[Fontconfig] How to make Arial support Vietnamese?

[Nguyen Thai Ngoc Duy]

Hi,

I would like to make arial the prefered Sans font in my system. It
works great if I use locale C. If I use locale vi_VN.UTF-8 then it
fails to recognize Vietnamese is supported by Arial and pass on. Is
there anyway to make it work? I'm using fontconfig 2.7.2.

The output of Arial in my machine is below. I guess field "charset" is
surprisingly short, but I don't know why.

Pattern has 30 elts (size 32)
	family: "Arial"(s)
	familylang: "en"(s)
	style: "Normal"(s)
	stylelang: "ca"(s)
	fullname: "Arial"(s)
	fullnamelang: "en"(s)
	slant: 0(i)(s)
	weight: 80(i)(s)
	width: 100(i)(s)
	size: 12(f)(s)
	pixelsize: 12.5(f)(s)
	foundry: "monotype"(s)
	hintstyle: 3(i)(s)
	hinting: FcTrue(s)
	verticallayout: FcFalse(s)
	autohint: FcFalse(s)
	globaladvance: FcTrue(s)
	file: "/usr/share/fonts/corefonts/arial.ttf"(s)
	index: 0(i)(s)
	outline: FcTrue(s)
	scalable: FcTrue(s)
	dpi: 75(f)(s)
	scale: 1(f)(s)
	charset:
	0000: 00000000 ffffffff ffffffff 7fffffff 00000000 ffffffff ffffffff ffffffff
	0001: ffffffff ffffffff ffffffff ffffffff 00048000 00018003 1fffe000 fc000000
	0002: 00000000 00000000 02000000 00000000 00000000 00000000 3f0002c0 00000000
	0003: 0000020b 00000008 00000000 40000000 ffffd7f0 fffffffb 00007fff 00000000
	0004: ffffdffe ffffffff dffeffff 00000000 3ccf0000 0f0fc00c 03000000 00000300
	0005: 00000000 00000000 00000000 00000000 00000000 fbff0000 ffff000f 001f07ff
	0006: 88001000 07fffffe 0007ffff 40022fff 01000040 00008210 00201000 03ff0000
	001e: 00000000 00000000 00000000 00000000 0000003f ffffffff ffffffff 03ffffff
	0020: 7fb8f000 560d7c47 00000010 8000fc00 00000000 00001c98 00000000 00000000
	0021: 00480020 00004044 78180000 00000000 003f0000 00000100 00000000 00000000
	0022: c6268044 00000a00 00000100 00000033 00000000 00000000 00000000 00000000
	0023: 00010004 00000003 00000000 00000000 00000000 00000000 00000000 00000000
	0025: 11111005 10101010 ffff0000 00001fff 000f1111 14041c03 03008c10 00000040
	0026: 00000000 1c000000 00000005 00000c69 00000000 00000000 00000000 00000000
	00e8: 0100003e 04000000 00000000 00000000 00000000 00000000 00000000 00000000
	00f0: fffffff6 0003ffff 00000000 00000000 00000000 00000000 00000000 00000000
	00fb: 00000006 5f7ffc01 03c0ffdb 3c000000 003fcc00 00000000 00000000 f0000000
	00fc: 00000000 00000000 c0000000 00000007 00000000 00000000 00000000 00000000
	00fd: 00000000 c0000000 00000000 00000000 00000000 00000000 00000000 00040000
	00fe: 00000000 00000000 00000000 00000000 ffffffff ffffffff ffffffff 1fffffff
	00ff: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 10000000
(s)
	lang: aa|af|ar|ast|av|ay|az-az|be|bg|bi|bin|br|bs|bua|ca|ce|ch|co|cs|cy|da|de|el|en|eo|es|et|eu|fa|fi|fj|fo|fr|fur|fy|gd|gl|gn|gv|he|ho|hr|hu|ia|ig|id|ie|ik|io|is|it|kaa|ki|kk|kl|kum|ky|la|lb|lez|lt|lv|mg|mh|mt|nb|nds|nl|nn|no|nr|nso|ny|oc|om|os|pl|pt|rm|ru|se|sel|sk|sl|sma|smj|smn|so|sq|sr|ss|st|sv|sw|tk|tl|tn|tr|ts|tt|tyv|ug|uk|uz|vo|vot|wa|wen|wo|xh|yap|yi|zu|an|crh|csb|fil|hsb|ht|jv|kj|ku-tr|kwm|lg|li|mn-mn|ms|na|ng|pap-an|pap-aw|rn|rw|sc|sg|sn|su|za(s)
	fontversion: 184812(i)(s)
	capability: "otlayout:arab"(s)
	fontformat: "TrueType"(s)
	embeddedbitmap: FcTrue(s)
	decorative: FcFalse(s)


My modified /etc/fonts/conf.d/60-latin.conf

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
	<alias>
		<family>serif</family>
		<prefer>
			<family>Times New Roman</family>
			<family>Bitstream Vera Serif</family>
			<family>DejaVu Serif</family>
			<family>Thorndale AMT</family>
			<family>Luxi Serif</family>
			<family>Nimbus Roman No9 L</family>
			<family>Times</family>
		</prefer>
	</alias>
	<alias>
		<family>sans-serif</family>
		<prefer>
			<family>Arial</family>
			<family>Bitstream Vera Sans</family>
			<family>DejaVu Sans</family>
			<family>Verdana</family>
			<family>Albany AMT</family>
			<family>Luxi Sans</family>
			<family>Nimbus Sans L</family>
			<family>Helvetica</family>
		</prefer>
	</alias>
	<alias>
		<family>monospace</family>
		<prefer>
			<family>Terpinus</family>
			<family>Courier New</family>
			<family>Bitstream Vera Sans Mono</family>
			<family>DejaVu Sans Mono</family>
			<family>Andale Mono</family>
			<family>Cumberland AMT</family>
			<family>Luxi Mono</family>
			<family>Nimbus Mono L</family>
			<family>Courier</family>
		</prefer>
	</alias>
</fontconfig>
-- 
Duy