[test-data] Add FEA-based test file generation

This adds support in the font-test-data crate for compiling fonts using
FEA (instead of TTX) as the 'source of truth'. This is motivated by
wanting to test glyph closure, where FEA is a much more manageable and
intelligible source than TTX.

font-test-data/test_data/README.md

@@ -1,8 +1,17 @@
 # test files
 
-This directory contains files used for testing. The masters are the ttx files;
-these are human readable/editable. From these, we generate the binary ttf
-files that are the actual test inputs.
+This directory contains files used for testing.
+
+## ttx
+
+The `ttx` directory contains ttx files describing test cases. These are compiled
+and stored in the `ttf` directory; the `ttf` files are the actual test inputs.
+
+## fea
+
+The `fea` directory contains fea files describing test cases. Similarly to ttx,
+these are compiled and stored in the `ttf` directory. Each test case is
+comprised of a FEA file and a corresponding glyph list.
 
 ## extracted data
 The extracted directory contains text files holding data computed by FreeType

font-test-data/test_data/compile_fea.py

@@ -0,0 +1,43 @@
+import sys
+import os
+
+from fontTools.ttLib import TTFont
+
+from fontTools.feaLib.builder import addOpenTypeFeatures
+
+def makeTTFont(glyph_list_path):
+    glyphs = get_glyph_list(glyph_list_path)
+    font = TTFont()
+    font.setGlyphOrder(glyphs)
+    return font
+
+def get_glyph_list(path):
+    with open(path) as f:
+        lines = f.read().splitlines()
+    return [l for l in lines if not l.startswith("#")]
+
+def main():
+    try:
+        fea_path = sys.argv[1]
+        out_path = sys.argv[2]
+    except IndexError:
+        print("Usage: compile_fea.py <fea_file> <out_file>")
+        sys.exit(1)
+
+
+    if not os.path.exists(fea_path):
+        print("Feature file not found: " + fea_path)
+        sys.exit(1)
+    glyph_list_path = os.path.splitext(fea_path)[0] + "_glyphs.txt"
+    if not os.path.exists(glyph_list_path):
+        print("Glyph list file not found: " + glyph_list_path)
+        sys.exit(1)
+
+    font = makeTTFont((glyph_list_path))
+    addOpenTypeFeatures(font, fea_path)
+    # if you want to manually inspect you can dump as TTX:
+    # font.saveXML(out_path, tables=[ 'GDEF', 'GSUB', 'GPOS'])
+    font.save(out_path)
+
+if __name__ == "__main__":
+    main()

font-test-data/test_data/fea/simple_closure.fea

@@ -0,0 +1,23 @@
+feature test {
+    lookup single_sub_f1 {
+        sub a by A;
+    } single_sub_f1;
+
+    lookup single_sub_f2 {
+    sub a by b;
+    # just to force format 2
+    sub X by Y;
+    } single_sub_f2;
+
+    lookup multiple_sub {
+        sub a by c d;
+    } multiple_sub;
+
+    lookup lig_sub {
+        sub a a by a_a;
+    } lig_sub;
+
+    lookup alt_sub {
+        sub a from [a.1 a.2];
+    } alt_sub;
+} test;

font-test-data/test_data/fea/simple_closure_glyphs.txt

@@ -0,0 +1,10 @@
+a
+b
+c
+d
+A
+a_a
+a.1
+a.2
+X
+Y

font-test-data/test_data/rebuild.sh

@@ -1,19 +1,21 @@
 #!/usr/bin/env bash
 
-# this script rebuilds the binary test fonts from their xml (ttx) sources
+# this script rebuilds the binary test fonts from their xml (ttx) or FEA sources
 
 set -o errexit
 set -o nounset
 set -o pipefail
 
 SCRIPT_DIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
 SRC_DIR=$SCRIPT_DIR/ttx
+FEA_DIR=$SCRIPT_DIR/fea
 OUT_DIR=$SCRIPT_DIR/ttf
 VENV_DIR=$SCRIPT_DIR/../../.venv
 REQUIREMENTS=$SCRIPT_DIR/requirements.txt
 PIP=$VENV_DIR/bin/pip
 TTX=$VENV_DIR/bin/ttx
 EXTRACT_GLYPHS=$SCRIPT_DIR/extract_glyphs.py
+COMPILE_FEA=$SCRIPT_DIR/compile_fea.py
 
 # check that we have python3 + virtualenv installed:
 if ! python3 -m venv -h  >/dev/null 2>&1; then
@@ -30,7 +32,13 @@ echo "Installing fonttools and freetype-py"
 $PIP install --upgrade pip
 $PIP install -r $REQUIREMENTS
 
+# compile ttx sources
 for f in $(ls $SRC_DIR/*.ttx); do
     $TTX -o $OUT_DIR/$(basename "$f" .ttx).ttf --no-recalc-timestamp -b $f
     $VENV_DIR/bin/python $EXTRACT_GLYPHS $OUT_DIR/$(basename "$f" .ttx).ttf
 done
+
+# compile FEA sources
+for f in $(ls $FEA_DIR/*.fea); do
+    $VENV_DIR/bin/python $COMPILE_FEA $f $OUT_DIR/$(basename "$f" .fea).ttf
+done