Get :debug-dump-page to work

qutebrowser/browser/commands.py

@@ -1294,22 +1294,20 @@ class CommandDispatcher:
             dest: Where to write the file to.
             plain: Write plain text instead of HTML.
         """
-        web_view = self._current_widget()
-        mainframe = web_view.page().mainFrame()
-        if plain:
-            data = mainframe.toPlainText()
-        else:
-            data = mainframe.toHtml()
-
+        tab = self._current_widget()
         dest = os.path.expanduser(dest)
 
-        try:
-            with open(dest, 'w', encoding='utf-8') as f:
-                f.write(data)
-        except OSError as e:
-            raise cmdexc.CommandError('Could not write page: {}'.format(e))
-        else:
-            message.info(self._win_id, "Dumped page to {}.".format(dest))
+        def callback(data):
+            try:
+                with open(dest, 'w', encoding='utf-8') as f:
+                    f.write(data)
+            except OSError as e:
+                message.error(self._win_id, 'Could not write page: {}'.format(e))
+            else:
+                message.info(self._win_id, "Dumped page to {}.".format(dest))
+
+        tab.dump_async(callback, plain=plain)
+
 
     @cmdutils.register(instance='command-dispatcher', name='help',
                        scope='window')

qutebrowser/browser/tab.py

@@ -150,6 +150,14 @@ class AbstractTab(QWidget):
     def openurl(self, url):
         raise NotImplementedError
 
+    def dump_async(self, callback=None, *, plain=False):
+        """Dump the current page to a file ascync.
+
+        The given callback will be called with the result when dumping is
+        complete.
+        """
+        raise NotImplementedError
+
     def __repr__(self):
         url = utils.elide(self.cur_url.toDisplayString(QUrl.EncodeUnicode),
                           100)

qutebrowser/browser/webengine/webenginetab.py

@@ -83,6 +83,12 @@ class WebEngineViewTab(tab.AbstractTab):
     def scroll_pos(self):
         return (0, 0)
 
+    def dump_async(self, callback=None, *, plain=False):
+        if plain:
+            self._widget.page().toPlainText(callback)
+        else:
+            self._widget.page().toHtml(callback)
+
     def _connect_signals(self):
         view = self._widget
         page = view.page()

qutebrowser/browser/webkit/webkittab.py

@@ -89,6 +89,13 @@ class WebViewTab(tab.AbstractTab):
     def scroll_pos(self):
         return self._widget.scroll_pos
 
+    def dump_async(self, callback=None, *, plain=False):
+        frame = self._widget.page().mainFrame()
+        if plain:
+            callback(frame.toPlainText())
+        else:
+            callback(frame.toHtml())
+
     def _connect_signals(self):
         view = self._widget
         page = view.page()