eventcontrollerscroll: Conditionally propagate ::scrollscroll-event-propagation

Currently, gtk_event_controller_scroll_handle_event() always returns
TRUE if it is handled, which stops the propagation of the event. If
there’s a single GtkEventControllerScroll in the widget hierarchy, that
means that no others will run, depending on the propagation phase. In
Nautilus, this can be observed when adding a scroll controller to the
GtkScrolledWindow (ctrl-scrolling controls the zoom level) - either the
scrolling or the zooming breaks.

Fixes https://gitlab.gnome.org/GNOME/gtk/issues/45

1 files changed, 4 insertions, 2 deletions

diff --git a/gtk/gtkscrolledwindow.c b/gtk/gtkscrolledwindow.c
index 4c502846ae..7bee752377 100644
--- a/gtk/gtkscrolledwindow.c
+++ b/gtk/gtkscrolledwindow.c
@@ -1279,7 +1279,7 @@ scroll_controller_scroll_begin (GtkEventControllerScroll *scroll,
   priv->smooth_scroll = TRUE;
 }
 
-static void
+static gboolean
 scroll_controller_scroll (GtkEventControllerScroll *scroll,
                           gdouble                   delta_x,
                           gdouble                   delta_y,
@@ -1290,7 +1290,7 @@ scroll_controller_scroll (GtkEventControllerScroll *scroll,
   GdkModifierType state;
 
   if (!gtk_get_current_event_state (&state))
-    return;
+    return FALSE;
 
   shifted = (state & GDK_SHIFT_MASK) != 0;
 
@@ -1349,6 +1349,8 @@ scroll_controller_scroll (GtkEventControllerScroll *scroll,
       g_source_set_name_by_id (priv->scroll_events_overshoot_id,
                                "[gtk+] start_scroll_deceleration_cb");
     }
+
+  return TRUE;
 }
 
 static void