[mutter] monitor-manager/native: Bail if gamma LUT size differs

[Marge Bot <marge-bot src gnome org>]

commit 15bbded86b70f86682f4cdc324199344885e4b94
Author: Jonas Ådahl <jadahl gmail com>
Date:   Tue Oct 26 11:09:41 2021 +0200

    monitor-manager/native: Bail if gamma LUT size differs
    
    Don't attempt to set a CRTC GAMMA LUT with a different size than what is
    already there.
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2141>

 src/backends/native/meta-monitor-manager-native.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)
---
diff --git a/src/backends/native/meta-monitor-manager-native.c 
b/src/backends/native/meta-monitor-manager-native.c
index f967fbf15b..74349888b8 100644
--- a/src/backends/native/meta-monitor-manager-native.c
+++ b/src/backends/native/meta-monitor-manager-native.c
@@ -493,6 +493,7 @@ meta_monitor_manager_native_set_crtc_gamma (MetaMonitorManager *manager,
     META_MONITOR_MANAGER_NATIVE (manager);
   MetaCrtcKms *crtc_kms;
   MetaKmsCrtc *kms_crtc;
+  const MetaKmsCrtcState *crtc_state;
   g_autofree char *gamma_ramp_string = NULL;
   MetaBackend *backend = meta_monitor_manager_get_backend (manager);
   ClutterStage *stage = CLUTTER_STAGE (meta_backend_get_stage (backend));
@@ -501,6 +502,17 @@ meta_monitor_manager_native_set_crtc_gamma (MetaMonitorManager *manager,
 
   crtc_kms = META_CRTC_KMS (crtc);
   kms_crtc = meta_crtc_kms_get_kms_crtc (META_CRTC_KMS (crtc));
+  crtc_state = meta_kms_crtc_get_current_state (kms_crtc);
+
+  if (size != crtc_state->gamma.size)
+    {
+      MetaKmsDevice *kms_device = meta_kms_crtc_get_device (kms_crtc);
+
+      g_warning ("Tried to set a different gamma LUT size on %u (%s)",
+                 meta_kms_crtc_get_id (kms_crtc),
+                 meta_kms_device_get_path (kms_device));
+      return;
+    }
 
   g_hash_table_replace (manager_native->crtc_gamma_cache,
                         GUINT_TO_POINTER (meta_crtc_get_id (crtc)),