Enable'), trigbool=self.enableSpellCheck)
 			self.actionSetLocale = self.act(self.tr('Set locale'), trig=self.changeLocale)
 		self.actionWebKit = self.act(self.tr('Use WebKit renderer'), trigbool=self.enableWebKit)
+		if ReTextWebPreview is None:
+			globalSettings.useWebKit = False
+			self.actionWebKit.setEnabled(False)
 		self.actionWebKit.setChecked(globalSettings.useWebKit)
 		self.actionShow = self.act(self.tr('Show directory'), 'system-file-manager', self.showInDir)
 		self.actionFind = self.act(self.tr('Next'), 'go-next', self.find,