appDisplay: Adapt to available extra space showing icon grids

Depending on the available horizontal space, we may want to manipulate
the icon grid and scroll view spacing to result in an optimal layout
that has space left to preview prev/next pages.

The main change here is that, when adapting to the available size, the
space given to a page does not necessarily match the available space,
as we need to be able to show more than one page at a time.

With this decoupling of available and page sizes in place, we now know
how much space there is available in order to extend the padding between
pages, or the fade effect applied to the previewed pages.

Underneath, we rely a bit less on hardcoded CSS paddings, and a bit more
on the StScrollView::content-padding property.

All put together, gives us proper space management from ultra-wide
displays, to display ratios that are close to the optimal grid ratio.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1630>

data/theme/gnome-shell-sass/widgets/_app-grid.scss

@@ -125,10 +125,8 @@ $app_grid_fg_color: #fff;
   }
 }
 
-// Some hacks I don't even know
 .apps-scroll-view {
-  // horizontal padding to make sure scrollbars or dash don't overlap content
+  padding: 0;
-  padding: 0 88px;
 }
 
 // shutdown and other actions in the grid
@@ -140,20 +138,26 @@ $app_grid_fg_color: #fff;
 }
 
 .page-navigation-hint {
-  background: rgba(255, 255, 255, 0.05);
+  width: 300px;
-  width: 88px;
 
   &.dnd {
     background: rgba(255, 255, 255, 0.1);
   }
 
-  &.next {
+  &.next:ltr,
-    &:ltr { border-radius: 15px 0px 0px 15px; }
+  &.previous:rtl {
-    &:rtl { border-radius: 0px 15px 15px 0px; }
+    background-gradient-start: rgba(255, 255, 255, 0.05);
+    background-gradient-end: transparent;
+    background-gradient-direction: horizontal;
+    border-radius: 15px 0px 0px 15px;
   }
-  &.previous {
+
-    &:ltr { border-radius: 0px 15px 15px 0px; }
+  &.previous:ltr,
-    &:rtl { border-radius: 15px 0px 0px 15px; }
+  &.next:rtl {
+    background-gradient-start: transparent;
+    background-gradient-end: rgba(255, 255, 255, 0.05);
+    background-gradient-direction: horizontal;
+    border-radius: 0px 15px 15px 0px;
   }
 }
 

js/ui/appDisplay.js

@@ -39,8 +39,11 @@ var APP_ICON_TITLE_COLLAPSE_TIME = 100;
 const FOLDER_DIALOG_ANIMATION_TIME = 200;
 
 const PAGE_PREVIEW_ANIMATION_TIME = 150;
-const PAGE_PREVIEW_FADE_EFFECT_OFFSET = 160;
+const PAGE_PREVIEW_ANIMATION_START_OFFSET = 100;
+const PAGE_PREVIEW_FADE_EFFECT_MAX_OFFSET = 300;
+const PAGE_PREVIEW_MAX_ARROW_OFFSET = 80;
 const PAGE_INDICATOR_FADE_TIME = 200;
+const MAX_PAGE_PADDING = 200;
 
 const OVERSHOOT_THRESHOLD = 20;
 const OVERSHOOT_TIMEOUT = 1000;
@@ -322,10 +325,22 @@ var BaseAppView = GObject.registerClass({
 
     _updateFadeForNavigation() {
         const fadeMargin = new Clutter.Margin();
-        fadeMargin.right = (this._pagesShown & SidePages.NEXT) !== 0
+        const rtl = this.get_text_direction() === Clutter.TextDirection.RTL;
-            ? -PAGE_PREVIEW_FADE_EFFECT_OFFSET : 0;
+        const showingNextPage = this._pagesShown & SidePages.NEXT;
-        fadeMargin.left = (this._pagesShown & SidePages.PREVIOUS) !== 0
+        const showingPrevPage = this._pagesShown & SidePages.PREVIOUS;
-            ? -PAGE_PREVIEW_FADE_EFFECT_OFFSET : 0;
+
+        if ((showingNextPage && !rtl) || (showingPrevPage && rtl)) {
+            fadeMargin.right = Math.max(
+                -PAGE_PREVIEW_FADE_EFFECT_MAX_OFFSET,
+                -(this._availWidth - this._grid.layout_manager.pageWidth) / 2);
+        }
+
+        if ((showingPrevPage && !rtl) || (showingNextPage && rtl)) {
+            fadeMargin.left = Math.max(
+                -PAGE_PREVIEW_FADE_EFFECT_MAX_OFFSET,
+                -(this._availWidth - this._grid.layout_manager.pageWidth) / 2);
+        }
+
         this._scrollView.update_fade_effect(fadeMargin);
     }
 
@@ -1077,10 +1092,61 @@ var BaseAppView = GObject.registerClass({
         const availWidth = box.get_width();
         const availHeight = box.get_height();
 
-        this._grid.adaptToSize(availWidth, availHeight);
+        const gridRatio = this._grid.layout_manager.columnsPerPage /
+            this._grid.layout_manager.rowsPerPage;
+        const spaceRatio = availWidth / availHeight;
+        let pageWidth, pageHeight;
+
+        if (spaceRatio > gridRatio * 1.1) {
+            // Enough room for some preview
+            pageHeight = availHeight;
+            pageWidth = availHeight * gridRatio;
+
+            if (spaceRatio > gridRatio * 1.5) {
+                // Ultra-wide layout, give some extra space for
+                // the page area, but up to an extent.
+                const extraPageSpace = Math.min(
+                    (availWidth - pageWidth) / 2, MAX_PAGE_PADDING);
+                pageWidth += extraPageSpace;
+                this._grid.layout_manager.pagePadding.left = extraPageSpace / 2;
+                this._grid.layout_manager.pagePadding.right = extraPageSpace / 2;
+            }
+        } else {
+            // Not enough room, needs to shrink horizontally
+            pageWidth = availWidth * 0.8;
+            pageHeight = availHeight;
+            this._grid.layout_manager.pagePadding.left = availWidth * 0.02;
+            this._grid.layout_manager.pagePadding.right = availWidth * 0.02;
+        }
+
+        this._grid.adaptToSize(pageWidth, pageHeight);
+
+        const horizontalPadding = (availWidth - this._grid.layout_manager.pageWidth) / 2;
+        const verticalPadding = (availHeight - this._grid.layout_manager.pageHeight) / 2;
+
+        this._scrollView.content_padding = new Clutter.Margin({
+            left: horizontalPadding,
+            right: horizontalPadding,
+            top: verticalPadding,
+            bottom: verticalPadding,
+        });
 
         this._availWidth = availWidth;
         this._availHeight = availHeight;
+
+        this._pageIndicatorOffset = horizontalPadding;
+        this._pageArrowOffset = Math.max(
+            horizontalPadding - PAGE_PREVIEW_MAX_ARROW_OFFSET, 0);
+    }
+
+    _getIndicatorOffset(page, progress, baseOffset) {
+        const rtl = this.get_text_direction() === Clutter.TextDirection.RTL;
+        const translationX =
+            (1 - progress) * PAGE_PREVIEW_ANIMATION_START_OFFSET;
+
+        page = rtl ? -page : page;
+
+        return (translationX - baseOffset) * page;
     }
 
     _getPagePreviewAdjustment(page) {
@@ -1108,18 +1174,18 @@ var BaseAppView = GObject.registerClass({
 
         const indicator = page > 0
             ? this._nextPageIndicator : this._prevPageIndicator;
-        const rtl = this.get_text_direction() === Clutter.TextDirection.RTL;
 
         const notifyId = adjustment.connect('notify::value', () => {
-            let translationX = (1 - adjustment.value) * 100 * page;
-            translationX = rtl ? -translationX : translationX;
             const nextPage = this._grid.currentPage + page;
             const hasFollowingPage = nextPage >= 0 &&
                 nextPage < this._grid.nPages;
 
             if (hasFollowingPage) {
                 const items = this._grid.getItemsAtPage(nextPage);
-                items.forEach(item => (item.translation_x = translationX));
+                items.forEach(item => {
+                    item.translation_x =
+                        this._getIndicatorOffset(page, adjustment.value, 0);
+                });
 
                 if (!(state & SidePages.DND)) {
                     const pageArrow = page > 0
@@ -1128,7 +1194,9 @@ var BaseAppView = GObject.registerClass({
                     pageArrow.set({
                         visible: true,
                         opacity: adjustment.value * 255,
-                        translationX,
+                        translation_x: this._getIndicatorOffset(
+                            page, adjustment.value,
+                            this._pageArrowOffset),
                     });
                 }
             }
@@ -1139,7 +1207,9 @@ var BaseAppView = GObject.registerClass({
                 indicator.set({
                     visible: true,
                     opacity: adjustment.value * 255,
-                    translationX,
+                    translation_x: this._getIndicatorOffset(
+                        page, adjustment.value,
+                        this._pageIndicatorOffset - indicator.width),
                 });
             }
             this._syncClip();
@@ -1382,6 +1452,7 @@ class AppDisplay extends BaseAppView {
         const [, indicatorHeight] = this._pageIndicators.get_preferred_height(-1);
         height -= indicatorHeight;
 
+        this._grid.findBestModeForSize(width, height);
         super.adaptToSize(width, height);
     }
 

js/ui/iconGrid.js

@@ -1223,7 +1223,7 @@ var IconGrid = GObject.registerClass({
         }
     }
 
-    _findBestModeForSize(width, height) {
+    findBestModeForSize(width, height) {
         const { pagePadding } = this.layout_manager;
         width -= pagePadding.left + pagePadding.right;
         height -= pagePadding.top + pagePadding.bottom;
@@ -1446,7 +1446,6 @@ var IconGrid = GObject.registerClass({
     }
 
     adaptToSize(width, height) {
-        this._findBestModeForSize(width, height);
         this.layout_manager.adaptToSize(width, height);
     }