Test Core Text fallback line height.

fallback.m

// Compile with: clang fallback.m -framework CoreGraphics -framework CoreText -framework Foundation -o fallback
// Run with: ./fallback "Fallback Font Family" "Text to Typeset"

#import <ApplicationServices/ApplicationServices.h>
#import <Foundation/Foundation.h>
 
int main(int argc, char *argv[])
{
    if (argc != 3)
        return 0;

    CTFontRef systemFont = CTFontCreateUIFontForLanguage(kCTFontSystemFontType, 12.0, CFSTR("en-US"));
    CFStringRef name = CTFontCopyFamilyName(systemFont);
    CFMutableDictionaryRef attributes =
        CFDictionaryCreateMutable(NULL, 0, &kCFTypeDictionaryKeyCallBacks,
                                  &kCFTypeDictionaryValueCallBacks);
    CFDictionaryAddValue(attributes, kCTFontFamilyNameAttribute, name);
    CFRelease(name);
 
    const void *descriptors[] = { CTFontDescriptorCreateWithNameAndSize((CFStringRef)[NSString stringWithUTF8String:argv[1]], 0) };
    CFArrayRef list = CFArrayCreate(kCFAllocatorDefault, descriptors, 1, &kCFTypeArrayCallBacks);
    CFDictionaryAddValue(attributes, kCTFontCascadeListAttribute, list);
    CFRelease(list);
 
    CTFontDescriptorRef descriptor = CTFontDescriptorCreateWithAttributes(attributes);
    CFRelease(attributes);
 
    CTFontRef font = CTFontCreateWithFontDescriptor(descriptor, 0.0, 0);
    CFRelease(descriptor);

    NSDictionary *stringAttributes = @{ (id)kCTFontAttributeName: (id)font };
    CFRelease(font);

    CFAttributedStringRef attrStr =
        CFAttributedStringCreate(kCFAllocatorDefault,
                                 (CFStringRef)[NSString stringWithUTF8String:argv[2]], // Test two lines: CFSTR("test\n中文"),
                                 (CFDictionaryRef)stringAttributes);
    CFRelease(stringAttributes);

    CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString(attrStr);

    CGPathRef path = CGPathCreateWithRect(CGRectMake(0, 0, 100, 200), NULL);
    CTFrameRef frame =
        CTFramesetterCreateFrame(framesetter,
                                 CFRangeMake(0, CFAttributedStringGetLength(attrStr)),
                                 path,
                                 NULL);
    CFRelease(path);
    CFRelease(attrStr);

    CFArrayRef lines = CTFrameGetLines(frame);
    for (CFIndex i = 0; i < CFArrayGetCount(lines); i++) {
        CTLineRef line = CFArrayGetValueAtIndex(lines, i);
        CFShow(line);
    }
 
    CFRelease(frame);

    return 0;
}