Replace hand-tuned kerning with HalfKern auto-kerning

.github/workflows/build.yaml

@@ -35,6 +35,8 @@ jobs:
     needs: validate-environment
     steps:
       - uses: actions/checkout@v4
+        with:
+          submodules: true
       - name: Install Nix
         uses: DeterminateSystems/nix-installer-action@v14
       - name: Nix cache

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "scripts/halfkern"]
+	path = scripts/halfkern
+	url = https://github.com/jul-sh/halfkern.git

documentation/font-comparison.py

@@ -34,7 +34,7 @@
 
 def render_text_to_array(text, font_path, size):
     """Render text to a numpy array for pixel-level comparison"""
-    font = ImageFont.truetype(font_path, size)
+    font = ImageFont.truetype(font_path, size, layout_engine=ImageFont.Layout.RAQM)
 
     # Create temporary image to measure text
     temp_img = Image.new("L", (1, 1))
@@ -100,9 +100,9 @@ def calc_height():
 
 # Title
 try:
-    title_font = ImageFont.truetype(f"{FONT_DIR_1}/IosevkaCharon-Bold.ttf", TITLE_SIZE)
-    subtitle_font = ImageFont.truetype(f"{FONT_DIR_1}/IosevkaCharon-Regular.ttf", SUBTITLE_SIZE)
-    legend_font = ImageFont.truetype(f"{FONT_DIR_1}/IosevkaCharon-Regular.ttf", 18)
+    title_font = ImageFont.truetype(f"{FONT_DIR_1}/IosevkaCharon-Bold.ttf", TITLE_SIZE, layout_engine=ImageFont.Layout.RAQM)
+    subtitle_font = ImageFont.truetype(f"{FONT_DIR_1}/IosevkaCharon-Regular.ttf", SUBTITLE_SIZE, layout_engine=ImageFont.Layout.RAQM)
+    legend_font = ImageFont.truetype(f"{FONT_DIR_1}/IosevkaCharon-Regular.ttf", 18, layout_engine=ImageFont.Layout.RAQM)
 except:
     print("Warning: Could not load title fonts, using default")
     title_font = ImageFont.load_default()

documentation/iosevka-charon-mono.py

@@ -25,9 +25,10 @@
 ORANGE = (206, 145, 80)  # brighter orange
 TEAL = (78, 201, 162)  # brighter teal
 
-regular = ImageFont.truetype(FONTS["regular"], FONT_SIZE)
-bold = ImageFont.truetype(FONTS["bold"], FONT_SIZE)
-small = ImageFont.truetype(FONTS["regular"], SMALL_SIZE)
+RAQM = ImageFont.Layout.RAQM
+regular = ImageFont.truetype(FONTS["regular"], FONT_SIZE, layout_engine=RAQM)
+bold = ImageFont.truetype(FONTS["bold"], FONT_SIZE, layout_engine=RAQM)
+small = ImageFont.truetype(FONTS["regular"], SMALL_SIZE, layout_engine=RAQM)
 
 
 # Calculate height

documentation/iosevka-charon.py

@@ -21,11 +21,12 @@
 WHITE = (255, 255, 255)
 GRAY = (140, 140, 140)
 
-regular = ImageFont.truetype(FONTS["regular"], FONT_SIZE)
-italic = ImageFont.truetype(FONTS["italic"], FONT_SIZE)
-bold = ImageFont.truetype(FONTS["bold"], FONT_SIZE)
-title = ImageFont.truetype(FONTS["regular"], TITLE_SIZE)
-small = ImageFont.truetype(FONTS["regular"], SMALL_SIZE)
+RAQM = ImageFont.Layout.RAQM
+regular = ImageFont.truetype(FONTS["regular"], FONT_SIZE, layout_engine=RAQM)
+italic = ImageFont.truetype(FONTS["italic"], FONT_SIZE, layout_engine=RAQM)
+bold = ImageFont.truetype(FONTS["bold"], FONT_SIZE, layout_engine=RAQM)
+title = ImageFont.truetype(FONTS["regular"], TITLE_SIZE, layout_engine=RAQM)
+small = ImageFont.truetype(FONTS["regular"], SMALL_SIZE, layout_engine=RAQM)
 
 
 # Calculate height

documentation/multilingual-test.py

@@ -21,9 +21,10 @@
 WHITE = (255, 255, 255)
 GRAY = (140, 140, 140)
 
-regular = ImageFont.truetype(FONTS["regular"], FONT_SIZE)
-bold = ImageFont.truetype(FONTS["bold"], FONT_SIZE)
-title = ImageFont.truetype(FONTS["bold"], TITLE_SIZE)
+RAQM = ImageFont.Layout.RAQM
+regular = ImageFont.truetype(FONTS["regular"], FONT_SIZE, layout_engine=RAQM)
+bold = ImageFont.truetype(FONTS["bold"], FONT_SIZE, layout_engine=RAQM)
+title = ImageFont.truetype(FONTS["bold"], TITLE_SIZE, layout_engine=RAQM)
 
 # Multilingual test text
 multilingual_text = [

flake.nix

@@ -79,6 +79,12 @@
           unicodedata2
           uharfbuzz
 
+          # Auto-kerning (HalfKern) dependencies
+          pycairo
+          numpy
+          scipy
+          scikit-fmm
+
           # Async concurrency
           trio
           outcome
@@ -153,6 +159,10 @@
             # Python environment with all font tools
             pythonEnv
 
+            # System libraries needed by HalfKern (cairoft.py dlopen)
+            cairo
+            freetype
+
             # Other useful tools
             git
             which
@@ -161,6 +171,9 @@
 
           shellHook = ''
             export PYTHONPATH="${pythonEnv}/${pythonEnv.sitePackages}"
+            # Make native libs findable by HalfKern's cairoft.py (ctypes.CDLL)
+            export DYLD_FALLBACK_LIBRARY_PATH="${pkgs.cairo}/lib:${pkgs.freetype}/lib:''${DYLD_FALLBACK_LIBRARY_PATH:-}"
+            export LD_LIBRARY_PATH="${pkgs.cairo}/lib:${pkgs.freetype}/lib:''${LD_LIBRARY_PATH:-}"
             # Workaround for protobuf compatibility with gflanguages
             export PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION=python
             # Install trio-parallel (not available in nixpkgs)