What is fully supported for CSS page-break properties?

[ddbeck]

On https://caniuse.com/css-page-break, no (contemporary) browser is shown as fully supporting page-break properties. Some of that data is out-of-date however, so I'm not sure how to change the data to be more accurate.

By inference with Presto Opera's full support, only page-break-* properties are required and to disregard the break-* properties for finding whether something is fully supported. Likewise, I know that avoid is required because IE is also shown as partially supported (despite the lack of the note about left and right).

That leaves one ambiguity: is support for left and right required for full support? Or is it avoid alone that prevents full support?

[Fyrd]

Great question, I just did a deep-dive into these properties and have updated the support with my latest findings.

Here's what's changed + an answer to your question:

1. As this feature is specific to page-break properties, I don't think the new break-* properties support is required, developers can still achieve the desired effect with these original properties.
2. Chromium started supporting page-break-before/page-break-after: avoid since Chromium 108. IMO This is the most notable support failure, so "fully supported" hinges on this functionality.
3. The spec mentions "A conforming user agent may interpret the values 'left' and 'right' as 'always'. " so I also believe this should not be required for "full support".

So I've updated support for Chromium browsers to reflect this, plus updated the notes to highlight that note no. 2 is the only one that's the cause of the "partial support" definition.

And if anyone's curious, here's my test suite I used to do the testing (+Print Preview in each browser):
https://tests.caniuse.com/page-break/

[ddbeck]

@Fyrd Thank you! That cleared up a lot of details for me—I'm especially grateful for the test cases—and led to me fixing the data in BCD as well. I'll close this up now. Thanks again.