Add OpenType font feature support via 'guifont' ":f" modifiers

runtime/doc/gui.txt

@@ -1158,6 +1158,22 @@ Apple documentation for `NSFontWeight` for possible values): >
     :set guifont=-monospace-Light:h11
     :set guifont=-monospace-Medium:h11
 <
+MacVim also supports the ":f" option for OpenType font features, using the
+same syntax as the Win32 GUI (see above): >
+    :set guifont=Maple\ Mono:h14:fss19=1:fcalt=0
+Each ":f" entry specifies a single feature as tag=value, where tag is a
+4-character OpenType feature tag and value is the parameter (0 to disable, 1
+or higher to enable/select a variant).  A bare tag is equivalent to "tag=1".
+This requires the font to support the given features (e.g. character variants
+"cv01"-"cv99" or stylistic sets "ss01"-"ss20"); unsupported features are
+ignored.  Default features (calt, liga, etc.) are preserved unless explicitly
+overridden.  Features in 'guifontwide' are ignored; the 'guifont' features
+apply to all rendered text.
+Note: This requires macOS 10.10 or later, and currently only has an effect if
+'Use Core Text renderer' is enabled in the GUI preferences pane.  Standard
+ligatures are controlled by 'macligatures', which takes precedence over a
+"liga" entry here.
+
 Mono-spaced fonts					*E236*
 
 Note that the fonts must be mono-spaced (all characters have the same width).

src/MacVim/MMBackend.h

@@ -134,6 +134,7 @@
 - (void)setFullScreenBackgroundColor:(int)color;
 
 - (void)setAntialias:(BOOL)antialias;
+- (void)setFontFeatures:(NSString *)features;
 - (void)setLigatures:(BOOL)ligatures;
 - (void)setThinStrokes:(BOOL)thinStrokes;
 - (void)setBlurRadius:(int)radius;

src/MacVim/MMBackend.m

@@ -1196,6 +1196,19 @@ - (void)setAntialias:(BOOL)antialias
     [self queueMessage:msgid data:nil];
 }
 
+- (void)setFontFeatures:(NSString *)features
+{
+    // NOTE: Unlike setFont:wide: an empty string must still be sent since it
+    // means "reset to the font's default features".
+    int len = (int)[features lengthOfBytesUsingEncoding:NSUTF8StringEncoding];
+    NSMutableData *data = [NSMutableData data];
+    [data appendBytes:&len length:sizeof(int)];
+    if (len > 0)
+        [data appendBytes:[features UTF8String] length:len];
+
+    [self queueMessage:SetFontFeaturesMsgID data:data];
+}
+
 - (void)setLigatures:(BOOL)ligatures
 {
     int msgid = ligatures ? EnableLigaturesMsgID : DisableLigaturesMsgID;

src/MacVim/MMCoreTextView.h

@@ -66,6 +66,8 @@ NS_ASSUME_NONNULL_BEGIN
     BOOL                        antialias;
     BOOL                        ligatures;
     BOOL                        thinStrokes;
+    NSString                    *fontFeatures;        ///< Raw OpenType font features string
+    NSArray                     *fontFeatureSettings; ///< Parsed kCTFontFeatureSettingsAttribute array, nil if none
 
     BOOL                        forceRefreshFont; // when true, don't early out of setFont calls.
 
@@ -138,6 +140,7 @@ NS_ASSUME_NONNULL_BEGIN
 - (void)setPreEditRow:(int)row column:(int)col;
 - (void)setMouseShape:(int)shape;
 - (void)setAntialias:(BOOL)state;
+- (void)setFontFeatures:(NSString *)features;
 - (void)setLigatures:(BOOL)state;
 - (void)setThinStrokes:(BOOL)state;
 - (void)setImControl:(BOOL)enable;

src/MacVim/MMCoreTextView.m

@@ -136,6 +136,23 @@ - (void)invertBlockFromRow:(int)row column:(int)col numRows:(int)nrows
     return [@"m" sizeWithAttributes:a].width;
 }
 
+/// Returns a font derived from the supplied one with the given OpenType
+/// feature settings (a kCTFontFeatureSettingsAttribute-style array) applied.
+    static NSFont *
+fontWithFeatureSettings(NSFont *base, NSArray *settings)
+{
+    if (settings == nil || base == nil)
+        return base;
+    CTFontDescriptorRef desc = CTFontDescriptorCreateWithAttributes(
+        (CFDictionaryRef)@{ (NSString *)kCTFontFeatureSettingsAttribute: settings });
+    CTFontRef derived = CTFontCreateCopyWithAttributes(
+        (CTFontRef)base, 0.0, NULL, desc);
+    CFRelease(desc);
+    if (derived == NULL)
+        return base;
+    return [(NSFont *)derived autorelease];
+}
+
 typedef struct {
     unsigned color;
     int shape;
@@ -284,6 +301,8 @@ - (void)dealloc
     [characterStrings release];  characterStrings = nil;
     [fontVariants release];  fontVariants = nil;
     [characterLines release];  characterLines = nil;
+    [fontFeatures release];  fontFeatures = nil;
+    [fontFeatureSettings release];  fontFeatureSettings = nil;
 
     [helper setTextView:nil];
     [helper release];  helper = nil;
@@ -582,6 +601,43 @@ - (void)setAntialias:(BOOL)state
     antialias = state;
 }
 
+- (void)setFontFeatures:(NSString *)features
+{
+    if (fontFeatures == features || [fontFeatures isEqualToString:features])
+        return;
+    [fontFeatures release];
+    fontFeatures = [features copy];
+    [fontFeatureSettings release];
+    fontFeatureSettings = nil;
+
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_10
+    if (features.length > 0) {
+        if (@available(macos 10.10, *)) {
+            // Parse the feature list ("tag" or "tag=N" entries, comma
+            // separated) into the array of dictionaries CoreText expects for
+            // kCTFontFeatureSettingsAttribute.
+            NSMutableArray *settings = [NSMutableArray array];
+            for (NSString *entry in [features componentsSeparatedByString:@","]) {
+                NSArray *kv = [entry componentsSeparatedByString:@"="];
+                NSString *tag = kv[0];
+                if (tag.length != 4)
+                    continue;  // already validated by Vim; be defensive
+                int value = kv.count > 1 ? [kv[1] intValue] : 1;
+                [settings addObject:@{
+                    (NSString *)kCTFontOpenTypeFeatureTag: tag,
+                    (NSString *)kCTFontOpenTypeFeatureValue: @(value),
+                }];
+            }
+            if (settings.count > 0)
+                fontFeatureSettings = [settings retain];
+        }
+    }
+#endif
+
+    [fontVariants removeAllObjects];
+    [characterLines removeAllObjects];
+}
+
 - (void)setLigatures:(BOOL)state
 {
     ligatures = state;
@@ -2116,6 +2172,7 @@ - (NSFont *)fontVariantForTextFlags:(int)textFlags {
             fontRef = [NSFontManager.sharedFontManager convertFont:fontRef toHaveTrait:NSFontItalicTrait];
         if (textFlags & DRAW_BOLD)
             fontRef = [NSFontManager.sharedFontManager convertFont:fontRef toHaveTrait:NSFontBoldTrait];
+        fontRef = fontWithFeatureSettings(fontRef, fontFeatureSettings);
 
         fontVariants[cacheFlags] = fontRef;
     }

src/MacVim/MMTextView.h

@@ -39,6 +39,7 @@
 - (void)performBatchDrawWithData:(NSData *)data;
 - (void)setMouseShape:(int)shape;
 - (void)setAntialias:(BOOL)antialias;
+- (void)setFontFeatures:(NSString *)features;
 - (void)setLigatures:(BOOL)ligatures;
 - (void)setThinStrokes:(BOOL)thinStrokes;
 - (void)setImControl:(BOOL)enable;

src/MacVim/MMTextView.m

@@ -307,6 +307,11 @@ - (void)setAntialias:(BOOL)state
     antialias = state;
 }
 
+- (void)setFontFeatures:(NSString *)features
+{
+    // Not supported by this renderer; only MMCoreTextView handles this.
+}
+
 - (void)setLigatures:(BOOL)state
 {
     ligatures = state;

src/MacVim/MMVimController.m

@@ -1185,6 +1185,17 @@ - (void)handleMessage:(int)msgid data:(NSData *)data
             [[[windowController vimView] textView] setAntialias:NO];
         }
         break;
+        case SetFontFeaturesMsgID:
+        {
+            const void *bytes = [data bytes];
+            int len = *((int*)bytes);  bytes += sizeof(int);
+            NSString *features = len > 0
+                ? [[[NSString alloc] initWithBytes:(void*)bytes length:len
+                                          encoding:NSUTF8StringEncoding] autorelease]
+                : @"";
+            [[[windowController vimView] textView] setFontFeatures:features];
+        }
+        break;
         case EnableLigaturesMsgID:
         {
             [[[windowController vimView] textView] setLigatures:YES];

src/MacVim/MacVim.h

@@ -359,6 +359,7 @@ extern const char * const MMVimMsgIDStrings[];
     MSG(EnableThinStrokesMsgID) \
     MSG(DisableThinStrokesMsgID) \
     MSG(ShowDefinitionMsgID) \
+    MSG(SetFontFeaturesMsgID) \
     MSG(LoopBackMsgID) /* Simple message that Vim will reflect back to MacVim */ \
     MSG(LastMsgID) \
 

src/MacVim/gui_macvim.m

@@ -42,6 +42,7 @@
 static BOOL MMShareFindPboard      = YES;
 
 static GuiFont gui_macvim_font_with_name(char_u *name);
+static NSString *fontFeaturesFromFontString(NSString *font);
 static int specialKeyToNSKey(int key);
 static int vimModMaskToEventModifierFlags(int mods);
 
@@ -1150,6 +1151,12 @@
                                                                  : font)
                                    wide:YES];
 
+    // Apply any OpenType font feature settings given as ":f" modifiers in
+    // the font description.  An empty list resets the renderer to the font's
+    // default features.
+    [[MMBackend sharedInstance] setFontFeatures:
+            fontFeaturesFromFontString((NSString *)font)];
+
     return OK;
 }
 
@@ -1164,6 +1171,51 @@
 }
 
 
+/*
+ * Check a single OpenType font feature setting from a ":f" 'guifont'
+ * modifier, e.g. "ss19=1": a four-character printable ASCII tag, optionally
+ * followed by "=" and a non-negative number (a bare tag is equivalent to
+ * "tag=1").
+ */
+    static BOOL
+isValidFontFeature(NSString *feature)
+{
+    if ([feature length] < 4)
+        return NO;
+    for (NSUInteger i = 0; i < 4; ++i) {
+        unichar ch = [feature characterAtIndex:i];
+        if (ch < 0x20 || ch > 0x7e || ch == ',' || ch == '=')
+            return NO;
+    }
+    if ([feature length] == 4)
+        return YES;
+    if ([feature characterAtIndex:4] != '=' || [feature length] == 5)
+        return NO;
+    for (NSUInteger i = 5; i < [feature length]; ++i) {
+        unichar ch = [feature characterAtIndex:i];
+        if (ch < '0' || ch > '9')
+            return NO;
+    }
+    return YES;
+}
+
+/*
+ * Extract the ":f" feature modifiers from a font description string
+ * ("Name:h12:fss19=1:fcalt=0") as a comma-separated list ("ss19=1,calt=0").
+ */
+    static NSString *
+fontFeaturesFromFontString(NSString *font)
+{
+    NSArray *components = [font componentsSeparatedByString:@":"];
+    NSMutableArray *features = [NSMutableArray array];
+    for (NSUInteger i = 1; i < [components count]; ++i) {
+        NSString *c = [components objectAtIndex:i];
+        if ([c length] >= 2 && [c characterAtIndex:0] == 'f')
+            [features addObject:[c substringFromIndex:1]];
+    }
+    return [features componentsJoinedByString:@","];
+}
+
 /*
  * Return GuiFont in allocated memory.  The caller must free it using
  * gui_mch_free_font().
@@ -1179,22 +1231,25 @@
     int size = MMDefaultFontSize;
     BOOL parseFailed = NO;
 
+    // The font description is the font name followed by optional
+    // colon-separated modifiers: "h<size>" and "f<feature>" (an OpenType font
+    // feature setting, using the same syntax as the Win32 GUI, see
+    // |gui-font|).  Example: "Menlo:h13:fss19=1:fcalt=0".
     NSArray *components = [fontName componentsSeparatedByString:@":"];
-    if ([components count] == 2) {
-        NSString *sizeString = [components lastObject];
-        if ([sizeString length] > 0
-                && [sizeString characterAtIndex:0] == 'h') {
-            sizeString = [sizeString substringFromIndex:1];
-            if ([sizeString length] > 0) {
-                size = (int)round([sizeString floatValue]);
-                fontName = [components objectAtIndex:0];
-            }
+    NSString *featureSuffix = @"";
+    for (NSUInteger i = 1; i < [components count] && !parseFailed; ++i) {
+        NSString *c = [components objectAtIndex:i];
+        if ([c length] >= 2 && [c characterAtIndex:0] == 'h') {
+            size = (int)round([[c substringFromIndex:1] floatValue]);
+        } else if ([c length] >= 2 && [c characterAtIndex:0] == 'f'
+                && isValidFontFeature([c substringFromIndex:1])) {
+            featureSuffix = [featureSuffix stringByAppendingFormat:@":%@", c];
         } else {
             parseFailed = YES;
         }
-    } else if ([components count] > 2) {
-        parseFailed = YES;
     }
+    if ([components count] > 1)
+        fontName = [components objectAtIndex:0];
 
     const BOOL isSystemFont = [fontName hasPrefix:MMSystemFontAlias];
     if (isSystemFont) {
@@ -1221,15 +1276,17 @@
         if ([fontName isEqualToString:MMDefaultFontName]
                 || isSystemFont
                 || [NSFont fontWithName:fontName size:size])
-            return [[NSString alloc] initWithFormat:@"%@:h%d", fontName, size];
+            return [[NSString alloc] initWithFormat:@"%@:h%d%@",
+                                            fontName, size, featureSuffix];
 
         // If font loading failed, try to replace underscores with spaces for
         // user convenience. This really only works if the name is a family
         // name because PostScript names should not have spaces.
         if ([fontName rangeOfString:@"_"].location != NSNotFound) {
             fontName = [fontName stringByReplacingOccurrencesOfString:@"_" withString:@" "];
             if ([NSFont fontWithName:fontName size:size]) {
-                return [[NSString alloc] initWithFormat:@"%@:h%d", fontName, size];
+                return [[NSString alloc] initWithFormat:@"%@:h%d%@",
+                                            fontName, size, featureSuffix];
             }
         }
     }

src/testdir/test_macvim.vim

@@ -76,3 +76,30 @@ func Test_macvim_invalid_options()
 
     call assert_fails("let &fuoptions='abcdef'", 'E474:')
 endfunc
+
+" Test OpenType font feature settings (":f" modifiers) in 'guifont'
+func Test_macvim_guifont_features()
+    " 'guifont' is only parsed and validated when the GUI is running.
+    if !has('gui_running')
+        throw 'Skipped: GUI not running'
+    endif
+
+    let save_guifont = &guifont
+
+    set guifont=Menlo:h13:fss01=1:fcalt=0
+    call assert_match(':fss01=1:fcalt=0', getfontname())
+    set guifont=Menlo:h13:fzero
+    call assert_match(':fzero', getfontname())
+
+    " Invalid feature settings must be rejected as invalid fonts.
+    call assert_fails("set guifont=Menlo:h13:fabc", 'E596:')
+    call assert_fails("set guifont=Menlo:h13:fabcde", 'E596:')
+    call assert_fails("set guifont=Menlo:h13:fss01=x", 'E596:')
+    call assert_fails("set guifont=Menlo:h13:fss01=", 'E596:')
+
+    " A font without features resets to the font's defaults.
+    set guifont=Menlo:h13
+    call assert_equal('Menlo:h13', getfontname())
+
+    let &guifont = save_guifont
+endfunc