Implement a --page-breaks-before option

src/calibre/ebooks/conversion/cli.py

@@ -128,7 +128,7 @@ def add_pipeline_options(parser, plumber):
                   [
                       'dont_split_on_page_breaks', 'chapter', 'chapter_mark',
                       'prefer_metadata_cover', 'remove_first_image',
-                      'insert_comments',
+                      'insert_comments', 'page_breaks_before',
                   ]
                   ),
 

src/calibre/ebooks/conversion/plumber.py

@@ -227,6 +227,14 @@ OptionRecommendation(name='extra_css',
                 'rules.')
         ),
 
+OptionRecommendation(name='page_breaks_before',
+            recommended_value="//*[name()='h1' or name()='h2']",
+            level=OptionRecommendation.LOW,
+            help=_('An XPath expression. Page breaks are inserted '
+            'before the specified elements.')
+        ),
+
+
 OptionRecommendation(name='margin_top',
         recommended_value=5.0, level=OptionRecommendation.LOW,
         help=_('Set the top margin in pts. Default is %default')),

src/calibre/ebooks/oeb/transforms/structure.py

@@ -45,6 +45,14 @@ class DetectStructure(object):
                 if not node.title or regexp.search(node.title) is not None:
                     self.oeb.toc.remove(node)
 
+        if opts.page_breaks_before is not None:
+            pb_xpath = XPath(opts.page_breaks_before)
+            for item in oeb.spine:
+                for elem in pb_xpath(item.data):
+                    style = elem.get('style', '')
+                    if style:
+                        style += '; '
+                    elem.set('style', style+'page-break-before:always')
 
     def detect_chapters(self):
         self.detected_chapters = []