fix: handle float rounding when extending boxes over page breaks

[aschmitz]

When a box would break over the edge of a page, its height is extended to the bottom of that page (per https://www.w3.org/TR/css-break-3/#box-splitting , primarily to allow backgrounds and borders to continue to the end of the page).

When this happened, sometimes the values that would be calculated for the height of the extended element would be rounded over the calculated height that remained on the page, forcing the entire containing box to wrap to the next page.

Rather than trying to carefully manage the order of operations to try to be safe in IEEE floats for directions, we apply a small "fudge factor": if an element fits very nearly (within a thousandth of a pixel) into the remaining space, it is still accepted.

[liZe]

Thanks for the pull request!

We’ll just change a bit the workaround to match the ones we already have:

WeasyPrint/weasyprint/layout/inline.py

Lines 680 to 686 in 21314bc

	# In some cases (shrink-to-fit result being the preferred width)
	# max_x is coming from Pango itself,
	# but floating point errors have accumulated:
	# width2 = (width + X) - X # in some cases, width2 < width
	# Increase the value a bit to compensate and not introduce
	# an unexpected line break. The 1e-9 value comes from PEP 485.
	max_x *= 1 + 1e-9