views/week-view: Adapt to high contrast

Part-of: <https://gitlab.gnome.org/GNOME/gnome-calendar/-/merge_requests/710>

src/gui/views/gcal-week-grid.c

@@ -862,6 +862,7 @@ gcal_week_grid_init (GcalWeekGrid *self)
   GcalContext *context = gcal_application_get_context (GCAL_DEFAULT_APPLICATION);
   GtkDropTarget *drop_target;
   GtkGesture *click_gesture;
+  AdwStyleManager *manager;
 
   self->selection.start = -1;
   self->selection.end = -1;
@@ -905,6 +906,13 @@ gcal_week_grid_init (GcalWeekGrid *self)
                            G_CALLBACK (gtk_widget_queue_resize),
                            self->now_strip,
                            G_CONNECT_SWAPPED);
+
+  manager = adw_style_manager_get_default ();
+  g_signal_connect_object (manager,
+                           "notify::high-contrast",
+                           G_CALLBACK (gtk_widget_queue_draw),
+                           self,
+                           G_CONNECT_SWAPPED);
 }
 
 /* Public API */

src/gui/views/gcal-week-view-common.c

@@ -18,6 +18,8 @@
  * SPDX-License-Identifier: GPL-3.0-or-later
  */
 
+#include <adwaita.h>
+
 #include "gcal-week-view-common.h"
 #include "gcal-utils.h"
 
@@ -28,16 +30,20 @@ gcal_week_view_common_snapshot_hour_lines (GtkWidget      *widget,
                                            gint            width,
                                            gint            height)
 {
+  AdwStyleManager *manager;
   GdkRGBA color;
-  gboolean ltr;
+  gboolean ltr, is_high_contrast;
   gdouble column_width;
   guint i;
 
   ltr = gtk_widget_get_direction (widget) != GTK_TEXT_DIR_RTL;
 
+  manager = adw_style_manager_get_default ();
+  is_high_contrast = adw_style_manager_get_high_contrast (manager);
+
   gtk_snapshot_save (snapshot);
   gtk_widget_get_color (widget, &color);
-  color.alpha = 0.15;
+  color.alpha = is_high_contrast ? 0.65 : 0.15;
   gtk_snapshot_restore (snapshot);
 
   column_width = width / (float) N_WEEKDAYS;