Hardware reference guide

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Chapter 3: The Software
System Structure
The taskbar registers itself with the OS. The OS sends the taskbar two kinds of
special messages:
• application creation and destruction events.
• certain key presses and key sequences.
Application creation and destruction events can be used for displaying buttons on
the taskbar for running applications.
Key presses and key sequences can be used by the shell for any purpose.
The taskbar displays the Task Manager on receiving Alt + Esc, cycles running
application windows on receiving Alt + Tab ; and it displays the start menu on
receiving a Menu (Blue + 0) key press. This start menu can be used to access
certain shell features.
The taskbar is also responsible for displaying the start menu when the Menu key
combination is pressed.
The System Tray
The system tray is a window within the taskbar. It registers a callback with the OS.
Once registered the OS will forward messages sent by applications to display notifi-
cation icons (Shell_NotifyIcon()) to the system tray.
The system tray task processes these messages and draws the notification icons in
the system tray window. The system tray also forwards any mouse or touch events
on the icons back to the window that registered them. The system tray also displays
the current time in its window when configured to do so.