[mutter] monitor: Add API to get GAMMA LUT size

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

commit c6c3f340ece541eb2a21bc21b844424fdedff255
Author: Jonas Ådahl <jadahl gmail com>
Date:   Tue Oct 26 11:45:17 2021 +0200

    monitor: Add API to get GAMMA LUT size
    
    Will be used to generate look up tables.
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2141>

 src/backends/meta-monitor-manager-private.h |  7 +++++++
 src/backends/meta-monitor-manager.c         |  2 +-
 src/backends/meta-monitor.c                 | 30 +++++++++++++++++++++++++++++
 src/backends/meta-monitor.h                 |  2 ++
 4 files changed, 40 insertions(+), 1 deletion(-)
---
diff --git a/src/backends/meta-monitor-manager-private.h b/src/backends/meta-monitor-manager-private.h
index c8255ba0c4..1943e81506 100644
--- a/src/backends/meta-monitor-manager-private.h
+++ b/src/backends/meta-monitor-manager-private.h
@@ -459,4 +459,11 @@ GList * meta_monitor_manager_get_virtual_monitors (MetaMonitorManager *manager);
 
 void meta_monitor_manager_maybe_emit_privacy_screen_change (MetaMonitorManager *manager);
 
+void meta_monitor_manager_get_crtc_gamma (MetaMonitorManager  *manager,
+                                          MetaCrtc            *crtc,
+                                          size_t              *size,
+                                          unsigned short     **red,
+                                          unsigned short     **green,
+                                          unsigned short     **blue);
+
 #endif /* META_MONITOR_MANAGER_PRIVATE_H */
diff --git a/src/backends/meta-monitor-manager.c b/src/backends/meta-monitor-manager.c
index 36e8a53e72..b58a05f2d8 100644
--- a/src/backends/meta-monitor-manager.c
+++ b/src/backends/meta-monitor-manager.c
@@ -1152,7 +1152,7 @@ update_has_builtin_panel (MetaMonitorManager *manager)
                             obj_props[PROP_HAS_BUILTIN_PANEL]);
 }
 
-static void
+void
 meta_monitor_manager_get_crtc_gamma (MetaMonitorManager  *manager,
                                      MetaCrtc            *crtc,
                                      size_t              *size,
diff --git a/src/backends/meta-monitor.c b/src/backends/meta-monitor.c
index e002f9d937..120fa2e604 100644
--- a/src/backends/meta-monitor.c
+++ b/src/backends/meta-monitor.c
@@ -618,6 +618,36 @@ meta_monitor_create_spec (MetaMonitor  *monitor,
   };
 }
 
+/**
+ * meta_monitor_get_gamma_lut_size:
+ * @monitor: The MetaMonitor instance to retrieve the size from.
+ *
+ * Get the size of the look-up tables (LUTs) for the monitor.
+ *
+ * Retrieve the size of the LUT used to implement the encoding or decoding
+ * transfer functions ("gamma", "degamma") for the CRTC or CRTCs that backs
+ * this monitor.
+ *
+ * Returns: The number of look-up table entries possible for the monitor. It is
+ *   assumed that each CRTC of a monitor has identical gamma LUT sizes.
+ */
+size_t
+meta_monitor_get_gamma_lut_size (MetaMonitor *monitor)
+{
+  MetaMonitorPrivate *priv = meta_monitor_get_instance_private (monitor);
+  MetaMonitorManager *monitor_manager =
+    meta_backend_get_monitor_manager (priv->backend);
+  MetaOutput *output;
+  MetaCrtc *crtc;
+  size_t size;
+
+  output = meta_monitor_get_main_output (monitor);
+  crtc = meta_output_get_assigned_crtc (output);
+  meta_monitor_manager_get_crtc_gamma (monitor_manager, crtc,
+                                       &size, NULL, NULL, NULL);
+  return size;
+}
+
 static void
 meta_monitor_normal_generate_modes (MetaMonitorNormal *monitor_normal)
 {
diff --git a/src/backends/meta-monitor.h b/src/backends/meta-monitor.h
index b24eaabfb6..cf0ffa99ca 100644
--- a/src/backends/meta-monitor.h
+++ b/src/backends/meta-monitor.h
@@ -295,4 +295,6 @@ gboolean meta_monitor_set_privacy_screen_enabled (MetaMonitor  *monitor,
                                                   gboolean      enabled,
                                                   GError      **error);
 
+size_t meta_monitor_get_gamma_lut_size (MetaMonitor *monitor);
+
 #endif /* META_MONITOR_H */