SECONDARY WINDOW
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Illustration
Context
… as your mobile device's display is too small and for that reason there is not enough screen real estate available to display multiple application windows, you want your mobile application to run in only one window - ONE TRUE WINDOW.
Sometimes, however, it might be useful and would make sense to display some information in additional windows.
Problem statement
When should additional information be presented in a window other than the application's main window? How should this window be designed?
Problem description with forces
Although we learned that mobile applications should only provide one single application window (see ONE TRUE WINDOW), there might be some reasons where displaying information in an additional secondary window inside the application would make sense.
For example if there is some important information that a user must read before continuing (such as an alert) or if some user input is needed to continue processing (e.g. in input dialogs), the user's attention must be caught.
Of course a full screen message or dialog would do as well. However, it is harder to distinguish such a full screen message from the "normal" application as it is less emphasized.
A pop-up window like they are known from graphical desktop user interfaces would do much better to call the user's attention.
Examples
Secondary windows are common interface elements in many mobile operating systems. However, their usage varies among different systems.
Psion Series 5mx for example provides secondary windows for dialogs like the email settings.
The dialog window is smaller than the applications main window and covers this window partly.
In Palm Os there are different approaches for displaying dialogs.
On the one hand there are small pop-up dialog windows that only partly cover the main application. The windows cannot be moved but as they are not full-sized they still leave the context of the dialog visible. The second approach in Palm OS displays dialogs in full-screen mode and therefore does not preserve the context.
In Microsoft Pocket PC several approaches are used to display dialogs.
One of these approaches (see illustration a) and also opening picture) provides secondary windows that are moveable and do not cover the applications main screen in the background. Thus these secondary windows preserve the context in which the window was opened. A different approach uses full screen dialog windows (see illustration b) and c)). Unfortunately there is no consistent use of full screen dialogs. So many applications provide their own confirmation and cancellation means. Agenda Fusion [1] for example provides a full screen dialog for entering tasks and appointments (illustration b)). The dialog can either be confirmed using the "ok"-button in the title bar, or it can be confirmed and cancelled using the icons in the menu bar. Microsoft Pocket Word provides no "ok"-button at all. Instead there is a confirmation and cancellation button included in the dialog (illustration c)).
Actually, full screen dialogs in Microsoft Pocket PC only differ in the "ok"- and "X"-button in the title bar.
This sometimes makes it hard to judge if actually a dialog is displayed or not.
Solution
Therefore:
Provide secondary windows to show dialogs, alerts and other notifications.
If possible, make the secondary window smaller than the applications main window to preserve the context in which it was opened. This is especially important if users are interrupted while interacting with the application.
Also make the secondary window movable to allow users look behind the window to get even more contextual information.
Have a standard way to confirm and cancel the secondary window to keep your application consistent.
Diagram
References
This is a basic pattern and has no further references in this pattern language.
Literature and Links
- Agenda Fusion Version 5.0 for Pocket PC; http://www.developerone.com/demo/fusion5.htm </OL>
