ReadViewSDK/Doc/WXRead/decompiled/DTCoreTextLayoutLine.m

//
//  DTCoreTextLayoutLine.m
//  WeRead
//
//  Reverse-engineered from binary analysis
//  Based on DTCoreText open-source library, customized by WeRead
//
//  This file contains pseudo-code reconstruction of the DTCoreTextLayoutLine
//  class based on ivar analysis, method signatures, and the open-source DTCoreText library.
//

#import "DTCoreTextLayoutLine.h"
#import "DTCoreTextGlyphRun.h"
#import <CoreText/CoreText.h>

#pragma mark - Private Interface

@interface DTCoreTextLayoutLine () {
    // Cached glyph runs
    NSArray<DTCoreTextGlyphRun *> *_cachedGlyphRuns;

    // Whether glyph runs have been extracted
    BOOL _glyphRunsExtracted;

    // Cached typographic metrics
    CGFloat _cachedAscent;
    CGFloat _cachedDescent;
    CGFloat _cachedLeading;
    CGFloat _cachedWidth;
    BOOL _metricsCached;

    // Internal lock
    NSLock *_lock;
}

@end

#pragma mark - DTCoreTextLayoutLine Implementation

@implementation DTCoreTextLayoutLine

#pragma mark - Lifecycle

- (instancetype)initWithCTLine:(CTLineRef)ctLine
                        origin:(CGPoint)origin
                         range:(NSRange)range
                         index:(NSUInteger)index {
    self = [super init];
    if (self) {
        _lock = [[NSLock alloc] init];

        // Store the CTLine with a retain
        if (ctLine) {
            _ctLine = (CTLineRef)CFRetain(ctLine);
        }

        _origin = origin;
        _stringRange = range;
        _lineIndex = index;

        // Initialize state
        _glyphRunsExtracted = NO;
        _metricsCached = NO;
        _baselineOffset = 0;
        _isLastLineInParagraph = NO;
        _isLineBreak = NO;
    }
    return self;
}

- (void)dealloc {
    if (_ctLine) {
        CFRelease(_ctLine);
        _ctLine = NULL;
    }
}

#pragma mark - Glyph Run Extraction

/**
 * Extracts glyph runs from the CTLine.
 *
 * This method iterates through the CTLine's runs and creates
 * DTCoreTextGlyphRun wrapper objects.
 *
 * Algorithm:
 * 1. Get array of CTRuns from CTLine
 * 2. For each CTRun:
 *    a. Get its string range
 *    b. Get glyph positions and advances
 *    c. Create DTCoreTextGlyphRun wrapper
 * 3. Cache the results
 */
- (void)extractGlyphRuns {
    if (_glyphRunsExtracted || !_ctLine) {
        return;
    }

    [_lock lock];

    // Get the runs from the CTLine
    CFArrayRef ctRuns = CTLineGetGlyphRuns(_ctLine);
    if (!ctRuns) {
        _cachedGlyphRuns = @[];
        _glyphRunsExtracted = YES;
        [_lock unlock];
        return;
    }

    CFIndex runCount = CFArrayGetCount(ctRuns);
    if (runCount == 0) {
        _cachedGlyphRuns = @[];
        _glyphRunsExtracted = YES;
        [_lock unlock];
        return;
    }

    NSMutableArray<DTCoreTextGlyphRun *> *runs = [NSMutableArray arrayWithCapacity:runCount];

    // Calculate the baseline x offset for this line
    CGFloat lineXOffset = _origin.x;

    for (CFIndex i = 0; i < runCount; i++) {
        CTRunRef ctRun = CFArrayGetValueAtIndex(ctRuns, i);

        // Get the string range for this run
        CFRange cfRange = CTRunGetStringRange(ctRun);
        NSRange range = NSMakeRange(cfRange.location, cfRange.length);

        // Get the run's typographic bounds
        CGFloat ascent, descent, leading;
        double width = CTRunGetTypographicBounds(ctRun, CFRangeMake(0, 0), &ascent, &descent, &leading);

        // Get the positions of the glyphs
        CFIndex glyphCount = CTRunGetGlyphCount(ctRun);
        CGPoint *positions = (CGPoint *)malloc(sizeof(CGPoint) * glyphCount);
        CTRunGetPositions(ctRun, CFRangeMake(0, 0), positions);

        // Get the attributes
        NSDictionary *attributes = (__bridge NSDictionary *)CTRunGetAttributes(ctRun);

        // Calculate the run's frame
        CGRect runFrame;
        if (glyphCount > 0) {
            CGFloat minX = positions[0].x;
            CGFloat maxX = positions[glyphCount - 1].x + width / glyphCount; // Approximate

            // More accurate: use the actual glyph advances
            CGGlyph *glyphs = (CGGlyph *)malloc(sizeof(CGGlyph) * glyphCount);
            CTRunGetGlyphs(ctRun, CFRangeMake(0, 0), glyphs);

            // Calculate actual bounds using the glyph advances
            CGFloat *advances = (CGFloat *)malloc(sizeof(CGFloat) * glyphCount);
            CTFontRef font = (__bridge CTFontRef)attributes[(__bridge NSString *)kCTFontAttributeName];

            if (font) {
                CTFontGetAdvancesForGlyphs(font, kCTFontOrientationHorizontal, glyphs, advances, glyphCount);
            }

            // Recalculate max X using actual advances
            maxX = minX;
            for (CFIndex j = 0; j < glyphCount; j++) {
                maxX += advances[j];
            }

            free(glyphs);
            free(advances);

            runFrame = CGRectMake(
                lineXOffset + minX,
                _origin.y - descent,
                maxX - minX,
                ascent + descent
            );
        } else {
            runFrame = CGRectZero;
        }

        free(positions);

        // Create glyph run wrapper
        DTCoreTextGlyphRun *glyphRun = [[DTCoreTextGlyphRun alloc]
            initWithCTRun:ctRun
                    frame:runFrame
                    range:range
                attributes:attributes
                     index:i];

        [runs addObject:glyphRun];
    }

    _cachedGlyphRuns = [runs copy];
    _glyphRunsExtracted = YES;

    [_lock unlock];
}

/**
 * Returns the array of glyph runs.
 */
- (NSArray<DTCoreTextGlyphRun *> *)glyphRuns {
    [self extractGlyphRuns];
    return _cachedGlyphRuns;
}

- (DTCoreTextGlyphRun *)glyphRunAtIndex:(NSUInteger)index {
    NSArray *runs = [self glyphRuns];
    if (index < [runs count]) {
        return runs[index];
    }
    return nil;
}

/**
 * Returns the glyph run containing the given string index.
 */
- (DTCoreTextGlyphRun *)glyphRunContainingStringIndex:(NSUInteger)index {
    NSArray<DTCoreTextGlyphRun *> *allRuns = [self glyphRuns];

    for (DTCoreTextGlyphRun *run in allRuns) {
        NSRange range = run.stringRange;

        if (index >= range.location && index < range.location + range.length) {
            return run;
        }
    }

    return nil;
}

#pragma mark - Typographic Metrics

/**
 * Calculates and caches typographic metrics.
 */
- (void)calculateMetrics {
    if (_metricsCached || !_ctLine) {
        return;
    }

    [_lock lock];

    // Get typographic bounds from CTLine
    _cachedWidth = CTLineGetTypographicBounds(_ctLine, &_cachedAscent, &_cachedDescent, &_cachedLeading);

    // Get trailing whitespace width
    _trailingWhitespaceWidth = CTLineGetTrailingWhitespaceWidth(_ctLine);

    _metricsCached = YES;

    [_lock unlock];
}

- (CGFloat)ascent {
    [self calculateMetrics];
    return _cachedAscent;
}

- (CGFloat)descent {
    [self calculateMetrics];
    return _cachedDescent;
}

- (CGFloat)leading {
    [self calculateMetrics];
    return _cachedLeading;
}

- (CGFloat)height {
    return [self ascent] + [self descent] + [self leading];
}

- (CGFloat)width {
    [self calculateMetrics];
    return _cachedWidth;
}

/**
 * Returns the typographic bounds of the line.
 */
- (CGFloat)getTypographicBoundsAscent:(CGFloat *)ascent
                              descent:(CGFloat *)descent
                              leading:(CGFloat *)leading {
    [self calculateMetrics];

    if (ascent) *ascent = _cachedAscent;
    if (descent) *descent = _cachedDescent;
    if (leading) *leading = _cachedLeading;

    return _cachedWidth;
}

/**
 * Returns the bounds of the line (bounding box).
 */
- (CGRect)bounds {
    [self calculateMetrics];

    return CGRectMake(0, -_cachedDescent, _cachedWidth, [self height]);
}

/**
 * Returns the frame of the line (position + bounds).
 */
- (CGRect)frame {
    return CGRectMake(_origin.x, _origin.y - _cachedDescent, _cachedWidth, [self height]);
}

#pragma mark - Hit Testing

/**
 * Returns the string index at the given point within this line.
 *
 * Uses CTLineGetStringIndexForPosition to find which character
 * is at the given point.
 *
 * @param point The point to test (in the line's coordinate system)
 * @return The string index, or NSNotFound
 */
- (NSUInteger)stringIndexAtPoint:(CGPoint)point {
    if (!_ctLine) {
        return NSNotFound;
    }

    // Convert point to line-relative coordinates
    CGPoint linePoint = CGPointMake(point.x - _origin.x, point.y - _origin.y);

    // Use CTLine to find the character index
    CFIndex index = CTLineGetStringIndexForPosition(_ctLine, linePoint);

    if (index == kCFNotFound) {
        return NSNotFound;
    }

    return (NSUInteger)index;
}

/**
 * Returns the offset for a given string index.
 *
 * @param index The string index
 * @return The horizontal offset from the line's origin
 */
- (CGFloat)offsetForStringIndex:(NSUInteger)index {
    if (!_ctLine) {
        return 0;
    }

    // CTLineGetOffsetForStringIndex returns the offset from the line's origin
    CGFloat offset = CTLineGetOffsetForStringIndex(_ctLine, index, NULL);

    return offset;
}

/**
 * Returns the rect for a given string index.
 */
- (CGRect)rectForStringIndex:(NSUInteger)index {
    CGFloat xOffset = [self offsetForStringIndex:index];

    return CGRectMake(
        _origin.x + xOffset,
        _origin.y - _cachedDescent,
        1, // Width of 1 character
        [self height]
    );
}

#pragma mark - String Operations

/**
 * Returns the substring represented by this line.
 */
- (NSString *)substringFromAttributedString:(NSAttributedString *)attributedString {
    if (!attributedString || _stringRange.location >= [attributedString length]) {
        return nil;
    }

    // Clamp the range to the string length
    NSUInteger maxLength = [attributedString length] - _stringRange.location;
    NSUInteger length = MIN(_stringRange.length, maxLength);

    return [[attributedString string] substringWithRange:NSMakeRange(_stringRange.location, length)];
}

/**
 * Returns the attributes at a given string index.
 */
- (NSDictionary *)attributesAtIndex:(NSUInteger)index
                fromAttributedString:(NSAttributedString *)attributedString {
    if (!attributedString || index >= [attributedString length]) {
        return nil;
    }

    return [attributedString attributesAtIndex:index effectiveRange:NULL];
}

#pragma mark - Line Comparison

/**
 * Compares this line to another line for ordering.
 */
- (NSComparisonResult)compareToLine:(DTCoreTextLayoutLine *)otherLine {
    // Compare by line index first
    if (_lineIndex < otherLine.lineIndex) {
        return NSOrderedAscending;
    } else if (_lineIndex > otherLine.lineIndex) {
        return NSOrderedDescending;
    }

    // If same index, compare by string range location
    if (_stringRange.location < otherLine.stringRange.location) {
        return NSOrderedAscending;
    } else if (_stringRange.location > otherLine.stringRange.location) {
        return NSOrderedDescending;
    }

    return NSOrderedSame;
}

/**
 * Returns whether this line contains the given string index.
 */
- (BOOL)containsStringIndex:(NSUInteger)index {
    return index >= _stringRange.location &&
           index < _stringRange.location + _stringRange.length;
}

/**
 * Returns whether this line intersects with the given range.
 */
- (BOOL)intersectsRange:(NSRange)range {
    NSRange intersection = NSIntersectionRange(_stringRange, range);
    return intersection.length > 0;
}

#pragma mark - Drawing

/**
 * Draws this line into a CGContext.
 *
 * @param context The CGContext to draw into
 */
- (void)drawInContext:(CGContextRef)context {
    if (!context || !_ctLine) {
        return;
    }

    // Save graphics state
    CGContextSaveGState(context);

    // Move to the line's origin
    CGContextSetTextPosition(context, _origin.x, _origin.y);

    // Draw the line
    CTLineDraw(_ctLine, context);

    // Restore graphics state
    CGContextRestoreGState(context);
}

/**
 * Draws this line with a specific color.
 *
 * @param context The CGContext to draw into
 * @param color The text color
 */
- (void)drawInContext:(CGContextRef)context withColor:(UIColor *)color {
    if (!context || !_ctLine || !color) {
        return;
    }

    // Save graphics state
    CGContextSaveGState(context);

    // Set the text color
    CGContextSetFillColorWithColor(context, color.CGColor);

    // Move to the line's origin
    CGContextSetTextPosition(context, _origin.x, _origin.y);

    // Draw the line
    CTLineDraw(_ctLine, context);

    // Restore graphics state
    CGContextRestoreGState(context);
}

@end