The preview is now drawn onto it's own window rather directly onto
the client area of the top level window. This is done to allow for
scrollbars, since the page won't usually fit in the window when zoomed in.
Refactoring was needed as a result of this, and in order to provide more
granularity for updates to avoid EM_FORMATRANGE messages being sent when
the page the same page is being displayed.
EM_FORMATRANGE will set rc.bottom within the FORMATRANGE struct to be the
bottom of the area actually printed to, so this must be reset between calls
to make sure that the page boundaries are consistent between the pages.
The cbSize field for the REBARBANDINFOW structure was previously set to
the sizeof(REBARBANDINFOW), however, new fields were added to this
structure for newer version of windows. Testing in Windows XP (or with
comctl32.dll from Windows XP) I found this larger size was rejected
causing the rebar to not be displayed in wordpad.