fontselect: coretext: allow to match fontname using the provider

Not all APIs cache everything the same way that fontconfig does. This allows
to first perform a match based on the font name and then score the matched
fonts using the common code using and in memory database approach.

The benefit is the application doesn't have to load all of the fonts and
query for weight, slant, width, path and fullnames.

I left both code paths inside ass_coretext.c. This allows to test matching
problems and have a term of comparison with the slower implementation.
To activate it one just has to flip the CT_FONTS_EAGER_LOAD define to 1.

Here are some benchmarks with a pretty typical OS X font library of ~600 fonts
and using Libass's test program to load a script with 'Helvetica Neue':

CT_FONTS_EAGER_LOAD=0
0.04s user 0.02s system 79% cpu 0.081 total

CT_FONTS_EAGER_LOAD=1
0.12s user 0.06s system 44% cpu 0.420 total

1 files changed, 58 insertions, 3 deletions

diff --git a/libass/ass_coretext.c b/libass/ass_coretext.c
index 802b511..75a5514 100644
--- a/libass/ass_coretext.c
+++ b/libass/ass_coretext.c
@@ -25,6 +25,9 @@
 
 #include "ass_coretext.h"
 
+#define CT_FONTS_EAGER_LOAD 0
+#define CT_FONTS_LAZY_LOAD  !CT_FONTS_EAGER_LOAD
+
 static char *cfstr2buf(CFStringRef string)
 {
     const char *buf_ptr = CFStringGetCStringPtr(string, kCFStringEncodingUTF8);
@@ -149,15 +152,15 @@ static void get_font_traits(CTFontDescriptorRef fontd,
 #endif
 }
 
-static void scan_fonts(ASS_Library *lib, ASS_FontProvider *provider)
+static void process_descriptors(ASS_FontProvider *provider, CFArrayRef fontsd)
 {
     ASS_FontProviderMetaData meta;
     char *families[1];
     char *identifiers[1];
     char *fullnames[1];
 
-    CTFontCollectionRef coll = CTFontCollectionCreateFromAvailableFonts(NULL);
-    CFArrayRef fontsd = CTFontCollectionCreateMatchingFontDescriptors(coll);
+    if (!fontsd)
+        return;
 
     for (int i = 0; i < CFArrayGetCount(fontsd); i++) {
         CTFontDescriptorRef fontd = CFArrayGetValueAtIndex(fontsd, i);
@@ -196,16 +199,66 @@ static void scan_fonts(ASS_Library *lib, ASS_FontProvider *provider)
 
         free(path);
     }
+}
+
+#if CT_FONTS_EAGER_LOAD
+static void scan_fonts(ASS_Library *lib, ASS_FontProvider *provider)
+{
+
+    CTFontCollectionRef coll = CTFontCollectionCreateFromAvailableFonts(NULL);
+    CFArrayRef fontsd = CTFontCollectionCreateMatchingFontDescriptors(coll);
+
+    process_descriptors(provider, fontsd);
 
     CFRelease(fontsd);
     CFRelease(coll);
 }
+#endif
+
+#if CT_FONTS_LAZY_LOAD
+static void match_fonts(ASS_Library *lib, ASS_FontProvider *provider,
+                        char *name)
+{
+    void *descr_ary[1];
+
+    CFStringRef cfname =
+        CFStringCreateWithCString(NULL, name, kCFStringEncodingUTF8);
+    CFMutableDictionaryRef cfattrs = CFDictionaryCreateMutable(NULL, 0, 0, 0);
+    CFDictionaryAddValue(cfattrs, kCTFontDisplayNameAttribute, cfname);
+    CTFontDescriptorRef ctdescr = CTFontDescriptorCreateWithAttributes(cfattrs);
+
+    descr_ary[0] = (void *)ctdescr;
+    CFArrayRef descriptors =
+        CFArrayCreate(NULL, (const void **)&descr_ary, 1, NULL);
+
+    CTFontCollectionRef ctcoll =
+        CTFontCollectionCreateWithFontDescriptors(descriptors, 0);
+
+    CFArrayRef fontsd =
+        CTFontCollectionCreateMatchingFontDescriptors(ctcoll);
+
+    process_descriptors(provider, fontsd);
+
+    if (fontsd)
+        CFRelease(fontsd);
+    CFRelease(ctcoll);
+    CFRelease(cfattrs);
+    CFRelease(ctdescr);
+    CFRelease(descriptors);
+    CFRelease(cfname);
+}
+#endif
 
 static ASS_FontProviderFuncs coretext_callbacks = {
     NULL,
     check_glyph,
     destroy_font,
+    NULL,
+#if CT_FONTS_EAGER_LOAD
     NULL
+#else
+    match_fonts
+#endif
 };
 
 ASS_FontProvider *
@@ -214,7 +267,9 @@ ass_coretext_add_provider(ASS_Library *lib, ASS_FontSelector *selector)
     ASS_FontProvider *provider =
         ass_font_provider_new(selector, &coretext_callbacks, NULL);
 
+#if CT_FONTS_EAGER_LOAD
     scan_fonts(lib, provider);
+#endif
 
     return provider;
 }