constraints: Try place popup on the same monitor as the anchor rect

When we'd place a popup, if the initially calculated position would be
on another monitor than the anchor rect on the parent window, the
later constrained position would end up on another monitor than the
parent window. This could for example happen if a popup menu opening
towards the right was opened very close to the screen edge of a right
most monitor in a two side by side monitor setup.

Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/1783
Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/1768
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2252>

(cherry picked from commit 0205398d96b4d8b352b774fffeb9a812f5a18681)

1 files changed, 50 insertions, 17 deletions

diff --git a/src/core/constraints.c b/src/core/constraints.c
index 4b1d95338..f5729354f 100644
--- a/src/core/constraints.c
+++ b/src/core/constraints.c
@@ -350,6 +350,7 @@ setup_constraint_info (ConstraintInfo      *info,
     meta_backend_get_monitor_manager (backend);
   MetaLogicalMonitor *logical_monitor;
   MetaWorkspace *cur_workspace;
+  MetaPlacementRule *placement_rule;
 
   info->orig    = *orig;
   info->current = *new;
@@ -405,9 +406,41 @@ setup_constraint_info (ConstraintInfo      *info,
   if (!info->is_user_action)
     info->fixed_directions = FIXED_DIRECTION_NONE;
 
-  logical_monitor =
-    meta_monitor_manager_get_logical_monitor_from_rect (monitor_manager,
-                                                        &info->current);
+  placement_rule = meta_window_get_placement_rule (window);
+  if (placement_rule)
+    {
+      MetaRectangle rect;
+      MetaRectangle parent_rect;
+
+      rect = placement_rule->anchor_rect;
+
+      parent_rect = placement_rule->parent_rect;
+      rect.x += parent_rect.x;
+      rect.y += parent_rect.y;
+      logical_monitor =
+        meta_monitor_manager_get_logical_monitor_from_rect (monitor_manager,
+                                                            &rect);
+      if (!logical_monitor)
+        {
+          logical_monitor =
+            meta_monitor_manager_get_logical_monitor_from_rect (monitor_manager,
+                                                                &parent_rect);
+        }
+    }
+  else
+    {
+      logical_monitor =
+        meta_monitor_manager_get_logical_monitor_from_rect (monitor_manager,
+                                                            &info->current);
+    }
+
+  if (!logical_monitor)
+    {
+      g_warning ("No sensible logical monitor could be used for constraining");
+      logical_monitor =
+        meta_monitor_manager_get_primary_logical_monitor (monitor_manager);
+    }
+
   meta_window_get_work_area_for_logical_monitor (window,
                                                  logical_monitor,
                                                  &info->work_area_monitor);
@@ -527,23 +560,23 @@ place_window_if_needed(MetaWindow     *window,
         {
           meta_window_place (window, orig_rect.x, orig_rect.y,
                              &placed_rect.x, &placed_rect.y);
+
+          /* placing the window may have changed the monitor.  Find the
+           * new monitor and update the ConstraintInfo
+           */
+          logical_monitor =
+            meta_monitor_manager_get_logical_monitor_from_rect (monitor_manager,
+                                                                &placed_rect);
+          info->entire_monitor = logical_monitor->rect;
+          meta_window_get_work_area_for_logical_monitor (window,
+                                                         logical_monitor,
+                                                         &info->work_area_monitor);
+          cur_workspace = window->display->workspace_manager->active_workspace;
+          info->usable_monitor_region =
+            meta_workspace_get_onmonitor_region (cur_workspace, logical_monitor);
         }
       did_placement = TRUE;
 
-      /* placing the window may have changed the monitor.  Find the
-       * new monitor and update the ConstraintInfo
-       */
-      logical_monitor =
-        meta_monitor_manager_get_logical_monitor_from_rect (monitor_manager,
-                                                            &placed_rect);
-      info->entire_monitor = logical_monitor->rect;
-      meta_window_get_work_area_for_logical_monitor (window,
-                                                     logical_monitor,
-                                                     &info->work_area_monitor);
-      cur_workspace = window->display->workspace_manager->active_workspace;
-      info->usable_monitor_region =
-        meta_workspace_get_onmonitor_region (cur_workspace, logical_monitor);
-
       info->current.x = placed_rect.x;
       info->current.y = placed_rect.y;