Fix for combining diacritics

xkcd-script/generator/pt5_svg_to_font.py

@@ -331,11 +331,6 @@ def charname(char):
 font.hhea_descent = -270; font.hhea_descent_add = False
 font.hhea_linegap = 77
 
-# Information to be conveyed to the next stage.
-# I wanted to use font.persistent, but it causes an error. Instead, I use a dummy glyph.
-font.createChar(-1, '_pad_space')
-font['_pad_space'].width = SPACE + RSPACE
-
 # Per-character size scaling applied after changeWeight, to fine-tune individual glyphs
 # that end up slightly too large despite correct stroke weight.
 _per_char_operation = {
@@ -443,6 +438,20 @@ def charname(char):
 c = font.createChar(0x000D, 'nonmarkingreturn')  # U+000D: carriage return, zero-width; required by OpenType
 c.width = 256
 
+# Information to be conveyed to the next stage.
+font.createChar(-1, '_pad_space')
+font['_pad_space'].width = SPACE + RSPACE
+TYPICAL_BOUNDINGWIDTH = 200
+font.createChar(-1, '_typical_bbox')
+c = fontforge.contour()
+l = SPACE // 2 + 20
+r = SPACE // 2 + TYPICAL_BOUNDINGWIDTH - 20
+_ascender_top = font['l'].boundingBox()[3]
+_descender_bottom = font['p'].boundingBox()[1]
+c.moveTo(l, _descender_bottom).lineTo(l, _ascender_top).lineTo(r, _ascender_top).lineTo(r, _descender_bottom).lineTo(l, _descender_bottom)
+font['_typical_bbox'].foreground += c
+font['_typical_bbox'].width = TYPICAL_BOUNDINGWIDTH + SPACE + RSPACE
+
 
 # ---------------------------------------------------------------------------
 # Glyphs imported from xkcd comic images

xkcd-script/generator/pt6_derived_chars.py

@@ -398,7 +398,6 @@ def _accented(cp, base_name, mark_name, gap=20, x_adj=0):
 _bb = _breve_mark.boundingBox()
 _breve_mark.transform(psMat.translate(-(_bb[0] + _bb[2]) / 2, 0))
 _breve_mark.transform(psMat.scale(0.5, 1))
-_breve_mark.transform(psMat.translate(-220, 0))
 
 # --- Marks composed from existing mark glyphs ---
 
@@ -460,8 +459,11 @@ def _accented(cp, base_name, mark_name, gap=20, x_adj=0):
 # Without GPOS anchors the renderer places marks at their native coordinates,
 # so we translate here to ensure they appear above even tall letters like l/L/b/h.
 # (Pre-composed glyphs are unaffected — _place_above computes its own dy.)
-_ascender_top = font['l'].boundingBox()[3]
+# Inter-stage contract: all above combining marks sit on top-center of _typical_bbox
+_typical_bbox = font['_typical_bbox'].boundingBox()
+_ascender_top = _typical_bbox[3]
 _combining_gap = 20
+_center_top = (_typical_bbox[0] + _typical_bbox[2]) / 2 - font['_typical_bbox'].width
 
 for cp, mark in [
     (0x0300, _grave_mark),
@@ -480,36 +482,37 @@ def _accented(cp, base_name, mark_name, gap=20, x_adj=0):
     c.clear()
     mark_bb = font[mark.glyphname].boundingBox()
     dy = _ascender_top + _combining_gap - mark_bb[1]
-    c.addReference(mark.glyphname, psMat.translate(0, dy))
+    c.addReference(mark.glyphname, psMat.translate(_center_top, dy))
     c.width = 0
 
 # Below combining marks share the macron-below shape at different vertical positions.
-_descender_bottom = font['p'].boundingBox()[1]
+_descender_bottom = font['_typical_bbox'].boundingBox()[1]
 _mb_bb = font['_macron_below_mark'].boundingBox()
+_center_bottom = (_typical_bbox[0] + _typical_bbox[2]) / 2 - font['_typical_bbox'].width
 
 # U+0331 ◌̱  COMBINING MACRON BELOW — below the descender.
 _c0331 = font.createMappedChar(0x0331)
 _c0331.clear()
-_c0331.addReference('_macron_below_mark', psMat.translate(0, _descender_bottom - _combining_gap - _mb_bb[3]))
+_c0331.addReference('_macron_below_mark', psMat.translate(_center_bottom, _descender_bottom - _combining_gap - _mb_bb[3]))
 _c0331.width = 0
 
 # U+0332 ◌̲  COMBINING LOW LINE — just below the baseline (underline position).
 _c0332 = font.createMappedChar(0x0332)
 _c0332.clear()
-_c0332.addReference('_macron_below_mark', psMat.translate(0, -_combining_gap - _mb_bb[3]))
+_c0332.addReference('_macron_below_mark', psMat.translate(_center_bottom, -_combining_gap - _mb_bb[3]))
 _c0332.width = 0
 
 # U+0320 ◌̠  COMBINING MINUS SIGN BELOW — halfway between baseline and descender.
 _c0320 = font.createMappedChar(0x0320)
 _c0320.clear()
-_c0320.addReference('_macron_below_mark', psMat.translate(0, _descender_bottom // 2 - _combining_gap - _mb_bb[3]))
+_c0320.addReference('_macron_below_mark', psMat.translate(_center_bottom, _descender_bottom // 2 - _combining_gap - _mb_bb[3]))
 _c0320.width = 0
 
 # U+0327 ◌̧  COMBINING CEDILLA — hook cedilla shape, positioned below descender.
 _hc_bb = font['_hook_cedilla_mark'].boundingBox()
 _c0327 = font.createMappedChar(0x0327)
 _c0327.clear()
-_c0327.addReference('_hook_cedilla_mark', psMat.translate(0, _descender_bottom - _combining_gap - _hc_bb[3]))
+_c0327.addReference('_hook_cedilla_mark', psMat.translate(_center_bottom, _descender_bottom - _combining_gap - _hc_bb[3]))
 _c0327.width = 0
 
 

xkcd-script/generator/pt7_font_properties.py

@@ -173,30 +173,39 @@ def getkern(left, right):
 font.addLookup('above', 'gpos_mark2base', (), [['mark', [['latn', ['dflt']]]]])
 font.addLookupSubtable('above', 'above_sub')
 font.addAnchorClass('above_sub', 'above')
+font.addLookup('mkmk', 'gpos_mark2mark', (), [['mkmk', [['latn', ['dflt']]]]], 'above')
+font.addLookupSubtable('mkmk', 'abovechain_sub')
+font.addAnchorClass('abovechain_sub', 'abovechain')
 
 # Combining mark codepoints registered in pt6, paired with their private glyph names.
 # The anchor sits at the bottom-centre of each combining mark glyph, adjusted by
 # a per-mark y offset: positive = mark sits lower (less gap), negative = higher (more gap).
 _COMBINING = [
     (0x0300, '_grave_mark', 0),
     (0x0301, '_acute_mark', 0),
-    (0x0302, '_circumflex_mark', 300),  # was too high
-    (0x0303, '_tilde_mark', 270),  # was too high
-    (0x0304, '_macron_mark', -90),  # was too low
-    (0x0307, '_dot_above_mark', -30),  # too low → raise
+    (0x0302, '_circumflex_mark', 0),
+    (0x0303, '_tilde_mark', 0),
+    (0x0304, '_macron_mark', 0),
+    (0x0307, '_dot_above_mark', 0),
     (0x0308, '_diaeresis_mark', 0),
-    (0x030A, '_ring_above_mark', 45),  # could be a little closer
+    (0x030A, '_ring_above_mark', 0),
     (0x030B, '_double_acute_mark', 0),
-    (0x030C, '_caron_mark', 280),  # was too high
+    (0x030C, '_caron_mark', 0),
+    (0x0306, '_breve_mark', 0),
 ]
 
+# Inter-stage contract: all above combining marks sit on top-center of _typical_bbox.
+# "Sit on" doesn't necessarily mean centering the bounding box. That design decision was
+# made in Stage 6, and here we just make sure not to mess up the results in the x direction.
+_typical_bbox = font['_typical_bbox'].boundingBox()
+cx = (_typical_bbox[0] + _typical_bbox[2]) / 2 - font['_typical_bbox'].width
+_MKMK_GAP = 20
 for cp, private_name, y_offset in _COMBINING:
     mark_glyph = font[cp]
-    # Use the private mark glyph's bbox (the encoded glyph is a composite whose
-    # bbox FontForge may not resolve; the private mark is a plain outline).
-    bb = font[private_name].boundingBox()
-    cx = (bb[0] + bb[2]) / 2
+    bb = font[cp].boundingBox()
     mark_glyph.addAnchorPoint('above', 'mark', cx, bb[1] + y_offset)
+    mark_glyph.addAnchorPoint('abovechain', 'mark', cx, bb[1] + y_offset)
+    mark_glyph.addAnchorPoint('abovechain', 'basemark', cx, bb[3] + _MKMK_GAP)
 
 # j's dot is to the right of the body centre; combining marks should sit above the dot.
 _j_layer = font['j'].foreground
@@ -219,6 +228,35 @@ def getkern(left, right):
     glyph.addAnchorPoint('above', 'base', cx, bb[3] + _BASE_GAP)
 
 
+# ---------------------------------------------------------------------------
+# ccmp GSUB: replacement rules that take priority over mark2base for dotlessi and dotleesj
+# ---------------------------------------------------------------------------
+
+font.addLookup('above_subst', 'gsub_ligature', (), [['ccmp', [['latn', ['dflt']]]]])
+font.addLookupSubtable('above_subst', 'ccmp')
+
+composition_tuple = tuple(['i', 'acutecomb'])
+font[0x00ED].addPosSub('ccmp', composition_tuple) # í
+composition_tuple = tuple(['i', 'uni030C'])
+font[0x01D0].addPosSub('ccmp', composition_tuple) # ǐ
+composition_tuple = tuple(['j', 'uni030C'])
+font[0x01F0].addPosSub('ccmp', composition_tuple) # ǰ
+composition_tuple = tuple(['i', 'uni0306'])
+font[0x012D].addPosSub('ccmp', composition_tuple) # ĭ
+composition_tuple = tuple(['i', 'uni0302'])
+font[0x00EE].addPosSub('ccmp', composition_tuple) # î
+composition_tuple = tuple(['j', 'uni0302'])
+font[0x0135].addPosSub('ccmp', composition_tuple) # ĵ
+composition_tuple = tuple(['i', 'gravecomb'])
+font[0x00EC].addPosSub('ccmp', composition_tuple) # ì
+composition_tuple = tuple(['i', 'tildecomb'])
+font[0x0129].addPosSub('ccmp', composition_tuple) # ĩ
+composition_tuple = tuple(['i', 'uni0308'])
+font[0x00EF].addPosSub('ccmp', composition_tuple) # ï
+composition_tuple = tuple(['i', 'uni0304'])
+font[0x012B].addPosSub('ccmp', composition_tuple) # ī
+
+
 # ---------------------------------------------------------------------------
 # Mark-to-base GPOS: position combining cedilla below base glyphs
 # ---------------------------------------------------------------------------