How to keep together few inseparable text blocks in QTextEdit at the end of current page (throw all on the next page)?

Question

Hello, i have a QTextEdit document which size is different by every print. In the middle of the document i have few blocks of text which are inseparable in the eyes of the user and i have to protect my blocks from splitting on two pages in case the document gets equivalent size. Have you got any solution?

Answer 1

The closest thing you have to something that does this is Unicode Paragraph Separator (U+2029). if you surround a body of text with paragraph separators then the renderer is not supposed to leave the first line or the last line of the paragraph on its own in a page. This behavior can be easily observed in MS-Word. If however the text of the block is four lines or more then you don't have a grantee that all four lines will be in the same page. they could split 2-2 between pages.

The concept you're talking about is widely used in a smaller scale between words and lines. If you put an NBSP (No-Break Space, U+00A0) between words instead of a normal space then the renderer knows that the line should not be broken in this space.
What you're actually looking for is a "No-Page-Break Line-Feed". Unfortunately Unicode does not have such a character.

What you can try is to write the whole block of text using NBSPs instead of spaces. Eventually your only-NBSP text is going to get larger than a line and it will have to break somewhere. this is a certain end-case of Unicode which I'm not sure is really defined. Perhaps there's a chance that the line break which will be generated is such that does not break between pages. This is even a further end-case to the end-case. The only way to know what happens in this situation is to try.

Answer 2

I am a great fan of Qt but I have not had an opportunity yet to use a QTextEdit. I would like to help though so I took a look through the documentation.

If you are using a sufficiently recent version of Qt you should find that a QTextEdit has an associated QTextDocument and it would seem that the functionality you seek may be there. A QTextDocument is a hierarchy of frames and blocks. A block is equivalent to a paragraph as you mention above.

The documentation seems to indicate that you could specify that your blocks be wrapped in a frame. Then, you should be able to set a format for the frame using QTextFrame::setFrameFormat. This format will allow you to specify a page break policy using some flags. The flags that are specified are PageBreak_Auto, PageBreak_AlwaysBefore and PageBreak_AlwaysAfter.

It would seem to me that if you set both the PageBreak_AlwaysBefore and PageBreak_AlwaysAfter flags for the frame, then your blocks should stay together.

I realize this is a fairly complex series. I hope that it helps and would really like to hear if it works.