iconGrid: Get max child size using existing array of visible children

Using a preexisting array to iterate over is much faster than iterating
over the actors children using a "for ... of" loop, that's because the
latter calls into C functions to get the next actor all the time.

Also, stop using array deconstruction here, it turned out that this is
extremely expensive. When profiling this part of the code, it turned out
that only 9% of the time spent in _getChildrenMaxSize() is spent calling
the get_preferred_height/width() methods. When not using array
deconstruction, this time increased to 22%, still not great, but a lot
better.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1713>

diff --git a/js/ui/iconGrid.js b/js/ui/iconGrid.js
index a06f92e57369d7e848b11fba7caab59782af2a6c..30d9cdde31cf0529bb154d172cb94e4728ff5c30 100644 (file)
--- a/js/ui/iconGrid.js
+++ b/js/ui/iconGrid.js
@@ -420,15 +420,19 @@ var IconGridLayout = GObject.registerClass({
             let minWidth = 0;
             let minHeight = 0;
 
-            for (const child of this._container) {
-                if (!child.visible)
-                    continue;
-
-                const [childMinHeight] = child.get_preferred_height(-1);
-                const [childMinWidth] = child.get_preferred_width(-1);
-
-                minWidth = Math.max(minWidth, childMinWidth);
-                minHeight = Math.max(minHeight, childMinHeight);
+            const nPages = this._pages.length;
+            for (let pageIndex = 0; pageIndex < nPages; pageIndex++) {
+                const page = this._pages[pageIndex];
+                const nVisibleItems = page.visibleChildren.length;
+                for (let itemIndex = 0; itemIndex < nVisibleItems; itemIndex++) {
+                    const item = page.visibleChildren[itemIndex];
+
+                    const childMinHeight = item.get_preferred_height(-1)[0];
+                    const childMinWidth = item.get_preferred_width(-1)[0];
+
+                    minWidth = Math.max(minWidth, childMinWidth);
+                    minHeight = Math.max(minHeight, childMinHeight);
+                }
             }
 
             this._childrenMaxSize = Math.max(minWidth, minHeight);