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#include <mbgl/text/local_glyph_rasterizer.hpp>
#include <mbgl/util/i18n.hpp>
#import <Foundation/Foundation.h>
#import <CoreText/CoreText.h>
#import <ImageIO/ImageIO.h>
namespace {
template <typename T, typename S, void (*Releaser)(S)>
struct CFHandle {
CFHandle(T t_): t(t_) {}
~CFHandle() { Releaser(t); }
T operator*() { return t; }
operator bool() { return t; }
private:
T t;
};
} // namespace
namespace mbgl {
/*
Initial implementation of darwin TinySDF support:
Draw any CJK glyphs using a default system font
Where to take this:
- Configure whether to use local fonts, and which fonts to use,
based on map or even style layer options
- Build heuristics for choosing fonts based on input FontStack
(maybe a globally configurable FontStack -> UIFontDescriptor map would make sense?
- Extract glyph metrics so that this can be used with more than just fixed width glyphs
*/
bool LocalGlyphRasterizer::canRasterizeGlyph(const FontStack&, GlyphID glyphID) {
// TODO: This is a rough approximation of the set of glyphs that will work with fixed glyph metrics
// Either narrow this down to be conservative, or actually extract glyph metrics in rasterizeGlyph
return util::i18n::allowsIdeographicBreaking(glyphID);
}
using CGContextHandle = CFHandle<CGContextRef, CGContextRef, CGContextRelease>;
using CGColorSpaceHandle = CFHandle<CGColorSpaceRef, CGColorSpaceRef, CGColorSpaceRelease>;
Glyph LocalGlyphRasterizer::rasterizeGlyph(const FontStack&, GlyphID glyphID) {
Glyph fixedMetrics;
fixedMetrics.id = glyphID;
fixedMetrics.metrics.width = 24;
fixedMetrics.metrics.height = 24;
fixedMetrics.metrics.left = 0;
fixedMetrics.metrics.top = -8;
fixedMetrics.metrics.advance = 24;
uint32_t width = 30;
uint32_t height = 30;
Size size(width, height);
fixedMetrics.bitmap = AlphaImage(size);
NSDictionary *fontAttributes =
[NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithFloat:24.0], (NSString *)kCTFontSizeAttribute,
nil];
// Create a descriptor.
CTFontDescriptorRef descriptor =
CTFontDescriptorCreateWithAttributes((CFDictionaryRef)fontAttributes);
// Create a font using the descriptor.
CTFontRef font = CTFontCreateWithFontDescriptor(descriptor, 0.0, NULL);
CFRelease(descriptor);
CFStringRef string = CFStringCreateWithCharacters(NULL, (UniChar*)&glyphID, 1);
PremultipliedImage image(size);
CGColorSpaceHandle colorSpace(CGColorSpaceCreateDeviceRGB());
// TODO: Is there a way to just draw a single alpha channel instead of copying it out of an RGB image? Doesn't seem like the grayscale colorspace is what I'm looking for...
if (!colorSpace) {
throw std::runtime_error("CGColorSpaceCreateDeviceRGB failed");
}
constexpr const size_t bitsPerComponent = 8;
constexpr const size_t bytesPerPixel = 4;
const size_t bytesPerRow = bytesPerPixel * width;
CGContextHandle context(CGBitmapContextCreate(
image.data.get(),
width,
height,
bitsPerComponent,
bytesPerRow,
*colorSpace,
kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedLast));
if (!context) {
throw std::runtime_error("CGBitmapContextCreate failed");
}
CFStringRef keys[] = { kCTFontAttributeName };
CFTypeRef values[] = { font };
CFDictionaryRef attributes =
CFDictionaryCreate(kCFAllocatorDefault, (const void**)&keys,
(const void**)&values, sizeof(keys) / sizeof(keys[0]),
&kCFTypeDictionaryKeyCallBacks,
&kCFTypeDictionaryValueCallBacks);
CFAttributedStringRef attrString =
CFAttributedStringCreate(kCFAllocatorDefault, string, attributes);
CFRelease(string);
CFRelease(attributes);
CTLineRef line = CTLineCreateWithAttributedString(attrString); // TODO: Get glyph runs (for metric extraction) and use showGlyphs API instead?
// Set text position and draw the line into the graphics context
CGContextSetTextPosition(*context, 0.0, 0.0);
CTLineDraw(line, *context);
CFRelease(line);
CFRelease(font);
CFRelease(string); // TODO: Surely leaking something here, wrap these up!
for (uint32_t i = 0; i < width * height; i++) {
fixedMetrics.bitmap.data[i] = image.data[4 * i + 3]; // alpha value
}
return fixedMetrics;
}
} // namespace mbgl
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