Add welcome page and improve generated code

data/res/meson.build

@@ -3,6 +3,7 @@ gnome = import('gnome')
 
 blueprints = custom_target('blueprints',
   input: files(
+    'welcome_page.blp',
     'window.blp'
   ),
   output: '.',

data/res/musicus.gresource.xml

@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <gresources>
   <gresource prefix="/de/johrpan/musicus">
+    <file preprocess="xml-stripblanks">welcome_page.ui</file>
     <file preprocess="xml-stripblanks">window.ui</file>
   </gresource>
 </gresources>

data/res/welcome_page.blp

@@ -0,0 +1,39 @@
+using Gtk 4.0;
+using Adw 1;
+
+template $MusicusWelcomePage : Adw.NavigationPage {
+  title: _("Welcome to Musicus");
+
+  Adw.ToolbarView {
+    [top]
+    Adw.HeaderBar header_bar {
+      [end]
+      MenuButton {
+        icon-name: "open-menu-symbolic";
+        menu-model: primary_menu;
+      }
+    }
+
+    Adw.StatusPage {
+      icon-name: "de.johrpan.musicus";
+      title: _("Welcome to Musicus");
+      description: _("Get started by choosing where to store your music library. Is this your first time using Musicus? If so, create a new empty folder for your library. Musicus will use this location to manage your recordings. You can also select a folder that already contains a music library created by Musicus.");
+      child: Gtk.Button choose_library_button {
+        styles ["suggested-action", "pill"]
+        halign: center;
+        label: _("Choose library folder");
+      };
+    }
+  }
+}
+
+menu primary_menu {
+  item {
+    label: _("_Preferences");
+    action: "app.preferences";
+  }
+  item {
+    label: _("_About Musicus");
+    action: "app.about";
+  }
+}

data/res/window.blp

@@ -2,35 +2,9 @@ using Gtk 4.0;
 using Adw 1;
 
 template $MusicusWindow : Adw.ApplicationWindow {
-  default-width: 600;
-  default-height: 300;
+  title: _("Musicus");
+  default-width: 800;
+  default-height: 600;
 
-  Box {
-    orientation: vertical;
-
-    HeaderBar header_bar {
-      [end]
-      MenuButton {
-        icon-name: "open-menu-symbolic";
-        menu-model: primary_menu;
-      }
-    }
-
-    Label label {
-      label: _("Hello, World!");
-      vexpand: true;
-      styles ["title-1"]
-    }
-  }
-}
-
-menu primary_menu {
-  item {
-    label: _("_Preferences");
-    action: "app.preferences";
-  }
-  item {
-    label: _("_About Musicus");
-    action: "app.about";
-  }
+  Adw.NavigationView navigation_view {}
 }