Builder and Glade

Until now we have created and arranged all widgets entirely using Julia code. While this works fine for small examples, it has the issue that we are tightly coupling the appearance from our application with the logic of our program code. In addition the linear way of procedural Julia code does not fit very well with complex user interfaces arranged in deeply nested tables and boxes.

Fortunately, there is a much better way to design user interfaces that strictly separate the layout from the code. This is done by an XML based file format that allows for describing any widget arrangements. The XML file is usually not manually created but designed graphically using Glade in a WYSIWYG (what you see is what you get) manner. In order to use the interface in your Julia Gtk application you will need GtkBuilder.

Glade

Glade lets you create complex user interfaces by graphically arranging them together in a user friendly way. There are many good tutorials out there so that we will skip a detailed introduction here.

The important thing when putting together the interface with glade is to give each widget that you later want to interface with a meaningful ID.

Builder

Once we have created the interface with Glade the result can be stored in an XML file that usually has the extension .glade. Lets assume we have created a file myapp.glade that looks like

<?xml version="1.0" encoding="UTF-8"?>
<interface>
  <!-- interface-requires gtk+ 3.0 -->
  <object class="GtkWindow" id="window1">
    <property name="can_focus">False</property>
    <child>
      <object class="GtkButton" id="button1">
        <property name="label" translatable="yes">button</property>
        <property name="use_action_appearance">False</property>
        <property name="visible">True</property>
        <property name="can_focus">True</property>
        <property name="receives_default">True</property>
        <property name="use_action_appearance">False</property>
      </object>
    </child>
  </object>
</interface>

In order to access the widgets from Julia we first create a GtkBuilder object that will serve as our connector between the XML definition and our Julia code.

b = GtkBuilder(filename="path/to/myapp.glade")

Alternatively, if we would store above XML definition in a Julia string myapp we can initialize the builder by

b = GtkBuilder(buffer=myapp)

Now we want to access a widget from the XML file in order to actually display it on the screen. To do so we call

win = b["window1"]
showall(win)

That is all that you need to know. You can thus see your builder as a kind of a widget store that you use when you need access to your widgets. It it therefore not really necessary to bind the widgets to local variables anymore but instead you can always use the builder object.

Callbacks

The XML file lets us only describe the visual structure of our widgets and not their behavior when the using is interacting with it. For this reason, we will have to add callbacks to the widgets which we do in Julia code as it was described in Signals and Callbacks.