diff --git a/common/opentype.c b/common/opentype.c
new file mode 100644
index 00000000..12d14699
--- /dev/null
+++ b/common/opentype.c
@@ -0,0 +1,227 @@
+// 14 february 2017
+#include "../ui.h"
+#include "uipriv.h"
+
+// note: each tag should only appear in quotes once; this allows automated tools to determine what we cover and don't cover
+
+typedef void (*specToOpenTypeEnumFunc)(const char *featureTag, uint32_t param, void *data);
+
+static void boolspec(uiAttributeSpec *spec, const char *featureTag, specToOpenTypeEnumFunc f, void *data)
+{
+	if (spec->Value != 0) {
+		(*f)(featureTag, 1, data);
+		return;
+	}
+	(*f)(featureTag, 0, data);
+}
+
+void specToOpenType(uiAttributeSpec *spec, specToOpenTypeEnumFunc f, void *data)
+{
+	switch (spec->Type) {
+	case uiAttributeStandardLigatures:
+		boolspec(spec, "liga", f, data);
+		return;
+	case uiAttributeRequiredLigatures:
+		boolspec(spec, "rlig", f, data);
+		return;
+	case uiAttributeDiscretionaryLigatures:
+		boolspec(spec, "dlig", f, data);
+		return;
+	case uiAttributeContextualLigatures:
+		boolspec(spec, "clig", f, data);
+		return;
+	case uiAttributeHistoricalLigatures:
+		boolspec(spec, "hlig", f, data);
+		return;
+	case uiAttributeUnicase:
+		boolspec(spec, "unic", f, data);
+		return;
+	// TODO is this correct or should we explicitly switch the rest off too?
+	case uiAttributeSuperscripts:
+		switch (spec->Value) {
+		case uiAttributeSuperscriptSuperscript:
+			(*f)("sups", 1, data);
+			break;
+		case uiAttributeSuperscriptSubscript:
+			(*f)("subs", 1, data);
+			break;
+		case uiAttributeSuperscriptOrdinal:
+			(*f)("ordn", 1, data);
+			break;
+		case uiAttributeSuperscriptScientificInferior:
+			(*f)("sinf", 1, data);
+			break;
+		}
+		return;
+	// TODO is this correct or should we explicitly switch the rest off too?
+	case uiAttributeFractionForms:
+		switch (spec->Value) {
+		case uiAttributeFractionFormVertical:
+			(*f)("afrc", 1, data);
+			break;
+		case uiAttributeFractionFormDiagonal:
+			(*f)("frac", 1, data);
+			break;
+		}
+		return;
+	case uiAttributeSlashedZero:
+		boolspec(spec, "zero", data);
+		return;
+	case uiAttributeMathematicalGreek:
+		boolspec(spec, "mgrk", data);
+		return;
+	case uiAttributeOrnamentalForms:
+		(*f)("ornm", (uint32_t) (spec->Value), data);
+		return;
+	case uiAttributeTitlingCapitalForms:
+		boolspec(spec, "titl", data);
+		return;
+	// TODO is this correct or should we explicitly switch the rest off too?
+	case uiAttributeHanCharacterForms:
+		switch (spec->Value) {
+		case uiAttributeHanCharacterFormTraditional:
+			(*f)("trad", 1, data);
+			break;
+		case uiAttributeHanCharacterFormSimplified:
+			(*f)("smpl", 1, data);
+			break;
+		case uiAttributeHanCharacterFormJIS1978:
+			(*f)("jp78", 1, data);
+			break;
+		case uiAttributeHanCharacterFormJIS1983:
+			(*f)("jp83", 1, data);
+			break;
+		case uiAttributeHanCharacterFormJIS1990:
+			(*f)("jp90", 1, data);
+			break;
+		case uiAttributeHanCharacterFormExpert:
+			(*f)("expt", 1, data);
+			break;
+		case uiAttributeHanCharacterFormJIS2004:
+			(*f)("jp04", 1, data);
+			break;
+		case uiAttributeHanCharacterFormHojo:
+			(*f)("hojo", 1, data);
+			break;
+		case uiAttributeHanCharacterFormNLC:
+			(*f)("nlck", 1, data);
+			break;
+		case uiAttributeHanCharacterFormTraditionalNames:
+			(*f)("tnam", 1, data);
+			break;
+		}
+		return;
+	case uiAttributeLowercaseNumbers:
+		boolspec(spec, "onum", data);
+		return;
+	case uiAttributeGlyphAnnotations:
+		(*f)("nalt", (uint32_t) (spec->Value), data);
+		return;
+	case uiAttributeCJKRomanToitalics:
+		boolspec(spec, "ital", data);
+		return;
+	case uiAttributeCaseSensitiveForms:
+		boolspec(spec, "case", data);
+		return;
+	case uiAttributeCapitalSpacing:
+		boolspec(spec, "cpsp", data);
+		return;
+	case uiAttributeAlternateHorizontalKana:
+		boolspec(spec, "hkna", data);
+		return;
+	case uiAttributeAlternateVerticalKana:
+		boolspec(spec, "vkna", data);
+		return;
+	case uiAttributeStylisticAlternative1:
+		boolspec(spec, "ss01", data);
+		return;
+	case uiAttributeStylisticAlternative2:
+		boolspec(spec, "ss02", data);
+		return;
+	case uiAttributeStylisticAlternative3:
+		boolspec(spec, "ss03", data);
+		return;
+	case uiAttributeStylisticAlternative4:
+		boolspec(spec, "ss04", data);
+		return;
+	case uiAttributeStylisticAlternative5:
+		boolspec(spec, "ss05", data);
+		return;
+	case uiAttributeStylisticAlternative6:
+		boolspec(spec, "ss06", data);
+		return;
+	case uiAttributeStylisticAlternative7:
+		boolspec(spec, "ss07", data);
+		return;
+	case uiAttributeStylisticAlternative8:
+		boolspec(spec, "ss08", data);
+		return;
+	case uiAttributeStylisticAlternative9:
+		boolspec(spec, "ss09", data);
+		return;
+	case uiAttributeStylisticAlternative10:
+		boolspec(spec, "ss10", data);
+		return;
+	case uiAttributeStylisticAlternative11:
+		boolspec(spec, "ss11", data);
+		return;
+	case uiAttributeStylisticAlternative12:
+		boolspec(spec, "ss12", data);
+		return;
+	case uiAttributeStylisticAlternative13:
+		boolspec(spec, "ss13", data);
+		return;
+	case uiAttributeStylisticAlternative14:
+		boolspec(spec, "ss14", data);
+		return;
+	case uiAttributeStylisticAlternative15:
+		boolspec(spec, "ss15", data);
+		return;
+	case uiAttributeStylisticAlternative16:
+		boolspec(spec, "ss16", data);
+		return;
+	case uiAttributeStylisticAlternative17:
+		boolspec(spec, "ss17", data);
+		return;
+	case uiAttributeStylisticAlternative18:
+		boolspec(spec, "ss18", data);
+		return;
+	case uiAttributeStylisticAlternative19:
+		boolspec(spec, "ss19", data);
+		return;
+	case uiAttributeStylisticAlternative20:
+		boolspec(spec, "ss20", data);
+		return;
+	case uiAttributeContextualAlternates:
+		boolspec(spec, "calt", data);
+		return;
+	case uiAttributeSwashes:
+		boolspec(spec, "swsh", data);
+		return;
+	case uiAttributeContextualSwashes:
+		boolspec(spec, "cswh", data);
+		return;
+	// TODO is this correct or should we explicitly switch the rest off too?
+	case uiAttributeLowercaseCapForms:
+		switch (spec->Value) {
+		case uiAttributeCapFormSmallCaps:
+			(*f)("smcp", 1, data);
+			break;
+		case uiAttributeCapFormPetiteCaps:
+			(*f)("pcap", 1, data);
+			break;
+		}
+		return;
+	// TODO is this correct or should we explicitly switch the rest off too?
+	case uiAttributeUppercaseCapForms:
+		switch (spec->Value) {
+		case uiAttributeCapFormSmallCaps:
+			(*f)("c2sc", 1, data);
+			break;
+		case uiAttributeCapFormPetiteCaps:
+			(*f)("c2pc", 1, data);
+			break;
+		}
+		return;
+	}
+}
diff --git a/ui_attrstr.h b/ui_attrstr.h
index a0b8a2d6..3da40fe1 100644
--- a/ui_attrstr.h
+++ b/ui_attrstr.h
@@ -62,7 +62,8 @@ _UI_ENUM(uiAttribute) {
 
 	// TODO kAllTypographicFeaturesType
 
-	uiAttributeCommonLigatures,		// 0 = off, 1 = on
+	// AAT calls these "common ligatures"
+	uiAttributeStandardLigatures,		// 0 = off, 1 = on
 	uiAttributeRequiredLigatures,		// 0 = off, 1 = on
 	// AAT calls these "rare ligatures"
 	uiAttributeDiscretionaryLigatures,	// 0 = off, 1 = on
@@ -132,6 +133,7 @@ _UI_ENUM(uiAttribute) {
 	// 8 = diamond
 	// 9 = inverted box
 	// 10 = inverted rounded box
+	// TODO rename to AnnotatedForms?
 	uiAttributeGlyphAnnotations,		// an integer from 0 to a font-specified upper bound
 	// TODO provide a function to get the upper bound?
 
@@ -148,13 +150,15 @@ _UI_ENUM(uiAttribute) {
 
 	uiAttributeCJKRomansToItalics,	// 0 = off, 1 = on
 
-	uiAttributeCaseSensitiveLayout,	// 0 = off, 1 = on
+	// AAT calls this "case-sensitive layout"
+	uiAttributeCaseSensitiveForms,	// 0 = off, 1 = on
 	// AAT: this is called "case-sensitive spacing"
 	uiAttributeCapitalSpacing,		// 0 = off, 1 = on
 
 	uiAttributeAlternateHorizontalKana,		// 0 = off, 1 = on
 	uiAttributeAlternateVerticalKana,	// 0 = off, 1 = on
 
+	// TODO "Alternate"? unify all this
 	uiAttributeStylisticAlternative1,		// 0 = off, 1 = on
 	uiAttributeStylisticAlternative2,		// 0 = off, 1 = on
 	uiAttributeStylisticAlternative3,		// 0 = off, 1 = on