week-view: add border around scrolled main area for distiction from toolbar

Currently, at the top there is an always visible border
which, due to having the same colour as the drop shadow,
slightly interferes with how the drop shadow looks, while
more severely, the bottom bar's start is not easily
distinguishable from the week grid's end, as there is
no border at all.

Styling the scrolled content itself with a border
elegantly solves these two issues, because now a drop
shadow is drawn when scrolling in a direction is
possible, and a border is drawn otherwise.

Closes: https://gitlab.gnome.org/GNOME/gnome-calendar/-/issues/1406

Signed-off-by: Markus Göllnitz <camelcasenick@bewares.it>
Part-of: <https://gitlab.gnome.org/GNOME/gnome-calendar/-/merge_requests/593>

src/gui/views/gcal-week-view.blp

@@ -36,8 +36,6 @@ template $GcalWeekView: Box {
     }
   }
 
-  Separator {}
-
   ScrolledWindow scrolled_window {
     hexpand: true;
     vexpand: true;
@@ -74,6 +72,10 @@ template $GcalWeekView: Box {
           vexpand: true;
           event-activated => $on_event_activated(template);
         }
+
+        styles [
+          "week-main-content",
+        ]
       }
     }
   }

src/theme/style.css

@@ -186,6 +186,11 @@ weekhourbar > label {
   color: rgb(from var(--window-fg-color) r g b / 15%);
 }
 
+.week-main-content {
+  border: 0 solid var(--border-color);
+  border-width: 1px 0;
+}
+
 weekgrid > widget.now-strip {
   background-color: rgb(from var(--accent-bg-color) r g b / 80%);
   margin: 0 0 0 1px;