Primary font ignores the fontconfig's charset property.

[huyuehui]

I reported an issue several days ago. Maybe at that time I didn't make myself clear. I guess that the following source blocks cause this issue.

In src/ft/mod.rs :
In my case, the function load_face_with_glyph(...) has never been called. Because in face_for_glyph(...), it always returns early inside the 'if let' block.

In the get_face(...) function, the 'coverage' of the 'Fallbacklist' struct doesn't include the charset of the primary font. So setting the charset property of the first matched font (the primary font) in fonts.conf doesn't work if no fallback is happened.

[chrisduerr]

Ah, I understand what you mean now. Seems like you're right and we do indeed not check the charset for the primary font. We check the char index to make sure the character is contained at all, but that's it.

It seems like the charset also isn't read for fallback fonts that have been loaded already (see the Some(face) branch in load_face_with_glyph).

Generally once a font is loaded, we only have access to FreeType things iirc. So at that point we don't check anything fontconfig anymore. But the charset would have to be checked every time a glyph load is attempted, we'd likely have to persist it from fontconfig after loading.

Curious if @kchibisov is aware of/has an opinion on this, since he did do a bunch of freetype/fontconfig stuff in the past.

[kchibisov]

@huyuehui would you mind providing example fontconfig configuration? I'm not into its syntax wrt charsets so it could help.

[huyuehui]

@kchibisov
It is something like the following:

...

  <match target="scan">
	  <test name="family"><string>Migu 1M</string></test>
	  <edit name="charset">
		  <charset>
			  <!-- 基本拉丁(ASCII) -->
			  <range><int>0x0020</int><int>0x007E</int></range>
			  <!-- 拉丁-1增补 + 拉丁扩展A/B -->
			  <range><int>0x00A0</int><int>0x0181</int></range>
			  <int>0x0186</int><int>0x0189</int><int>0x018A</int>
			  <range><int>0x018E</int><int>0x0194</int></range>
			  <range><int>0x0198</int><int>0x019B</int></range>
			  <range><int>0x019D</int><int>0x01A1</int></range>
			  <range><int>0x01AF</int><int>0x01B1</int></range>
			  <range><int>0x01B3</int><int>0x01B6</int></range>
			  <range><int>0x01BF</int><int>0x01E3</int></range>
			  <range><int>0x01E6</int><int>0x01ED</int></range>
			  <range><int>0x01EF</int><int>0x01F5</int></range>
			  <range><int>0x01F7</int><int>0x01FF</int></range>
			  <range><int>0x0218</int><int>0x021F</int></range>
			  <range><int>0x0230</int><int>0x0233</int></range>
			  <int>0x0237</int><int>0x023D</int>
			  <!-- 国际音标 + 空格调整字母 -->
			  <range><int>0x0250</int><int>0x02FF</int></range>
			  <!-- 希腊语 -->
			  <range><int>0x0372</int><int>0x0375</int></range>
			  <int>0x037A</int><int>0x037E</int><int>0x038C</int>
			  <range><int>0x0384</int><int>0x038A</int></range>
			  <range><int>0x038E</int><int>0x03A1</int></range>
			  <range><int>0x03A3</int><int>0x03E1</int></range>
			  <!-- 西里尔语 -->
			  <range><int>0x0400</int><int>0x045F</int></range>
			  <int>0x0462</int><int>0x0463</int>
			  <range><int>0x0472</int><int>0x0475</int></range>
			  <int>0x0480</int><int>0x0481</int><int>0x0490</int><int>0x0491</int>
			  <int>0x04AE</int><int>0x04AF</int><int>0x04E8</int><int>0x04E9</int>
			  <!-- 货币符号 -->
			  <int>0x20A1</int><range><int>0x20A8</int><int>0x20AC</int></range>
			  <range><int>0x20AF</int><int>0x20B3</int></range><int>0x20B5</int>
			  <!-- 字母符号 -->
			  <int>0x2103</int><int>0x2113</int><int>0x2116</int><int>0x211E</int>
			  <int>0x2121</int><int>0x2122</int><int>0x2126</int><int>0x2127</int>
			  <!-- 数字形式(罗马) -->
			  <range><int>0x2160</int><int>0x216B</int></range>
			  <range><int>0x2170</int><int>0x217B</int></range>
			  <!-- 箭头 -->
			  <range><int>0x2190</int><int>0x2199</int></range>
			  <range><int>0x21B0</int><int>0x21B5</int></range>
			  <range><int>0x21C4</int><int>0x21CA</int></range>
			  <range><int>0x21D0</int><int>0x21D9</int></range>
			  <range><int>0x21E4</int><int>0x21ED</int></range>
			  <!-- 控制图片 -->
			  <range><int>0x2400</int><int>0x2426</int></range>
			  <!-- 带圈的字母与数字 -->
			  <range><int>0x2460</int><int>0x2473</int></range>
			  <range><int>0x24D0</int><int>0x24FF</int></range>
			  <range><int>0x2776</int><int>0x2793</int></range>
			  <!-- 数学乘号 + 拉丁扩展C -->
			  <int>0x2A2F</int><int>0x2C71</int><int>0x2C7D</int>
			  <!-- 平假名 + 片假名 + 片假名语音扩展 -->
			  <range><int>0x3041</int><int>0x3096</int></range>
			  <range><int>0x3099</int><int>0x30FF</int></range>
			  <range><int>0x31F0</int><int>0x31FF</int></range>
			  <!-- 拉丁扩展D -->
			  <int>0xA78B</int><int>0xA78C</int>
			  <!-- 拉丁组合字 -->
			  <range><int>0xFB00</int><int>0xFB04</int></range>
			  <!-- 字节顺序标记 -->
			  <int>0xFEFF</int>
		  </charset>
	  </edit>
  </match> 

...

[kchibisov]

Ok, I'll try to take a look when I have time...