Created attachment 321557 [details]
Safari Technology Preview 40 and Safari 11
This issue is also present in Safari 11.
When a user sets font-sizes to be displayed no less than 9px in Safari preferences and a website uses a line-height set with px values it can result in massive heights on elements.
The issue can be worked around by setting line-heights with a number rather than length but it is less than ideal as many existing websites may break.
I have not found it straightforward to create a reduction. However on a live site I am working with (https://www.bet365.com/?&cb=1032648335#/AA/B2/C101/D20170922/E20548296/F67258375/P10/) the issue exhibits clearly. The attachment is the page with those options set in the technology preview.
Created attachment 321558 [details]
Page in Safari 10
Comparison of same page in Safari 10
I have narrow it down.
When you setting a layout with "line-height" and "font-size:0", then setting the "Never use font size smaller than" will tigger this.
Created attachment 321935 [details]
This is more like an Accessibility bug. "font-size:0" should let the Accessibility make it bigger, obviously it goes mad...
Dig a little bit more.
it actually change the line-height to
This looks like the max value of double.
Maybe Somewhere we (unsigned double) 0 - 1
Correction for my last comment, just forgot that there is no unsigned double.
Is this the same as bug 177573?
the test is nearly same as the one I uploaded here.
*** This bug has been marked as a duplicate of bug 177573 ***