Form rendering basics

Get the essentials about form rendering.

In graphical mode (GUI mode), application forms can display complex layouts. During program execution, a window may be resized by the end user, or is resized because the front-end platform allows different screen orientations like with mobile devices.

There are two approaches to define forms for your application:
  • For desktop-only applications, design adaptive-layout forms, where the resizing of an application window only affects some resizable form elements like TABLE/TREE/SCROLLGRID containers, WEBCOMPONENT, TEXTEDIT and IMAGE fields. Such type of forms are typically defined with several layout tags in a single GRID container.
  • For mobile, web and desktop applications, design responsive-layout forms, where all form elements can adapt to the screen size. Such type of forms are defined with a tree of HBOX/VBOX containers with containes such as GRID, and where element attributes are defined with a screen-size specifier, to control their visibility, stretchability and orientation.

When developing with command line tools, forms are designed with .per form specification files, which are text files. In order to display text-based forms in graphical screens, the .per form definitions must be converted to graphical widgets, implying specific layout rules explained in this chapter.

With the GBC front end, use GBC Themes to adapt the form rendering to the user needs and preferences. A GBC Theme specific front call API is available to manage themes. For more details about GBC Themes, see "Theme reference" chapter in the Genero Browser Client User Guide.

In GUI mode, the size of a window depends in its type. See Window geometry in GUI mode for more details.