More stuff. I should probably write that OpenType features test now.

darwin/attrstr.m

@@ -372,6 +372,8 @@ static void applyAndFreeFontAttributes(struct foreachParams *p)
 		font = defaultFont;
 		CFRetain(font);
 	} else
+		// note that this handles the difference between NULL and empty uiOpenTypeFeatures properly as far as conversion to native data formats is concerned (NULL does not generate a features dictionary; empty just produces an empty one)
+		// TODO but what about from the OS's perspective on all OSs?
 		font = [cfa toCTFont];
 	CFAttributedStringSetAttribute(p->mas, range, kCTFontAttributeName, font);
 	CFRelease(font);

ui_attrstr.h

@@ -92,7 +92,7 @@ _UI_ENUM(uiDrawUnderlineColor) {
 // a glyph shape to use.
 // 
 // If a font does not support a certain feature, that feature will be
-// ignored.
+// ignored. (TODO verify this on all OSs)
 // 
 // See the OpenType specification at
 // https://www.microsoft.com/typography/otspec/featuretags.htm

unix/attrstr.c

@@ -154,7 +154,10 @@ static uiForEach processAttribute(uiAttributedString *s, uiAttributeSpec *spec,
 		}
 		break;
 	case uiAttributeFeatures:
-		// TODO make sure NULLs are handled properly on all platforms in this part of the code
+		// only generate an attribute if spec->Features is not NULL
+		// TODO state that this is allowed
+		if (spec->Features == NULL)
+			break;
 		featurestr = otfToPangoCSSString(spec->Features);
 		addattr(p, start, end,
 			FUTURE_pango_attr_font_features_new(featurestr));

windows/attrstr.cpp

@@ -174,7 +174,9 @@ static uiForEach processAttribute(uiAttributedString *s, uiAttributeSpec *spec,
 		}
 		break;
 	case uiAttributeFeatures:
-		// TODO make sure this behaves properly if spec->Features is NULL
+		// only generate an attribute if spec->Features is not NULL
+		if (spec->Features == NULL)
+			break;
 		dt = otfToDirectWrite(spec->Features);
 		hr = p->layout->SetTypography(dt, range);
 		if (hr != S_OK)