Implement scroll.pos_perc for QtWebEngine

qutebrowser/browser/webengine/webenginetab.py

@@ -54,9 +54,21 @@ class WebEngineCaret(tab.AbstractCaret):
 
 class WebEngineScroller(tab.AbstractScroller):
 
-    ## TODO
+    def pos_perc(self):
+        page = self._widget.page()
+        try:
+            size = page.contentsSize()
+            pos = page.scrollPosition()
+        except AttributeError:
+            # Added in Qt 5.7
+            return (None, None)
+        else:
+            # FIXME is this correct?
+            perc_x = 100 / size.width() * pos.x()
+            perc_y = 100 / size.height() * pos.y()
+            return (perc_x, perc_y)
 
-    pass
+    ## TODO
 
 
 class WebEngineHistory(tab.AbstractHistory):

qutebrowser/mainwindow/statusbar/percentage.py

@@ -46,6 +46,8 @@ class Percentage(textbase.TextBase):
             self.setText('[top]')
         elif y == 100:
             self.setText('[bot]')
+        elif y is None:
+            self.setText('[???]')
         else:
             self.setText('[{:2}%]'.format(y))
 

qutebrowser/mainwindow/tabwidget.py

@@ -128,7 +128,9 @@ class TabWidget(QTabWidget):
             fields['host'] = ''
 
         y = widget.scroll.pos_perc()[1]
-        if y <= 0:
+        if y is None:
+            scroll_pos = '???'
+        elif y <= 0:
             scroll_pos = 'top'
         elif y >= 100:
             scroll_pos = 'bot'