Update hinting again

(Handling old-style kerning and other various changes will be handled via kobo-font-fix.)

.github/workflows/build.yml

@@ -0,0 +1,73 @@
+name: Build fonts
+
+on:
+  push:
+    branches: [main, develop]
+    tags: ["*"]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    container:
+      image: ghcr.io/nicoverbruggen/fntbld-oci:latest
+
+    steps:
+      - uses: actions/checkout@v5
+
+      - name: Build fonts
+        run: python3 build.py
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v6
+        with:
+          name: Readerly
+          path: out/ttf/*.ttf
+
+      - name: Upload Kobo artifact
+        uses: actions/upload-artifact@v6
+        with:
+          name: KF_Readerly
+          path: out/kf/*.ttf
+
+      - name: Zip TTFs for release
+        if: startsWith(github.ref, 'refs/tags/')
+        run: |
+          cd out/ttf && zip -j ../../Readerly.zip *.ttf
+          cd ../../out/kf && zip -j ../../KF_Readerly.zip *.ttf
+
+      - name: Upload release zips
+        if: startsWith(github.ref, 'refs/tags/')
+        uses: actions/upload-artifact@v6
+        with:
+          name: Readerly-release
+          path: |
+            Readerly.zip
+            KF_Readerly.zip
+
+  release:
+    needs: build
+    if: startsWith(github.ref, 'refs/tags/')
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+
+    steps:
+      - uses: actions/download-artifact@v6
+        with:
+          name: Readerly-release
+
+      - name: Create release
+        uses: softprops/action-gh-release@v2
+        with:
+          draft: false
+          name: ${{ github.ref_name }}
+          body: |
+            > [!TIP]
+            > **If you are using a Kobo device and reading books purchased from the Kobo Store or reading `kepub` files converted via Calibre**, you should download KF_Readerly.zip, which has fonts slightly altered for optimal kerning for the `kepub` renderer.
+
+            ### Learn more
+
+            Readerly is part of the `ebook-fonts` collection. For more information about those fonts, screenshots and how to install them, please consult the [README](https://github.com/nicoverbruggen/ebook-fonts/blob/main/README.md). The FAQ also includes an entry on how to enable ligatures on Kobo devices, which is highly recommended.
+          files: |
+            Readerly.zip
+            KF_Readerly.zip

README.md

@@ -12,6 +12,13 @@ The goal was to get a metrically/visually similar font, without actually copying
 
 To get to the final result, I decided to use the variable font and work on it. The original is located in `src` and is available under the same OFL as the end result, which is included in `LICENSE`.
 
+## Downloads
+
+Two versions are generated via the pipeline of the [latest release](../../releases/latest):
+
+- **KF_Readerly.zip** — Kobo-optimized TrueType fonts with a legacy kern table and `KF` prefix. Use this if you have a Kobo e-reader, this version contains optimizations made with [Kobo Font Fix](https://github.com/nicoverbruggen/kobo-font-fix).
+- **Readerly.zip** — The standard, unmodified fonts, as TrueType files. Useful for other e-readers and use on your desktop computer or smartphone.
+
 ## Project structure
 
 - `src`: Newsreader variable font TTFs
@@ -22,7 +29,6 @@ To get to the final result, I decided to use the variable font and work on it. T
 
 After running `build.py`, you should get:
 
-- `out/sfd`: FontForge source files (generated)
 - `out/ttf`: final TTF fonts (generated)
 
 ## Prerequisites
@@ -30,28 +36,53 @@ After running `build.py`, you should get:
 - **Python 3**
 - **[fontTools](https://github.com/fonttools/fonttools)** — install with `pip install fonttools`
 - **[FontForge](https://fontforge.org)** — the build script auto-detects FontForge from PATH, Flatpak, or the macOS app bundle
+- **[ttfautohint](https://freetype.org/ttfautohint/)** — required for proper rendering on Kobo e-readers
 
 ### Linux preparation
 
 ```
+sudo apt install ttfautohint        # Debian/Ubuntu
+sudo dnf install ttfautohint        # Fedora
+brew install ttfautohint            # Bazzite (immutable Fedora)
 pip install fonttools
 flatpak install flathub org.fontforge.FontForge
 ```
 
 ### macOS preparation
 
+#### System Python
+
 On macOS, if you're using the built-in version of Python (via Xcode), you may need to first add a folder to your `PATH` to make `font-line` available, like:
 
 ```bash
 echo 'export PATH="$HOME/Library/Python/3.9/bin:$PATH"' >> ~/.zshrc
-brew install fontforge
+brew install fontforge ttfautohint
 brew unlink python3 # ensure that python3 isn't linked via Homebrew
 pip3 install fonttools font-line
 source ~/.zshrc
 ```
 
+#### Homebrew Python
+
+If you're using `brew install python`, pip requires a virtual environment:
+
+```bash
+brew install fontforge ttfautohint
+python3 -m venv .venv
+source .venv/bin/activate
+pip install fonttools
+```
+
 ## Building
 
+**Note**: If you're using `venv`, you will need to activate it first:
+
+```
+source .venv/bin/activate
+```
+
+If you are just using the system Python, you can skip that step and simply run:
+
 ```
 python3 build.py
 ```
@@ -62,4 +93,4 @@ To customize the font family name, disable old-style kerning, or skip outline fi
 python3 build.py --customize
 ```
 
-The build script (`build.py`) uses `fontTools` and FontForge to transform the Newsreader variable fonts into Readerly. Configuration and step-by-step details live in the header comments of `build.py`.
+The build script (`build.py`) uses `fontTools` and FontForge to transform the Newsreader variable fonts into Readerly. After export, it post-processes the TTFs: clamping x-height overshoots that cause uneven rendering on e-ink, normalizing style flags, and autohinting with `ttfautohint` for Kobo's FreeType renderer. Configuration and step-by-step details live in the header comments of `build.py`.

VERSION

@@ -1 +1 @@
-1.2
+1.5

build.py

@@ -7,7 +7,8 @@ Orchestrates the full font build pipeline:
   1. Instances variable fonts into static TTFs (fontTools.instancer)
   2. Applies vertical scale (scale.py) via FontForge
   3. Applies vertical metrics, line height, rename (metrics.py, lineheight.py, rename.py)
-  4. Exports to SFD and TTF → ./out/sfd/ and ./out/ttf/
+  4. Exports to TTF → ./out/ttf/
+  5. Post-processes TTFs: style flags, kern pairs, autohinting
 
 Uses FontForge (detected automatically).
 Run with: python3 build.py
@@ -24,7 +25,7 @@ import textwrap
 # ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
 #
 # Most of these values are safe to tweak. The --customize flag only toggles
-# a small subset at runtime (family name, old-style kerning, outline fixes).
+# a small subset at runtime (family name, outline fixes).
 #
 # Quick reference (what each knob does):
 # - REGULAR_VF / ITALIC_VF: input variable fonts from ./src
@@ -35,13 +36,14 @@ import textwrap
 # - LINE_HEIGHT: Typo line height (default line spacing)
 # - SELECTION_HEIGHT: Win/hhea selection box height and clipping
 # - ASCENDER_RATIO: ascender share of total height
+# - KERN_PAIRS: explicit GPOS kern pairs (for devices without ligatures)
 # - STYLE_MAP: naming/weight metadata per style
 
 ROOT_DIR    = os.path.dirname(os.path.abspath(__file__))
 SRC_DIR     = os.path.join(ROOT_DIR, "src")
 OUT_DIR     = os.path.join(ROOT_DIR, "out")
-OUT_SFD_DIR = os.path.join(OUT_DIR, "sfd")  # generated FontForge sources
 OUT_TTF_DIR = os.path.join(OUT_DIR, "ttf")  # generated TTFs
+OUT_KF_DIR  = os.path.join(OUT_DIR, "kf")   # Kobo (KF) variants
 
 REGULAR_VF = os.path.join(SRC_DIR, "Newsreader-VariableFont_opsz,wght.ttf")
 ITALIC_VF  = os.path.join(SRC_DIR, "Newsreader-Italic-VariableFont_opsz,wght.ttf")
@@ -87,6 +89,41 @@ LINE_HEIGHT = 1.0
 SELECTION_HEIGHT = 1.3
 ASCENDER_RATIO = 0.8
 
+# Step 4: ttfautohint options (hinting for Kobo's FreeType renderer)
+# - Kobo uses FreeType grayscale, so the 1st char of --stem-width-mode
+#   matters: n=natural (least distortion), q=quantized, s=strong.
+# - x-height snapping is disabled to avoid inconsistent glyph heights.
+AUTOHINT_OPTS = [
+    "--no-info",
+    "--stem-width-mode=nss",
+    "--increase-x-height=0",
+    '--x-height-snapping-exceptions=-',
+]
+
+# Baseline alignment: deepen the bottom anti-aliasing of non-serifed
+# glyphs via hinting-only touch deltas (no outline changes).  This
+# shifts their bottom points down during rasterization so they produce
+# more gray below the baseline, visually matching serifed characters.
+# Each entry is (shift_px, ppem_min, ppem_max).  Shifts are in pixels
+# (multiples of 1/8, max 1.0).  Set to empty list to disable.
+BASELINE_HINT_SHIFTS = [
+    (0.125, 6, 53),
+]
+
+# Per-glyph Y ceiling: cap the top of specific glyphs to reduce
+# oversized or awkward serifs.  (glyph_name, max_y)
+# Points above max_y are clamped down to max_y.
+GLYPH_Y_CEILING = [
+    ("u", 1062),  # flatten tiny top serif tips to platform level
+]
+
+# Explicit kern pairs: (left_glyph, right_glyph, kern_value_in_units).
+# Negative values tighten spacing. These are added on top of any existing
+# kerning from the source variable font.
+KERN_PAIRS = [
+    ("f", "i", -100), # this emulates the `fi` ligature
+]
+
 # Step 3: Naming and style metadata (used by the rename step)
 STYLE_MAP = {
     "Regular":    ("Regular",     "Book", 400),
@@ -505,19 +542,15 @@ def ff_license_script():
     """)
 
 
-def build_export_script(sfd_path, ttf_path, old_kern=True):
+def build_export_script(sfd_path, ttf_path):
     """Build a FontForge script that opens an .sfd and exports to TTF."""
-    if old_kern:
-        flags_line = 'flags = ("opentype", "old-kern", "no-FFTM-table", "winkern")'
-    else:
-        flags_line = 'flags = ("opentype", "no-FFTM-table")'
     return textwrap.dedent(f"""\
         import fontforge
 
         f = fontforge.open({sfd_path!r})
         print("Exporting: " + f.fontname)
 
-        {flags_line}
+        flags = ("opentype", "no-FFTM-table")
         f.generate({ttf_path!r}, flags=flags)
 
         print("  -> " + {ttf_path!r})
@@ -587,6 +620,7 @@ def clean_ttf_degenerate_contours(ttf_path):
     font.close()
 
 
+
 def fix_ttf_style_flags(ttf_path, style_suffix):
     """Normalize OS/2 fsSelection and head.macStyle for style linking."""
     try:
@@ -621,10 +655,306 @@ def fix_ttf_style_flags(ttf_path, style_suffix):
     print(f"  Normalized style flags for {style_suffix}")
 
 
+def add_kern_pairs(ttf_path):
+    """Prepend explicit kern pairs to the GPOS kern table.
+
+    Devices that don't support OpenType ligatures (e.g. some e-readers)
+    fall back to individual glyphs. Without kern pairs, combinations
+    like 'fi' render with a visible gap.
+
+    Pairs are inserted at the front of the first PairPos subtable so
+    they take priority even on renderers that truncate the kern list.
+    """
+    if not KERN_PAIRS:
+        return
+
+    try:
+        from fontTools.ttLib import TTFont
+        from fontTools.ttLib.tables.otTables import PairValueRecord, ValueRecord
+    except Exception:
+        print("  [warn] Skipping kern pairs: fontTools not available", file=sys.stderr)
+        return
+
+    font = TTFont(ttf_path)
+    gpos = font.get("GPOS")
+    if gpos is None:
+        font.close()
+        print("  [warn] No GPOS table, skipping kern pairs", file=sys.stderr)
+        return
+
+    cmap = font.getBestCmap()
+    # Map glyph names: try cmap first, fall back to glyph order
+    glyph_order = set(font.getGlyphOrder())
+
+    def resolve(name):
+        # If it's a single character, look up via cmap
+        if len(name) == 1:
+            cp = ord(name)
+            if cp in cmap:
+                return cmap[cp]
+        # Otherwise treat as a glyph name
+        if name in glyph_order:
+            return name
+        return None
+
+    # Build resolved pairs
+    pairs = []
+    for left, right, value in KERN_PAIRS:
+        l = resolve(left)
+        r = resolve(right)
+        if l and r:
+            pairs.append((l, r, value))
+        else:
+            print(f"  [warn] Kern pair {left}+{right}: glyph not found", file=sys.stderr)
+
+    if not pairs:
+        font.close()
+        return
+
+    # Find the first Format 1 (individual pairs) PairPos subtable in kern
+    pair_pos = None
+    for lookup in gpos.table.LookupList.Lookup:
+        if lookup.LookupType == 2:  # PairPos
+            for subtable in lookup.SubTable:
+                if subtable.Format == 1:
+                    pair_pos = subtable
+                    break
+            if pair_pos:
+                break
+
+    if pair_pos is None:
+        font.close()
+        print("  [warn] No Format 1 PairPos subtable found, skipping kern pairs", file=sys.stderr)
+        return
+
+    count = 0
+    for left_glyph, right_glyph, value in pairs:
+        # Find or create the PairSet for the left glyph
+        try:
+            idx = pair_pos.Coverage.glyphs.index(left_glyph)
+        except ValueError:
+            # Left glyph not in coverage — add it
+            pair_pos.Coverage.glyphs.append(left_glyph)
+            from fontTools.ttLib.tables.otTables import PairSet
+            ps = PairSet()
+            ps.PairValueRecord = []
+            ps.PairValueCount = 0
+            pair_pos.PairSet.append(ps)
+            pair_pos.PairSetCount = len(pair_pos.PairSet)
+            idx = len(pair_pos.Coverage.glyphs) - 1
+
+        pair_set = pair_pos.PairSet[idx]
+
+        # Remove existing pair for same right glyph
+        pair_set.PairValueRecord = [
+            pvr for pvr in pair_set.PairValueRecord
+            if pvr.SecondGlyph != right_glyph
+        ]
+
+        # Prepend new pair so it appears first
+        pvr = PairValueRecord()
+        pvr.SecondGlyph = right_glyph
+        vr = ValueRecord()
+        vr.XAdvance = value
+        pvr.Value1 = vr
+        pair_set.PairValueRecord.insert(0, pvr)
+        pair_set.PairValueCount = len(pair_set.PairValueRecord)
+        count += 1
+
+    font.save(ttf_path)
+    font.close()
+    print(f"  Added {count} kern pair(s) to GPOS")
+
+
+
+def apply_glyph_y_ceiling(ttf_path):
+    """Clamp glyph points above a Y ceiling down to the ceiling value."""
+    if not GLYPH_Y_CEILING:
+        return
+
+    from fontTools.ttLib import TTFont
+    font = TTFont(ttf_path)
+    glyf = font["glyf"]
+    modified = []
+
+    for glyph_name, max_y in GLYPH_Y_CEILING:
+        g = glyf.get(glyph_name)
+        if not g or not g.numberOfContours or g.numberOfContours <= 0:
+            continue
+        coords = g.coordinates
+        clamped = 0
+        for j in range(len(coords)):
+            if coords[j][1] > max_y:
+                coords[j] = (coords[j][0], max_y)
+                clamped += 1
+        if clamped:
+            modified.append(f"{glyph_name}({clamped}pts)")
+
+    if modified:
+        font.save(ttf_path)
+        print(f"  Clamped Y ceiling: {', '.join(modified)}")
+    font.close()
+
+
+def _generate_baseline_shift_ctrl(ttf_path):
+    """Generate touch deltas to deepen bottom anti-aliasing of non-serifed glyphs.
+
+    For lowercase glyphs without a flat baseline (no serif foot), shifts
+    the bottom-most points down during rasterization.  Uses graduated
+    shifts from BASELINE_HINT_SHIFTS — stronger at small ppem sizes
+    where alignment is most noticeable.  No outline changes.
+    """
+    if not BASELINE_HINT_SHIFTS:
+        return ""
+
+    from fontTools.ttLib import TTFont
+    font = TTFont(ttf_path)
+    glyf = font["glyf"]
+    cmap = font.getBestCmap()
+    lines = []
+
+    for char in "abcdefghijklmnopqrstuvwxyz":
+        code = ord(char)
+        if code not in cmap:
+            continue
+        name = cmap[code]
+        g = glyf[name]
+        if not g.numberOfContours or g.numberOfContours <= 0:
+            continue
+        coords = g.coordinates
+        ys = set(c[1] for c in coords)
+        if 0 in ys:
+            continue  # has serif baseline
+        bottom_pts = [i for i, (x, y) in enumerate(coords) if y <= 0]
+        if not bottom_pts:
+            continue
+        pts_str = ", ".join(str(p) for p in bottom_pts)
+        for shift_px, ppem_min, ppem_max in BASELINE_HINT_SHIFTS:
+            shift = -abs(shift_px)
+            lines.append(
+                f"{name} touch {pts_str} yshift {shift:.3f} @ {ppem_min}-{ppem_max}"
+            )
+
+    font.close()
+    return "\n".join(lines)
+
+
+def autohint_ttf(ttf_path):
+    """Run ttfautohint to add proper TrueType hinting.
+
+    Kobo uses FreeType for font rasterization. Without embedded hints,
+    FreeType's auto-hinter computes "blue zones" from the outlines.
+    When a glyph (e.g. italic 't') has a curved tail that dips just
+    below the baseline, the auto-hinter snaps that edge up to y=0 —
+    shifting the entire glyph upward relative to its neighbors. This
+    is most visible at small sizes.
+
+    ttfautohint replaces FreeType's built-in auto-hinter with its own
+    hinting, which may handle sub-baseline overshoots more gracefully.
+    The resulting bytecode is baked into the font, so FreeType uses
+    the TrueType interpreter instead of falling back to auto-hinting.
+
+    Additionally generates per-font touch deltas to deepen the
+    baseline anti-aliasing of non-serifed glyphs.
+    """
+    if not shutil.which("ttfautohint"):
+        print("  [warn] ttfautohint not found, skipping", file=sys.stderr)
+        return
+
+    # Generate control instructions for this specific font's points
+    ctrl_text = _generate_baseline_shift_ctrl(ttf_path)
+    ctrl_path = ttf_path + ".ctrl.tmp"
+    ctrl_count = 0
+    opts = list(AUTOHINT_OPTS)
+    if ctrl_text:
+        with open(ctrl_path, "w") as f:
+            f.write(ctrl_text)
+        opts += [f"--control-file={ctrl_path}"]
+        ctrl_count = ctrl_text.count("\n") + 1
+
+    tmp_path = ttf_path + ".autohint.tmp"
+    result = subprocess.run(
+        ["ttfautohint"] + opts + [ttf_path, tmp_path],
+        capture_output=True, text=True,
+    )
+
+    if os.path.exists(ctrl_path):
+        os.remove(ctrl_path)
+
+    if result.returncode != 0:
+        print(f"  [warn] ttfautohint failed: {result.stderr.strip()}", file=sys.stderr)
+        if os.path.exists(tmp_path):
+            os.remove(tmp_path)
+        return
+
+    os.replace(tmp_path, ttf_path)
+    hint_msg = "Autohinted with ttfautohint"
+    if ctrl_count:
+        hint_msg += f" ({ctrl_count} serif control hints)"
+    print(f"  {hint_msg}")
+
+
 # ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
 # MAIN
 # ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
 
+def check_ttfautohint():
+    """Verify ttfautohint is installed before starting the build."""
+    if shutil.which("ttfautohint"):
+        return
+    print(
+        "ERROR: ttfautohint not found.\n"
+        "\n"
+        "ttfautohint is required for proper rendering on Kobo e-readers.\n"
+        "Install it with:\n"
+        "  macOS/Bazzite:      brew install ttfautohint\n"
+        "  Debian/Ubuntu:      sudo apt install ttfautohint\n"
+        "  Fedora:             sudo dnf install ttfautohint\n"
+        "  Arch:               sudo pacman -S ttfautohint\n",
+        file=sys.stderr,
+    )
+    sys.exit(1)
+
+
+KOBOFIX_URL = (
+    "https://raw.githubusercontent.com/nicoverbruggen/kobo-font-fix/main/kobofix.py"
+)
+
+
+def _download_kobofix(dest):
+    """Download kobofix.py if not already cached."""
+    if os.path.isfile(dest):
+        print(f"  Using cached kobofix.py")
+        return
+    import urllib.request
+    print(f"  Downloading kobofix.py ...")
+    urllib.request.urlretrieve(KOBOFIX_URL, dest)
+    print(f"  Saved to {dest}")
+
+
+def _run_kobofix(kobofix_path, variant_names):
+    """Run kobofix.py --preset kf on built TTFs, move KF_ files to out/kf/."""
+    ttf_files = [os.path.join(OUT_TTF_DIR, f"{n}.ttf") for n in variant_names]
+    cmd = [sys.executable, kobofix_path, "--preset", "kf"] + ttf_files
+    result = subprocess.run(cmd, capture_output=True, text=True)
+    if result.stdout:
+        print(result.stdout, end="")
+    if result.returncode != 0:
+        print("\nERROR: kobofix.py failed", file=sys.stderr)
+        if result.stderr:
+            print(result.stderr, file=sys.stderr)
+        sys.exit(1)
+
+    os.makedirs(OUT_KF_DIR, exist_ok=True)
+    import glob
+    moved = 0
+    for kf_file in glob.glob(os.path.join(OUT_TTF_DIR, "KF_*.ttf")):
+        dest = os.path.join(OUT_KF_DIR, os.path.basename(kf_file))
+        shutil.move(kf_file, dest)
+        moved += 1
+    print(f"  Moved {moved} KF font(s) to {OUT_KF_DIR}/")
+
+
 def main():
     print("=" * 60)
     print("  Readerly Build")
@@ -632,22 +962,29 @@ def main():
 
     ff_cmd = find_fontforge()
     print(f"  FontForge: {' '.join(ff_cmd)}")
+    check_ttfautohint()
+    print(f"  ttfautohint: {shutil.which('ttfautohint')}")
 
     family   = DEFAULT_FAMILY
-    old_kern = False
     outline_fix  = True
 
+    # --name "Foo" sets the family name directly
+    if "--name" in sys.argv:
+        idx = sys.argv.index("--name")
+        if idx + 1 < len(sys.argv):
+            family = sys.argv[idx + 1]
+        else:
+            print("ERROR: --name requires a value", file=sys.stderr)
+            sys.exit(1)
+
     if "--customize" in sys.argv:
         print()
-        family = input(f"  Font family name [{DEFAULT_FAMILY}]: ").strip() or DEFAULT_FAMILY
-        old_kern_input = input("  Export with old-style kerning? [y/N]: ").strip().lower()
-        old_kern = old_kern_input in ("y", "yes")
+        family = input(f"  Font family name [{family}]: ").strip() or family
         outline_input = input("  Apply outline fixes (remove overlaps + zero-area cleanup)? [Y/n]: ").strip().lower()
         outline_fix = outline_input not in ("n", "no")
 
     print()
     print(f"  Family:    {family}")
-    print(f"  Old kern:  {'yes' if old_kern else 'no'}")
     print(f"  Outline fix: {'yes' if outline_fix else 'no'}")
     print()
 
@@ -657,12 +994,12 @@ def main():
     os.makedirs(tmp_dir)
 
     try:
-        _build(tmp_dir, family=family, old_kern=old_kern, outline_fix=outline_fix)
+        _build(tmp_dir, family=family, outline_fix=outline_fix)
     finally:
         shutil.rmtree(tmp_dir, ignore_errors=True)
 
 
-def _build(tmp_dir, family=DEFAULT_FAMILY, old_kern=True, outline_fix=True):
+def _build(tmp_dir, family=DEFAULT_FAMILY, outline_fix=True):
     variants = [(f"{family}-{style}", vf, wght, opsz)
                 for style, vf, wght, opsz in VARIANT_STYLES]
     variant_names = [name for name, _, _, _ in variants]
@@ -746,7 +1083,6 @@ def _build(tmp_dir, family=DEFAULT_FAMILY, old_kern=True, outline_fix=True):
 
     # Step 4: Export to out/sfd and out/ttf
     print("\n── Step 4: Export ──\n")
-    os.makedirs(OUT_SFD_DIR, exist_ok=True)
     os.makedirs(OUT_TTF_DIR, exist_ok=True)
 
     for name in variant_names:
@@ -754,22 +1090,28 @@ def _build(tmp_dir, family=DEFAULT_FAMILY, old_kern=True, outline_fix=True):
         ttf_path = os.path.join(OUT_TTF_DIR, f"{name}.ttf")
         style_suffix = name.split("-")[-1] if "-" in name else "Regular"
 
-        # Copy final SFD to out/sfd/
-        shutil.copy2(sfd_path, os.path.join(OUT_SFD_DIR, f"{name}.sfd"))
-        print(f"  -> {OUT_SFD_DIR}/{name}.sfd")
-
         # Export TTF
-        script = build_export_script(sfd_path, ttf_path, old_kern=old_kern)
+        script = build_export_script(sfd_path, ttf_path)
         run_fontforge_script(script)
         if outline_fix:
             clean_ttf_degenerate_contours(ttf_path)
         fix_ttf_style_flags(ttf_path, style_suffix)
+        add_kern_pairs(ttf_path)
+        apply_glyph_y_ceiling(ttf_path)
+        autohint_ttf(ttf_path)
 
 
+    # Step 5: Generate Kobo (KF) variants via kobofix.py
+    print("\n── Step 5: Generate Kobo (KF) variants ──\n")
+
+    kobofix_path = os.path.join(tmp_dir, "kobofix.py")
+    _download_kobofix(kobofix_path)
+    _run_kobofix(kobofix_path, variant_names)
+
     print("\n" + "=" * 60)
     print("  Build complete!")
-    print(f"  SFD fonts are in: {OUT_SFD_DIR}/")
     print(f"  TTF fonts are in: {OUT_TTF_DIR}/")
+    print(f"  KF fonts are in:  {OUT_KF_DIR}/")
     print("=" * 60)