I’m using CTTypesetter to layout messages read in from JSON from a server. However, on certain particular messages it crashes, namely those with unusual Unicode characters like the one below.
CFAttributedStringRef attrString = CFAttributedStringCreate(NULL, @"❝Ｗｅ ｍｕｓｔ ｌｅａｒｎ ｔｏ ｌｉｖｅ ｔｏｇｅｔｈｅｒ ａｓ ｂｒｏｔｈｅｒｓ ｏｒ ｐｅｒｉｓｈ ｔｏｇｅｔｈｅｒ ａｓ ｆｏｏｌｓ❞ ~Martin Luther King Jr. #HappyMLKDay", nil);
CTTypesetterRef typesetter = CTTypesetterCreateWithAttributedString(attrString);
That crashes with the below stack trace.
#0 0x33a4684e in TBaseFont::CopyCharacterSet() const ()
#1 0x33a2c0d4 in CompareCharSet(__CFCharacterSet const*, TBaseFont const*) ()
#2 0x33a2f03e in TDescriptorSource::CopyDescriptorsForRequestFromArray(__CFArray const*, __CFDictionary const*, long (*)(void const*, void const*, void*), void*, unsigned long, bool) const ()
#3 0x33a2ead0 in TDescriptorSource::CopyDescriptorsForRequest(__CFDictionary const*, __CFSet const*, long (*)(void const*, void const*, void*), void*, unsigned long) const ()
#4 0x33a2e624 in TDescriptorSource::CopyDescriptorForRequest(__CFDictionary const*, __CFSet const*, long (*)(void const*, void const*, void*), void*, unsigned long) const ()
#5 0x33a2e532 in TDescriptorSource::CopySystemWideFallbackDescriptor(CGFont*, unsigned short const*, long) const ()
#6 0x33a2e79c in TDescriptorSource::CopySystemWideFallbackDescriptor(CGFont*, __CFString const*, CFRange) const ()
#7 0x33a27c78 in TFontCascade::CreateSystemWideFallback(__CTFont const*, __CFString const*, CFRange) const ()
#8 0x33a27b28 in TFontCascade::CreateFallback(__CTFont const*, __CFString const*, CFRange) const ()
#9 0x33a185ec in TGlyphEncoder::AppendUnmappedCharRun(CTRun*, CFRange, CFRange, TGlyphList<TDeletedGlyphIndex>&, TGlyphList<TDeletedGlyphIndex>&, TFontCascade const&, bool) ()
#10 0x33a184b8 in TGlyphEncoder::RunUnicodeEncoderRecursively(CTRun*, adopted_t const&, CFRange, TGlyphList<TDeletedGlyphIndex>&, TGlyphList<TDeletedGlyphIndex>&, TFontCascade const*, bool) ()
#11 0x33a186e4 in TGlyphEncoder::AppendUnmappedCharRun(CTRun*, CFRange, CFRange, TGlyphList<TDeletedGlyphIndex>&, TGlyphList<TDeletedGlyphIndex>&, TFontCascade const&, bool) ()
#12 0x33a184b8 in TGlyphEncoder::RunUnicodeEncoderRecursively(CTRun*, adopted_t const&, CFRange, TGlyphList<TDeletedGlyphIndex>&, TGlyphList<TDeletedGlyphIndex>&, TFontCascade const*, bool) ()
#13 0x33a1824c in TGlyphEncoder::RunUnicodeEncoder(CTRun*, adopted_t const&, CFRange, TGlyphList<TDeletedGlyphIndex>&, TFontCascade const*) ()
#14 0x33a07a1a in TGlyphEncoder::EncodeChars(CFRange, TAttributes const&, TGlyphList<TDeletedGlyphIndex>&, TGlyphEncoder::Fallbacks) ()
#15 0x33a0665c in TTypesetterAttrString::Initialize(__CFAttributedString const*) ()
#16 0x33a064a4 in TTypesetterAttrString::TTypesetterAttrString(__CFAttributedString const*) ()
#17 0x33a06418 in TTypesetterAttrString::TTypesetterAttrString(__CFAttributedString const*) ()
#18 0x33a1e78c in CTTypesetterCreateWithAttributedString ()
I created an empty project to try and reproduce the crash, however in this environment it works fine.
The documentation has this to say:
Multicore Considerations: All individual functions in Core Text are
thread safe. Font objects (CTFont, CTFontDescriptor, and associated
objects) can be used by simultaneously by multiple operations, work
queues, or threads. However, the layout objects (CTTypesetter,
CTFramesetter, CTRun, CTLine, CTFrame, and associated objects) should
be used in a single operation, work queue, or thread.
To this end I’ve taken out all kind of threading, namely a few dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ...), in an attempt to resolve this. I don’t know what else I can try to solve it besides gutting what is a >20 KSLOC project.
It only crashes the actual iPad (all 3 models tested with both 5.0 and 5.1), not the simulator.
What can I try to solve this? I’m about to resort to embedding modified versions of Helvetica with as many fallback fonts merged into them as possible, but that’s a far from optimal solution.
Any input at all would be incredibly appreciated, as you can see this has been driving me insane since January!
I just solved it.
I was referencing 43 fonts in my info.plist. All were valid, all were otf’s or ttf’s in my resource bundle. I just removed a few and it started working.
Damn Apple bug.