allView: Add support for custom positioning

Use the new 'icon-grid-layout' key to sort the applications and folders
as it is saved. Applications that are not in the key are appended, and
when compared to each other, fallback to alphabetical order.

Because the 'icon-grid-layout' key is, by default, empty, this means that
all icons and folders are sorted alphabetically the first time they are
displayed, preserving the current behavior.

This commit does not add any way to change the order without modifying
the GSettings key directly.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/603

js/ui/appDisplay.js

@@ -160,6 +160,10 @@ class BaseAppView {
             this._grid.addItem(item, index);
         });
 
+        this._allItems.forEach((item, index) => {
+            this._grid.set_child_at_index(item.actor, index);
+        });
+
         this.emit('view-loaded');
     }
 
@@ -379,6 +383,12 @@ var AllView = class AllView extends BaseAppView {
             Main.queueDeferredWork(this._redisplayWorkId);
         });
 
+        this._gridSettings = new Gio.Settings({ schema_id: 'org.gnome.shell' });
+        this._gridChangedId = this._gridSettings.connect('changed::icons-data', () => {
+            if (!this._blockGridSettings)
+                Main.queueDeferredWork(this._redisplayWorkId);
+        });
+
         Main.overview.connect('item-drag-begin', this._onDragBegin.bind(this));
         Main.overview.connect('item-drag-end', this._onDragEnd.bind(this));
 
@@ -430,6 +440,10 @@ var AllView = class AllView extends BaseAppView {
         let appSys = Shell.AppSystem.get_default();
 
         this.folderIcons = [];
+        let appsInFolder = [];
+
+        let iconsData = this._gridSettings.get_value('icons-data').deep_unpack();
+        let customPositionedIcons = [];
 
         let folders = this._folderSettings.get_strv('folder-children');
         folders.forEach(id => {
@@ -439,8 +453,14 @@ var AllView = class AllView extends BaseAppView {
                 icon = new FolderIcon(id, path, this);
                 icon.connect('apps-changed', this._redisplay.bind(this));
             }
-            newApps.push(icon);
             this.folderIcons.push(icon);
+
+            if (iconsData[id])
+                customPositionedIcons.push(icon);
+            else
+                newApps.push(icon);
+
+            icon.getAppIds().forEach(appId => appsInFolder.push(appId));
         });
 
         // Allow dragging of the icon only if the Dash would accept a drop to
@@ -451,13 +471,46 @@ var AllView = class AllView extends BaseAppView {
         // but we hope that is not used much.
         let favoritesWritable = global.settings.is_writable('favorite-apps');
 
+        // First, add only the app icons that do not have a custom position
+        // set. These icons will be sorted alphabetically.
         apps.forEach(appId => {
             let app = appSys.lookup_app(appId);
 
             let icon = new AppIcon(app, this,
                                    { isDraggable: favoritesWritable });
+
+            if (iconsData[appId])
+                customPositionedIcons.push(icon);
+            else
                 newApps.push(icon);
         });
+        newApps.sort((a, b) => a.name.localeCompare(b.name));
+
+        // The stored position is final. That means we need to add the custom
+        // icons in order (first to last) otherwise they end up with in the
+        // wrong position
+        customPositionedIcons.sort((a, b) => {
+            let indexA = iconsData[a.id].deep_unpack()['position'].deep_unpack();
+            let indexB = iconsData[b.id].deep_unpack()['position'].deep_unpack();
+
+            return indexA - indexB;
+        });
+
+        // Now add the icons with a custom position set. Because 'newApps' has
+        // literally all apps -- including the ones that will be hidden -- we
+        // need to translate from visible position to the real position.
+        let visibleApps = newApps.filter(app => !appsInFolder.includes(app.id));
+
+        customPositionedIcons.forEach((icon, index) => {
+            let iconData = iconsData[icon.id].deep_unpack();
+            let position = iconData['position'].deep_unpack();
+
+            // Because we are modifying 'newApps' here, compensate the number
+            // of added items by subtracting 'index'
+            let visibleAppAtPosition = visibleApps[position - index];
+            let realPosition = newApps.indexOf(visibleAppAtPosition);
+            newApps.splice(realPosition, 0, icon);
+        });
 
         return newApps;
     }