2.1.87 [CSS-Level2-2009] Section 13.3.3, Allowed page breaks

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V0135:

The specification states:

 These breaks are subject to the following rules:
  
 Rule A: Breaking at (1) is allowed only if the 'page-break-after' and 'page-break-
 before' properties of all the elements generating boxes that meet at this margin 
 allow it, which is when at least one of them has the value 'always', 'left', or 
 'right', or when all of them are 'auto'. 
  
 Rule B: However, if all of them are 'auto' and a common ancestor of all the 
 elements has a 'page-break-inside' value of 'avoid', then breaking here is not 
 allowed. 
  
 Rule C: Breaking at (2) is allowed only if the number of line boxes between the 
 break and the start of the enclosing block box is the value of 'orphans' or more, 
 and the number of line boxes between the break and the end of the box is the value 
 of 'widows' or more.
  
 Rule D: In addition, breaking at (2) or (3) is allowed only if the 'page-break-
 inside' property of the element and all its ancestors is 'auto'.

Quirks Mode and IE7 Mode (All Versions)

The following variations apply:

  • Page breaks are allowed after elements even with page-break-after set to avoid; page breaks are allowed before elements even with page-break-before set to avoid.

  • Page breaks are not made in the vertical margins if the ancestor has page-break-inside set to avoid.

  • Rule C is not supported. Page-breaking occurs irrespective of the number of line boxes between the break on the condition that the start of the enclosing block box is the value of orphans or greater, and that the number of line boxes between the break and the end of the box is the value of widows or greater.

  • Page breaks occur even if an element or ancestor has page-break-inside set to avoid.

IE8 Mode and IE9 Mode (All Versions)

  • Page breaks are made in the vertical margins if ancestor has page-break-inside set to avoid.

V0136:

The specification states:

 If the above does not provide enough break points to keep content from overflowing 
 the page boxes, then rules A, B and D are dropped in order to find additional 
 breakpoints. If that still does not lead to sufficient break points, rule C is 
 dropped as well, to find still more break points.

Quirks Mode and IE7 Mode (All Versions)

Rule D is dropped. Page breaks occur within blocks when there aren’t enough break points to keep content from overflowing the page boxes.