private PageLayout ApplyPageBreak()
{
// Collapse any space layouts at the top of the page. Space layouts are
// intended to provide space _between_ layouts and thus are not appropriate
// at the top of a page. We collapse top space after drafting so that we know
// where the space layouts fall on this page, but before applying the next
// page break because lower layouts might now fit on this page.
CollapseTopSpace();
PageDisposition disposition = AssessPageBreak(_bodyBox);
// Avoid infinite overflow. If any layout starts at the top of the page and
// is longer than the page, then it will return disposition overflow or split
// and its page split index will be zero. Splitting at index zero is the same
// thing as overflowing. Overflowing a full page will cause this page to move
// all of its content onto a new page, leaving itself empty, and this will lead
// to infinite overflow. So just stop the overflow right now. This will give us
// an oversized page, but that's better than making a report with an infinite
// number of empty pages. (In the current implementation, AssessPageBreak here on
// a page layout will never return overflow because SetPageSplitIndex always
// converts overflow to split, and then because a page can split it doesn't convert
// it back to overflow. But for semantic clarity we still check for overflow here.)
if ((disposition == PageDisposition.Overflow)
||
(disposition == PageDisposition.Split && _pageSplitIndex == 0))
{
// If we can split as requested then do so. Otherwise bump the page split
// index from zero to one - this will leave the oversized layout on this
// page but overflow subsequent layouts to the next. If it's not possible
// to bump the index then return an empty page to stop the overflow.
Bump bump = BumpPageSplitIndex();
switch (bump)
{
case Bump.Bumped:
case Bump.Unnecessary:
// The split index has been moved beyond zero (or was already there)
// and so we can now do the normal page break. This may still leave
// the oversized layout on this page, but later layouts are moved
// to the next page.
break;
case Bump.Impossible:
// Couldn't fix the situation by splitting further down, so
// just accept the oversized layout
return((PageLayout)ShallowCopy());
}
}
PageLayout overflow = (PageLayout)DoPageBreak();
// This page now contains only the content that can fit in it. Content
// that must be moved to the next page, or a later page, is now contained
// in the overflow page. If the overflow page is empty then this is the last
// page.
// Redraft this page to set the layouts' bottoms so that they can
// draw borders correctly, and redraft the new page so that its contents
// start at the top of the page.
Redraft(_bodyBox.Top);
overflow?.Redraft(overflow._bodyBox.Top);
return(overflow);
}
