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Groups > comp.sys.acorn.misc > #4971

Re: Increasing default line spacing in RISC OS fonts

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In message <367a758252.Matthew@sinenomine.freeserve.co.uk>
          Matthew Phillips <spam2011m@yahoo.co.uk> wrote:

> I must have a look into the PRMs to get a better understanding of what
> happens if an application uses Font_FindFont without specifying an encoding,
> and what happens if it calls Font_FindFont specifying an encoding not
> supported by a font.

> I'm afraid I had assumed that if an application is running in a Latin-1
> environment and calls Font_FindFont without giving an encoding, then the font
> handle returned would suit the current alphabet, but perhaps it just returns
> the default encoding for a font?

Either can happen, depending on whether the font is a "language" font 
based on a base encoding (i.e., with an "IntMetrics<N>" file) or a 
"symbol" font with an "IntMetrics" file. Only "language" fonts are 
mapped to the system alphabet (strictly speaking, to the current 
alphabet with the Unicode FontManager or the territory default 
alphabet with the traditional FontManager). The behaviour for 
"language" fonts is not relevant in this scenario though because the 
kind of Latin-2 Jon wants to create could not be a "language" font.

With the notable exception of the 3 ROM language fonts, most RISC OS 
fonts are "symbol" fonts in the above sense. For instance, a typical 
EFF Latin-1 font comes with an IntMetrics file and an Encoding file 
describing the font's encoding (in this example, EFF Latin1, which is 
a superset of ISO Latin1, but different from Acorn Latin1). An EFF 
Latin-2 font comes with a Latin-2 Encoding file (presumably, I have 
not seen one yet).

If Jon did create a "language" font containing just the Latin-2 
glyphs, then this would not have the effect he wanted. Opening it 
without specifying an encoding on a Latin-1 system with the Unicode 
FontManager would result in a Latin-1 encoded font, but then, only the 
Latin-1 subset of the font's glyphs would be accessible and they would 
be at their Latin-1 codepoints, so the effect would be a font for a 
subset of Latin-1 instead of a Latin-2 font.

To achieve the desired effect (a font that turns out to be Latin-2 
encoded when being opened without specifying an encoding) he would 
have to create a "symbol" font, i.e., a font with an "IntMetrics" file 
(and, hopefully, a local encodings file, otherwise, PostScript 
printing would go wrong), and in that case, the current system 
alphabet would not be relevant when opening it without specifying an 
encoding. So, the result would be a Latin-2 encoded font.

To see the difference between opening a font without an encoding and 
with an explicit Latin-1 encoding, try XChars and view an EFF font in 
"Default" (i.e., no encoding specified, just as most applications do) 
and "Latin1" encodings. The layout of the font changes because it is a 
"symbol" font, so it is opened in "Glyph" encoding by default. Nothing 
changes with "Homerton" because it is opened in Latin-1 by default. 
Try viewing Homerton with an explicit "Greek" encoding - that maps the 
one Greek character Homerton has (the "mu") in the correct place for 
Greek, but leaves the other Greek characters empty because the font 
does not have them. You would see the same effect with a Latin-2 
"language" font.

> Time to do some reading....

In addition to the PRMs it is worth while reading the RO5 FontManager 
document, section 2.2 "Default encodings."

-- 
Martin
---------------------------------------------------------------------
Martin Wuerthner         MW Software      http://www.mw-software.com/
        RISC OS Software for Design, Printing and Publishing
---------------------------------------------------------------------

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Thread

Increasing default line spacing in RISC OS fonts castlevarich <castlevarich@yahoo.co.uk> - 2012-03-24 05:17 -0700
  Re: Increasing default line spacing in RISC OS fonts Jim Nagel <jimnewsm10d@abbeypress.co.uk> - 2012-03-26 22:27 +0100
    Re: Increasing default line spacing in RISC OS fonts Stewart Brodie <stewart.brodie@ntlworld.com> - 2012-03-26 22:42 +0100
      Re: Increasing default line spacing in RISC OS fonts Martin Wuerthner <spamtrap@mw-software.com> - 2012-03-27 00:18 +0200
        Re: Increasing default line spacing in RISC OS fonts castlevarich <castlevarich@yahoo.co.uk> - 2012-04-04 08:39 -0700
          Re: Increasing default line spacing in RISC OS fonts Russell Hafter News <see.sig@walkingingermany.invalid> - 2012-04-04 20:27 +0100
          Re: Increasing default line spacing in RISC OS fonts Martin Wuerthner <spamtrap@mw-software.com> - 2012-04-05 01:17 +0200
            Re: Increasing default line spacing in RISC OS fonts castlevarich <castlevarich@yahoo.co.uk> - 2012-04-05 08:38 -0700
              Re: Increasing default line spacing in RISC OS fonts Martin Wuerthner <spamtrap@mw-software.com> - 2012-04-05 18:10 +0200
                Re: Increasing default line spacing in RISC OS fonts castlevarich <castlevarich@yahoo.co.uk> - 2012-04-16 08:42 -0700
                Re: Increasing default line spacing in RISC OS fonts Matthew Phillips <spam2011m@yahoo.co.uk> - 2012-04-18 07:24 +0100
                Re: Increasing default line spacing in RISC OS fonts Martin Wuerthner <spamtrap@mw-software.com> - 2012-04-18 17:06 +0200
                Re: Increasing default line spacing in RISC OS fonts Matthew Phillips <spam2011m@yahoo.co.uk> - 2012-04-18 18:55 +0100
                Re: Increasing default line spacing in RISC OS fonts Martin Wuerthner <spamtrap@mw-software.com> - 2012-04-19 11:09 +0200
                Re: Increasing default line spacing in RISC OS fonts Russell Hafter News <see.sig@walkingingermany.invalid> - 2012-04-19 10:37 +0100
                Re: Increasing default line spacing in RISC OS fonts Paul Sprangers <Paul@sprie.nl> - 2012-04-19 11:48 +0200
                Re: Increasing default line spacing in RISC OS fonts Martin Wuerthner <spamtrap@mw-software.com> - 2012-04-19 16:39 +0200
                Re: Increasing default line spacing in RISC OS fonts Paul Sprangers <Paul@sprie.nl> - 2012-04-20 00:22 +0200
                Re: Increasing default line spacing in RISC OS fonts Martin Wuerthner <spamtrap@mw-software.com> - 2012-04-20 11:10 +0200
                Re: Increasing default line spacing in RISC OS fonts Paul Sprangers <Paul@sprie.nl> - 2012-04-20 15:50 +0200
                Re: Increasing default line spacing in RISC OS fonts Martin Wuerthner <spamtrap@mw-software.com> - 2012-04-20 17:10 +0200
                Re: Increasing default line spacing in RISC OS fonts Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-04-20 18:06 +0200
                Re: Increasing default line spacing in RISC OS fonts "John Williams (News)" <UCEbin@tiscali.co.uk> - 2012-04-20 18:31 +0200
                Re: Increasing default line spacing in RISC OS fonts druck <news@druck.org.uk> - 2012-04-20 22:21 +0100
                Re: Increasing default line spacing in RISC OS fonts Stewart Brodie <stewart.brodie@ntlworld.com> - 2012-04-21 02:15 +0100
                Re: Increasing default line spacing in RISC OS fonts Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-04-21 05:06 +0200
                Re: Increasing default line spacing in RISC OS fonts Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-04-20 17:54 +0200
                Re: Increasing default line spacing in RISC OS fonts Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-04-20 17:47 +0200
                Re: Increasing default line spacing in RISC OS fonts Martin Wuerthner <spamtrap@mw-software.com> - 2012-04-23 08:00 +0200
                Re: Increasing default line spacing in RISC OS fonts Paul Sprangers <Paul@sprie.nl> - 2012-04-23 10:16 +0200
                Re: Increasing default line spacing in RISC OS fonts Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-04-19 17:00 +0200
                Re: Increasing default line spacing in RISC OS fonts Matthew Phillips <spam2011m@yahoo.co.uk> - 2012-04-20 23:30 +0100
                Re: Increasing default line spacing in RISC OS fonts castlevarich <castlevarich@yahoo.co.uk> - 2012-04-21 04:38 -0700

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