On 22.01.2003 23:55:14 Arnd Bei▀ner wrote:
> Hello there,
> 
> after some research I found and fixed a bug in the PS renderer
> that can be a real nuisance.

Yeah, one that I never got round to fix.

> The problem is as follows: The ascii (and Unicode) minus
> character is mapped to the hyphen character by the PDF
> renderer. The PostScript renderer instead maps it tho the
> minus character. This happens because the generated
> PS code reencodes the fonts to ISO Latin 1 encoding, which
> handles ascii code 45 differently from the standard PS font
> encoding.
> 
> Typograpically, the character at 45 in ISOLatin1 is a real minus,
> and the character at 45 in Standard Encoding is a hyphen, which
> is about half as wide as the minus in your average font. The
> difference in your PS output can be quite destructive, as FOP
> always formats assuming the width of the hyphen character...
> 
> A "patch" follows. The reason I'm not yet submitting a real diff
> to Bugzilla is that I am a) extremely overloaded right now and
> b) this really needs to be discussed:
> 
> Some thoughts on this
> (by 'FOP' I mean formatter+PDF renderer code):
> 
> 1. Who's right and who's wrong?
> Either FOP  - or - the PS renderer is right, but who?

I'm sure that the PS renderer is wrong. When I wrote it I've used
ISOLatin1 encoding because it got more characters right than with
StandardEncoding. :-) I didn't want to spend too much time on this
because at that time the PS renderer was merely a proof-of-concept.

> 2. If FOP is right, then the PS renderer must be
> fixed. This can be done either by fixing the method
> renderWordArea or by changing the PS procedures.
> However, the latter would increase PS file size
> (can't copy the ISO latin 1 enconding as opposed
> to the standard encoding), so I opted for changing
> renderWordArea.

Not happy with that on the long run. For immediately fixing this it's ok.
When I rewrite the PS renderer for the redesign I intend to get that
right from the beginning. The problem is not just the hyphen character.
There are others. The problem is that the base14 fonts are set to
WinAnsiEncoding (see org.apache.fop.render.pdf.fonts.Helvetica) and the
PS renderer uses ISOLatin1. So, depending on the characters used you get
multiple mismatches not just the hyphen character. What we probably need
is a custom encoding scheme like Acrobat Reader uses when converting PDF
to PostScript (PDFEncoding). That'll be some work...

> 3. If FOP is wrong, then probably someone else
> must fix it - I suppose I won't find the right place
> for the fix easily.

FOP is right.

> Personally I think the PS renderer is wrong, since
> the original Adobe PS character encoding maps
> ascii 45 to the hyphen character and Adobe usually
> knows what they're doing. Still, at that point in time,
> Unicode wasn't there yet, so...
> 
> This is an issue that we may possible want 
> to solve before 0.20.5 goes final. Personally, I won't
> have time before the weekend to check with
> the Unicode and/or XSL spec.
> 
> Any comments/ideas?
> 
> --------------- temp fix that I use ---------------------------
<snip/>

I'll put your fix in but I can't guarantee that it'll be before
Christian does the release.

Jeremias Maerki


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