iconGrid: Save class variables to local ones

It's quite slow to access class variables in JS, especially when they're
backed by GObject properties. To avoid accessing them in every iteration
when we're looping through the children of iconGrid, store those values
to another variable and reuse that inside the loop.

This shaves off another 0.2 ms from iconGrids vfunc_allocate(), getting
the average time spent in that function down from 1.3 ms to 1.1 ms.

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 8f6b547019bb8bf5e9b64812c6d8ce982a4b46db..0fc37a49c54cc9ae22e3d085ed61ecb16d635c7e 100644 (file)
--- a/js/ui/iconGrid.js
+++ b/js/ui/iconGrid.js
@@ -662,9 +662,9 @@ var IconGridLayout = GObject.registerClass({
         return [leftEmptySpace, topEmptySpace, hSpacing, vSpacing];
     }
 
-    _getRowPadding(items, itemIndex, childSize, spacing) {
-        if (this.lastRowAlign === Clutter.ActorAlign.START ||
-            this.lastRowAlign === Clutter.ActorAlign.FILL)
+    _getRowPadding(align, items, itemIndex, childSize, spacing) {
+        if (align === Clutter.ActorAlign.START ||
+            align === Clutter.ActorAlign.FILL)
             return 0;
 
         const nRows = Math.ceil(items.length / this.columnsPerPage);
@@ -685,7 +685,7 @@ var IconGridLayout = GObject.registerClass({
         const isRtl =
             Clutter.get_default_text_direction() === Clutter.TextDirection.RTL;
 
-        switch (this.lastRowAlign) {
+        switch (align) {
         case Clutter.ActorAlign.CENTER:
             rowAlign = availableWidth / 2;
             break;
@@ -784,32 +784,38 @@ var IconGridLayout = GObject.registerClass({
         const childBox = new Clutter.ActorBox();
 
         let nChangedIcons = 0;
+        const columnsPerPage = this.columnsPerPage;
+        const orientation = this._orientation;
+        const pageWidth = this._pageWidth;
+        const pageHeight = this._pageHeight;
+        const pageSizeChanged = this._pageSizeChanged;
+        const lastRowAlign = this.lastRowAlign;
 
         this._pages.forEach((page, pageIndex) => {
-            if (isRtl && this._orientation === Clutter.Orientation.HORIZONTAL)
+            if (isRtl && orientation === Clutter.Orientation.HORIZONTAL)
                 pageIndex = swap(pageIndex, this._pages.length);
 
             page.visibleChildren.forEach((item, itemIndex) => {
-                const row = Math.floor(itemIndex / this.columnsPerPage);
-                let column = itemIndex % this.columnsPerPage;
+                const row = Math.floor(itemIndex / columnsPerPage);
+                let column = itemIndex % columnsPerPage;
 
                 if (isRtl)
-                    column = swap(column, this.columnsPerPage);
+                    column = swap(column, columnsPerPage);
 
-                const rowPadding = this._getRowPadding(page.visibleChildren,
-                    itemIndex, childSize, hSpacing);
+                const rowPadding = this._getRowPadding(lastRowAlign,
+                    page.visibleChildren, itemIndex, childSize, hSpacing);
 
                 // Icon position
                 let x = leftEmptySpace + rowPadding + column * (childSize + hSpacing);
                 let y = topEmptySpace + row * (childSize + vSpacing);
 
                 // Page start
-                switch (this._orientation) {
+                switch (orientation) {
                 case Clutter.Orientation.HORIZONTAL:
-                    x += pageIndex * this._pageWidth;
+                    x += pageIndex * pageWidth;
                     break;
                 case Clutter.Orientation.VERTICAL:
-                    y += pageIndex * this._pageHeight;
+                    y += pageIndex * pageHeight;
                     break;
                 }
 
@@ -821,7 +827,7 @@ var IconGridLayout = GObject.registerClass({
                     Math.max(childSize, naturalHeight));
 
                 // Only ease icons when the page size didn't change
-                if (this._pageSizeChanged)
+                if (pageSizeChanged)
                     item.allocate(childBox);
                 else if (animateIconPosition(item, childBox, nChangedIcons))
                     nChangedIcons++;