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Graphical Windowing Architecture

This topic describes the graphical windowing architecture of the BlackDog.

Deployment on the BlackDog

The BlackDog uses X11 for graphical displays. By design, the BlackDog has no application display window of its own; instead it uses X11 to project application GUIs onto the host PC monitor. BlackDog users interact with applications running on the BlackDog using the projected display and the PC's keyboard and mouse.

Components

X11 consists of an X11 Server and an X11 Client:

• X11 Display Server, which runs on the host (as Realm-windowing.exe), is automatically configured by the Realm Platform's autorun facilities when BlackDog is inserted into a Windows host PC. When BlackDog is inserted into a Linux host PC, the existing X11 Server is used. The X11 Server manages the display for programs running on the BlackDog device. When the user interacts with BlackDog applications via the display on the host PC, the X11 Server forwards the user keystrokes and mouse clicks back to the applications running on the device.
• X11 Clients run on the BlackDog and communicate to the X11 Server using the X11 protocol. Each graphical application on the BlackDog is an X11 Client.

Security

Using X11 windowing on the host PC, the host monitor displays the UI for BlackDog applications running locally or remotely on the device. BlackDog users employ the host PC's monitor, keyboard, and mouse to interact with BlackDog applications displayed on the host. Because the BlackDog only projects the application GUI display to the host PC, the application is not subject to vulnerabilities on the host PC such as spyware (key loggers) and other malware. Further, applications never store temporary data on the disk or in any memory of the host PC. The X11 projected GUI is an important aspect of BlackDog security.

Consistent User Experience

Because X11 graphical applications are platform independent, X11 applications running on the BlackDog will look the same (other than window decorations) on Windows and Linux hosts.

GTK+ 2 Toolkit

The Platform GUI toolkit is GTK+ 2. GTK+ 2 abstracts the details of X11 away from developers by providing a high-level widget library and event/callback model for graphical programs. Developers need only use the GTK+ 2 API to interoperate with the X11 architecture on the BlackDog platform.

Deployment on the SDK

The SDK does not automatically display an X11 Server, like the BlackDog does. However like the BlackDog, applications are run in the emulator and are only projected and displayed on the host PC.

X11 Server Shutdown

When the BlackDog is unplugged from the Windows host PC, the connection is broken between any applications running and the X11 Server, and the application window disappears. Realm-manager.exe detects the unplug event, terminates the X11 Server, and cleans up any temporary files left behind.

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