[gnome-shell/gbsneto/pagination] WIP: Add pagination to the folder dialog

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit f137f574f8e5068ca5ee7edcffe24c452e2d6594
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Wed May 20 19:20:15 2020 -0300

    WIP: Add pagination to the folder dialog
    
    https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1271

 data/theme/gnome-shell-sass/widgets/_app-grid.scss | 13 +++++
 js/ui/appDisplay.js                                | 68 +++++++++++++++++++---
 2 files changed, 74 insertions(+), 7 deletions(-)
---
diff --git a/data/theme/gnome-shell-sass/widgets/_app-grid.scss 
b/data/theme/gnome-shell-sass/widgets/_app-grid.scss
index 8a024f3ca5..b8291eefe7 100644
--- a/data/theme/gnome-shell-sass/widgets/_app-grid.scss
+++ b/data/theme/gnome-shell-sass/widgets/_app-grid.scss
@@ -65,6 +65,19 @@ $app_grid_fg_color: #fff;
       & > StIcon { icon-size: 16px }
     }
   }
+
+  & .icon-grid {
+    row-spacing: $base_spacing * 2;
+    column-spacing: $base_spacing * 5;
+  }
+
+  & .page-indicators {
+    margin-bottom: 18px;
+
+    .page-indicator {
+      padding: 15px 12px;
+    }
+  }
 }
 .app-folder-dialog-container {
   padding: 12px;
diff --git a/js/ui/appDisplay.js b/js/ui/appDisplay.js
index 6f87a46b0e..c04ad761d0 100644
--- a/js/ui/appDisplay.js
+++ b/js/ui/appDisplay.js
@@ -1002,6 +1002,24 @@ var AppSearchProvider = class AppSearchProvider {
     }
 };
 
+var FolderGrid = GObject.registerClass(
+class FolderGrid extends IconGrid.IconGrid {
+    _init() {
+        super._init({
+            allow_incomplete_pages: false,
+            orientation: Clutter.Orientation.HORIZONTAL,
+            columns_per_page: 3,
+            rows_per_page: 3,
+            page_halign: Clutter.ActorAlign.CENTER,
+            page_valign: Clutter.ActorAlign.CENTER,
+        });
+    }
+
+    adaptToSize(width, height) {
+        this.layout_manager.adaptToSize(width, height);
+    }
+});
+
 var FolderView = GObject.registerClass(
 class FolderView extends BaseAppView {
     _init(folder, id, parentView) {
@@ -1011,6 +1029,8 @@ class FolderView extends BaseAppView {
             y_expand: true,
         });
 
+        this._grid = new FolderGrid();
+
         // If it not expand, the parent doesn't take into account its preferred_width when allocating
         // the second time it allocates, so we apply the "Standard hack for ClutterBinLayout"
         this._grid.x_expand = true;
@@ -1024,17 +1044,37 @@ class FolderView extends BaseAppView {
             x_expand: true,
             y_expand: true,
         });
-        this._scrollView.set_policy(St.PolicyType.NEVER, St.PolicyType.EXTERNAL);
-        this.add_actor(this._scrollView);
+        this._scrollView.set_policy(St.PolicyType.EXTERNAL, St.PolicyType.NEVER);
+        this._scrollView.add_actor(this._grid);
 
-        let scrollableContainer = new St.BoxLayout({
+        const box = new St.BoxLayout({
             vertical: true,
             reactive: true,
             x_expand: true,
             y_expand: true,
         });
-        scrollableContainer.add_actor(this._grid);
-        this._scrollView.add_actor(scrollableContainer);
+        box.add_actor(this._scrollView);
+
+        // Page Dots
+        this._adjustment = this._scrollView.hscroll.adjustment;
+        this._adjustment.connect('notify::value', adj => {
+            this._pageIndicators.setCurrentPosition(adj.value / adj.page_size);
+        });
+
+        this._pageIndicators = new PageIndicators.PageIndicators(Clutter.Orientation.HORIZONTAL);
+        this._pageIndicators.y_expand = false;
+        this._pageIndicators.connect('page-activated',
+            (indicators, pageIndex) => {
+                this._grid.goToPage(pageIndex);
+            });
+        this._pageIndicators.connect('scroll-event', (actor, event) => {
+            this._scrollView.event(event, false);
+        });
+        box.add_actor(this._pageIndicators);
+        this.add_actor(box);
+
+        this._availWidth = 0;
+        this._availHeight = 0;
 
         let action = new Clutter.PanAction({ interpolate: true });
         action.connect('pan', this._onPan.bind(this));
@@ -1079,10 +1119,24 @@ class FolderView extends BaseAppView {
     }
 
     adaptToSize(width, height) {
-        this._parentAvailableWidth = width;
-        this._parentAvailableHeight = height;
+        const oldNPages = this._grid.nPages;
+        const [, indicatorHeight] = this._pageIndicators.get_preferred_height(-1);
+        height -= indicatorHeight;
 
         this._grid.adaptToSize(width, height);
+
+        if (this._availWidth != width || this._availHeight != height || oldNPages != this._grid.nPages) {
+            Meta.later_add(Meta.LaterType.BEFORE_REDRAW, () => {
+                this._adjustment.value = 0;
+                this._grid.currentPage = 0;
+                this._pageIndicators.setNPages(this._grid.nPages);
+                this._pageIndicators.setCurrentPosition(0);
+                return GLib.SOURCE_REMOVE;
+            });
+        }
+
+        this._availWidth = width;
+        this._availHeight = height;
     }
 
     _loadApps() {