818236 - SVG render differences Inkscape vs. Firefox - font is wider in Firefox

Status: UNCONFIRMED

(Core :: SVG, defect)

Description

[David Mathog]

Attachment: ink_fire_test_manual_boxes.svg

User Agent: Mozilla/5.0 (Windows NT 5.1; rv:17.0) Gecko/17.0 Firefox/17.0 SeaMonkey/2.14
Build ID: 20121118021014

Steps to reproduce:

The attached file was created in Inkscape.  It uses 18 pt Arial text.  In the
SVG file everything is in px, so 22.5px font, as inkscape is 90dpi internally.  On
each line a red boundary box was drawn manually from the leading edge of the
first period to the trailing edge of the last "A".  When this SVG is viewed in
Firefox the text is slightly wider than the boundary, but the height is
correct.  (Zoom in to see this clearly.)

So inkscape is apparently doing something different with this text than firefox
is, otherwise the text would be exactly in the box in Firefox too.

One possibility is that the browser is using some font other than Arial, which
is a bit wider (but the same height).  Is there some way to make the unmodified
browser cough up this information? If this is the case, is there something that
can be added to SVG to force it to use the specified font?

Or is something else going on?

Comment 1

[David Mathog]

Cross reference to same bug filed in Inkscape:

https://bugzilla.mozilla.org/show_bug.cgi?id=818236

Comment 2

[Robert Longson [:longsonr]]

what does the Graphics section of about:support say?

Try toggling gfx.font_rendering.directwrite.enabled using about:config too

could be Inkscape is using GDI+ while Firefox is using DirectWrite font rendering or vice versa.

Comment 3

[Robert Longson [:longsonr]]

(In reply to David Mathog from comment #1)
> Cross reference to same bug filed in Inkscape:
> 
> https://bugzilla.mozilla.org/show_bug.cgi?id=818236

No, that's just this bug right here!

Comment 4

[David Mathog]

oops, sorry.  The cross reference is:

   https://bugs.launchpad.net/inkscape/+bug/1086126

Graphics section of "about:support"

Adapter Description NVIDIA Quadro FX 1400
Vendor ID0x10de
Device ID0x00ce
Adapter RAM Unknown
Adapter Drivers nv4_disp
Driver Version 6.14.13.593
Driver Date8-18-2012
WebGL Renderer Google Inc. -- ANGLE (NVIDIA Quadro FX 1400) -- OpenGL ES 2.0 (ANGLE 1.0.0.1242)
GPU Accelerated Windows1/1 Direct3D 9
AzureCanvasBackend cairo
AzureFallbackCanvasBackend none
AzureContentBackend none

toggling gfx.font_rendering.directwrite.enabled did not change anything.  (Neither did toggling any of the other true/false settings that I tried.)  Do these take effect immediately or must Firefox be restarted between each one?

Note, the problem is seen on firefox on both linux and windows, so GDI(+) cannot
be the issue.

Is there a way to turn on some sort of logging so that firefox will say which font it actually used?

Comment 5

[Cameron McCormack (:heycam)]

Could it be for example that we are applying kerning information from the font and Inkscape isn't?

Comment 6

[David Mathog]

Attachment: Both Inkscape and Firefox do kerning

Both programs use kerning, as shown in this example.  Open it in Inkscape and the final "P" is in a different position in each line, while the initial "W"'s are aligned.  It looks like that in Firefox too, but the text is, again, outside the text boundary box drawn in Inkscape.

Comment 7

[David Mathog]

Attachment: "Sans" is not rendered as "Sans"

This is another test case made with lp988601 inkscape.  The red boxes were not redrawn for each set, but the font was changed.  The idea being that if this was just a case of the font "Arial" in inkscape being a different font in Firefox, then one of the others would have lined  up in Firefox.  However none did, so that is less likely to be the problem.  (Still could be if it was some other obscure font I did not try.)

However, this turned up another problem.  Look at the "SANS" font in this example in Firefox - whatever it is it is not Sans, since it is a Serif font.  The other sans-serif fonts stayed that way.

Comment 8

[Cameron McCormack (:heycam)]

Do you have a font named "Sans" installed locally?  It sounds like Inkscape is mapping font names to fonts differently from Firefox.

Comment 9

[David Mathog]

Inkscape uses Fontconfig.  There is no font on the test system(s) named simply "Sans".  It is most likely using DejaVu Sans because:

% fc-match sans
DejaVuSans.ttf: "DejaVu Sans" "Book"

Not sure how firefox is doing it, but if it is through fontconfig then it must be using its own, different, set of fontconfig rule files, since whatever that Serif font is that it filled in for "Sans", it certainly is not "DejaVu Sans".

The simplest hypothesis for all of this is that the two font substitution systems are using different fonts - except none of the obvious contenders from the system font directory matched.  Does Firefox use its own fonts???

Comment 10

[Robert Longson [:longsonr]]

Firefox does not use its own fonts.

Comment 11

[ebrahim]

I think this is due the fact browsers unlike SVG renderers don't recognize "sans" alias but they like "sans-serif" instead. I guess if you use both, "font-family: sans-serif, sans;", both would be happy.