megatest start + improvements

src/pixie/fontformats/opentype.nim

@@ -543,6 +543,8 @@ proc parseKernTable(buf: string, offset: int): KernTable =
         failUnsupported()
       subTable.length = buf.readUint16(i + 2).swap()
       subTable.coverage = buf.readUint16(i + 4).swap()
+      if subTable.coverage shr 8 != 0:
+        failUnsupported()
       subTable.nPairs = buf.readUint16(i + 6).swap()
       subTable.searchRange = buf.readUint16(i + 8).swap()
       subTable.entrySelector = buf.readUint16(i + 10).swap()

src/pixie/fonts.nim

@@ -40,24 +40,6 @@ proc lineGap*(font: Font): float32 {.inline.} =
   ## The font line gap value in font units.
   font.opentype.hhea.lineGap.float32
 
-proc getGlyphPath*(font: Font, rune: Rune): Path =
-  if rune notin font.glyphPaths:
-    font.glyphPaths[rune] = font.opentype.parseGlyph(rune)
-    font.glyphPaths[rune].transform(scale(vec2(1, -1)))
-  font.glyphPaths[rune]
-
-proc getGlyphAdvance*(font: Font, rune: Rune): float32 =
-  let glyphId = font.opentype.getGlyphId(rune).int
-  if glyphId < font.opentype.hmtx.hMetrics.len:
-    font.opentype.hmtx.hMetrics[glyphId].advanceWidth.float32
-  else:
-    font.opentype.hmtx.hMetrics[^1].advanceWidth.float32
-
-proc getKerningAdjustment*(font: Font, left, right: Rune): float32 =
-  let pair = (left, right)
-  if pair in font.kerningPairs:
-    result = font.kerningPairs[pair]
-
 proc scale*(font: Font): float32 =
   ## The scale factor to transform font units into pixels.
   font.size / font.opentype.head.unitsPerEm.float32
@@ -66,6 +48,29 @@ proc defaultLineHeight*(font: Font): float32 =
   ## The default line height in pixels for the current font size.
   round((font.ascent + abs(font.descent) + font.lineGap) * font.scale)
 
+proc getGlyphPath*(font: Font, rune: Rune): Path =
+  ## The glyph path for the parameter rune.
+  if rune notin font.glyphPaths:
+    font.glyphPaths[rune] = font.opentype.parseGlyph(rune)
+    font.glyphPaths[rune].transform(scale(vec2(1, -1)))
+  font.glyphPaths[rune]
+
+proc getGlyphAdvance*(font: Font, rune: Rune): float32 =
+  ## The advance for the parameter rune in pixels.
+  let glyphId = font.opentype.getGlyphId(rune).int
+  if glyphId < font.opentype.hmtx.hMetrics.len:
+    result = font.opentype.hmtx.hMetrics[glyphId].advanceWidth.float32
+  else:
+    result = font.opentype.hmtx.hMetrics[^1].advanceWidth.float32
+  result *= font.scale
+
+proc getKerningAdjustment*(font: Font, left, right: Rune): float32 =
+  ## The kerning adjustment for the parameter rune pair, in pixels.
+  let pair = (left, right)
+  if pair in font.kerningPairs:
+    result = font.kerningPairs[pair]
+  result *= font.scale
+
 proc convertTextCase(runes: var seq[Rune], textCase: TextCase) =
   case textCase:
   of tcNormal:
@@ -111,9 +116,9 @@ proc typeset*(
       prevCanWrap = i
 
     if i > 0:
-      at.x += font.getKerningAdjustment(runes[i - 1], rune) * font.scale
+      at.x += font.getKerningAdjustment(runes[i - 1], rune)
 
-    let advance = font.getGlyphAdvance(rune) * font.scale
+    let advance = font.getGlyphAdvance(rune)
     if bounds.x > 0 and at.x + advance > bounds.x: # Wrap to new line
       at.x = 0
       at.y += lineHeight
@@ -122,9 +127,9 @@ proc typeset*(
       if prevCanWrap > 0 and prevCanWrap != i:
         for j in prevCanWrap + 1 ..< i:
           if j > 0:
-            at.x += font.getKerningAdjustment(runes[j - 1], runes[j]) * font.scale
+            at.x += font.getKerningAdjustment(runes[j - 1], runes[j])
           positions[j] = at
-          at.x += font.getGlyphAdvance(runes[j]) * font.scale
+          at.x += font.getGlyphAdvance(runes[j])
 
     positions[i] = at
     at.x += advance
@@ -142,14 +147,22 @@ proc parseOtf*(buf: string): Font =
 
   if result.opentype.kern != nil:
     for table in result.opentype.kern.subTables:
-      for pair in table.kernPairs:
-        if pair.value != 0 and
-          pair.left in result.opentype.cmap.glyphIdToRune and
-          pair.right in result.opentype.cmap.glyphIdToRune:
-          result.kerningPairs[(
-            result.opentype.cmap.glyphIdToRune[pair.left],
-            result.opentype.cmap.glyphIdToRune[pair.right]
-          )] = pair.value.float32
+      if (table.coverage and 1) != 0: # Horizontal data
+        for pair in table.kernPairs:
+          if pair.value != 0 and
+            pair.left in result.opentype.cmap.glyphIdToRune and
+            pair.right in result.opentype.cmap.glyphIdToRune:
+            let key = (
+              result.opentype.cmap.glyphIdToRune[pair.left],
+              result.opentype.cmap.glyphIdToRune[pair.right]
+            )
+            var value = pair.value.float32
+            if key in result.kerningPairs:
+              if (table.coverage and 0b1000) != 0: # Override
+                discard
+              else: # Accumulate
+                value += result.kerningPairs[key]
+            result.kerningPairs[key] = value
 
 proc parseTtf*(buf: string): Font =
   parseOtf(buf)

tests/fonts_megatest.nim

@@ -0,0 +1,10 @@
+import common, pixie
+
+# Clone https://github.com/google/fonts
+# Check out commit ebaa6a7aab9b700da4e30a4682687acdf427eae7
+
+let fontPaths = findAllFonts("../fonts")
+
+for fontPath in fontPaths:
+  echo fontPath
+  let font = readFont(fontPath)