Slide 6.18: Line-by-line anatomy of Hello.c (cont.)   Slide 6.20: Line-by-line anatomy of Hello.c (cont.)   Home

Line-by-line Anatomy of Hello.c (Cont.)

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if ( cmd == sysAppLaunchCmdNormalLaunch ) {
An application launches when it receives a launch code. Launch Codes are a means of communication between the Palm OS and the application (or between two applications). Each launch code may be accompanied by two types of information:

• A parameter block, a pointer to a structure that contains several parameters. These parameters contain information necessary to handle the associated launch code.


• Launch flags indicate how the application should behave. For example, a flag could be used to specify whether or not the UI should be displayed.

For example, an application typically launches when a user presses one of the buttons on the device or selects an application icon from the application launcher screen. When this happens, the system generates the launch code sysAppLaunchCmdNormalLaunch, which tells the application to perform a full launch and display its user interface.

WinDrawChars( "Hello, world!", 13, 55, 60 );
A window defines a drawing region. This region may be on the display or in a memory buffer. All forms are windows, but not all windows are forms. The Window object is the portion of the Form object that determines how the form's window looks and behaves. A window object contains viewing coordinates of the window and clipping bounds. The function

void WinDrawChars( const Char *chars, Int16 len, Coord x, Coord y )

draws the specified characters in the draw window.

• chars: Pointer to the characters to draw.
• len: Length in bytes of the characters to draw.
• x: x coordinate of the first character to draw (left bound).
• y: y coordinate of the first character to draw (top bound).