Legacy Document

Inside Macintosh: Macintosh Toolbox Essentials /

Chapter 4 - Window Manager / Window Manager Reference

Window Manager Routines / Low-Level Routines

CheckUpdate

The Event Manager uses the CheckUpdate function to scan the window list for windows that need updating.

FUNCTION CheckUpdate (VAR theEvent: EventRecord): Boolean;

theEvent

An event record to be filled in if a window needs updating.

DESCRIPTION

The CheckUpdate function scans the window list from front to back, checking for a visible window that needs updating (that is, a visible window whose update region is not empty). If it finds one whose window record contains a picture handle, it redraws the window itself and continues through the list. If it finds a window record whose update region is not empty and whose window record does not contain a picture handle, it stores an update event in the parameter theEvent and returns TRUE. If it finds no such window, it returns FALSE.

The Event Manager is the only software that ordinarily calls CheckUpdate.