Add Swash test harness

.gitmodules

@@ -19,3 +19,6 @@
 [submodule "src/third_party/allsorts/allsorts-tools"]
 	path = src/third_party/allsorts/allsorts-tools
 	url = https://github.com/yeslogic/allsorts-tools
+[submodule "src/third_party/swash/swash"]
+	path = src/third_party/swash/swash
+	url = https://github.com/dfrg/swash

README.md

@@ -14,7 +14,7 @@ $ for engine in CoreText FreeStack TehreerStack fontkit OpenType.js Allsorts ; d
 
 ## Supported Platforms
 
-Currently, the test suite supports six OpenType implementations:
+Currently, the test suite supports seven OpenType implementations:
 
 * With `--engine=FreeStack`, the tests are run on the free/libre
 open-source text rendering stack with [FreeType](https://www.freetype.org/),
@@ -45,12 +45,21 @@ text rendering stack consisting of [FreeType](https://www.freetype.org/),
   a parsing and shaping engine implemented in [Rust](https://www.rust-lang.org/).
 — [Test report for Allsorts](https://rawgit.com/unicode-org/text-rendering-tests/master/reports/Allsorts.html).
 
-It’s trivial to test other implementations; simply write a small
-wrapper tool. For the [Go font
+* With `--engine=Swash`, the tests are run using [Swash](https://github.com/dfrg/swash),
+  a parsing, shaping, and scaling/rendering engine also implemented in [Rust](https://www.rust-lang.org/).
+— [Test report for Swash](https://rawgit.com/unicode-org/text-rendering-tests/master/reports/Swash.html).
+
+It’s trivial to test other implementations; simply write a small wrapper
+tool:
+
+- For the [Go font
 library](https://godoc.org/golang.org/x/image/font/sfnt), see
-[here](https://github.com/golang/go/issues/20208). For the [Rust font
-library](https://github.com/google/font-rs), see
-[here](https://github.com/google/font-rs/issues/17).
+[here](https://github.com/golang/go/issues/20208).
+
+- For the [Rust font library](https://github.com/google/font-rs), see
+[here](https://github.com/google/font-rs/issues/17). You may be able to
+reuse (or factor out) the argument parsing and SVG-writing parts of the
+[Swash test harness](./src/fonttest-swash-harness/) as a starting point.
 
 
 ## Test Cases

check.py

@@ -46,6 +46,10 @@ def __init__(self, engine):
             self.command = (
                 "src/third_party/allsorts/allsorts-tools/target/release/allsorts"
             )
+        elif self.engine == "Swash":
+            self.command = (
+                "src/fonttest-swash-harness/target/release/fonttest-swash-harness"
+            )
         else:
             self.command = "build/fonttest/fonttest"
         self.datestr = self.make_datestr()
@@ -54,7 +58,7 @@ def __init__(self, engine):
         self.observed = {}  # testcase --> SVG ElementTree
 
     def get_version(self):
-        if self.engine in {"CoreText", "FreeStack", "TehreerStack", "Allsorts"}:
+        if self.engine in {"CoreText", "FreeStack", "TehreerStack", "Allsorts", "Swash"}:
             return subprocess.check_output(
                 [self.command, "--version", "--engine=" + self.engine]
             ).decode("utf-8")
@@ -237,6 +241,16 @@ def build(engine):
                 "src/third_party/allsorts/allsorts-tools/Cargo.toml",
             ]
         )
+    elif engine == "Swash":
+        subprocess.check_call(
+            [
+                "cargo",
+                "build",
+                "--release",
+                "--manifest-path",
+                "src/fonttest-swash-harness/Cargo.toml",
+            ]
+        )
     else:
         if not os.path.exists("build"):
             os.mkdir("build")
@@ -258,6 +272,7 @@ def main():
             "OpenType.js",
             "fontkit",
             "Allsorts",
+            "Swash"
         ],
         default="FreeStack",
     )

src/fonttest-swash-harness/.gitignore

@@ -0,0 +1 @@
+/target

src/fonttest-swash-harness/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "fonttest-swash-harness"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+# If you update swash, be sure to update the version number in src/main.rs as well!
+swash = { path = "../third_party/swash/swash" }
+lexopt = "0.3"
+quick-xml = "0.37"
+ttf-parser = "0.25"
+unicode-bidi = "0.3"