[gnome-shell] st/viewport: Only extend child allocation when scrolled

[Florian Müllner <fmuellner src gnome org>]

commit 481014ac9edf0e79601140727c2be817b1f72c12
Author: Florian Müllner <fmuellner gnome org>
Date:   Mon Jun 29 00:16:58 2020 +0200

    st/viewport: Only extend child allocation when scrolled
    
    When scrolled, the container's allocation is smaller than the allocation
    of the content. To account for that, commit 2717ca9d080eb added the
    additional size reported by the layout manager to the content allocation.
    
    However as it did so unconditionally, we now allow children to extend
    outside the parent even when *not* scrolled, which breaks any constraints
    set on the container (like "width" or "max-height").
    
    Fix this by only extending the child allocation in scrollable dimensions.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/2491

 src/st/st-viewport.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/src/st/st-viewport.c b/src/st/st-viewport.c
index fb1df91d90..039eebf461 100644
--- a/src/st/st-viewport.c
+++ b/src/st/st-viewport.c
@@ -261,8 +261,10 @@ st_viewport_allocate (ClutterActor           *actor,
   clutter_actor_set_allocation (actor, box);
 
   content_box = viewport_box;
-  content_box.x2 += MAX (0, min_width - avail_width);
-  content_box.y2 += MAX (0, min_height - avail_height);
+  if (priv->hadjustment)
+    content_box.x2 += MAX (0, min_width - avail_width);
+  if (priv->vadjustment)
+    content_box.y2 += MAX (0, min_height - avail_height);
 
   clutter_layout_manager_allocate (layout, CLUTTER_CONTAINER (actor),
                                    &content_box);