Inkscape

value of pixel is incorrect according to CSS2+errata

  1. Series experimental
  2. Bug #510433
Bug #510433 reported by Linda Walsh
10
This bug affects 1 person
Affects Status Importance Assigned to Milestone
Inkscape
Fix Released
Low
Tavmjong Bah
Inkscape 0.92 "0.92"
Experimental
Fix Committed
Undecided
Tavmjong Bah

Bug Description

In the file 'units.txt', a pixel is listed as 1/90th of an inch and gives CSS as a source for this.

However, according to the CSS3 standard at http://www.w3.org/TR/css3-values/#reference,
the normative value is 96 dpi (at a 28 inch distance). As it is based on the size of an area of a visual
angle, then at closer distances (I usually work closer to my monitor than 28 inches) it would be a higher number. But in any event, I'd like to suggest it be changed to 967 dpi. to conform with CSS3. I've never seen a reference saying 90dpi is a CSS standard, but I don't know CSS from ages ago -- but SVG wasn't part of the web spec ages ago either.

This is a mostly a 'doc' bug, but it could change the shipped default if it remains at the 1'inch value of dots (would change shipped value from 90 to 96).

Revision history for this message
Linda Walsh (inkscape-tlinx) wrote :

Oh...presumably this would also affect the value of a pixel in 'units.xml'.

Revision history for this message
Jon A. Cruz (jon-joncruz) wrote :

CSS2 is specified by SVG 1.1. In the CSS2 spec, the reference pixel size is 90 DPI

http://www.w3.org/TR/2008/REC-CSS2-20080411/syndata.html#length-units

Changed in inkscape:
status: New → Won't Fix
importance: Undecided → Low
assignee: nobody → Jon A. Cruz (jon-joncruz)
Revision history for this message
LucaDC (lucadc) wrote :

I already tried to point this out: please check the corrections made to CSS 2.0:

http://www.w3.org/TR/CSS2/changes.html#q8
See C.3.6 Section 4.3.2 Lengths

And tell me where I'm wrong, at least.

Thanks.

Revision history for this message
LucaDC (lucadc) wrote :

Sorry, it would have been more appropriate to cite this errata:

http://www.w3.org/Style/css2-updates/REC-CSS2-19980512-errata.html

Section 4.3.2 Lengths

Revision history for this message
Linda Walsh (inkscape-tlinx) wrote :

According to the errata pointed out above:

    Section 4.3.2 Lengths

[2001-08-28] The suggested reference pixel is based on a 96 dpi device, not 90 dpi. The visual angle is thus about 0.0213 degrees instead of 0.0227, and a pixel at arm's length is about 0.26 mm instead of 0.28

---
It seems that CSS2 also was based on a 96dpi device -- as it was corrected in 2001 (9 years ago). So inkscape is using the wrong value, or am I misunderstanding something?

Changed in inkscape:
status: Won't Fix → Confirmed
Revision history for this message
Jon A. Cruz (jon-joncruz) wrote :

SVG does not yet use CSS3, so we won't be addressing this specifically.

Also... the specs do say that any user agent is free to use the values it deems appropriate. The correct fix from the SVG viewpoint is to 1) adjust to screen/display resolution and 2) to properly user viewbox, etc.

Changed in inkscape:
status: Confirmed → Won't Fix
Revision history for this message
Jon A. Cruz (jon-joncruz) wrote :

(changing things require changing the code... which in turn means that if the code is changed we should just do the proper thing)

Changed in inkscape:
status: Won't Fix → Confirmed
Revision history for this message
Jon A. Cruz (jon-joncruz) wrote :

(Note that the description change was critical to move it from "won't fix")

summary: - value of pixel is incorrect according to CSS3 standard
+ value of pixel is incorrect according to CSS2+errata
Revision history for this message
su_v (suv-lp) wrote :

Committed to lp:inkscape/experimental in revision 13380
<http://bazaar.launchpad.net/~inkscape.dev/inkscape/experimental/revision/13380>

See also:
<http://thread.gmane.org/gmane.comp.graphics.inkscape.devel/43430>
<http://thread.gmane.org/gmane.comp.graphics.inkscape.devel/44118>

Revision history for this message
su_v (suv-lp) wrote :

Setting milestone to 0.91 based on recent discussion on the mailing list:
<http://thread.gmane.org/gmane.comp.graphics.inkscape.devel/44118>

su_v (suv-lp)
no longer affects: inkscape/0.91.x
Changed in inkscape:
milestone: 0.91 → 0.92
Revision history for this message
su_v (suv-lp) wrote :

The experimental branch was merged into trunk in r13641.

Changed in inkscape:
status: Confirmed → Fix Committed
Bryce Harrington (bryce)
Changed in inkscape:
status: Fix Committed → Fix Released
To post a comment you must log in.
This report contains Public information  
Everyone can see this information.
Subscribing...

Other bug subscribers

Remote bug watches

Bug watches keep track of this bug in other bug trackers.