[connections/onboarding-dialog-button-visibility] onboarding-dialog: Toggle back/next button visibility

[Felipe Borges <felipeborges src gnome org>]

commit 89373c9897e404e6898f380b3bae574af4a4870c
Author: Felipe Borges <felipeborges gnome org>
Date:   Wed Jun 23 13:24:06 2021 +0200

    onboarding-dialog: Toggle back/next button visibility
    
    We shouldn't show a "back" button on the first page of the carousel,
    neither show a "next" button on the last page.
    
    See https://gitlab.gnome.org/GNOME/connections/-/issues/39#note_1183302

 src/onboarding-dialog.vala  | 13 +++++++++++++
 src/ui/onboarding-dialog.ui |  1 +
 2 files changed, 14 insertions(+)
---
diff --git a/src/onboarding-dialog.vala b/src/onboarding-dialog.vala
index f47997d..b757f0e 100644
--- a/src/onboarding-dialog.vala
+++ b/src/onboarding-dialog.vala
@@ -29,6 +29,10 @@ namespace Connections {
         private unowned Carousel paginator;
         [GtkChild]
         private unowned OnboardingDialogPage homepage;
+        [GtkChild]
+        private unowned Button go_back_button;
+        [GtkChild]
+        private unowned Button go_next_button;
 
         private GLib.List<unowned OnboardingDialogPage> pages;
 
@@ -49,6 +53,8 @@ namespace Connections {
 
                 onboarding_page.description += " <a href=\'help:gnome-connections/connect\'>%s</a>".printf 
(learn_more_label);;
             }
+
+            on_position_changed ();
         }
 
         public OnboardingDialog (Window window) {
@@ -72,5 +78,12 @@ namespace Connections {
 
             paginator.scroll_to (pages.nth_data (index));
         }
+
+        [GtkCallback]
+        private void on_position_changed () {
+            var position = (int)paginator.position;
+            go_back_button.visible = (position > 0);
+            go_next_button.visible = (position < (pages.length () - 1));
+        }
     }
 }
diff --git a/src/ui/onboarding-dialog.ui b/src/ui/onboarding-dialog.ui
index e7da3a5..ef73418 100644
--- a/src/ui/onboarding-dialog.ui
+++ b/src/ui/onboarding-dialog.ui
@@ -51,6 +51,7 @@
                 <property name="visible">True</property>
                 <property name="animation-duration">400</property>
                 <property name="margin-bottom">12</property>
+                <signal name="notify::position" handler="on_position_changed"/>
 
                 <child>
                   <object class="ConnectionsOnboardingDialogPage" id="homepage">