night-light: Add Color Temperature slider

This adds a scale to change the color temperature from 3000K to
6000K. A mark is added to the default value and a second one for
aesthetics.

Initial implementation by Benjamin Berg
Color choices by Daniel Foré and elementary OS

Closes #147

panels/display/cc-night-light-dialog.c

@@ -33,6 +33,7 @@ struct _CcNightLightDialog {
 
   GtkWidget           *box_manual;
   GtkWidget           *infobar_disabled;
+  GtkWidget           *scale_color_temperature;
   GtkWidget           *spinbutton_from_hours;
   GtkWidget           *spinbutton_from_minutes;
   GtkWidget           *spinbutton_to_hours;
@@ -48,6 +49,7 @@ struct _CcNightLightDialog {
   GtkAdjustment       *adjustment_from_minutes;
   GtkAdjustment       *adjustment_to_hours;
   GtkAdjustment       *adjustment_to_minutes;
+  GtkAdjustment       *adjustment_color_temperature;
 
   GSettings           *settings_display;
   GSettings           *settings_clock;
@@ -147,6 +149,7 @@ dialog_update_state (CcNightLightDialog *self)
   self->ignore_value_changed = FALSE;
 
   gtk_widget_set_sensitive (self->box_manual, enabled && !automatic);
+  gtk_widget_set_sensitive (self->scale_color_temperature, enabled);
 
   /* Don't show the off button if it can't be turned off */
   /* Don't allow choosing Manual or "Sunset to Sunrise" if it can't be turned on */
@@ -225,6 +228,10 @@ dialog_update_state (CcNightLightDialog *self)
                                      self->adjustment_to_minutes,
                                      self->stack_to);
 
+  self->ignore_value_changed = TRUE;
+  value = (gdouble) g_settings_get_uint (self->settings_display, "night-light-temperature");
+  gtk_adjustment_set_value (self->adjustment_color_temperature, value);
+  self->ignore_value_changed = FALSE;
 }
 
 static gboolean
@@ -361,6 +368,22 @@ dialog_time_to_value_changed_cb (GtkAdjustment      *adjustment,
   g_settings_set_double (self->settings_display, "night-light-schedule-to", value);
 }
 
+static void
+dialog_color_temperature_value_changed_cb (GtkAdjustment      *adjustment,
+                                           CcNightLightDialog *self)
+{
+  gdouble value;
+
+  if (self->ignore_value_changed)
+    return;
+
+  value = gtk_adjustment_get_value (adjustment);
+
+  g_debug ("new value = %.0f", value);
+
+  g_settings_set_uint (self->settings_display, "night-light-temperature", (guint) value);
+}
+
 static void
 dialog_color_properties_changed_cb (GDBusProxy         *proxy,
                                     GVariant           *changed_properties,
@@ -571,8 +594,10 @@ cc_night_light_dialog_class_init (CcNightLightDialogClass *klass)
   gtk_widget_class_bind_template_child (widget_class, CcNightLightDialog, adjustment_from_minutes);
   gtk_widget_class_bind_template_child (widget_class, CcNightLightDialog, adjustment_to_hours);
   gtk_widget_class_bind_template_child (widget_class, CcNightLightDialog, adjustment_to_minutes);
+  gtk_widget_class_bind_template_child (widget_class, CcNightLightDialog, adjustment_color_temperature);
   gtk_widget_class_bind_template_child (widget_class, CcNightLightDialog, box_manual);
   gtk_widget_class_bind_template_child (widget_class, CcNightLightDialog, infobar_disabled);
+  gtk_widget_class_bind_template_child (widget_class, CcNightLightDialog, scale_color_temperature);
   gtk_widget_class_bind_template_child (widget_class, CcNightLightDialog, spinbutton_from_hours);
   gtk_widget_class_bind_template_child (widget_class, CcNightLightDialog, spinbutton_from_minutes);
   gtk_widget_class_bind_template_child (widget_class, CcNightLightDialog, spinbutton_to_hours);
@@ -592,6 +617,7 @@ cc_night_light_dialog_class_init (CcNightLightDialogClass *klass)
   gtk_widget_class_bind_template_callback (widget_class, dialog_mode_changed_cb);
   gtk_widget_class_bind_template_callback (widget_class, dialog_time_from_value_changed_cb);
   gtk_widget_class_bind_template_callback (widget_class, dialog_time_to_value_changed_cb);
+  gtk_widget_class_bind_template_callback (widget_class, dialog_color_temperature_value_changed_cb);
   gtk_widget_class_bind_template_callback (widget_class, dialog_undisable_clicked_cb);
 
 }
@@ -601,9 +627,28 @@ cc_night_light_dialog_init (CcNightLightDialog *self)
 {
   g_autoptr(GtkCssProvider) provider = NULL;
   g_autoptr(GError) error = NULL;
+  g_autofree gchar *text = NULL;
 
   gtk_widget_init_template (GTK_WIDGET (self));
 
+  text = g_strdup_printf ("%s", "More Warm");
+  gtk_scale_add_mark (GTK_SCALE (self->scale_color_temperature),
+                      3000, GTK_POS_BOTTOM,
+                      text);
+
+  gtk_scale_add_mark (GTK_SCALE (self->scale_color_temperature),
+                      4000, GTK_POS_BOTTOM,
+                      NULL);
+
+  gtk_scale_add_mark (GTK_SCALE (self->scale_color_temperature),
+                      5000, GTK_POS_BOTTOM,
+                      NULL);
+
+  text = g_strdup_printf ("%s", "Less Warm");
+  gtk_scale_add_mark (GTK_SCALE (self->scale_color_temperature),
+                      6000, GTK_POS_BOTTOM,
+                      text);
+
   self->cancellable = g_cancellable_new ();
   self->settings_display = g_settings_new (DISPLAY_SCHEMA);
 
@@ -624,20 +669,7 @@ cc_night_light_dialog_init (CcNightLightDialog *self)
 
   /* use custom CSS */
   provider = gtk_css_provider_new ();
-  if (!gtk_css_provider_load_from_data (provider,
-                                        ".padded-spinbutton {\n"
-                                        "    font-size: 110%;\n"
-                                        "    min-width: 50px;\n"
-                                        "}\n"
-                                        ".unpadded-button {\n"
-                                        "    padding: 6px;\n"
-                                        "}\n",
-                                        -1,
-                                        &error))
-    {
-      g_error ("Failed to load CSS: %s", error->message);
-    }
-
+  gtk_css_provider_load_from_resource (provider, "/org/gnome/control-center/display/night-light.css");
   gtk_style_context_add_provider_for_screen (gdk_screen_get_default (),
                                              GTK_STYLE_PROVIDER (provider),
                                              GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);

panels/display/cc-night-light-dialog.ui

@@ -438,6 +438,36 @@
                     </child>
                   </object>
                 </child>
+                <child>
+                  <object class="GtkLabel">
+                    <property name="visible">True</property>
+                    <property name="can_focus">False</property>
+                    <property name="halign">start</property>
+                    <property name="hexpand">True</property>
+                    <property name="label" translatable="yes">Color Temperature</property>
+                    <attributes>
+                      <attribute name="weight" value="bold"/>
+                    </attributes>
+                  </object>
+                </child>
+                <child>
+                  <object class="GtkScale" id="scale_color_temperature">
+                    <property name="visible">True</property>
+                    <property name="can_focus">True</property>
+                    <property name="hexpand">True</property>
+                    <property name="adjustment">adjustment_color_temperature</property>
+                    <property name="inverted">True</property>
+                    <property name="restrict_to_fill_level">False</property>
+                    <property name="fill_level">1</property>
+                    <property name="digits">0</property>
+                    <property name="draw_value">False</property>
+                    <property name="has_origin">False</property>
+                    <property name="value_pos">bottom</property>
+                    <style>
+                      <class name="night-light-temperature"/>
+                    </style>
+                  </object>
+                </child>
               </object>
             </child>
           </object>
@@ -478,4 +508,11 @@
     <property name="page_increment">10</property>
     <signal name="value-changed" handler="dialog_time_to_value_changed_cb" object="CcNightLightDialog" swapped="no" />
   </object>
+  <object class="GtkAdjustment" id="adjustment_color_temperature">
+    <property name="lower">3000</property>
+    <property name="upper">6000</property>
+    <property name="step_increment">100</property>
+    <property name="page_increment">500</property>
+    <signal name="value-changed" handler="dialog_color_temperature_value_changed_cb" object="CcNightLightDialog" swapped="no" />
+  </object>
 </interface>

panels/display/display.gresource.xml

@@ -3,5 +3,6 @@
   <gresource prefix="/org/gnome/control-center/display">
     <file preprocess="xml-stripblanks">cc-night-light-dialog.ui</file>
     <file>display-arrangement.css</file>
+    <file>night-light.css</file>
   </gresource>
 </gresources>

panels/display/night-light.css

@@ -0,0 +1,28 @@
+/* color selection by Daniel Foré and elementary OS */
+@define-color ORANGE_100 #ffc27d;
+@define-color ORANGE_500 #f37329;
+@define-color base_color white;
+@define-color bg_color shade (@base_color, 0.96);
+
+/* Hide the marks at the beginning and the end */
+.night-light-temperature mark indicator:nth-child(even) {
+   color:transparent;
+}
+
+.night-light-temperature trough {
+    min-height: 8px;
+    background-image: linear-gradient(to right, mix(@bg_color, @ORANGE_100, 0.5), @ORANGE_500);
+}
+
+.night-light-temperature:dir(rtl) trough {
+    background-image: linear-gradient(to left, mix(@bg_color, @ORANGE_100, 0.5), @ORANGE_500);
+}
+
+.padded-spinbutton {
+    font-size: 110%;
+    min-width: 50px;
+}
+
+.unpadded-button {
+    padding: 6px;
+}