[gnome-shell] iconGrid: Cache visible children of pages

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

commit 8e938064535a61f307740c10a10ddfb5196d6d1e
Author: Jonas Dreßler <verdre v0yd nl>
Date:   Tue Feb 23 19:52:46 2021 +0100

    iconGrid: Cache visible children of pages
    
    We need to access the visible children of a page in inside
    vfunc_allocate(), and since getting those children is quite slow (it
    involves iterating over all the children of the actor) let's avoid that
    and cache the array instead.
    
    This reduces average time spent in vfunc_allocate() of the iconGrid from
    1.6 ms down to 1.4 ms.
    
    Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1713>

 js/ui/iconGrid.js | 33 ++++++++++++++++++---------------
 1 file changed, 18 insertions(+), 15 deletions(-)
---
diff --git a/js/ui/iconGrid.js b/js/ui/iconGrid.js
index 12f1ac0251..a06f92e573 100644
--- a/js/ui/iconGrid.js
+++ b/js/ui/iconGrid.js
@@ -437,8 +437,9 @@ var IconGridLayout = GObject.registerClass({
         return this._childrenMaxSize;
     }
 
-    _getVisibleChildrenForPage(pageIndex) {
-        return this._pages[pageIndex].children.filter(actor => actor.visible);
+    _updateVisibleChildrenForPage(pageIndex) {
+        this._pages[pageIndex].visibleChildren =
+            this._pages[pageIndex].children.filter(actor => actor.visible);
     }
 
     _updatePages() {
@@ -476,14 +477,14 @@ var IconGridLayout = GObject.registerClass({
         if (pageIndex >= this._pages.length - 1)
             return;
 
-        const visiblePageItems = this._getVisibleChildrenForPage(pageIndex);
+        const visiblePageItems = this._pages[pageIndex].visibleChildren;
         const itemsPerPage = this.columnsPerPage * this.rowsPerPage;
 
         // No reduce needed
         if (visiblePageItems.length === itemsPerPage)
             return;
 
-        const visibleNextPageItems = this._getVisibleChildrenForPage(pageIndex + 1);
+        const visibleNextPageItems = this._pages[pageIndex + 1].visibleChildren;
         const nMissingItems = Math.min(itemsPerPage - visiblePageItems.length, visibleNextPageItems.length);
 
         // Append to the current page the first items of the next page
@@ -505,8 +506,10 @@ var IconGridLayout = GObject.registerClass({
 
         page.children.splice(itemIndex, 1);
 
+        this._updateVisibleChildrenForPage(pageIndex);
+
         // Delete the page if this is the last icon in it
-        const visibleItems = this._getVisibleChildrenForPage(pageIndex);
+        const visibleItems = this._pages[pageIndex].visibleChildren;
         if (visibleItems.length === 0)
             this._removePage(pageIndex);
 
@@ -515,7 +518,7 @@ var IconGridLayout = GObject.registerClass({
     }
 
     _relocateSurplusItems(pageIndex) {
-        const visiblePageItems = this._getVisibleChildrenForPage(pageIndex);
+        const visiblePageItems = this._pages[pageIndex].visibleChildren;
         const itemsPerPage = this.columnsPerPage * this.rowsPerPage;
 
         // No overflow needed
@@ -559,6 +562,8 @@ var IconGridLayout = GObject.registerClass({
             visibleId: item.connect('notify::visible', () => {
                 const itemData = this._items.get(item);
 
+                this._updateVisibleChildrenForPage(itemData.pageIndex);
+
                 if (item.visible)
                     this._relocateSurplusItems(itemData.pageIndex);
                 else if (!this.allowIncompletePages)
@@ -572,6 +577,7 @@ var IconGridLayout = GObject.registerClass({
         item.icon.setIconSize(this._iconSize);
 
         this._pages[pageIndex].children.splice(index, 0, item);
+        this._updateVisibleChildrenForPage(pageIndex);
         this._relocateSurplusItems(pageIndex);
     }
 
@@ -779,21 +785,18 @@ var IconGridLayout = GObject.registerClass({
         let nChangedIcons = 0;
 
         this._pages.forEach((page, pageIndex) => {
-            const visibleItems =
-                page.children.filter(actor => actor.visible);
-
             if (isRtl && this._orientation === Clutter.Orientation.HORIZONTAL)
                 pageIndex = swap(pageIndex, this._pages.length);
 
-            visibleItems.forEach((item, itemIndex) => {
+            page.visibleChildren.forEach((item, itemIndex) => {
                 const row = Math.floor(itemIndex / this.columnsPerPage);
                 let column = itemIndex % this.columnsPerPage;
 
                 if (isRtl)
                     column = swap(column, this.columnsPerPage);
 
-                const rowPadding = this._getRowPadding(visibleItems, itemIndex,
-                    childSize, hSpacing);
+                const rowPadding = this._getRowPadding(page.visibleChildren,
+                    itemIndex, childSize, hSpacing);
 
                 // Icon position
                 let x = leftEmptySpace + rowPadding + column * (childSize + hSpacing);
@@ -929,7 +932,7 @@ var IconGridLayout = GObject.registerClass({
             return [-1, -1];
 
         const itemData = this._items.get(item);
-        const visibleItems = this._getVisibleChildrenForPage(itemData.pageIndex);
+        const visibleItems = this._pages[itemData.pageIndex].visibleChildren;
 
         return [itemData.pageIndex, visibleItems.indexOf(item)];
     }
@@ -947,7 +950,7 @@ var IconGridLayout = GObject.registerClass({
         if (page < 0 || page >= this._pages.length)
             return null;
 
-        const visibleItems = this._getVisibleChildrenForPage(page);
+        const visibleItems = this._pages[page].visibleChildren;
 
         if (position < 0 || position >= visibleItems.length)
             return null;
@@ -1056,7 +1059,7 @@ var IconGridLayout = GObject.registerClass({
 
         const halfHSpacing = hSpacing / 2;
         const halfVSpacing = vSpacing / 2;
-        const visibleItems = this._getVisibleChildrenForPage(page);
+        const visibleItems = this._pages[page].visibleChildren;
 
         for (const item of visibleItems) {
             const childBox = item.allocation.copy();