[gnome-flashback] monitor-manager: derive configured global scale using common value

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 74ce4bf5b58eeb45de87142334cd4fbb207e4409
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Sun Sep 12 23:03:39 2021 +0300

    monitor-manager: derive configured global scale using common value
    
    Based on mutter commit:
    https://gitlab.gnome.org/GNOME/mutter/-/commit/1ab79c79a529

 backends/gf-monitor-manager.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)
---
diff --git a/backends/gf-monitor-manager.c b/backends/gf-monitor-manager.c
index b6310c9..0bf9593 100644
--- a/backends/gf-monitor-manager.c
+++ b/backends/gf-monitor-manager.c
@@ -357,11 +357,19 @@ static gfloat
 derive_configured_global_scale (GfMonitorManager *manager,
                                 GfMonitorsConfig *config)
 {
-  GfLogicalMonitorConfig *logical_monitor_config;
+  GList *l;
 
-  logical_monitor_config = config->logical_monitor_configs->data;
+  for (l = config->logical_monitor_configs; l; l = l->next)
+    {
+      GfLogicalMonitorConfig *monitor_config;
+
+      monitor_config = l->data;
+
+      if (is_global_scale_matching_in_config (config, monitor_config->scale))
+        return monitor_config->scale;
+    }
 
-  return logical_monitor_config->scale;
+  return 1.0f;
 }
 
 static gfloat