[gnome-shell] boxpointer: Compute arrowStride using sourceActor monitor as reference

[Florian Müllner <fmuellner src gnome org>]

commit 4892a87dfeacbba504fc20e1837a46cc2773eb42
Author: Marco Trevisan (Treviño) <mail 3v1n0 net>
Date:   Fri Mar 8 14:21:28 2019 -0600

    boxpointer: Compute arrowStride using sourceActor monitor as reference
    
    I suppose this was also the goal of commit 96e14dc, but because it was checking
    the value of the always-undefined this.sourceActor, it really never worked as
    expected.
    
    So, now since we assume that this._sourceActor is always defined just use it
    as reference to compute the monitor menu position.
    
    Fixes https://gitlab.gnome.org/GNOME/gnome-shell/issues/1029
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/435

 js/ui/boxpointer.js | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)
---
diff --git a/js/ui/boxpointer.js b/js/ui/boxpointer.js
index 11b2bdda8..59c91f037 100644
--- a/js/ui/boxpointer.js
+++ b/js/ui/boxpointer.js
@@ -623,10 +623,7 @@ var BoxPointer = GObject.registerClass({
     _calculateArrowSide(arrowSide) {
         let sourceAllocation = Shell.util_get_transformed_allocation(this._sourceActor);
         let [minWidth, minHeight, boxWidth, boxHeight] = this.get_preferred_size();
-        let monitorActor = this.sourceActor;
-        if (!monitorActor)
-            monitorActor = this;
-        let monitorIndex = Main.layoutManager.findIndexForActor(monitorActor);
+        let monitorIndex = Main.layoutManager.findIndexForActor(this._sourceActor);
         let workarea = Main.layoutManager.getWorkAreaForMonitor(monitorIndex);
 
         switch (arrowSide) {