Implemented uiAttributeLanguage on OS X. Untested.

darwin/attrstr.m

@@ -1,6 +1,8 @@
 // 12 february 2017
 #import "uipriv_darwin.h"
 
+// LONGTERM FUTURE for typographic features, on 10.10 we can use OpenType tags directly!
+
 // this is what AppKit does internally
 // WebKit does this too; see https://github.com/adobe/webkit/blob/master/Source/WebCore/platform/graphics/mac/GraphicsContextMac.mm
 static NSColor *spellingColor = nil;
@@ -70,8 +72,9 @@ struct foreachParams {
 struct fontParams {
 	uiDrawFontDescriptor desc;
 	uint16_t featureTypes[maxFeatures];
-	uint16_t featureSpecifiers[maxFeatures];
+	uint16_t featureSelectors[maxFeatures];
 	size_t nFeatures;
+	const char *language;
 };
 
 static void ensureFontInRange(struct foreachParams *p, size_t start, size_t end)
@@ -239,18 +242,27 @@ static int processAttribute(uiAttributedString *s, uiAttributeSpec *spec, size_t
 		if (spec->Value == uiDrawUnderlineColorCustom)
 			CFRelease(color);
 		break;
+	// locale identifiers are specified as BCP 47: https://developer.apple.com/reference/corefoundation/cflocale?language=objc
+	case uiAttributeLanguage:
+		// LONGTERM FUTURE when we move to 10.9, switch to using kCTLanguageAttributeName
+		ensureFontInRange(p, start, end);
+		adjustFontInRange(p, start, end, ^(struct fontParams *fp) {
+			fp->language = (const char *) (spec->Value);
+		});
+		break;
 	// TODO
 	}
 	return 0;
 }
 
-static CTFontRef fontdescToCTFont(uiDrawFontDescriptor *fd)
+static CTFontRef fontdescToCTFont(struct fontParams *fp)
 {
 	CTFontDescriptorRef desc;
 	CTFontRef font;
 
-	desc = fontdescToCTFontDescriptor(fd);
+	desc = fontdescToCTFontDescriptor(&(fp->desc));
-	font = CTFontCreateWithFontDescriptor(desc, fd->Size, NULL);
+	desc = fontdescAppendFeatures(desc, fp->featureTypes, fp->featureSelectors, fp->nFeatures, fp->language);
+	font = CTFontCreateWithFontDescriptor(desc, fp->desc.Size, NULL);
 	CFRelease(desc);			// TODO correct?
 	return font;
 }
@@ -263,7 +275,7 @@ static void applyAndFreeFontAttributes(struct foreachParams *p)
 		CFRange range;
 
 		fp = (struct fontParams *) [val pointerValue];
-		font = fontdescToCTFont(&(fp->desc));
+		font = fontdescToCTFont(fp);
 		range.location = [key integerValue];
 		range.length = 1;
 		CFAttributedStringSetAttribute(p->mas, range, kCTFontAttributeName, font);
@@ -305,6 +317,7 @@ CFAttributedStringRef attrstrToCoreFoundation(uiDrawTextLayoutParams *p, NSArray
 	CFAttributedStringRef base;
 	CFMutableAttributedStringRef mas;
 	struct foreachParams fep;
+	struct fontParams ffp;
 
 	cfstr = CFStringCreateWithCharacters(NULL, attrstrUTF16(p->String), attrstrUTF16Len(p->String));
 	if (cfstr == NULL) {
@@ -316,7 +329,9 @@ CFAttributedStringRef attrstrToCoreFoundation(uiDrawTextLayoutParams *p, NSArray
 	if (defaultAttrs == NULL) {
 		// TODO
 	}
-	defaultCTFont = fontdescToCTFont(p->DefaultFont);
+	memset(&ffp, 0, sizeof (struct fontParams));
+	ffp.desc = *(p->DefaultFont);
+	defaultCTFont = fontdescToCTFont(&ffp);
 	CFDictionaryAddValue(defaultAttrs, kCTFontAttributeName, defaultCTFont);
 	CFRelease(defaultCTFont);
 	ps = mkParagraphStyle(p);

darwin/fontmatch.m

@@ -254,6 +254,115 @@ CTFontDescriptorRef fontdescToCTFontDescriptor(uiDrawFontDescriptor *fd)
 		stretchesToCTWidths[fd->Stretch]);
 }
 
+// fortunately features that aren't supported are simply ignored, so we can copy them all in
+// LONGTERM FUTURE when we switch to 10.9, the language parameter won't be needed anymore
+// LONGTERM FUTURE and on 10.10 we can use OpenType tags directly!
+CTFontDescriptorRef fontdescAppendFeatures(CTFontDescriptorRef desc, const uint16_t *types, const uint16_t *selectors, size_t n, const char *language)
+{
+	CTFontDescriptorRef new;
+	CFMutableArrayRef outerArray;
+	CFDictionaryRef innerDict;
+	CFNumberRef numType, numSelector;
+	const void *keys[2], *values[2];
+	size_t i;
+	CFArrayRef languages;
+	CFIndex il, nl;
+	CFStringRef curlang;
+	char d[2];
+
+	outerArray = CFArrayCreateMutable(NULL, 0, &kCFTypeArrayCallBacks);
+	if (outerArray == NULL) {
+		// TODO
+	}
+	keys[0] = kCTFontFeatureTypeIdentifierKey;
+	keys[1] = kCTFontFeatureSelectorIdentifierKey;
+	for (i = 0; i < n; i++) {
+		numType = CFNumberCreate(NULL, kCFNumberSInt16Type,
+			(const SInt16 *) (types + i));
+		numSelector = CFNumberCreate(NULL, kCFNumberSInt16Type,
+			(const SInt16 *) (selectors + i));
+		values[0] = numType;
+		values[1] = numSelector;
+		innerDict = CFDictionaryCreate(NULL,
+			keys, values, 2,
+			// TODO are these correct?
+			&kCFCopyStringDictionaryKeyCallBacks,
+			&kCFTypeDictionaryValueCallBacks);
+		if (innerDict == NULL) {
+			// TODO
+		}
+		CFArrayAppendValue(outerArray, innerDict);
+		CFRelease(innerDict);
+		CFRelease(numSelector);
+		CFRelease(numType);
+	}
+
+	// now we have to take care of the language
+	// TODO can we assume this is present?
+	if (language != NULL) {
+		languages = CTFontDescriptorCopyAttribute(desc, kCTFontLanguagesAttribute);
+		nl = CFArrayGetCount(languages);
+		d[0] = language[0];
+		if (d[0] >= 'A' && d[0] <= 'Z')
+			d[0] += 'a' - 'A';
+		d[1] = language[1];
+		if (d[1] >= 'A' && d[1] <= 'Z')
+			d[1] += 'a' - 'A';
+		for (il = 0; il < nl; il++) {
+			char c[2];
+	
+			curlang = (CFStringRef) CFArrayGetValueAtIndex(languages, il);
+			// TODO check for failure
+			CFStringGetBytes(curlang, CFRangeMake(0, 2),
+				kCFStringEncodingUTF8, 0, false,
+				(UInt8 *) c, 2, NULL);
+			if (c[0] >= 'A' && c[0] <= 'Z')
+				c[0] += 'a' - 'A';
+			if (c[1] >= 'A' && c[1] <= 'Z')
+				c[1] += 'a' - 'A';
+			if (c[0] == d[0] && c[1] == d[1])
+				break;
+		}
+		if (il != nl) {
+			uint16_t typ;
+	
+			typ = kLanguageTagType;
+			numType = CFNumberCreate(NULL, kCFNumberSInt16Type,
+				(const SInt16 *) (&typ));
+			numSelector = CFNumberCreate(NULL, kCFNumberCFIndexType,
+				&il);
+			values[0] = numType;
+			values[1] = numSelector;
+			innerDict = CFDictionaryCreate(NULL,
+				keys, values, 2,
+				// TODO are these correct?
+				&kCFCopyStringDictionaryKeyCallBacks,
+				&kCFTypeDictionaryValueCallBacks);
+			if (innerDict == NULL) {
+				// TODO
+			}
+			CFArrayAppendValue(outerArray, innerDict);
+			CFRelease(innerDict);
+			CFRelease(numSelector);
+			CFRelease(numType);
+		}
+		CFRelease(languages);
+	}
+
+	keys[0] = kCTFontFeatureSettingsAttribute;
+	values[0] = outerArray;
+	innerDict = CFDictionaryCreate(NULL,
+		keys, values, 1,
+		// TODO are these correct?
+		&kCFCopyStringDictionaryKeyCallBacks,
+		&kCFTypeDictionaryValueCallBacks);
+	CFRelease(outerArray);
+	new = CTFontDescriptorCreateCopyWithAttributes(desc, innerDict);
+	CFRelease(desc);
+	CFRelease(innerDict);
+	return new;
+}
+
 // TODO deduplicate this from italicCloseness()
 static uiDrawTextItalic italicFromCTItalic(CTFontDescriptorRef desc, CFDictionaryRef traits)
 {

darwin/uipriv_darwin.h

@@ -142,6 +142,7 @@ extern void doManualResize(NSWindow *w, NSEvent *initialEvent, uiWindowResizeEdg
 
 // fontmatch.m
 extern CTFontDescriptorRef fontdescToCTFontDescriptor(uiDrawFontDescriptor *fd);
+extern CTFontDescriptorRef fontdescAppendFeatures(CTFontDescriptorRef desc, const uint16_t *types, const uint16_t *selectors, size_t n, const char *language);
 extern void fontdescFromCTFontDescriptor(CTFontDescriptorRef ctdesc, uiDrawFontDescriptor *uidesc);
 
 // attrstr.m