Keeping a heading with next paragraph in QTextDocument

Question

I'm learning how to use QTextDocument in PySide6, and it seems to have most features for displaying rich text, but I can't see how to keep a heading with the next paragraph.

In this example, "Heading 13" is at the bottom of page 2 and its following paragraph is at the top of page 3. How can I move "Heading 13" to page 3 so they stay together? A page break in the middle of a paragraph doesn't bother me, I just don't like a heading all by itself.

from PySide6.QtGui import QPdfWriter, QPageSize, QTextDocument, QTextCursor
from PySide6.QtWidgets import QApplication


app = QApplication()
pdf = QPdfWriter('example.pdf')
pdf.setPageSize(QPageSize.Letter)

document = QTextDocument()
cursor = QTextCursor(document)
cursor.insertHtml('<h1>Title</h1>')
for i in range(1, 21):
    cursor.insertText('\n')
    cursor.insertHtml(f'<h3>Heading {i}</h3>')
    cursor.insertText('\n')
    cursor.insertHtml('<p>Lorem ipsum dolor sit amet, consectetur '
                      'adipiscing elit. Aliquam sed congue mauris. '
                      'Curabitur a lobortis odio. Maecenas non metus id '
                      'sapien congue sagittis quis ac ipsum. Sed ut '
                      'tincidunt ex. Proin sed neque at nunc sollicitudin '
                      'sagittis eget molestie mauris. Integer condimentum '
                      'lacus quis enim scelerisque, at cursus orci porta. '
                      'Aenean non tellus arcu. Sed quis odio turpis. '
                      'Vivamus facilisis.</p>')
document.print_(pdf)

Answer 1

For example, do you want to do like this?

import PySide6
from PySide6.QtGui import QPdfWriter, QPageSize, QTextDocument, QTextCursor
from PySide6.QtWidgets import QApplication
import sys, os, re
dirname  =  os.path.dirname(PySide6.__file__)
plugin_path  =  os.path.join(dirname, 'plugins', 'platforms')
os.environ['QT_QPA_PLATFORM_PLUGIN_PATH']  =  plugin_path
app = QApplication()
pdf = QPdfWriter('example.pdf')
pdf.setPageSize(QPageSize.Letter)
  
document = QTextDocument()
cursor = QTextCursor(document)
cursor.insertHtml('<h1>Title</h1>')
    
document.setPageSize(QPageSize.size(QPageSize.A4, QPageSize.Point))
pagesize = document.pageSize()
pagecount = 0
bottom = 0
average_height = 0
pagebreak = False
for i in range(1, 21):
    firstinsert_rect = document.documentLayout().blockBoundingRect(document.findBlockByNumber(cursor.block().blockNumber()))
    pagecount = int(document.documentLayout().blockBoundingRect(document.findBlockByNumber(cursor.block().blockNumber())).y()/pagesize.height()) + 1
    if pagecount != int((bottom + average_height)/pagesize.height()) + 1:
        bf = cursor.blockFormat()
        bf.setPageBreakPolicy(bf.PageBreak_AlwaysAfter)
        cursor.setBlockFormat(bf)
        pagebreak = True
    cursor.insertText('\n')
    if pagebreak:
        pagebreak = False
        bf = cursor.blockFormat()
        bf.setPageBreakPolicy(bf.PageBreak_Auto)
        cursor.setBlockFormat(bf)
    cursor.insertHtml(f'<h3>Heading {i}</h3>')
    cursor.insertText('\n')
    cursor.insertHtml('<p>Lorem ipsum dolor sit amet, consectetur '
                          'adipiscing elit. Aliquam sed congue mauris. '
                          'Curabitur a lobortis odio. Maecenas non metus id '
                          'sapien congue sagittis quis ac ipsum. Sed ut '
                          'tincidunt ex. Proin sed neque at nunc sollicitudin '
                          'sagittis eget molestie mauris. Integer condimentum '
                          'lacus quis enim scelerisque, at cursus orci porta. '
                          'Aenean non tellus arcu. Sed quis odio turpis. '
                          'Vivamus facilisis.</p>')
    lastinsert_rect = document.documentLayout().blockBoundingRect(document.findBlockByNumber(cursor.block().blockNumber()))
    average_height = lastinsert_rect.bottom() - firstinsert_rect.y()
    bottom = lastinsert_rect.bottom()
        
document.print_(pdf)