480869 - <marquee> display doesn't match IE7 at fairly large font sizes

Status: NEW

(Core :: Layout, defect)

Description

[[e-mail]]

As you increase the test size on reftest 386470-1.html IE7's display does not change at all. However Gecko suffers from two rendering errors. The first only applies to huge font sizes, and that is that when IE7 renders a marquee on its own line (because text cannot fit on the same line) then it shrinks the line height for that one line to the height of the marquee. However the other bug that applies to fairly large font sizes is that the inner box is baseline aligned instead of top aligned, which takes effect when the baseline is larger than the inner box's size.

Comment 1

[[e-mail]]

Attachment: Proposed patch

Comment 2

[Martijn Wargers (dead)]

Hmm, apparently, I forgot to move those marquee reftests into the layout/reftests/marquee folder (among others I also forgot).

Comment 3

[David Baron :dbaron: (⌚️UTC-5, no longer working on Mozilla)]

I need to look closely here to check whether these changes are emulating some IE bug that we don't otherwise emulate only for marquee, which isn't something we'd want to do.

Comment 4

[David Baron :dbaron: (⌚️UTC-5, no longer working on Mozilla)]

So I'm having trouble understanding what's going on here.  Could you explain?

Also, could you point to an example of a non-editable marquee for which this changes the behavior?

Also, could you add a reftest, and not change the existing test?

Comment 5

[[e-mail]]

Attachment: Updated patch

Sorry for the delay. The problem seems to be that the vertical alignment of the marquee is wrong. IE7/8 display the two files identically.

I don't know of a real case of a non-editable marquee. I discovered this accidentally by running a reftest at a large zoom by mistake.

Comment 6

[[e-mail]]

Attachment: --git version for checkin

Comment 7

[David Baron :dbaron: (⌚️UTC-5, no longer working on Mozilla)]

Why do you think that this particular change to the code is the right thing to do?

Comment 8

[[e-mail]]

As I said, the error appears to be to do with the vertical alignment, and I determined that this does correct the appearance of the test. I don't know of other potential solutions or indeed alternative causes of the apparent error.

Comment 9

[David Baron :dbaron: (⌚️UTC-5, no longer working on Mozilla)]

Making a single testcase appear more like it looks in IE isn't a good enough reason.  What is the set of cases where we behave differently from IE, what's the general explanation for the difference, and why is this particular use of 'vertical-align' a sensible way to change our behavior (what is being aligned with what)?

Comment 10

[David Baron :dbaron: (⌚️UTC-5, no longer working on Mozilla)]

Comment on attachment 380810 [details] [diff] [review]
Updated patch

Removing superreview request (but leaving review request) per new review rules.

(I still need to look into writing additional test cases here to figure out whether this is the correct fix.  And need-me-to-write-the-tests reviews are low priority.)

Comment 11

[David Baron :dbaron: (⌚️UTC-5, no longer working on Mozilla)]

Comment on attachment 380810 [details] [diff] [review]
Updated patch

I'd like to see more testcases demonstrating that this change makes sense before accepting this patch.

The initial description of the problem in the bug sounds like it could just be a statement that IE implements the CSS inline box model less correctly than we do, and not related to anything specific to marquee.  Before reviewing this patch, I'd like to see testcases that demonstrate both that:
 * the problem you're trying to fix is really specific to marquee (and doesn't happen for, e.g., form controls or inline-block)
 * IE's behavior actually differs with respect to the vertical alignment.

Such testcase should probably test different values of the 'vertical-align' property on both marquee and other similar elements (inline-block, form controls) in cases where:
 * there is or is not a tall image earlier in the line (try with both vertical-align: text-top and text-bottom on the image)
 * the font in the marquee is much smaller or much larger than that of the surrounding text


I'm particularly suspicious of 'vertical-align: top' because it's one of the non-anchored values of 'vertical-align', and I think those (top and bottom) are rarely appropriate in default styles.

Comment 12

[BugBot [:suhaib / :marco/ :calixte]]

The bug assignee is inactive on Bugzilla, so the assignee is being reset.