[mutter] kms/crtc: Don't report predicted gamma changes

[Robert Mader <rmader src gnome org>]

commit d985069542cfaf356192d0891c2601367074afb1
Author: Jonas Ådahl <jadahl gmail com>
Date:   Tue Jul 26 11:02:32 2022 +0200

    kms/crtc: Don't report predicted gamma changes
    
    We started to report resource changes using prediction when an update
    had been successfully committed. While at it, gamma changes were
    reported too, but this was problematic, as gsd-color will listen for the
    MonitorsChanged D-Bus signal and naively set the gamma again, even if it
    didn't change. There aren't currently any actual use cases for being
    told when gamma changes from a prediction, so just ignore it and just
    report privacy screen changes.
    
    This avoids a feedback loop between mutter and gsd-color.
    
    Fixes: 81b28a1d975f2511d8800faa2c187703eb66ce63
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2531>

 src/backends/native/meta-kms-crtc-private.h | 4 ++--
 src/backends/native/meta-kms-crtc.c         | 6 +-----
 src/backends/native/meta-kms-impl-device.c  | 7 +------
 3 files changed, 4 insertions(+), 13 deletions(-)
---
diff --git a/src/backends/native/meta-kms-crtc-private.h b/src/backends/native/meta-kms-crtc-private.h
index 79a5f0fe64..baf5f4099a 100644
--- a/src/backends/native/meta-kms-crtc-private.h
+++ b/src/backends/native/meta-kms-crtc-private.h
@@ -42,8 +42,8 @@ MetaKmsResourceChanges meta_kms_crtc_update_state (MetaKmsCrtc *crtc);
 
 void meta_kms_crtc_disable (MetaKmsCrtc *crtc);
 
-MetaKmsResourceChanges meta_kms_crtc_predict_state (MetaKmsCrtc   *crtc,
-                                                    MetaKmsUpdate *update);
+void meta_kms_crtc_predict_state (MetaKmsCrtc   *crtc,
+                                  MetaKmsUpdate *update);
 
 uint32_t meta_kms_crtc_get_prop_id (MetaKmsCrtc     *crtc,
                                     MetaKmsCrtcProp  prop);
diff --git a/src/backends/native/meta-kms-crtc.c b/src/backends/native/meta-kms-crtc.c
index 707dfd4b8c..ee9e19d2d9 100644
--- a/src/backends/native/meta-kms-crtc.c
+++ b/src/backends/native/meta-kms-crtc.c
@@ -278,14 +278,13 @@ meta_kms_crtc_disable (MetaKmsCrtc *crtc)
   crtc->current_state.drm_mode = (drmModeModeInfo) { 0 };
 }
 
-MetaKmsResourceChanges
+void
 meta_kms_crtc_predict_state (MetaKmsCrtc   *crtc,
                              MetaKmsUpdate *update)
 {
   GList *mode_sets;
   GList *crtc_gammas;
   GList *l;
-  MetaKmsResourceChanges changes = META_KMS_RESOURCE_CHANGE_NONE;
 
   mode_sets = meta_kms_update_get_mode_sets (update);
   for (l = mode_sets; l; l = l->next)
@@ -338,11 +337,8 @@ meta_kms_crtc_predict_state (MetaKmsCrtc   *crtc,
       crtc->current_state.gamma.blue =
         g_memdup2 (gamma->blue, gamma->size * sizeof (uint16_t));
 
-      changes |= META_KMS_RESOURCE_CHANGE_GAMMA;
       break;
     }
-
-  return changes;
 }
 
 static void
diff --git a/src/backends/native/meta-kms-impl-device.c b/src/backends/native/meta-kms-impl-device.c
index 653a96f719..dc2ac31ef4 100644
--- a/src/backends/native/meta-kms-impl-device.c
+++ b/src/backends/native/meta-kms-impl-device.c
@@ -923,12 +923,7 @@ meta_kms_impl_device_predict_states (MetaKmsImplDevice *impl_device,
   MetaKmsResourceChanges changes = META_KMS_RESOURCE_CHANGE_NONE;
   GList *l;
 
-  for (l = priv->crtcs; l; l = l->next)
-    {
-      MetaKmsCrtc *crtc = l->data;
-
-      changes |= meta_kms_crtc_predict_state (crtc, update);
-    }
+  g_list_foreach (priv->crtcs, (GFunc) meta_kms_crtc_predict_state, update);
 
   for (l = priv->connectors; l; l = l->next)
     {