VB 4.0 Calls the FreezeEvents Method to Inform OLE Controls

• Standard, Professional, and Enterprise Editions of Microsoft Visual Basic, 16-bit and 32-bit, for Windows, version 4.0

SUMMARY

Visual Basic version 4.0 uses the FreezeEvents method to inform an OLE control of its readiness to accept events at key points during execution.

MORE INFORMATION

This information is quoted from the OLE Control Developer's Kit, Part 4, Appendix D:

   The FreezeEvents method determines whether the control should fire
   events. When initially created, the control's freeze count is at zero,
   and the control is free to fire events when appropriate. If the
   container calls FreezeEvents(TRUE), then the freeze count is
   incremented, and the control should not fire any events until the freeze
   count returns to zero by the container calling FreezeEvents(FALSE).
   This mechanism gives the container a way to suppress events being fired
   until it is fully ready to deal with them.

   The control is free to decide whether to discard events triggered when
   the control is frozen, or to queue them up and fire them when the
   control becomes unfrozen. Normally, a control makes this decision based
   on how important the event is to the control's contract. If discarding
   the event is likely to break users' assumptions and therefore their
   code, then the control should queue the event.

• Before starting to load a form, FreezeEvents(TRUE) is called on all existing controls. Any controls on the form being loaded will have FreezeEvents(TRUE) called immediately before their SetClientSite is called. FreezeEvents(FALSE) is called on all controls immediately after the Form_Load event is fired. This is to guarantee that Form_Load is the first event fired once a form is loaded.
• Before dynamically loading a control, FreezeEvents(TRUE) is called on all existing controls. The control being dynamically loaded will have FreezeEvents(TRUE) called immediately before its SetClientSite is called. FreezeEvents(FALSE) is called on all controls after the new control is completely loaded.
• FreezeEvents(TRUE) is called on all controls before a modal dialog or message box is put up. FreezeEvents(FALSE) is called after that dialog or messagebox is destroyed.
• In design mode, whenever a control is first drawn on a form, its FreezeEvents(TRUE) is called immediately before its SetClientSite is called.
• FreezeEvents(TRUE) is called on all controls whenever you exit run mode, whether transitioning to break or design mode. This is only interesting in the run-to-break transition in the design environment because in the run-to-design transition (or in built-EXEs), the controls are in the process of being destroyed.
• FreezeEvents(FALSE) is called on all controls whenever you enter run mode from break mode. However, this doesn't apply to built EXEs.