IUP/Layout

Layout Composition

Abstract Layout

Most interface toolkits employ the concrete layout model, that is, control positioning in the dialog is absolute in coordinates relative to the upper left corner of the dialog’s client area. This makes it easy to position the controls on it by using an interactive tool usually provided with the system. It is also easy to dimension them. Of course, this positioning intrinsically depends on the graphics system’s resolution. Moreover, when the dialog size is altered, the elements remain on the same place, thus generating an empty area below and to the right of the elements. Besides, if the graphics system’s resolution changes, the dialog inevitably will look larger or smaller according to the resolution increase or decrease.

IUP implements an abstract layout concept, in which the positioning of controls is done relatively instead of absolutely. For such, composition elements are necessary for composing the interface elements. They are boxes and fillings invisible to the user, but that play an important part. When the dialog size changes, these containers expand or retract to adjust the positioning of the controls to the new situation.

Watch the codes below. The first one refers to the creation of a dialog for the Microsoft Windows environment using its own resource API. The second uses IUP. Note that, apart from providing the specification greater flexibility, the IUP specification is simpler, though a little larger. In fact, creating a dialog on IUP with several elements will force you to plan your dialog more carefully – on the other hand, this will actually make its implementation easier.

Moreover, this IUP dialog has an indirect advantage: if the user changes its size, the elements (due to being positioned on an abstract layout) are automatically re-positioned horizontally, because of the iupfill elements.

The composition elements are vertical boxes (vbox), horizontal boxes (hbox) and filling (fill). There is also a depth box (zbox) in which layers of elements can be created for the same dialog, and the elements in each layer are only visible when that given layer is active.

<source lang=lua>

   dialogo = iup.dialog
   {
     iup.hbox
     {
       iup.fill{},
       iup.button{title="Ok",size="40"}, 
       iup.button{title="Cancel",size="40"},
       iup.fill{},
       margin="15x15",
       gap="10"
     },
     title="Título"
   }

</source>

Following, the abstract layout representation of this dialog:

Layout Hierarchy	Layout Visualization
Dialog HBox Fill Button Button Fill	INSERT IMAGE HERE

Layout Hierarchy

The layout of the elements of a dialog in IUP has a natural hierarchy because of the way they are composed together. The dialog is the root of the hierarchy tree. To retrieve the dialog of a control you can simply call IupGetDialog, but there are other ways to navigate in the hierarchy tree.

To get all the children of a container use IupGetNextChild. To get just the next control with the same parent use IupGetBrother.

The hierarchy tree can also be dynamically created, but before mapping to the native system. You can add and remove elements from a container using IupAppend and IupDetach, but only before mapping into the native system.