Add ttfautohint dependency check

README.md

@@ -30,10 +30,14 @@ 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
 ```
@@ -44,7 +48,7 @@ On macOS, if you're using the built-in version of Python (via Xcode), you may ne
 
 ```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

build.py

@@ -659,6 +659,24 @@ def autohint_ttf(ttf_path):
 # 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)
+
+
 def main():
     print("=" * 60)
     print("  Readerly Build")
@@ -666,6 +684,8 @@ 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