[gnome-shell] workspacesView: Center active workspace in allocation

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

commit ed1170906b0c5ea3b8655b535f59605b9241c2f9
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Wed Dec 30 12:44:00 2020 -0300

    workspacesView: Center active workspace in allocation
    
    When vertically snapping, WorkspacesView currently allocates workspaces
    side-by-side, then applies an extra step of translation to center to
    the active workspace. This extra step, however, gets in our way because
    now we need tighter control of the workspaces positions in allocation,
    in order to properly interpolate them.
    
    Move the translation of workspaces to the allocation code itself, and
    remove the extra translation step.
    
    Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1613>

 js/ui/workspacesView.js | 56 +++++++++++--------------------------------------
 1 file changed, 12 insertions(+), 44 deletions(-)
---
diff --git a/js/ui/workspacesView.js b/js/ui/workspacesView.js
index 93782f431b..36a15a71ff 100644
--- a/js/ui/workspacesView.js
+++ b/js/ui/workspacesView.js
@@ -162,15 +162,22 @@ class WorkspacesView extends WorkspacesViewBase {
         const [width, height] = box.get_size();
         const [workspace] = this._workspaces;
 
+        const rtl = this.text_direction === Clutter.TextDirection.RTL;
+        const adj = this._scrollAdjustment;
+        const currentWorkspace = vertical || !rtl
+            ? adj.value : adj.upper - adj.value;
+
         // Single fit mode implies centered too
         let x1 = 0;
         let y1 = 0;
         if (vertical) {
             const [, workspaceHeight] = workspace.get_preferred_height(width);
             y1 += (height - workspaceHeight) / 2;
+            y1 -= currentWorkspace * (workspaceHeight + spacing);
         } else {
             const [, workspaceWidth] = workspace.get_preferred_width(height);
             x1 += (width - workspaceWidth) / 2;
+            x1 -= currentWorkspace * (workspaceWidth + spacing);
         }
 
         const fitSingleBox = new Clutter.ActorBox({ x1, y1 });
@@ -257,8 +264,6 @@ class WorkspacesView extends WorkspacesViewBase {
                     fitAllBox.y1);
             }
         });
-
-        this._updateScrollPosition();
     }
 
     getActiveWorkspace() {
@@ -270,7 +275,6 @@ class WorkspacesView extends WorkspacesViewBase {
     animateToOverview() {
         for (let w = 0; w < this._workspaces.length; w++)
             this._workspaces[w].zoomToOverview();
-        this._updateScrollPosition();
         this._updateVisibility();
     }
 
@@ -306,10 +310,13 @@ class WorkspacesView extends WorkspacesViewBase {
         let workspaceManager = global.workspace_manager;
         let active = workspaceManager.get_active_workspace_index();
 
+        const fitMode = this._fitModeAdjustment.value;
+        const singleFitMode = fitMode === FitMode.SINGLE;
+
         for (let w = 0; w < this._workspaces.length; w++) {
             let workspace = this._workspaces[w];
 
-            if (this._animating || this._gestureActive)
+            if (this._animating || this._gestureActive || !singleFitMode)
                 workspace.show();
             else
                 workspace.visible = Math.abs(w - active) <= 1;
@@ -342,8 +349,6 @@ class WorkspacesView extends WorkspacesViewBase {
             this._workspaces[j].destroy();
             this._workspaces.splice(j, 1);
         }
-
-        this._updateScrollPosition();
     }
 
     _activeWorkspaceChanged(_wm, _from, _to, _direction) {
@@ -406,44 +411,7 @@ class WorkspacesView extends WorkspacesViewBase {
             metaWorkspace.activate(global.get_current_time());
         }
 
-        this._updateScrollPosition();
-    }
-
-    _updateScrollPosition() {
-        if (!this.has_allocation())
-            return;
-
-        const adj = this._scrollAdjustment;
-
-        if (adj.upper == 1)
-            return;
-
-        const workspaceManager = global.workspace_manager;
-        const vertical = workspaceManager.layout_rows === -1;
-        const rtl = this.text_direction === Clutter.TextDirection.RTL;
-        const fitMode = this._fitModeAdjustment.value;
-        let progress = vertical || !rtl
-            ? adj.value : adj.upper - adj.value - 1;
-        progress = Util.lerp(progress / (adj.upper - 1), 0, fitMode);
-
-        // Use workspaces geometry to determine the size to offset
-        const firstWorkspaceBox = rtl
-            ? this._workspaces[this._workspaces.length - 1].allocation
-            : this._workspaces[0].allocation;
-        const lastWorkspaceBox = rtl
-            ? this._workspaces[0].allocation
-            : this._workspaces[this._workspaces.length - 1].allocation;
-        const [workspaceWidth, workspaceHeight] = firstWorkspaceBox.get_size();
-        const size = vertical
-            ? lastWorkspaceBox.y2 - firstWorkspaceBox.y1 - workspaceHeight
-            : lastWorkspaceBox.x2 - firstWorkspaceBox.x1 - workspaceWidth;
-
-        for (const ws of this._workspaces) {
-            if (vertical)
-                ws.translation_y = -progress * size;
-            else
-                ws.translation_x = -progress * size;
-        }
+        this.queue_relayout();
     }
 });