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Final weight and metrics adjustments

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Nico Verbruggen
2026-03-02 03:36:35 +01:00
parent 1ef62915f7
commit 379400d875
3 changed files with 30 additions and 104 deletions
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116
scripts/metrics.py
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@@ -1,31 +1,17 @@
"""
FontForge: Set Vertical Metrics
───────────────────────────────
Follows the Google Fonts vertical-metrics methodology:
• OS/2 Typo → controls line spacing (with USE_TYPO_METRICS / fsSelection bit 7)
• OS/2 Win → clipping boundary on Windows (must cover every glyph)
• hhea → line spacing + clipping on macOS/iOS
Measures design landmarks, sets OS/2 Typo metrics to the ink boundaries,
and enables USE_TYPO_METRICS. Win/hhea are set to initial values here
but will be overridden by lineheight.py.
Run inside FontForge (File → Execute Script → paste, or fontforge -script).
"""
import fontforge
import math
f = fontforge.activeFont()
# ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
# CONFIGURATION
# ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
# Extra padding on Win and hhea metrics, as a fraction of UPM.
# Prevents clipping of glyphs that sit right at the bounding-box edge.
# 0.0 = trust the bounding boxes exactly
# 0.01 = 1% pad (conservative)
# 0.02 = 2% pad (safe for hinting artefacts / composites)
CLIP_MARGIN = 0.01
# ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
# HELPERS
# ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
@@ -34,7 +20,7 @@ def _bbox(name):
"""Return bounding box (xmin, ymin, xmax, ymax) or None."""
if name in f and f[name].isWorthOutputting():
bb = f[name].boundingBox()
if bb != (0, 0, 0, 0): # skip empty glyphs (space, CR, …)
if bb != (0, 0, 0, 0):
return bb
return None
@@ -42,8 +28,8 @@ def _bbox(name):
def measure_chars(chars, *, axis="top"):
"""
Measure a set of reference characters.
axis="top" → return the highest yMax (ascenders, cap height)
axis="bottom" → return the lowest yMin (descenders)
axis="top" → return the highest yMax
axis="bottom" → return the lowest yMin
Returns (value, display_char) or (None, None).
"""
idx = 3 if axis == "top" else 1
@@ -86,15 +72,11 @@ cap_h, cap_c = measure_chars("HIOXE", axis="top")
asc_h, asc_c = measure_chars("bdfhkl", axis="top")
xht_h, xht_c = measure_chars("xzouv", axis="top")
dsc_h, dsc_c = measure_chars("gpqyj", axis="bottom")
acc_h, acc_c = measure_chars("\u00c0\u00c1\u00c2\u00c3\u00c4\u00c5\u00c8\u00c9\u00ca\u00cb", axis="top")
acd_h, acd_c = measure_chars("\u00c7\u015e\u0162", axis="bottom")
for label, val, ch in [("Cap height", cap_h, cap_c),
("Ascender", asc_h, asc_c),
("Accent top", acc_h, acc_c),
("x-height", xht_h, xht_c),
("Descender", dsc_h, dsc_c),
("Accent bot", acd_h, acd_c)]:
("Descender", dsc_h, dsc_c)]:
if val is not None:
print(f" {label:12s} {int(val):>6} ('{ch}')")
else:
@@ -111,12 +93,11 @@ print(f" Highest glyph: {int(font_ymax):>6} ({ymax_name})")
print(f" Lowest glyph: {int(font_ymin):>6} ({ymin_name})")
# ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
# STEP 3 — Compute the three metric sets
# STEP 3 — Set OS/2 Typo to ink boundaries
# ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
upm = f.em
# Design top = tallest Latin ascender (fall back to cap height)
design_top = asc_h if asc_h is not None else cap_h
design_bot = dsc_h # negative value
@@ -126,98 +107,55 @@ if design_top is None or design_bot is None:
" Make sure your font contains basic Latin glyphs (H, b, p, etc.)."
)
# ── OS/2 Typo metrics ────────────────────────────────────────────────────────
# These define line spacing when USE_TYPO_METRICS is on.
# Strategy: ascender and descender sit at the design's actual ink boundaries;
# lineGap absorbs all extra leading. This keeps the text vertically
# centred on the line, which matters for UI / web layout.
typo_ascender = int(round(design_top))
typo_descender = int(round(design_bot)) # negative
typo_extent = typo_ascender - typo_descender # total ink span (positive)
typo_linegap = 0
typo_descender = int(round(design_bot))
# ── Win / hhea metrics ───────────────────────────────────────────────────────
# Clipping boundaries. Based on the design ascender/descender with a small
# margin. Accented capitals and stacked diacritics may clip, but line
# height stays tight on all platforms.
f.os2_typoascent = typo_ascender
f.os2_typodescent = typo_descender
f.os2_typolinegap = 0
margin = int(math.ceil(upm * CLIP_MARGIN))
win_ascent = int(math.ceil(design_top)) + margin
win_descent = int(math.ceil(abs(design_bot))) + margin
hhea_ascent = win_ascent
hhea_descent = -win_descent # negative
hhea_linegap = 0
# Win/hhea set to same initial values; lineheight.py overrides these.
f.os2_winascent = typo_ascender
f.os2_windescent = abs(typo_descender)
f.hhea_ascent = typo_ascender
f.hhea_descent = typo_descender
f.hhea_linegap = 0
# ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
# STEP 4 — Apply to font
# STEP 4 — USE_TYPO_METRICS (fsSelection bit 7)
# ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
# Keep f.ascent / f.descent at their current values — they define UPM
# (f.ascent + f.descent = f.em) and must not be changed.
# OS/2 table
f.os2_typoascent = typo_ascender
f.os2_typodescent = typo_descender
f.os2_typolinegap = typo_linegap
f.os2_winascent = win_ascent
f.os2_windescent = win_descent
# hhea table
f.hhea_ascent = hhea_ascent
f.hhea_descent = hhea_descent
f.hhea_linegap = hhea_linegap
# USE_TYPO_METRICS — fsSelection bit 7
# FontForge exposes this differently across versions. We try three known paths.
typo_metrics_set = False
# Method 1: dedicated boolean (FontForge ≥ 2020-ish)
if hasattr(f, "os2_use_typo_metrics"):
f.os2_use_typo_metrics = True
typo_metrics_set = True
# Method 2: direct fsSelection manipulation (if exposed)
if not typo_metrics_set and hasattr(f, "os2_fsselection"):
f.os2_fsselection |= (1 << 7)
typo_metrics_set = True
# Method 3: via the OS/2 version (some builds gate the flag on version ≥ 4)
if not typo_metrics_set:
if hasattr(f, "os2_version") and f.os2_version < 4:
f.os2_version = 4
if not typo_metrics_set:
print("⚠ Could not set USE_TYPO_METRICS programmatically.")
print(" → In Font Info → OS/2 → Misc, tick 'USE_TYPO_METRICS'.\n")
print(" WARNING: Could not set USE_TYPO_METRICS programmatically.")
print(" -> In Font Info -> OS/2 -> Misc, tick 'USE_TYPO_METRICS'.\n")
# ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
# STEP 5 — Report
# ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
typo_line = typo_ascender - typo_descender + typo_linegap
hhea_line = hhea_ascent - hhea_descent + hhea_linegap
win_total = win_ascent + win_descent
typo_line = typo_ascender - typo_descender
print("\n─── Applied metrics ───\n")
print(f" UPM: {upm}\n")
print(f" {'':18s} {'Ascender':>9s} {'Descender':>10s} {'LineGap':>8s} {'Total':>6s}")
print(f" {'─'*18} {'─'*9} {'─'*10} {'─'*8} {'─'*6}")
print(f" {'OS/2 Typo':18s} {typo_ascender:>9d} {typo_descender:>10d} {typo_linegap:>8d} {typo_line:>6d}")
print(f" {'hhea':18s} {hhea_ascent:>9d} {hhea_descent:>10d} {hhea_linegap:>8d} {hhea_line:>6d}")
print(f" {'OS/2 Win':18s} {win_ascent:>9d} {'-'+str(win_descent):>10s} {'n/a':>8s} {win_total:>6d}")
print(f"\n Effective line height: {typo_line} ({typo_line/upm:.2f}× UPM)")
print(f" Design ink span: {typo_extent} ({typo_extent/upm:.2f}× UPM)")
print(f" Clipping headroom: +{win_ascent - int(round(font_ymax))} above, "
f"+{win_descent - int(round(abs(font_ymin)))} below")
print(f"\n─── Applied metrics ───\n")
print(f" UPM: {upm}")
print(f" Typo: {typo_ascender} / {typo_descender} (ink span: {typo_line}, {typo_line/upm:.2f}x UPM)")
if cap_h is not None:
print(f"\n Cap height: {int(cap_h)}")
print(f" Cap height: {int(cap_h)}")
if xht_h is not None:
print(f" x-height: {int(xht_h)}")
print("\nDone. Review in Font Info → OS/2 and Font Info → General.")
print("\nDone.")

2
scripts/scale.py
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@@ -25,7 +25,7 @@ f = fontforge.activeFont()
# ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
SCALE_X = 1.03
SCALE_Y = 1.10
SCALE_Y = 1.08
# ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
# APPLY