[libadwaita/wip/exalm/tab-bg] tab-box: Remove bg from a single expanded tab

[Alexander Mikhaylenko <alexm src gnome org>]

commit 96eb23068e648632e06b7dd26187befd517c9793
Author: Alexander Mikhaylenko <alexm gnome org>
Date:   Tue Jul 26 23:12:50 2022 +0400

    tab-box: Remove bg from a single expanded tab
    
    This is mainly for Builder, to avoid a super prominent tab when there's
    only one.

 src/adw-tab-box.c                     | 27 +++++++++++++++++++++++++++
 src/stylesheet/widgets/_tab-view.scss | 10 ++++++++++
 2 files changed, 37 insertions(+)
---
diff --git a/src/adw-tab-box.c b/src/adw-tab-box.c
index 4dfc5b0d..7d5e9c74 100644
--- a/src/adw-tab-box.c
+++ b/src/adw-tab-box.c
@@ -495,6 +495,24 @@ update_separators (AdwTabBox *self)
   }
 }
 
+/* Single tab style */
+
+static void
+update_single_tab_style (AdwTabBox *self)
+{
+  if (self->pinned)
+    return;
+
+  if (self->view &&
+      adw_tab_view_get_n_pages (self->view) <= 1 &&
+      adw_tab_view_get_n_pinned_pages (self->view) == 0 &&
+      self->expand_tabs &&
+      self->tab_resize_mode == TAB_RESIZE_NORMAL)
+    gtk_widget_add_css_class (GTK_WIDGET (self), "single-tab");
+  else
+    gtk_widget_remove_css_class (GTK_WIDGET (self), "single-tab");
+}
+
 /* Tab resize delay */
 
 static void
@@ -567,6 +585,8 @@ set_tab_resize_mode (AdwTabBox     *self,
 
   self->tab_resize_mode = mode;
 
+  update_single_tab_style (self);
+
   if (notify)
     g_object_notify_by_pspec (G_OBJECT (self), props[PROP_RESIZE_FROZEN]);
 }
@@ -3793,6 +3813,11 @@ adw_tab_box_set_view (AdwTabBox  *self,
     g_signal_connect_object (self->view, "page-reordered", G_CALLBACK (page_reordered_cb), self, 
G_CONNECT_SWAPPED);
 
     if (!self->pinned) {
+      g_signal_connect_object (self->view, "notify::n-pages", G_CALLBACK (update_single_tab_style), self, 
G_CONNECT_SWAPPED);
+      g_signal_connect_object (self->view, "notify::n-pinned-pages", G_CALLBACK (update_single_tab_style), 
self, G_CONNECT_SWAPPED);
+
+      update_single_tab_style (self);
+
       self->view_drop_target = GTK_EVENT_CONTROLLER (gtk_drop_target_new (ADW_TYPE_TAB_PAGE, 
GDK_ACTION_MOVE));
 
       g_signal_connect_object (self->view_drop_target, "drop", G_CALLBACK (view_drag_drop_cb), self, 
G_CONNECT_SWAPPED);
@@ -3937,6 +3962,8 @@ adw_tab_box_set_expand_tabs (AdwTabBox *self,
 
   self->expand_tabs = expand_tabs;
 
+  update_single_tab_style (self);
+
   gtk_widget_queue_resize (GTK_WIDGET (self));
 }
 
diff --git a/src/stylesheet/widgets/_tab-view.scss b/src/stylesheet/widgets/_tab-view.scss
index 4b608780..b18dabf4 100644
--- a/src/stylesheet/widgets/_tab-view.scss
+++ b/src/stylesheet/widgets/_tab-view.scss
@@ -51,6 +51,16 @@ tabbar {
     &:active { background-color: $view_active_color; }
   }
 
+  tabbox.single-tab tab {
+    &, &:hover, &:active {
+      background: none;
+
+      @if $contrast == 'high' {
+        box-shadow: none;
+      }
+    }
+  }
+
   .start-action,
   .end-action {
     padding: 5px;