perf: subset tabler-icons font/CSS to used icons only (801KB -> 18KB woff2, 217KB -> 4KB CSS)

- Remove unused .ttf and .woff font files
- Fix preload URL mismatch causing double font download
- Remove content-visibility: auto (Firefox freeze on tab hover)
- Add font-display: swap for non-blocking font loading
- Add tools/subset-icons.py for future icon subsetting

tools/subset-icons.py

@@ -0,0 +1,181 @@
+#!/usr/bin/env python3
+"""
+Tabler Icons Subset Tool for Keywarden
+=======================================
+Scans all HTML templates for used ti-* icon classes, then generates:
+  1. A subsetted woff2 font with only the needed glyphs
+  2. A minimal CSS file with only the matching icon rules
+
+Prerequisites (one-time):
+  pip install fonttools brotli
+
+Usage:
+  python tools/subset-icons.py
+
+Source files (full Tabler Icons 3.6.0) are stored in tools/tabler-icons-full/.
+Output goes directly to web/static/css/ and web/static/css/fonts/.
+"""
+
+import os
+import re
+import subprocess
+import sys
+
+# ── Paths (relative to project root) ──
+SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
+PROJECT_ROOT = os.path.dirname(SCRIPT_DIR)
+
+TEMPLATE_DIR = os.path.join(PROJECT_ROOT, "web", "templates")
+FULL_CSS = os.path.join(SCRIPT_DIR, "tabler-icons-full", "tabler-icons.min.css")
+FULL_FONT = os.path.join(SCRIPT_DIR, "tabler-icons-full", "tabler-icons.woff2")
+
+OUT_CSS = os.path.join(PROJECT_ROOT, "web", "static", "css", "tabler-icons.min.css")
+OUT_FONT = os.path.join(PROJECT_ROOT, "web", "static", "css", "fonts", "tabler-icons.woff2")
+
+
+def find_used_icons():
+    """Scan all .html templates for ti-* class names."""
+    icons = set()
+    pattern = re.compile(r"ti-[a-z][a-z0-9-]+")
+    for root, _, files in os.walk(TEMPLATE_DIR):
+        for f in files:
+            if not f.endswith(".html"):
+                continue
+            with open(os.path.join(root, f), encoding="utf-8") as fh:
+                for match in pattern.finditer(fh.read()):
+                    icons.add(match.group(0))
+    # ti-spin is a CSS animation class, not an icon glyph
+    icons.discard("ti-spin")
+    return sorted(icons)
+
+
+def extract_codepoints(css_text, icons):
+    """Extract Unicode codepoints from the full CSS for each icon."""
+    codepoints = []
+    missing = []
+    for icon in icons:
+        pat = re.escape("." + icon) + r':before\{content:"\\([0-9a-f]+)"\}'
+        m = re.search(pat, css_text)
+        if m:
+            codepoints.append(m.group(1))
+        else:
+            missing.append(icon)
+    return codepoints, missing
+
+
+def build_subset_css(css_text, icons):
+    """Build a minimal CSS containing only the @font-face, .ti base rule,
+    and the individual icon rules for the used icons."""
+    # Extract header comment + @font-face + .ti base rule
+    m = re.match(r'(/\*[\s\S]*?\*/)(@font-face\{[^}]+\})(\.ti\{[^}]+\})', css_text)
+    if not m:
+        print("ERROR: Could not parse base CSS rules from full source")
+        sys.exit(1)
+
+    # Patch @font-face: keep only woff2 and add font-display:swap
+    font_face = m.group(2)
+    # Remove woff and truetype sources, keep only woff2
+    font_face = re.sub(
+        r',url\("[^"]*\.woff\?[^"]*"\)\s*format\("woff"\)', '', font_face
+    )
+    font_face = re.sub(
+        r',url\("[^"]*\.ttf[^"]*"\)\s*format\("truetype"\)', '', font_face
+    )
+    # Add font-display:swap if not present
+    if "font-display" not in font_face:
+        font_face = font_face.replace(
+            "font-weight:400;",
+            "font-weight:400;font-display:swap;"
+        )
+
+    header = m.group(1) + font_face + m.group(3)
+
+    # Extract individual icon rules
+    rules = []
+    for icon in icons:
+        pat = re.escape("." + icon) + r':before\{content:"\\[0-9a-f]+"\}'
+        match = re.search(pat, css_text)
+        if match:
+            rules.append(match.group(0))
+
+    # Keep .ti-spin animation if present
+    result = header + "".join(rules)
+    spin_kf = re.search(r'@keyframes\s+spin\{[^}]+\{[^}]+\}\}', css_text)
+    spin_cls = re.search(r'\.ti-spin\{[^}]+\}', css_text)
+    if spin_kf:
+        result += spin_kf.group(0)
+    if spin_cls:
+        result += spin_cls.group(0)
+
+    return result, len(rules)
+
+
+def subset_font(codepoints):
+    """Run pyftsubset to create a woff2 with only the needed glyphs."""
+    unicodes = ",".join(f"U+{cp}" for cp in codepoints)
+    cmd = [
+        sys.executable, "-m", "fontTools.subset",
+        FULL_FONT,
+        f"--output-file={OUT_FONT}",
+        "--flavor=woff2",
+        "--no-layout-closure",
+        "--drop-tables+=GSUB,GPOS,GDEF",
+        f"--unicodes={unicodes}",
+    ]
+    result = subprocess.run(cmd, capture_output=True, text=True)
+    if result.returncode != 0:
+        print("ERROR: pyftsubset failed:")
+        print(result.stderr)
+        sys.exit(1)
+
+
+def main():
+    # Verify source files exist
+    for path in (FULL_CSS, FULL_FONT):
+        if not os.path.exists(path):
+            print(f"ERROR: Source file missing: {path}")
+            print("These should be in tools/tabler-icons-full/")
+            sys.exit(1)
+
+    # Try importing fonttools
+    try:
+        import fontTools  # noqa: F401
+    except ImportError:
+        print("ERROR: fonttools not installed. Run: pip install fonttools brotli")
+        sys.exit(1)
+
+    print("Scanning templates for icon usage...")
+    icons = find_used_icons()
+    print(f"  Found {len(icons)} unique icons")
+
+    print("Reading full CSS source...")
+    with open(FULL_CSS, encoding="utf-8") as f:
+        full_css = f.read()
+
+    print("Extracting Unicode codepoints...")
+    codepoints, missing = extract_codepoints(full_css, icons)
+    if missing:
+        print(f"  WARNING: No codepoint found for: {', '.join(missing)}")
+    print(f"  Mapped {len(codepoints)} codepoints")
+
+    print("Subsetting font...")
+    subset_font(codepoints)
+    orig_size = os.path.getsize(FULL_FONT)
+    new_size = os.path.getsize(OUT_FONT)
+    print(f"  {orig_size//1024} KB -> {new_size//1024} KB ({100-round(new_size/orig_size*100,1)}% smaller)")
+
+    print("Building subset CSS...")
+    css_out, rule_count = build_subset_css(full_css, icons)
+    with open(OUT_CSS, "w", encoding="utf-8") as f:
+        f.write(css_out)
+    orig_css_size = os.path.getsize(FULL_CSS)
+    new_css_size = os.path.getsize(OUT_CSS)
+    print(f"  {rule_count} icon rules, {orig_css_size//1024} KB -> {new_css_size//1024} KB")
+
+    print("\nDone! Subsetted files written to:")
+    print(f"  Font: {os.path.relpath(OUT_FONT, PROJECT_ROOT)}")
+    print(f"  CSS:  {os.path.relpath(OUT_CSS, PROJECT_ROOT)}")
+
+
+if __name__ == "__main__":
+    main()