Port 'Spin Button' demo to Vala (#171)

Author: BharatAtbrat

src/Spin Button/main.vala

@@ -0,0 +1,43 @@
+#! /usr/bin/env -S vala workbench.vala --pkg libadwaita-1
+
+private Gtk.SpinButton hours;
+private Gtk.SpinButton minutes;
+
+string tell_time () {
+    return (@"The time selected is $(hours.text):$(minutes.text)");
+}
+
+public void main () {
+    hours = (Gtk.SpinButton) workbench.builder.get_object ("hours");
+    minutes = (Gtk.SpinButton) workbench.builder.get_object ("minutes");
+
+    hours.text = "00";
+    minutes.text = "00";
+
+    hours.value_changed.connect (() => {
+        message (@"$(tell_time ())");
+    });
+
+    minutes.value_changed.connect (() => {
+        message (@"$(tell_time ())");
+    });
+
+
+    hours.output.connect (() => {
+        var value = (int) hours.adjustment.value;
+        hours.text = "%02d".printf (value);
+        return true;
+    });
+
+    minutes.output.connect (() => {
+        var value = (int) minutes.adjustment.value;
+        minutes.text = "%02d".printf (value);
+        return true;
+    });
+
+    // This only works for one direction
+    // Add any extra logic to account for wrapping in both directions
+    minutes.wrapped.connect (() => {
+        hours.spin (STEP_FORWARD, 1);
+    });
+}