From ed1170906b0c5ea3b8655b535f59605b9241c2f9 Mon Sep 17 00:00:00 2001
From: Georges Basile Stavracas Neto <georges.stavracas@gmail.com>
Date: Wed, 30 Dec 2020 12:44:00 -0300
Subject: [PATCH] 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 93782f431..36a15a71f 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();
     }
 });