1205724 - Text in buttons on about:support has different height if HWA (hardware acceleration) is enabled/disabled

Status: RESOLVED DUPLICATE of bug 643781

(Core :: Layout: Text and Fonts, defect)

Description

[arni2033]

Attachment: buttons on about-support page.xht

STR:   (Win7_64, Nightly 43, 32bit, ID 20150916030203, new profile, safe mode)
1. Set HWA -> on, restart browser
2. Open attached page
3. Open Inspector, notice that left button has height=31px, right button has height=30px
4. Set HWA -> off, restart browser
5. Both buttons have same height

I attached a reduced copy of about:support page
Leaving it unconfirmed because maybe I'm the only one encountering this issue.

Comment 1

[:Gijs (he/him)]

I'm a little confused by the testcase - that no longer has min-height:30px. Is it supposed to?

Comment 2

[Jonathan Kew [:jfkthame]]

The attached testcase has different styles for the two buttons -- one is 'height:auto' and the other is 'height:30px' -- so it's hardly surprising if they end up with different heights. The exact results will depend on the font used and on how font metrics are handled (which differs between DirectWrite and GDI backends, hence the difference between HWA on/off behavior).

If the issue here is simply that DirectWrite and GDI result in different font metrics, see bug 643781.

Comment 3

[arni2033]

(In reply to Gijs Kruitbosch (gone until Tue 22 Sep) from comment #1)
> that no longer has min-height:30px. Is it supposed to?
No, the only important part was removing 'hardcoded' "height:30px" in the bug we discussed.

(In reply to Jonathan Kew (:jfkthame) from comment #2)
> so it's hardly surprising if they end up with different heights
Yeah... That's why I chose the current summary, not "Elements with different CSS looks different" (lol)
The right button was there only for testing purposes, or to compare it with the left one.

Bug 643781 looks like the right dupe, except for the summary.