Platform Package reference: Type XViewportProc

Description of the type definition XViewportProc available in all Platform Packages for ANSI C compatible target systems. This type definition is intended to be used when integrating the Embedded Wizard created GUI application with the underlying graphics subsystem, graphics hardware or other external GUI applications coexisting on the same system.


typedef void (*XViewportProc)


  XViewport*      aViewport,

  unsigned long   aHandle,

  void*           aDisplay1,

  void*           aDisplay2,

  void*           aDisplay3,

  XRect           aArea




Viewport which has called the callback function.


Low level reference to the real viewport, the framebuffer, the window instance, etc. This value depends on the particular platform system.

aDisplay1, aDisplay2, aDisplay3

Platform dependent values, where already existing framebuffer or drawing context, etc. are stored. These values are passed during the initialization of the viewport (see EwInitViewport()).


Area modified by the update relative to the top-left corner of the viewport.


The type declaration XViewportProc defines a prototype of a user defined function, which can be passed as callback during the initialization of a viewport when calling the function EwInitViewport(). This callback function will then be called each time the viewport update cycle terminates. In this manner some kind of viewport specific completion can be implemented.