Honour region subtags (#749)

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LLM Contributions: Regression testing, CI changes (GPT 5.5 Sol).

Fixes #748.

| Before | After |
| ------ | ------ |
| Subtag not honoured (same glyphs throughout) | Subtag honoured |
| <img width="205" height="215" alt="before_subtag"
src="https://github.com/user-attachments/assets/be445fcb-ac7f-4183-9278-88c80aa2677a"
/> | <img width="205" height="215" alt="after_subtag"
src="https://github.com/user-attachments/assets/e8b1e782-fbaf-49f4-905c-770801019478"
/> |


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**Changelog**

> ### Fixed
>
> - Honours script and region sub tags for correct shaping of, for
example, zh-Hans and zh-Hant.

Author: taj-p

…_dev/assets/fonts/noto_fonts/LICENSE.txt …ts/noto_fonts/LICENSE-NotoKufiArabic.txtparley_dev/assets/fonts/noto_fonts/LICENSE.txt renamed to parley_dev/assets/fonts/noto_fonts/LICENSE-NotoKufiArabic.txt parley_dev/assets/fonts/noto_fonts/LICENSE.txt renamed to parley_dev/assets/fonts/noto_fonts/LICENSE-NotoKufiArabic.txt

@@ -0,0 +1,92 @@
+This Font Software is licensed under the SIL Open Font License,
+Version 1.1.
+
+This license is copied below, and is also available with a FAQ at:
+http://scripts.sil.org/OFL
+
+-----------------------------------------------------------
+SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
+-----------------------------------------------------------
+
+PREAMBLE
+The goals of the Open Font License (OFL) are to stimulate worldwide
+development of collaborative font projects, to support the font
+creation efforts of academic and linguistic communities, and to
+provide a free and open framework in which fonts may be shared and
+improved in partnership with others.
+
+The OFL allows the licensed fonts to be used, studied, modified and
+redistributed freely as long as they are not sold by themselves. The
+fonts, including any derivative works, can be bundled, embedded,
+redistributed and/or sold with any software provided that any reserved
+names are not used by derivative works. The fonts and derivatives,
+however, cannot be released under any other type of license. The
+requirement for fonts to remain under this license does not apply to
+any document created using the fonts or their derivatives.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this license and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Reserved Font Name" refers to any names specified as such after the
+copyright statement(s).
+
+"Original Version" refers to the collection of Font Software
+components as distributed by the Copyright Holder(s).
+
+"Modified Version" refers to any derivative made by adding to,
+deleting, or substituting -- in part or in whole -- any of the
+components of the Original Version, by changing formats or by porting
+the Font Software to a new environment.
+
+"Author" refers to any designer, engineer, programmer, technical
+writer or other person who contributed to the Font Software.
+
+PERMISSION & CONDITIONS
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Font Software, to use, study, copy, merge, embed,
+modify, redistribute, and sell modified and unmodified copies of the
+Font Software, subject to the following conditions:
+
+1) Neither the Font Software nor any of its individual components, in
+Original or Modified Versions, may be sold by itself.
+
+2) Original or Modified Versions of the Font Software may be bundled,
+redistributed and/or sold with any software, provided that each copy
+contains the above copyright notice and this license. These can be
+included either as stand-alone text files, human-readable headers or
+in the appropriate machine-readable metadata fields within text or
+binary files as long as those fields can be easily viewed by the user.
+
+3) No Modified Version of the Font Software may use the Reserved Font
+Name(s) unless explicit written permission is granted by the
+corresponding Copyright Holder. This restriction only applies to the
+primary font name as presented to the users.
+
+4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
+Software shall not be used to promote, endorse or advertise any
+Modified Version, except to acknowledge the contribution(s) of the
+Copyright Holder(s) and the Author(s) or with their explicit written
+permission.
+
+5) The Font Software, modified or unmodified, in part or in whole,
+must be distributed entirely under this license, and must not be
+distributed under any other license. The requirement for fonts to
+remain under this license does not apply to any document created using
+the Font Software.
+
+TERMINATION
+This license becomes null and void if any of the above conditions are
+not met.
+
+DISCLAIMER
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
+OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
+DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
+OTHER DEALINGS IN THE FONT SOFTWARE.

parley_dev/assets/fonts/noto_fonts/LICENSE-NotoSansCJK.txt

@@ -23,6 +23,7 @@ pub fn font_dirs() -> impl Iterator<Item = PathBuf> {
 pub const FONT_FAMILIES: &[&str] = &[
     "Arimo",
     "Roboto",
+    "Noto Sans CJK SC",
     "Noto Kufi Arabic",
     "Noto Color Emoji",
     "Noto Color Emoji CBTF",

parley_dev/assets/fonts/noto_fonts/NotoSansCJKsc-Regular.otf

@@ -303,7 +303,7 @@ fn shape_segment(
         let language = options
             .language
             .as_ref()
-            .and_then(|lang| lang.language().parse::<harfrust::Language>().ok());
+            .and_then(|lang| lang.as_str().parse::<harfrust::Language>().ok());
         scx.features.clear();
         for feature in options.features {
             scx.features.push(harfrust::Feature::new(

parley_dev/src/lib.rs

@@ -5,7 +5,9 @@
 
 use crate::test_name;
 use crate::util::TestEnv;
-use parley::{Alignment, AlignmentOptions, PositionedLayoutItem, StyleProperty, TextWrapMode};
+use parley::{
+    Alignment, AlignmentOptions, FontFamily, PositionedLayoutItem, StyleProperty, TextWrapMode,
+};
 
 /// Test that rendering RTL text doesn't affect subsequent LTR layouts.
 /// See <https://github.com/linebender/parley/issues/489>.
@@ -114,3 +116,33 @@ Third line that ends with newlines\n\n";
     env.with_name("max_context_with_mandatory_breaks")
         .check_layout_snapshot(&layout);
 }
+
+/// Test that script and region subtags select the corresponding OpenType language system.
+/// See <https://github.com/linebender/parley/issues/748>.
+#[test]
+fn issue_748_language_subtags() {
+    let mut env = TestEnv::new(test_name!(), None);
+    let text = "zh: 骨\nzh-Hans: 骨\nzh-Hant: 骨\nzh-TW: 骨\nzh-HK: 骨";
+
+    let mut builder = env.ranged_builder(text);
+    builder.push_default(StyleProperty::FontSize(32.0));
+    for ((start, marker), language) in text
+        .match_indices('骨')
+        .zip(["zh", "zh-Hans", "zh-Hant", "zh-TW", "zh-HK"])
+    {
+        let range = start..start + marker.len();
+        builder.push(
+            StyleProperty::FontFamily(FontFamily::named("Noto Sans CJK SC")),
+            range.clone(),
+        );
+        builder.push(
+            StyleProperty::Locale(Some(language.parse().unwrap())),
+            range,
+        );
+    }
+
+    let mut layout = builder.build(text);
+    layout.break_all_lines(None);
+    layout.align(Alignment::Start, AlignmentOptions::default());
+    env.check_layout_snapshot(&layout);
+}