782253 - getBBox height regression on SVG text elements

Status: VERIFIED INVALID

(Core :: SVG, defect)

Description

[Evan Trimboli]

Attachment: test.html

User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.60 Safari/537.1

Steps to reproduce:

I am measuring the height of a text SVG element.


Actual results:

In FF14 (and the latest nightly), the value returned is 15.


Expected results:

In FF13 and below, the value returned is 13. This may be a regression.

Comment 1

[Evan Trimboli]

Also, in WebKit browsers, 13 is also returned as the value for the same code.

Comment 2

[Robert Longson [:longsonr]]

I get 13 both on a nightly and on 14 on Windows 7.

If things have changed for you perhaps you could find a regression range?

Do do that you would follow the instructions here: https://quality.mozilla.org/docs/bugzilla/guide-to-triaging-bugs-for-firefox/finding-a-regression-window/

type about:buildconfig in the address bar in the last build that returns 13 and first build that returns 15 and post the Built from link from each

Comment 3

[Evan Trimboli]

It seems I may have been premature. When I run FF14.01 in safe mode I get the correct value, sorry about that.

If I run in normal mode, I've removed all my extensions and disabled all the plugins  via the UI, but it still returns the incorrect value. I'm trying to isolate which plugin is causing the problem, is there anything obvious I'm missing in between switching to safe mode and disabling all the available plugins/removing extensions?

Comment 4

[Robert Longson [:longsonr]]

Safe mode disables hardware acceleration too.

Comment 5

[Jonathan Watt [:jwatt]]

(In reply to Robert Longson from comment #4)
> Safe mode disables hardware acceleration too.

That shouldn't affect the value returned by getBBox though.

Comment 6

[Jonathan Watt [:jwatt]]

(In reply to Evan Trimboli from comment #3)
> If I run in normal mode, I've removed all my extensions and disabled all the
> plugins  via the UI, but it still returns the incorrect value.

On that basis, reopening for the moment, since I'd like to know why we're returning different values with safe mode on/off here.

Comment 7

[Evan Trimboli]

I can confirm that disabling hardware acceleration and then restarting the browser gave 13 as expected, it was not add-on related at all. Would be interested to hear any further thoughts.

Comment 8

[Robert Longson [:longsonr]]

You get different font metrics with hardware acceleration.

Comment 9

[Robert Longson [:longsonr]]

The fact that DirectWrite (used when hardware acceleration is on) and GDI (used by default when it's off) give slightly different font metrics is not a bug. Sites should not be assuming that metrics will remain exactly the same across different systems and platforms.

Comment 10

[Jonathan Watt [:jwatt]]

Ah, of course. Thanks, Robert.