1058203 - line-height: normal is handled differently for non-floating ::first-letter

Status: NEW

(Core :: Layout: Block and Inline, defect)

Description

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

line-height: normal somehow produces different results for non-floating ::first-letter than it does for regular inlines.  I don't think this should be the case.

I ran into this while adjusting the tests for layout/reftests/first-letter/429968-1* in bug 1055865 patch 5.  I think those tests ought to work with line-height: normal instead of the explicit line-height: 1.2 that I had to add, although I might be missing something.

Comment 1

[Daniel Holbert [:dholbert]]

Attachment: testcase 1

Comment 2

[Daniel Holbert [:dholbert]]

Attachment: reference case 1

Comment 3

[Daniel Holbert [:dholbert]]

Attachment: screenshot of testcase 1

Here's a screenshot of testcase 1, taken on Windows 11 with Nightly 143.0a1 (2025-08-04) (64-bit)

Comment 4

[Daniel Holbert [:dholbert]]

Comment on attachment 9505048 [details]
screenshot of testcase 1

(sorry, obsoleting/reposting; trying to capture a screenshot of testcase/reference with exact same window size, and I inadvertently resized my window in between. :) )

Comment 5

[Daniel Holbert [:dholbert]]

Attachment: screenshot of testcase 1

Comment 6

[Daniel Holbert [:dholbert]]

Attachment: screenshot of reference case 1

Comment 7

[Daniel Holbert [:dholbert]]

I can't reproduce with testcase 1 / reference case 1 on Ubuntu 25.04, but I think that's because the normal line-height behavior is font-dependent and the default font on Ubuntu happens to use a normal value that Just Works for the purposes of this bug.

However, some other fonts do reproduce it; e.g. DejaVu Sans Mono (the font that I get for the monospace generic font-family) seems to trigger the bug on LInux.

Comment 8

[Daniel Holbert [:dholbert]]

Attachment: testcase 2 (requesting a font that reproduces the bug on Linux)

Comment 9

[Daniel Holbert [:dholbert]]

Attachment: reference case 2

Comment 10

[Daniel Holbert [:dholbert]]

Attachment: screenshot of testcase 2 (left) vs reference case 2 (right) in Nightly on Linux

Here's testcase 2 / reference case 2 in side-by-side Nightly windows on Ubuntu 25.04.

The reference case's text is placed slightly further down the page than the testcase's text, due to a slightly different line-height value.