[gnome-shell] dash: Fix drag placeholder position in RTL

[Marge Bot <marge-bot src gnome org>]

commit 4735193456e525edada2bbc5ab11b609e4eabd81
Author: Florian Müllner <fmuellner gnome org>
Date:   Sat Feb 26 18:35:47 2022 +0100

    dash: Fix drag placeholder position in RTL
    
    The position corresponds to a child index, which means it must
    be mirrored when starting to count from the right.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/4574
    
    Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2219>

 js/ui/dash.js | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)
---
diff --git a/js/ui/dash.js b/js/ui/dash.js
index e5f81fca74..24d3a8907e 100644
--- a/js/ui/dash.js
+++ b/js/ui/dash.js
@@ -883,10 +883,12 @@ var Dash = GObject.registerClass({
         }
 
         let pos;
-        if (!this._emptyDropTarget)
-            pos = Math.floor(x * numChildren / boxWidth);
+        if (this._emptyDropTarget)
+            pos = 0; // always insert at the start when dash is empty
+        else if (this.text_direction === Clutter.TextDirection.RTL)
+            pos = numChildren - Math.floor(x * numChildren / boxWidth);
         else
-            pos = 0; // always insert at the top when dash is empty
+            pos = Math.floor(x * numChildren / boxWidth);
 
         // Put the placeholder after the last favorite if we are not
         // in the favorites zone