195206 - [ps] Mozilla's PS code does poor rendering because of coordinate rounding (e.g. letter spacing)

Status: RESOLVED FIXED

(Core :: Printing: Output, defect)

Description

[Harald Koenig]

User-Agent:       Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.3b) Gecko/20030210
Build Identifier: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.3b) Gecko/20030210

the PS output created by Mozilla uses the default PS coordinate space with 1/72"
units (1 pt). unfortuneately Mozilla only outputs integer X coordinates in
moveto(), which can give poor rendering.

example URL for "just" poor/bad rendering:

http://www.davidson.com.au/products/pressure/pcb/theory/driving-cable-theory.asp

this URL uses CSS for (IMHO ugly) letter spacing e.g.

    { font-family: Helvetica; font-size: 10px; letter-spacing: -0.3pt }

but, because of X coordinate rounding, that letter spacing/kerning
gets rounded to next integert coordinate, which looks much worse than
it should be.



possible fixes:

using floating point coordinates in PS output would solve both problems,
but of course increases output file size.

using a higher resolution integer coordinate systems (0.1 pt, 1/100 pt or 1200
dpi) would work around problem (b).the image/colorimage operators.


I tried mozilla 1.0.1, 1.2.1 and 1.3-beta, all show the same deficiencies in PS
rendering.



Reproducible: Always

Steps to Reproduce:
1.
2.
3.

Comment 1

[Harald Koenig]

here is another example for wrong rendering due to coordinate rounding
(which in turn is a side effect of the fix/workaround for for Bug 191684 in
attachment 115349 [details]):

it completely suppresses rendering of "lines" with withs up to 0.5pt, which is a
perfectly reasonable width for a (not too thin) line.

example: compare PS output for those two URLs:

http://www.tat.physik.uni-tuebingen.de/~koenig/hello1.html
http://www.tat.physik.uni-tuebingen.de/~koenig/hello2.html

Comment 2

[Harald Koenig]

*** Bug 194703 has been marked as a duplicate of this bug. ***

Comment 3

[Boris Zbarsky [:bzbarsky]]

Confirming; bstell, who's actually working on our PS stuff nowadays?  Would you
mind reassigning to them?

Comment 4

[kill this account]

please check with [e-mail] and [e-mail]

Comment 5

[Pete Zha]

-> Myself

Comment 6

[Kenneth Herron]

Because of the compressed spacing, the postscript for this page positions and
draws each character individually, instead of doing complete strings at once. As
noted, mozilla was limited to integral coordinates at 72 units per inch,
resulting in some unusually wide or narrow inter-character spaces from
coordinate rounding.

The patch for bug 80190 changes mozilla to generate postscript using 1440 units
per inch, the same system used internally by the layout module. With this change
the spacing problems are virtually nonexistant.

Resolving fixed by bug 80190.