Implemented uiAttributeTypeBackground for OS X 10.12 and newer using the attribute included with Core Text. Also laid out a non-block-based API for drawing backgrounds on older versions of OS X (not implemented here yet, however; that will require bringing back the old metrics code).

darwin/attrstr.h

@@ -74,5 +74,17 @@ extern void uiprivProcessFontVariation(uiprivFontStyleData *d, NSDictionary *axi
 // attrstr.m
 extern void uiprivInitUnderlineColors(void);
 extern void uiprivUninitUnderlineColors(void);
-typedef void (^backgroundBlock)(uiDrawContext *c, uiDrawTextLayout *layout, double x, double y);
+extern CFAttributedStringRef uiprivAttributedStringToCFAttributedString(uiDrawTextLayoutParams *p, NSArray **backgroundParams);
-extern CFAttributedStringRef uiprivAttributedStringToCFAttributedString(uiDrawTextLayoutParams *p, NSArray **backgroundBlocks);
+
+// drawtext.m
+@interface uiprivDrawTextBackgroundParams : NSObject {
+	size_t start;
+	size_t end;
+	double r;
+	double g;
+	double b;
+	double a;
+}
+- (id)initWithStart:(size_t)s end:(size_t)e r:(double)red g:(double)green b:(double)blue a:(double)alpha;
+- (void)draw:(CGContextRef)c layout:(uiDrawTextLayout *)layout at:(double)x y:(double)y utf8Mapping:(const size_t *)u16tou8;
+@end

darwin/attrstr.m

@@ -65,7 +65,7 @@ void uiprivUninitUnderlineColors(void)
 // TODO in fact I should just write something to explain everything in this file...
 struct foreachParams {
 	CFMutableAttributedStringRef mas;
-	NSMutableArray *backgroundBlocks;
+	NSMutableArray *backgroundParams;
 };
 
 // unlike the other systems, Core Text rolls family, size, weight, italic, width, AND opentype features into the "font" attribute
@@ -271,20 +271,6 @@ static void addFontAttributeToRange(struct foreachParams *p, size_t start, size_
 	}
 }
 
-static backgroundBlock mkBackgroundBlock(size_t start, size_t end, double r, double g, double b, double a)
-{
-	return Block_copy(^(uiDrawContext *c, uiDrawTextLayout *layout, double x, double y) {
-		uiDrawBrush brush;
-
-		brush.Type = uiDrawBrushTypeSolid;
-		brush.R = r;
-		brush.G = g;
-		brush.B = b;
-		brush.A = a;
-//TODO		drawTextBackground(c, x, y, layout, start, end, &brush, 0);
-	});
-}
-
 static CGColorRef mkcolor(double r, double g, double b, double a)
 {
 	CGColorSpaceRef colorspace;
@@ -305,20 +291,38 @@ static CGColorRef mkcolor(double r, double g, double b, double a)
 	return color;
 }
 
+static void addBackgroundAttribute(struct foreachParams *p, size_t start, size_t end, double r, double g, double b, double a)
+{
+	uiprivDrawTextBackgroundParams *dtb;
+
+	// TODO make sure this works properly with line paragraph spacings (after figuring out what that means, of course)
+	if (FUTURE_kCTBackgroundColorAttributeName != NULL) {
+		CGColorRef color;
+		CFRange range;
+
+		color = mkcolor(r, g, b, a);
+		range.location = start;
+		range.length = end - start;
+		CFAttributedStringSetAttribute(p->mas, range, *FUTURE_kCTBackgroundColorAttributeName, color);
+		CFRelease(color);
+		return;
+	}
+
+	dtb = [[uiprivDrawTextBackgroundParams alloc] initWithStart:start end:end r:r g:g b:b a:a];
+	[p->backgroundParams addObject:dtb];
+	[dtb release];
+}
+
 static uiForEach processAttribute(const uiAttributedString *s, const uiAttribute *attr, size_t start, size_t end, void *data)
 {
 	struct foreachParams *p = (struct foreachParams *) data;
 	CFRange range;
 	CGColorRef color;
-	size_t ostart, oend;
-	backgroundBlock block;
 	int32_t us;
 	CFNumberRef num;
 	double r, g, b, a;
 	uiUnderlineColor colorType;
 
-	ostart = start;
-	oend = end;
 	start = uiprivAttributedStringUTF8ToUTF16(s, start);
 	end = uiprivAttributedStringUTF8ToUTF16(s, end);
 	range.location = start;
@@ -340,9 +344,7 @@ static uiForEach processAttribute(const uiAttributedString *s, const uiAttribute
 		break;
 	case uiAttributeTypeBackground:
 		uiAttributeColor(attr, &r, &g, &b, &a);
-		block = mkBackgroundBlock(ostart, oend, r, g, b, a);
+		addBackgroundAttribute(p, start, end, r, g, b, a);
-		[p->backgroundBlocks addObject:block];
-		Block_release(block);
 		break;
 	// TODO turn into a class, like we did with the font attributes, or even integrate *into* the font attributes
 	case uiAttributeTypeUnderline:
@@ -453,7 +455,7 @@ static CTParagraphStyleRef mkParagraphStyle(uiDrawTextLayoutParams *p)
 }
 
 // TODO either rename this to uiprivDrawTextLayoutParams... or rename this file or both or split the struct or something else...
-CFAttributedStringRef uiprivAttributedStringToCFAttributedString(uiDrawTextLayoutParams *p, NSArray **backgroundBlocks)
+CFAttributedStringRef uiprivAttributedStringToCFAttributedString(uiDrawTextLayoutParams *p, NSArray **backgroundParams)
 {
 	CFStringRef cfstr;
 	CFMutableDictionaryRef defaultAttrs;
@@ -493,11 +495,11 @@ CFAttributedStringRef uiprivAttributedStringToCFAttributedString(uiDrawTextLayou
 
 	CFAttributedStringBeginEditing(mas);
 	fep.mas = mas;
-	fep.backgroundBlocks = [NSMutableArray new];
+	fep.backgroundParams = [NSMutableArray new];
 	uiAttributedStringForEachAttribute(p->String, processAttribute, &fep);
 	applyFontAttributes(mas, p->DefaultFont);
 	CFAttributedStringEndEditing(mas);
 
-	*backgroundBlocks = fep.backgroundBlocks;
+	*backgroundParams = fep.backgroundParams;
 	return mas;
 }

darwin/drawtext.m

@@ -8,7 +8,7 @@
 // in the usual case, the separate copy will just be identical to the regular one, with extra references to everything within
 @interface uiprivTextFrame : NSObject {
 	CFAttributedStringRef attrstr;
-	NSArray *backgroundBlocks;
+	NSArray *backgroundParams;
 	CTFramesetterRef framesetter;
 	CGSize size;
 	CGPathRef path;
@@ -20,6 +20,29 @@
 - (CFArrayRef)lines;
 @end
 
+@implementation uiprivDrawTextBackgroundParams
+
+- (id)initWithStart:(size_t)s end:(size_t)e r:(double)red g:(double)green b:(double)blue a:(double)alpha
+{
+	self = [super init];
+	if (self) {
+		self->start = s;
+		self->end = e;
+		self->r = red;
+		self->g = green;
+		self->b = blue;
+		self->a = alpha;
+	}
+	return self;
+}
+
+- (void)draw:(CGContextRef)c layout:(uiDrawTextLayout *)layout at:(double)x y:(double)y utf8Mapping:(const size_t *)u16tou8
+{
+	// TODO
+}
+
+@end
+
 @implementation uiprivTextFrame
 
 - (id)initWithLayoutParams:(uiDrawTextLayoutParams *)p
@@ -31,7 +54,7 @@
 
 	self = [super init];
 	if (self) {
-		self->attrstr = uiprivAttributedStringToCFAttributedString(p, &(self->backgroundBlocks));
+		self->attrstr = uiprivAttributedStringToCFAttributedString(p, &(self->backgroundParams));
 		// TODO kCTParagraphStyleSpecifierMaximumLineSpacing, kCTParagraphStyleSpecifierMinimumLineSpacing, kCTParagraphStyleSpecifierLineSpacingAdjustment for line spacing
 		self->framesetter = CTFramesetterCreateWithAttributedString(self->attrstr);
 		if (self->framesetter == NULL) {
@@ -71,22 +94,22 @@
 	CFRelease(self->frame);
 	CFRelease(self->path);
 	CFRelease(self->framesetter);
-	[self->backgroundBlocks release];
+	[self->backgroundParams release];
 	CFRelease(self->attrstr);
 	[super dealloc];
 }
 
 - (void)draw:(uiDrawContext *)c textLayout:(uiDrawTextLayout *)tl at:(double)x y:(double)y
 {
-	backgroundBlock b;
+	uiprivDrawTextBackgroundParams *dtb;
 	CGAffineTransform textMatrix;
 
 	CGContextSaveGState(c->c);
 	// save the text matrix because it's not part of the graphics state
 	textMatrix = CGContextGetTextMatrix(c->c);
 
-	for (b in self->backgroundBlocks)
+	for (dtb in self->backgroundParams)
-		b(c, tl, x, y);
+		/* TODO */;
 
 	// Core Text doesn't draw onto a flipped view correctly; we have to pretend it was unflipped
 	// see the iOS bits of the first example at https://developer.apple.com/library/mac/documentation/StringsTextFonts/Conceptual/CoreText_Programming/LayoutOperations/LayoutOperations.html#//apple_ref/doc/uid/TP40005533-CH12-SW1 (iOS is naturally flipped)

darwin/future.m

@@ -8,6 +8,9 @@
 CFStringRef *FUTURE_kCTFontOpenTypeFeatureTag = NULL;
 CFStringRef *FUTURE_kCTFontOpenTypeFeatureValue = NULL;
 
+// added in OS X 10.12; we need 10.8
+CFStringRef *FUTURE_kCTBackgroundColorAttributeName = NULL;
+
 // note that we treat any error as "the symbols aren't there" (and don't care if dlclose() failed)
 void loadFutures(void)
 {
@@ -20,6 +23,7 @@ void loadFutures(void)
 #define GET(var, fn) *((void **) (&var)) = dlsym(handle, #fn)
 	GET(FUTURE_kCTFontOpenTypeFeatureTag, kCTFontOpenTypeFeatureTag);
 	GET(FUTURE_kCTFontOpenTypeFeatureValue, kCTFontOpenTypeFeatureValue);
+	GET(FUTURE_kCTBackgroundColorAttributeName, kCTBackgroundColorAttributeName);
 	dlclose(handle);
 }
 

darwin/uipriv_darwin.h

@@ -145,6 +145,7 @@ extern void doManualResize(NSWindow *w, NSEvent *initialEvent, uiWindowResizeEdg
 // future.m
 extern CFStringRef *FUTURE_kCTFontOpenTypeFeatureTag;
 extern CFStringRef *FUTURE_kCTFontOpenTypeFeatureValue;
+extern CFStringRef *FUTURE_kCTBackgroundColorAttributeName;
 extern void loadFutures(void);
 extern void FUTURE_NSLayoutConstraint_setIdentifier(NSLayoutConstraint *constraint, NSString *identifier);
 extern BOOL FUTURE_NSWindow_performWindowDragWithEvent(NSWindow *w, NSEvent *initialEvent);