horizontal scroll using shift+scroll works with webkit backend

Author: MatthieuMeert

src/timeline/js/controllers.js

@@ -284,6 +284,13 @@ App.controller("TimelineCtrl", function ($scope) {
     scrolling_tracks.scrollLeft(new_cursor_x);
   };
 
+  // Scroll the timeline horizontally of a certain amount (scrol_value)
+  $scope.scrollLeft = function (scroll_value) {
+    var scrolling_tracks = $("#scrolling_tracks");
+    var horz_scroll_offset = scrolling_tracks.scrollLeft();
+    scrolling_tracks.scrollLeft(horz_scroll_offset + scroll_value);
+  };
+
   // Center the timeline on a given time position
   $scope.centerOnTime = function (centerTime) {
     // Get the width of the timeline

src/windows/views/webview.py

@@ -2783,14 +2783,17 @@ def update_zoom(self, newValue):
 
     # Capture wheel event to alter zoom slider control
     def wheelEvent(self, event):
-        if int(QCoreApplication.instance().keyboardModifiers() & Qt.ControlModifier) > 0:
+        if event.modifiers() & Qt.ControlModifier:
+            event.accept()
+            zoom = self.window.sliderZoom
             # For each 120 (standard scroll unit) adjust the zoom slider
             tick_scale = 120
             steps = int(event.angleDelta().y() / tick_scale)
-            self.window.sliderZoom.setValue(self.window.sliderZoom.value() - self.window.sliderZoom.pageStep() * steps)
+            delta = zoom.pageStep() * steps
+            log.debug("Zooming by %d steps", -steps)
+            zoom.setValue(zoom.value() - delta)
         else:
-            # Otherwise pass on to implement default functionality (scroll in QWebEngineView)
-            super(type(self), self).wheelEvent(event)
+            super().wheelEvent(event)
 
     # An item is being dragged onto the timeline (mouse is entering the timeline now)
     def dragEnterEvent(self, event):

src/windows/views/webview_backend/webkit.py

@@ -123,3 +123,20 @@ def keyPressEvent(self, event):
         else:
             # Ignore most keypresses
             event.ignore()
+
+    def wheelEvent(self, event):
+        """ Mousewheel scrolling """
+        if event.modifiers() & Qt.ShiftModifier:
+            event.accept()
+            frame = self.page().mainFrame()
+            # Compute scroll offset from wheel motion
+            tick_scale = 120
+            steps = int(event.angleDelta().y() / tick_scale)
+            delta = -(steps * 100)
+            log.debug("Scrolling horizontally by %d pixels", delta)
+            # Update the scroll position using AngularJS
+            js = f"$('body').scope().scrollLeft({delta});"
+            frame.evaluateJavaScript(js)
+        else:
+            super().wheelEvent(event)
+