[...] forward.clicked.connect ( () => { this.current_file ++; this.image_viewer.open (this.files_in_dir.nth_data (this.current_file)); }); backward.clicked.connect ( () => { this.current_file --; this.image_viewer.open (this.files_in_dir.nth_data (this.current_file); }); [...] } We just in- or decrement current_file and then open the file at this index. Saving States To make your application start where the user left it, we use dconf/GSettings to save some things that may need to be remembered. For an image viewer it would not make sense to save something like the last opened image, but saving the last use geometry or position could make sense. To do so, we first need to create an XML file defining our schema in a file called “org.pantheon.photoviewer.gschema.xml” which we place in our data directory: 500

Window Width

Saves the window width for restoring it later. 450

Window Height

Saves the window height for restoring it later. -1

X position of window

Saves the window’s X position for restoring it later. -1

Y position of window

Saves the window’s Y position for restoring it later. As you can see we have a schemalist as root element in which we put individual schemas. If you have a bunch of keys to save (see Noise for one example), it makes sense to put those in logic portions into different schemas. Inside the schemas, we have keys. Those have a name and a type, which is “i” here for integer. You can use other ones like “s” for string or “u” for unsigned int. Next we make the schema being installed my cmake. You just have to add the following two lines, usually somewhere near the end of your main CMakeLists.txt: include(GSettings) add_schema("data/org.pantheon.photoviewer.gschema.xml") In order to make it work, you need to run “sudo make install”, otherwise, if you request this schema in your app, it will just break and not start anymore. So lastly, we have to integrate it in our application code. There is a very handy class for this task in granite which we will use public class Settings : Granite.Services.Settings { public int window_width { get; set; } public int window_height { get; set; } public int opening_x { get; set; } public int opening_y { get; set; } static Settings? instance = null; public Settings () { base (“org.pantheon.photoviewer”); } public static Settings get_default () { if (instance == null) instance = new Settings (); return instance; } } As we only need one instance of this class, we use the get_default() method to access this single one. We save a static instance of the class itself and then return it when requested. The properties have to have the same names as in our schema, except that the dash (“-”) has to be replaced with an undescore (“_”). Also you need to place “{ get; set; }” after each property to make sure Vala translates it to an actual property which is important for the internals to work. In the constructor we initialize the base class with the path to our schema. Next we write and read in the schema. We do this by connecting to the window’s delete-event which is emitted before the window is destroyed, so when the user closes it in the constructor. window.delete_event.connect (() => { int x, y, w, h; main_window.get_position (out x, out y);