Your application can now make use of the doPreRefresh and/or doRefresh events (or ignore them both) without having to store and restore the affected window’s update region. The following technical information is only for those who are interested in the mechanics of how this is accomplished.
When your application receives a doPreRefresh event, it can either use the event to draw objects that appear behind Tools Plus objects (such as a background picture that is drawn behind picture buttons), or your application can ignore the event.
The next time your application calls PollSystem, Tools Plus reapplies the window’s original update region (in case it was cleared by a BeginUpdate/EndUpdate structure responding to the doPreRefresh event), then it draws its _own_ objects (buttons, scroll bars, editing fields, picture buttons, etc.) within the window’s update region.
Tools Plus then generates a doRefresh event. At this point, the window’s update region is modified to exclude Tools Plus’s objects. When your application receives a doRefresh event, it can either use the event to update objects that are drawn after Tools Plus objects (such as static text or pictures), or your application can ignore the event.
The next time your application calls PollSystem, Tools Plus clears the window’s update region (if your application has not already done so in the doRefresh cycle).