forked from pool/int10h-oldschoolpc-fonts
Jan Engelhardt
b1ea056549
OBS-URL: https://build.opensuse.org/package/show/M17N:fonts/int10h-oldschoolpc-fonts?expand=0&rev=6
93 lines
2.9 KiB
Plaintext
93 lines
2.9 KiB
Plaintext
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== Introduction ==
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In classic IBM PC text mode, the graphics card stretches the font
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such that it fills the screen.
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A 9x16 font over 80x25 columns is displayed as a 720x400 image.
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Assuming a 4:3 monitor as typically was present in the days, this
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leads to a pixel aspect ratio of 20:27.
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Font size Image size aspect decimal inverse
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------------------------------------------------------------
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8x8 640x200 5:12 0.42 2.40
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8x14 640x350 35:48 0.73 1.37
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8x16 640x400 5:6 0.83 1.20
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9x16 720x400 20:27 0.74 1.35
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To faithfully recreate the same visual look as such a monitor would
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show, this aspect ratio needs to be applied when making use of the
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font.
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== Application support for stretching ==
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For cool-retro-term, there is a "Font Width" slider in the settings;
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set it to 74%, 83%, or whatever is necessary. (Notice the pattern of
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the "decimal" column of our table.)
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For xterm, a fontconfig matrix can be specified like so:
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xterm -fa "Px437 ATI 9x16:matrix=0.74 0 0 1"
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xterm -fa "Px437 ATI 9x16:matrix=1 0 0 1.35"
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One can either horizontally compress the glyphs, or vertically
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stretch them to get to the result. The compress/stretch action
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influences how many characters will be visible in a fullscreen
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setting, so the basic font size may need to be adjusted.
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xterm -fa "Px437 ATI 9x16:size=32:matrix=0.74 0 0 1"
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xterm -fa "Px437 ATI 9x16:size=24:matrix=1 0 0 1.35"
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produce an equivalent result.
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Extra caveat: When using a matrix, you should also specify the -fd
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parameter *and* specify the same matrix inside the -fd font
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specification. Otherwise, CJK characters will be rendered in a
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different size than the main characters. For a stretching matrix like
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1/1.35, not specifying -fd and, as a result, having smaller CJK chars
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is not as bad a problem as having bigger truncated CJK chars with a
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compressing matrix like 0.74/1.
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== Application-independent approach ==
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Not all programs support specifying a matrix or a scaling factor.
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Under systems using fontconfig (such as Linux distributions),
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it is possible to override the stretch for an existing font
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like so (~/.config/fontconfig/fonts.conf):
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<?xml version='1.0'?>
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<!DOCTYPE fontconfig SYSTEM 'fonts.dtd'>
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<fontconfig>
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<match target="font">
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<test qual="any" name="family">
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<string>Px437 IBM VGA 9x16</string>
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</test>
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<edit name="matrix" mode="assign">
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<times>
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<name>matrix</name>
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<matrix>
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<double>0.73</double>
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<double>0</double>
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<double>0</double>
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<double>1</double>
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</matrix>
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</times>
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</edit>
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</match>
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<dir>~/.fonts</dir>
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</fontconfig>
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== Framework-independent approach ==
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The int10h project offers font files that have their aspect
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correction applied at the font level. As a result, they won't need
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support from fontconfig or applications at all. These font files are
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provided in the
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int10h-oldschoolpc-fonts-stretched
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subpackage in openSUSE.
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