653417 - Monospace Courier New font not displayed mono-spaced

Status: UNCONFIRMED

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

Description

[[e-mail]]

User-Agent:       Mozilla/5.0 (Windows NT 6.1; WOW64; rv:2.0) Gecko/20100101 Firefox/4.0
Build Identifier: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:2.0) Gecko/20100101 Firefox/4.0

The default mono-spaced fault 'Courier New' on Windows 7 is not being displayed with all characters the same width.  The example URL contains a block of monospaced text, which if you look at the closing brackets on each line, has not quite been monospaced.

Changing the font to Consolas (e.g. using Firebug) makes the problem go away.

Reproducible: Always

Steps to Reproduce:
Any block of Courier New text of sufficient size can be seen to not align quite perfectly.  Simple example is to write out ten asterisks followed by a bar, and on the line below, ten spaces followed by a bar.  The two bar characters will not line up.

Actual Results:  
Spaces are very slightly narrower than e.g. asterisks.  

Expected Results:  
Mono-spaced characters should all be rendered at the same width.

Potentially this could be related to bug 652760, which talks about problems dealing with the width of characters under DirectWrite, where characters can have non-integer width.

The problem does not occur under Windows XP using GDI.

Comment 1

[[e-mail]]

Attachment: 'Monospaced' code header

Comment 2

[[e-mail]]

Problem is very apparent in the attached screenshot - this is part of a standard copyright header, which was pasted into an internal Wiki.  All lines in the block section are the same number of characters.

Comment 3

[Jonathan Kew [:jfkthame]]

Offhand it looks like the width of the space character is getting rounded down to an integer number of pixels. This may well be a bug in how we initialize the metrics fields in our dwrite font class.

Comment 4

[Jonathan Kew [:jfkthame]]

Does the effect vary if you zoom the page in or out, by the way? I'm guessing it will....

Comment 5

[[e-mail]]

I hadn't checked this, but yes it does.  The attached screenshot is at standard zoom.  Zooming in by 1 increment, it appears the space is slightly wider than the asterisk, such that the line with spaces is around 2.6 character widths longer than the first line.

Comment 6

[Jonathan Kew [:jfkthame]]

I can't seem to reproduce this problem on my Win7 machine, with either DirectWrite or GDI font rendering. Could you please post the contents of about:support from your system, to see if that offers any clues? (use the "Copy all to clipboard" button in the about:support window, as manually copying the content loses linebreaks). Thanks.

Comment 7

[[e-mail]]

Here you go:

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          Open Containing Folder

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        Vendor ID
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        Device ID
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        Adapter Drivers
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Comment 8

[Jonathan Kew [:jfkthame]]

Does it make any difference if you disable the extensions you have installed, and/or create a new profile?

Comment 9

[[e-mail]]

It doesn't seem to change anything - I've tried Help -> Restart with Add-ons Disabled, which gives exactly the same results.  I also unticked 'Use hardware acceleration when available' in Options -> Advanced -> General.

I checked about:support after disabling hardware acceleration, and Direct2D was set false, but DirectWrite was still true.

Is there anything I can do to not use DirectWrite?  I found this key in about:config:
gfx.font_rendering.directwrite.enabled

But the default value is already false, yet I can see from about:support that it is enabled.

Comment 10

[Jonathan Kew [:jfkthame]]

(In reply to comment #9)
> It doesn't seem to change anything - I've tried Help -> Restart with Add-ons
> Disabled, which gives exactly the same results.  I also unticked 'Use hardware
> acceleration when available' in Options -> Advanced -> General.
> 
> I checked about:support after disabling hardware acceleration, and Direct2D was
> set false, but DirectWrite was still true.

Had you restarted the browser after disabling h/w acc? This requires a restart to fully take effect. After that, DirectWrite should not be active, I believe.

> Is there anything I can do to not use DirectWrite?  I found this key in
> about:config:
> gfx.font_rendering.directwrite.enabled
> 
> But the default value is already false, yet I can see from about:support that
> it is enabled.

With D2D enabled, DirectWrite will always be used regardless of this setting. But with D2D disabled, you should get GDI font rendering unless this key is explicitly set to true. Remember that a browser restart is required for such changes to take effect.

What happens if you restart in Safe Mode?

Comment 11

[[e-mail]]

I've finished at work now, so I've just tried this again through
Remote Desktop from a Windows XP machine.  It renders correctly over
remote desktop, which I guess isn't too surprising since as I
understand it, that just sends GDI commands over the network.  From
the last section of the support info, I can see that both Direct2D /
DirectWrite are now disabled when Firefox is opened through RDP:

Graphics
Adapter Description RDPDD Chained DD
Vendor ID 0000
Device ID 0000
Adapter RAM Unknown
Adapter Drivers RDPDD
Driver Version
Driver Date
Direct2D Enabled Blocked on your graphics card because of unresolved
driver issues.
DirectWrite Enabled false (6.1.7601.17563, font cache n/a)
WebGL Renderer (WebGL unavailable)
GPU Accelerated Windows 0/1

Us lucky lot in England get an extra days hols tomorrow for the royal
wedding, so I think I'll have to park this until Tuesday, as I don't
have any Windows 7 machine to test on at home.

Thanks for all your help!

Andy

Comment 12

[[e-mail]]

Just managed to get D2D and DirectWrite disabled on a normal Firefox invocation, and I can see that monospace is rendering correctly again now.

Here are the graphics sections with monospace working correctly:

Adapter Description
NVIDIA GeForce 9600M GS
Vendor ID
10de
Device ID
0648
Adapter RAM
512
Adapter Drivers
nvd3dumx,nvwgf2umx,nvwgf2umx nvd3dum,nvwgf2um,nvwgf2um
Driver Version
8.17.12.6776
Driver Date
3-17-2011
Direct2D Enabled
false
DirectWrite Enabled
false (6.1.7601.17563, font cache n/a)
WebGL Renderer
Google Inc. -- ANGLE -- OpenGL ES 2.0 (ANGLE 0.0.0.541)
GPU Accelerated Windows
0/1