From 7c87c1c24f3fdf1e640aca2725072effb281ae84 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marco=20Trevisan=20=28Trevi=C3=B1o=29?= <mail@3v1n0.net>
Date: Thu, 29 Nov 2018 23:04:17 -0500
Subject: [PATCH] monitor-manager: Check if all monitor scales are matching in
 global mode

When global scaling is set we need to ensure that all the requested scale
configurations are matching, otherwise we'd end up in a mixed setup that
we don't support in this scenario.

Fixes https://gitlab.gnome.org/GNOME/mutter/issues/407

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/336>
---
 src/backends/meta-monitor-manager.c | 51 ++++++++++++++++++++++++++---
 1 file changed, 46 insertions(+), 5 deletions(-)

diff --git a/src/backends/meta-monitor-manager.c b/src/backends/meta-monitor-manager.c
index 1e08f3a82..71ff8a2a3 100644
--- a/src/backends/meta-monitor-manager.c
+++ b/src/backends/meta-monitor-manager.c
@@ -125,6 +125,10 @@ meta_monitor_manager_get_active_monitor (MetaMonitorManager *manager);
 static void
 meta_monitor_manager_real_read_current_state (MetaMonitorManager *manager);
 
+static gboolean
+is_global_scale_matching_in_config (MetaMonitorsConfig *config,
+                                    float               scale);
+
 MetaBackend *
 meta_monitor_manager_get_backend (MetaMonitorManager *manager)
 {
@@ -1761,6 +1765,43 @@ meta_monitor_manager_is_scale_supported (MetaMonitorManager          *manager,
   return FALSE;
 }
 
+static gboolean
+is_global_scale_matching_in_config (MetaMonitorsConfig *config,
+                                    float               scale)
+{
+  GList *l;
+
+  for (l = config->logical_monitor_configs; l; l = l->next)
+    {
+      MetaLogicalMonitorConfig *logical_monitor_config = l->data;
+
+      if (!G_APPROX_VALUE (logical_monitor_config->scale, scale, FLT_EPSILON))
+        return FALSE;
+    }
+
+  return TRUE;
+}
+
+static gboolean
+meta_monitor_manager_is_scale_supported_for_config (MetaMonitorManager *manager,
+                                                    MetaMonitorsConfig *config,
+                                                    MetaMonitor        *monitor,
+                                                    MetaMonitorMode    *monitor_mode,
+                                                    float               scale)
+{
+  if (meta_monitor_manager_is_scale_supported (manager, config->layout_mode,
+                                               monitor, monitor_mode, scale))
+    {
+      if (meta_monitor_manager_get_capabilities (manager) &
+          META_MONITOR_MANAGER_CAPABILITY_GLOBAL_SCALE_REQUIRED)
+        return is_global_scale_matching_in_config (config, scale);
+
+      return TRUE;
+    }
+
+  return FALSE;
+}
+
 static gboolean
 meta_monitor_manager_is_config_applicable (MetaMonitorManager *manager,
                                            MetaMonitorsConfig *config,
@@ -1799,11 +1840,11 @@ meta_monitor_manager_is_config_applicable (MetaMonitorManager *manager,
               return FALSE;
             }
 
-          if (!meta_monitor_manager_is_scale_supported (manager,
-                                                        config->layout_mode,
-                                                        monitor,
-                                                        monitor_mode,
-                                                        scale))
+          if (!meta_monitor_manager_is_scale_supported_for_config (manager,
+                                                                   config,
+                                                                   monitor,
+                                                                   monitor_mode,
+                                                                   scale))
             {
               g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
                            "Scale not supported by backend");