workspaceThumbnail: Do not update scale while collapsing

The scale property tracks the relative size at which we display thumbnails
given the space we have available.

That assumes that the allocation represents that available space, but it will
actually be smaller while the minimap itself is collapsing.

Luckily we have an easy option to avoid a distorted scale: Just don't update
it while collapsing. We expect scale changes when adding or removing thumbnails,
but as we freeze those during transitions, we can do the same with the scale.

https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3739

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1696>

diff --git a/js/ui/workspaceThumbnail.js b/js/ui/workspaceThumbnail.js
index 03e97f1752a9ad1a078fe5912289ef9638a2eb34..6f009b8a088081598215bc32c1d19a41921290dc 100644 (file)
--- a/js/ui/workspaceThumbnail.js
+++ b/js/ui/workspaceThumbnail.js
@@ -1288,27 +1288,31 @@ var ThumbnailsBox = GObject.registerClass({
         const portholeHeight = this._porthole.height;
         const spacing = themeNode.get_length('spacing');
 
-        // Compute the scale we'll need once everything is updated
         const nWorkspaces = this._thumbnails.length;
-        let totalSpacing = (nWorkspaces - 1) * spacing;
-        const availableWidth = (box.get_width() - totalSpacing) / nWorkspaces;
-
-        const hScale = availableWidth / portholeWidth;
-        const vScale = box.get_height() / portholeHeight;
-        const newScale = Math.min(hScale, vScale);
-
-        if (newScale != this._targetScale) {
-            if (this._targetScale > 0) {
-                // We don't do the tween immediately because we need to observe the ordering
-                // in queueUpdateStates - if workspaces have been removed we need to slide them
-                // out as the first thing.
-                this._targetScale = newScale;
-                this._pendingScaleUpdate = true;
-            } else {
-                this._targetScale = this._scale = newScale;
-            }
 
-            this._queueUpdateStates();
+        // Compute the scale we'll need once everything is updated,
+        // unless we are currently transitioning
+        if (this._expandFraction === 1) {
+            const totalSpacing = (nWorkspaces - 1) * spacing;
+            const availableWidth = (box.get_width() - totalSpacing) / nWorkspaces;
+
+            const hScale = availableWidth / portholeWidth;
+            const vScale = box.get_height() / portholeHeight;
+            const newScale = Math.min(hScale, vScale);
+
+            if (newScale !== this._targetScale) {
+                if (this._targetScale > 0) {
+                    // We don't ease immediately because we need to observe the
+                    // ordering in queueUpdateStates - if workspaces have been
+                    // removed we need to slide them out as the first thing.
+                    this._targetScale = newScale;
+                    this._pendingScaleUpdate = true;
+                } else {
+                    this._targetScale = this._scale = newScale;
+                }
+
+                this._queueUpdateStates();
+            }
         }
 
         const ratio = portholeWidth / portholeHeight;