switcherPopup: Fix spacing calculation for empty lists

Without special-casing, our current spacing calculation results in
negative size requests for empty lists, which will trigger a Clutter
assert later.
While the list is never supposed to be empty, bugs happen; crashing
users' systems is the least graceful way of handling this, so don't
do it.

https://bugzilla.gnome.org/show_bug.cgi?id=722434

diff --git a/js/ui/switcherPopup.js b/js/ui/switcherPopup.js
index 3b1532f335c98e4928c52d34f3a072371152570b..176bc6abac22d7efd42156e90191099d1c0199c7 100644 (file)
--- a/js/ui/switcherPopup.js
+++ b/js/ui/switcherPopup.js
@@ -513,7 +513,7 @@ const SwitcherList = new Lang.Class({
     _getPreferredWidth: function (actor, forHeight, alloc) {
         let [maxChildMin, maxChildNat] = this._maxChildWidth(forHeight);
 
-        let totalSpacing = this._list.spacing * (this._items.length - 1);
+        let totalSpacing = Math.max(this._list.spacing * (this._items.length - 1), 0);
         alloc.min_size = this._items.length * maxChildMin + totalSpacing;
         alloc.natural_size = alloc.min_size;
         this._minSize = alloc.min_size;
@@ -543,7 +543,7 @@ const SwitcherList = new Lang.Class({
         let childHeight = box.y2 - box.y1;
 
         let [maxChildMin, maxChildNat] = this._maxChildWidth(childHeight);
-        let totalSpacing = this._list.spacing * (this._items.length - 1);
+        let totalSpacing = Math.max(this._list.spacing * (this._items.length - 1), 0);
 
         let childWidth = Math.floor(Math.max(0, box.x2 - box.x1 - totalSpacing) / this._items.length);