These Human Interface Guidelines are primarily targeted towards new GTK+ and GNOME applications, with an emphasis on GNOME 3 integration. However, they are also intended to be useful to cross-platform applications, as well as older applications, which may have been designed and implemented in accordance with the GNOME 2 HIG.
The HIG provides cross-platform for those design patterns and UI elements that require special treatment in cross-platform cases. Otherwise, all the design patterns provided in these guidelines can be used in a cross-platform manner.
Since some platforms provide system-level integration for menu bars, this pattern is of special relevance for cross-platform applications.
These Human Interface Guidelines are an evolution of the GNOME 2 HIG, and represent an improvement on the previous version. Applications that follow the new version of the HIG will use space more efficiently, will provide a more focused user experience, and will use modern interpretations of key functionality, such as search, online integration, or notifications.
Following some of the design patterns in these guidelines may imply larger-scale design changes for GNOME 2 style applications, particularly if those applications are complex. In particular, replacing window title bars and menu bars with a header bar could be a big change for your application.
However, much of the advice contained within this HIG can be incorporated into GNOME 2 style applications with minimal disruption, and will lead to an improved experience for users. This includes:
Utilizing new user interface elements, such as popovers.
Guidance on new GTK+ abilities, like animations.
Modernized guidance on subjects such as visual layout, typography and icon usage.
Incorporating these elements of the guidelines can enhance your application without requiring a major redesign, and all GTK+ and GNOME applications can benefit from them.
These Human Interface Guidelines have been designed to assist you in determining the best design for your application, rather than proposing a single template to be used in all applications. As such, while they recommend header bars over menu bars, they provide guidance on both approaches.