keming machine dot removal directive

CONTRIBUTING.md

@@ -46,8 +46,8 @@ Rightmost vertical column (should be 20 px tall) contains the tags. Tags are def
       W  |= Width of the character
       W  |
       W -'
-      m --Is this character lowheight?
       K -,
+      K  |
       K  |= Tags used by the "Keming Machine"
       K -'
       Q ---Compiler Directive (see below)

OTFbuild/font_builder.py

@@ -370,10 +370,9 @@ def build_font(assets_dir, output_path, no_bitmap=False, no_features=False):
             x_offset = 0
         x_offset -= g.props.nudge_x * SCALE
 
-        # For STACK_DOWN marks (below-base diacritics), negative nudge_y
-        # means "shift content down to below baseline".  The sign convention
-        # is opposite to non-marks where positive nudge_y means shift down.
-        if g.props.stack_where == SC.STACK_DOWN and g.props.write_on_top >= 0:
+        # For marks (write_on_top >= 0), positive nudge_y means shift UP
+        # in the bitmap engine (opposite to non-marks where positive = down).
+        if g.props.write_on_top >= 0:
             y_offset = g.props.nudge_y * SCALE
         else:
             y_offset = -g.props.nudge_y * SCALE

OTFbuild/opentype_features.py

@@ -1878,12 +1878,16 @@ def _generate_mark(glyphs, has):
         lines.append(f"lookup {mkmk_name} {{")
 
         if scat == 'up':
-            m2y = SC.ASCENT + SC.H_DIACRITICS * SC.SCALE
+            m2y_base = SC.ASCENT + SC.H_DIACRITICS * SC.SCALE
         else:  # 'dn'
-            m2y = SC.ASCENT - SC.H_DIACRITICS * SC.SCALE
+            m2y_base = SC.ASCENT - SC.H_DIACRITICS * SC.SCALE
 
         for cp, g in mark_list:
             mx = mark_anchors.get(cp, 0)
+            # Cascade nudge_y: the mark2 anchor includes this mark's
+            # nudge so that the next stacked mark inherits the shift,
+            # matching the Kotlin engine's nudgeUpwardCounter / nudgeDownwardCounter.
+            m2y = m2y_base + g.props.nudge_y * SC.SCALE
             lines.append(
                 f"    pos mark {glyph_name(cp)}"
                 f" <anchor {mx} {m2y}> mark {class_name};"

keming_machine.txt

@@ -106,3 +106,5 @@ dot removal for diacritics:
 - encoding:
     - <MSB> RRRRRRRR GGGGGGGG BBBBBBBB <LSB>
 
+--- Pixel 3
+Unused for now.

src/net/torvald/terrarumsansbitmap/GlyphProps.kt

@@ -1,5 +1,7 @@
 package net.torvald.terrarumsansbitmap
 
+import net.torvald.terrarumsansbitmap.gdx.CodePoint
+
 /**
  * Created by minjaesong on 2021-11-25.
  */
@@ -29,6 +31,8 @@ data class GlyphProps(
         val isKernYtype: Boolean = false,
         val kerningMask: Int = 255,
 
+        val dotRemoval: CodePoint? = null,
+
         val directiveOpcode: Int = 0, // 8-bits wide
         val directiveArg1: Int = 0, // 8-bits wide
         val directiveArg2: Int = 0, // 8-bits wide

src/net/torvald/terrarumsansbitmap/gdx/TerrarumSansBitmap.kt

@@ -921,9 +921,9 @@ class TerrarumSansBitmap(
             val isLowHeight = (pixmap.getPixel(codeStartX, codeStartY + 5).and(255) != 0)
 
             // Keming machine parameters
-            val kerningBit1 = pixmap.getPixel(codeStartX, codeStartY + 6).tagify()
-            val kerningBit2 = pixmap.getPixel(codeStartX, codeStartY + 7).tagify()
-            val kerningBit3 = pixmap.getPixel(codeStartX, codeStartY + 8).tagify()
+            val kerningBit1 = pixmap.getPixel(codeStartX, codeStartY + 6).tagify() // glyph shape
+            val kerningBit2 = pixmap.getPixel(codeStartX, codeStartY + 7).tagify() // dot removal
+            val kerningBit3 = pixmap.getPixel(codeStartX, codeStartY + 8).tagify() // unused
             var isKernYtype = ((kerningBit1 and 0x80000000.toInt()) != 0)
             var kerningMask = kerningBit1.ushr(8).and(0xFFFFFF)
             val hasKernData = kerningBit1 and 255 != 0//(kerningBit1 and 255 != 0 && kerningMask != 0xFFFF)
@@ -971,7 +971,9 @@ class TerrarumSansBitmap(
                 GlyphProps.STACK_DONT
             else (0..1).fold(0) { acc, y -> acc or ((pixmap.getPixel(codeStartX, codeStartY + y + 18).and(255) != 0).toInt() shl y) }
 
-            glyphProps[code] = GlyphProps(width, isLowHeight, nudgeX, nudgeY, diacriticsAnchors, alignWhere, writeOnTop, stackWhere, IntArray(15), hasKernData, isKernYtype, kerningMask, directiveOpcode, directiveArg1, directiveArg2)
+            val dotRemoval = if (kerningBit2 == 0) null else kerningBit2.ushr(8)
+
+            glyphProps[code] = GlyphProps(width, isLowHeight, nudgeX, nudgeY, diacriticsAnchors, alignWhere, writeOnTop, stackWhere, IntArray(15), hasKernData, isKernYtype, kerningMask, dotRemoval, directiveOpcode, directiveArg1, directiveArg2)
 
             // extra info
             val extCount = glyphProps[code]?.requiredExtInfoCount() ?: 0
@@ -1533,8 +1535,8 @@ class TerrarumSansBitmap(
 
             }
             // for lowercase i and j, if cNext is a diacritic that goes on top, remove the dots
-            else if (diacriticDotRemoval.containsKey(c) && (glyphProps[cNext]?.writeOnTop ?: -1) >= 0 && glyphProps[cNext]?.stackWhere == GlyphProps.STACK_UP) {
-                seq.add(diacriticDotRemoval[c]!!)
+            else if (glyphProps[c]!!.dotRemoval != null && (glyphProps[cNext]?.writeOnTop ?: -1) >= 0 && glyphProps[cNext]?.stackWhere == GlyphProps.STACK_UP) {
+                seq.add(glyphProps[c]!!.dotRemoval!!)
             }
 
             // BEGIN of tamil subsystem implementation
@@ -2747,11 +2749,6 @@ class TerrarumSansBitmap(
                 0x20..0x7F,
         )
 
-        private val diacriticDotRemoval = hashMapOf(
-            'i'.toInt() to 0x131,
-            'j'.toInt() to 0x237
-        )
-
         internal fun Int.charInfo() = "U+${this.toString(16).padStart(4, '0').toUpperCase()}: ${Character.getName(this)}"
 
         const val NQSP = 0x2000