From 7adc8ab2d61c63bdcf6eba16fde90979c03725fe Mon Sep 17 00:00:00 2001
From: Florian Bruhin <git@the-compiler.org>
Date: Fri, 15 Jul 2016 12:52:27 +0200
Subject: [PATCH] QtWebEngine: Implement scroll position based on JS

---
 qutebrowser/browser/browsertab.py             |  5 ++-
 qutebrowser/browser/webengine/webenginetab.py | 42 ++++++++++++-------
 qutebrowser/javascript/scroll.js              | 25 +++++++++++
 3 files changed, 56 insertions(+), 16 deletions(-)

diff --git a/qutebrowser/browser/browsertab.py b/qutebrowser/browser/browsertab.py
index 30979d255..fa91bc37f 100644
--- a/qutebrowser/browser/browsertab.py
+++ b/qutebrowser/browser/browsertab.py
@@ -354,6 +354,9 @@ class AbstractScroller(QObject):
         self._tab = tab
         self._widget = None
 
+    def _init_widget(self, widget):
+        self._widget = widget
+
     def pos_px(self):
         raise NotImplementedError
 
@@ -513,7 +516,7 @@ class AbstractTab(QWidget):
         self._layout = WrapperLayout(widget, self)
         self._widget = widget
         self.history._history = widget.history()
-        self.scroll._widget = widget
+        self.scroll._init_widget(widget)
         self.caret._widget = widget
         self.zoom._widget = widget
         self.search._widget = widget
diff --git a/qutebrowser/browser/webengine/webenginetab.py b/qutebrowser/browser/webengine/webenginetab.py
index a03ab24e4..322e72c25 100644
--- a/qutebrowser/browser/webengine/webenginetab.py
+++ b/qutebrowser/browser/webengine/webenginetab.py
@@ -182,6 +182,14 @@ class WebEngineScroller(browsertab.AbstractScroller):
 
     """QtWebEngine implementations related to scrolling."""
 
+    def __init__(self, tab, parent=None):
+        super().__init__(tab, parent)
+        self._pos_perc = (None, None)
+
+    def _init_widget(self, widget):
+        super()._init_widget(widget)
+        self._on_scroll_pos_changed()
+
     def _key_press(self, key, count=1):
         # FIXME:qtwebengine Abort scrolling if the minimum/maximum was reached.
         press_evt = QKeyEvent(QEvent.KeyPress, key, Qt.NoModifier, 0, 0, 0)
@@ -193,24 +201,25 @@ class WebEngineScroller(browsertab.AbstractScroller):
             QApplication.postEvent(recipient, press_evt)
             QApplication.postEvent(recipient, release_evt)
 
+    @pyqtSlot()
+    def _on_scroll_pos_changed(self):
+        def update_scroll_pos_perc(jsret):
+            assert len(jsret) == 2, jsret
+            self._pos_perc = jsret
+            self.perc_changed.emit(*jsret)
+
+        js_code = """
+            {scroll_js}
+            scroll_pos_perc();
+        """.format(scroll_js=utils.read_file('javascript/scroll.js'))
+        self._tab.run_js_async(js_code, update_scroll_pos_perc)
+
     def pos_px(self):
         log.stub()
         return QPoint(0, 0)
 
     def pos_perc(self):
-        page = self._widget.page()
-        try:
-            size = page.contentsSize()
-            pos = page.scrollPosition()
-        except AttributeError:
-            # Added in Qt 5.7
-            log.stub('on Qt < 5.7')
-            return (None, None)
-        else:
-            # FIXME:qtwebengine is this correct?
-            perc_x = 100 / size.width() * pos.x()
-            perc_y = 100 / size.height() * pos.y()
-            return (perc_x, perc_y)
+        return self._pos_perc
 
     def to_perc(self, x=None, y=None):
         js_code = """
@@ -409,5 +418,8 @@ class WebEngineTab(browsertab.AbstractTab):
             view.iconChanged.connect(self.icon_changed)
         except AttributeError:
             log.stub('iconChanged, on Qt < 5.7')
-        # FIXME:qtwebengine stub this?
-        # view.scroll.pos_changed.connect(self.scroll.perc_changed)
+        try:
+            page.scrollPositionChanged.connect(
+                self.scroll._on_scroll_pos_changed)
+        except AttributeError:
+            log.stub('scrollPositionChanged, on Qt < 5.7')
diff --git a/qutebrowser/javascript/scroll.js b/qutebrowser/javascript/scroll.js
index 77076d1bb..b15edf3d4 100644
--- a/qutebrowser/javascript/scroll.js
+++ b/qutebrowser/javascript/scroll.js
@@ -38,3 +38,28 @@ function scroll_delta_page(x, y) {
     var dy = document.documentElement.clientHeight * y;
     window.scrollBy(dx, dy);
 }
+
+function scroll_pos_perc() {
+    var elem = document.documentElement;
+    var dx = (elem.scrollWidth - elem.clientWidth);
+    var dy = (elem.scrollHeight - elem.clientHeight);
+
+    var perc_x, perc_y;
+
+    if (dx === 0) {
+        perc_x = 0;
+    } else {
+        perc_x = 100 / dx * window.scrollX;
+    }
+
+    if (dy === 0) {
+        perc_y = 0;
+    } else {
+        perc_y = 100 / dy * window.scrollY;
+    }
+
+    // console.log(perc_x);
+    // console.log(perc_y);
+
+    return [perc_x, perc_y];
+}