core/debug-control: Allow changing the reference luminance of outputs

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3953>

data/dbus-interfaces/org.gnome.Mutter.DebugControl.xml

@@ -8,6 +8,7 @@
     <property name="ColorManagementProtocol" type="b" access="readwrite" />
     <property name="EnableHDR" type="b" access="readwrite" />
     <property name="ForceLinearBlending" type="b" access="readwrite" />
+    <property name="LuminancePercentage" type="u" access="readwrite" />
 
   </interface>
 

src/backends/meta-color-device.c

@@ -671,18 +671,32 @@ update_color_state (MetaColorDevice *color_device)
   MetaMonitor *monitor = color_device->monitor;
   MetaBackend *backend =
     meta_color_manager_get_backend (color_device->color_manager);
+  MetaContext *context = meta_backend_get_context (backend);
+  MetaDebugControl *debug_control = meta_context_get_debug_control (context);
   ClutterContext *clutter_context = meta_backend_get_clutter_context (backend);
   g_autoptr (ClutterColorState) color_state = NULL;
   ClutterColorspace colorspace;
   ClutterTransferFunction transfer_function;
+  float min_lum, max_lum, ref_lum;
+  float reference_luminance_factor;
   UpdateResult result = 0;
 
   colorspace = get_color_space_from_monitor (monitor);
   transfer_function = get_transfer_function_from_monitor (monitor);
 
-  color_state = clutter_color_state_new (clutter_context,
+  clutter_transfer_function_get_default_luminances (transfer_function,
-                                         colorspace,
+                                                    &min_lum,
-                                         transfer_function);
+                                                    &max_lum,
+                                                    &ref_lum);
+
+  reference_luminance_factor =
+    meta_debug_control_get_luminance_percentage (debug_control) / 100.0f;
+  ref_lum = ref_lum * reference_luminance_factor;
+
+  color_state = clutter_color_state_new_full (clutter_context,
+                                              colorspace,
+                                              transfer_function,
+                                              min_lum, max_lum, ref_lum);
 
   if (!color_device->color_state ||
       !clutter_color_state_equals (color_device->color_state, color_state))
@@ -698,6 +712,9 @@ MetaColorDevice *
 meta_color_device_new (MetaColorManager *color_manager,
                        MetaMonitor      *monitor)
 {
+  MetaBackend *backend = meta_color_manager_get_backend (color_manager);
+  MetaContext *context = meta_backend_get_context (backend);
+  MetaDebugControl *debug_control = meta_context_get_debug_control (context);
   MetaColorDevice *color_device;
 
   color_device = g_object_new (META_TYPE_COLOR_DEVICE, NULL);
@@ -724,6 +741,11 @@ meta_color_device_new (MetaColorManager *color_manager,
                           color_device);
     }
 
+  g_signal_connect_object (debug_control, "notify::luminance-percentage",
+                           G_CALLBACK (meta_color_device_update),
+                           color_device,
+                           G_CONNECT_SWAPPED | G_CONNECT_AFTER);
+
   return color_device;
 }
 

src/core/meta-debug-control-private.h

@@ -25,3 +25,5 @@ gboolean meta_debug_control_is_color_management_protocol_enabled (MetaDebugContr
 gboolean meta_debug_control_is_linear_blending_forced (MetaDebugControl *debug_control);
 
 gboolean meta_debug_control_is_hdr_enabled (MetaDebugControl *debug_control);
+
+unsigned int meta_debug_control_get_luminance_percentage (MetaDebugControl *debug_control);

src/core/meta-debug-control.c

@@ -182,6 +182,8 @@ meta_debug_control_init (MetaDebugControl *debug_control)
     g_strcmp0 (getenv ("MUTTER_DEBUG_FORCE_LINEAR_BLENDING"), "1") == 0;
   meta_dbus_debug_control_set_force_linear_blending (dbus_debug_control,
                                                      force_linear_blending);
+
+  meta_dbus_debug_control_set_luminance_percentage (dbus_debug_control, 100);
 }
 
 gboolean
@@ -211,6 +213,15 @@ meta_debug_control_is_hdr_enabled (MetaDebugControl *debug_control)
   return meta_dbus_debug_control_get_enable_hdr (dbus_debug_control);
 }
 
+unsigned int
+meta_debug_control_get_luminance_percentage (MetaDebugControl *debug_control)
+{
+  MetaDBusDebugControl *dbus_debug_control =
+    META_DBUS_DEBUG_CONTROL (debug_control);
+
+  return meta_dbus_debug_control_get_luminance_percentage (dbus_debug_control);
+}
+
 void
 meta_debug_control_set_exported (MetaDebugControl *debug_control,
                                  gboolean          exported)

tools/debug-control.py

@@ -15,6 +15,25 @@ def bool_to_string(value):
     else:
         return "false"
 
+def string_to_bool(value):
+    if value == "true":
+        return True
+    if value == "false":
+        return False
+    raise BaseException(f"bad boolean value: {value}")
+
+def value_to_string(value):
+    if isinstance(value, dbus.Boolean):
+        return bool_to_string(value)
+    return f"{value}"
+
+def string_to_value(current, value):
+    if isinstance(current, dbus.Boolean):
+        return dbus.Boolean(string_to_bool(value), variant_level=1)
+    if isinstance(current, dbus.UInt32):
+        return dbus.UInt32(int(value), variant_level=1)
+    return value
+
 def get_debug_control():
     bus = dbus.SessionBus()
     try:
@@ -28,8 +47,9 @@ def get_debug_control():
 def status():
     debug_control = get_debug_control()
     props = debug_control.GetAll(INTERFACE, dbus_interface=PROPS_IFACE)
-    for prop in props:
+    for prop, value in props.items():
-        print(f"{prop}: {bool_to_string(props[prop])}")
+        value = value_to_string (value)
+        print(f"{prop}: {value}")
 
 def enable(prop):
     debug_control = get_debug_control()
@@ -48,6 +68,14 @@ def toggle(prop):
     debug_control.Set(INTERFACE, prop, dbus.Boolean(not value, variant_level=1),
                       dbus_interface=PROPS_IFACE)
 
+def set_value(kv):
+    debug_control = get_debug_control()
+    [prop, value] = kv
+
+    current = debug_control.Get(INTERFACE, prop, dbus_interface=PROPS_IFACE)
+    value = string_to_value (current, value)
+
+    debug_control.Set(INTERFACE, prop, value, dbus_interface=PROPS_IFACE)
 
 if __name__ == '__main__':
     parser = argparse.ArgumentParser(description='Get and set debug state')
@@ -56,6 +84,7 @@ if __name__ == '__main__':
     parser.add_argument('--enable', metavar='PROPERTY', type=str, nargs='?')
     parser.add_argument('--disable', metavar='PROPERTY', type=str, nargs='?')
     parser.add_argument('--toggle', metavar='PROPERTY', type=str, nargs='?')
+    parser.add_argument('--set', metavar='PROPERTY', type=str, nargs=2)
 
     args = parser.parse_args()
     if args.status:
@@ -66,5 +95,7 @@ if __name__ == '__main__':
         disable(args.disable)
     elif args.toggle:
         toggle(args.toggle)
+    elif args.set:
+        set_value(args.set)
     else:
         parser.print_usage()