ppub-viewer/src/ZoomSpinButton.vala

using Adw;
using Gtk;

namespace PpubViewer {

    public class ZoomSpinButton : Gtk.Box {

        private Button zoom_out_button;
        private Button reset_zoom_button;
        private Button zoom_in_button;

        public Adjustment adjustment {get; set;}

        public int default_value {get; set;}

        public ZoomSpinButton(bool compact) {
            orientation = Orientation.HORIZONTAL;
            halign = Align.END;

            
            zoom_out_button = new Button.from_icon_name ("zoom-out-symbolic");
            zoom_in_button = new Button.from_icon_name ("zoom-in-symbolic");
            adjustment = new Adjustment(100, 80, 300, 10, 50, 0);
            default_value = 100;
            
            
            adjustment.value_changed.connect(() => zoom_level_changed((int)adjustment.value));
            
            append(zoom_out_button);
            if(!compact) {
                reset_zoom_button = new Button();
                append(reset_zoom_button);
                add_css_class("linked");
                zoom_level_changed.connect(update_label);
                update_label(default_value);
            }
            append(zoom_in_button);
            
            zoom_in_button.clicked.connect(zoom_in);
            zoom_out_button.clicked.connect(zoom_out);
            reset_zoom_button.clicked.connect(reset_zoom);

        }

        public signal void zoom_level_changed(int percentage);

        private void update_label(int percentage) {
            reset_zoom_button.label = @"$percentage%";
        }

        public void zoom_in() {
            adjustment.value += adjustment.step_increment;
        }

        public void zoom_out() {
            adjustment.value -= adjustment.step_increment;
        }

        public void reset_zoom() {
            adjustment.value = default_value;
        }
    }
}