ReadViewSDK/Doc/WXRead/decompiled/DTCoreTextLayoutFrame.m

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

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

#pragma mark - Private Interface

@interface DTCoreTextLayoutFrame () {
    // The CoreText frame object
    CTFrameRef _ctFrame;

    // Cached layout lines
    NSArray<DTCoreTextLayoutLine *> *_cachedLines;

    // Cached glyph runs
    NSArray<DTCoreTextGlyphRun *> *_cachedGlyphRuns;

    // Cached line origins
    NSArray<NSValue *> *_cachedLineOrigins;

    // Whether lines have been extracted
    BOOL _linesExtracted;

    // Whether glyph runs have been extracted
    BOOL _glyphRunsExtracted;

    // Internal lock
    NSLock *_lock;

    // Cached content height
    CGFloat _cachedContentHeight;
    BOOL _contentHeightCached;

    // Visible string range
    NSRange _visibleStringRange;

    // Whether the frame is truncated
    BOOL _isTruncated;

    // Truncation range
    NSRange _truncatedRange;
}

@end

#pragma mark - DTCoreTextLayoutFrame Implementation

@implementation DTCoreTextLayoutFrame

#pragma mark - Lifecycle

- (instancetype)initWithAttributedString:(NSAttributedString *)attributedString
                                   range:(NSRange)range
                                ctFrame:(CTFrameRef)ctFrame {
    self = [super init];
    if (self) {
        _attributedString = attributedString;
        _range = range;
        _lock = [[NSLock alloc] init];

        // Store the CTFrame
        if (ctFrame) {
            _ctFrame = (CTFrameRef)CFRetain(ctFrame);
        }

        // Initialize state
        _linesExtracted = NO;
        _glyphRunsExtracted = NO;
        _contentHeightCached = NO;
        _needsLayout = YES;

        // Get the frame path bounds
        if (_ctFrame) {
            CGPathRef path = CTFrameGetPath(_ctFrame);
            _frame = CGPathGetPathBoundingBox(path);
        }

        // Initialize visible range to full range
        _visibleStringRange = range;
    }
    return self;
}

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

#pragma mark - Line Extraction

/**
 * Extracts layout lines from the CTFrame.
 *
 * This method iterates through the CTFrame's lines and creates
 * DTCoreTextLayoutLine wrapper objects with position information.
 *
 * Algorithm:
 * 1. Get array of CTLines from CTFrame
 * 2. For each CTLine:
 *    a. Get its origin from CTFrameGetLineOrigins
 *    b. Get the string range from CTLineGetStringRange
 *    c. Create DTCoreTextLayoutLine wrapper
 * 3. Cache the results
 */
- (void)extractLines {
    if (_linesExtracted || !_ctFrame) {
        return;
    }

    [_lock lock];

    // Get the lines from the CTFrame
    CFArrayRef ctLines = CTFrameGetLines(_ctFrame);
    if (!ctLines) {
        _cachedLines = @[];
        _linesExtracted = YES;
        [_lock unlock];
        return;
    }

    CFIndex lineCount = CFArrayGetCount(ctLines);
    if (lineCount == 0) {
        _cachedLines = @[];
        _linesExtracted = YES;
        [_lock unlock];
        return;
    }

    // Get line origins
    CGPoint *origins = (CGPoint *)malloc(sizeof(CGPoint) * lineCount);
    CTFrameGetLineOrigins(_ctFrame, CFRangeMake(0, 0), origins);

    NSMutableArray<DTCoreTextLayoutLine *> *lines = [NSMutableArray arrayWithCapacity:lineCount];

    for (CFIndex i = 0; i < lineCount; i++) {
        CTLineRef ctLine = CFArrayGetValueAtIndex(ctLines, i);

        // Get the string range for this line
        CFRange cfRange = CTLineGetStringRange(ctLine);
        NSRange range = NSMakeRange(cfRange.location, cfRange.length);

        // Create layout line wrapper
        DTCoreTextLayoutLine *layoutLine = [[DTCoreTextLayoutLine alloc]
            initWithCTLine:ctLine
                    origin:origins[i]
                     range:range
                     index:i];

        [lines addObject:layoutLine];
    }

    free(origins);

    _cachedLines = [lines copy];
    _cachedLineOrigins = nil; // Invalidate origin cache
    _linesExtracted = YES;

    [_lock unlock];
}

/**
 * Returns the array of layout lines.
 * Triggers extraction if not already done.
 */
- (NSArray<DTCoreTextLayoutLine *> *)lines {
    [self extractLines];
    return _cachedLines;
}

- (NSUInteger)numberOfLines {
    return [[self lines] count];
}

- (DTCoreTextLayoutLine *)lineAtIndex:(NSUInteger)index {
    NSArray *lines = [self lines];
    if (index < [lines count]) {
        return lines[index];
    }
    return nil;
}

/**
 * Returns the line that contains the given string index.
 */
- (DTCoreTextLayoutLine *)lineContainingStringIndex:(NSUInteger)index {
    NSArray<DTCoreTextLayoutLine *> *allLines = [self lines];

    for (DTCoreTextLayoutLine *line in allLines) {
        NSRange range = line.stringRange;

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

    return nil;
}

/**
 * Returns the index of the line containing the given point.
 */
- (NSUInteger)lineIndexContainingPoint:(CGPoint)point {
    NSArray<DTCoreTextLayoutLine *> *allLines = [self lines];

    for (NSUInteger i = 0; i < [allLines count]; i++) {
        DTCoreTextLayoutLine *line = allLines[i];

        // Check if point is within the line's vertical bounds
        CGFloat lineTop = line.origin.y + line.ascent;
        CGFloat lineBottom = line.origin.y - line.descent;

        if (point.y >= lineBottom && point.y <= lineTop) {
            return i;
        }
    }

    return NSNotFound;
}

#pragma mark - Glyph Run Extraction

/**
 * Extracts glyph runs from all lines.
 *
 * This method iterates through all lines and extracts their glyph runs,
 * creating a flat array of all glyph runs in the frame.
 */
- (void)extractGlyphRuns {
    if (_glyphRunsExtracted) {
        return;
    }

    [_lock lock];

    NSArray<DTCoreTextLayoutLine *> *allLines = [self lines];
    NSMutableArray<DTCoreTextGlyphRun *> *allRuns = [NSMutableArray array];

    for (DTCoreTextLayoutLine *line in allLines) {
        NSArray<DTCoreTextGlyphRun *> *lineRuns = [line glyphRuns];
        [allRuns addObjectsFromArray:lineRuns];
    }

    _cachedGlyphRuns = [allRuns copy];
    _glyphRunsExtracted = YES;

    [_lock unlock];
}

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

#pragma mark - Drawing

/**
 * Draws the layout frame content into a CGContext.
 *
 * This method draws the text content using CTFrameDraw.
 *
 * @param context The CGContext to draw into
 */
- (void)drawInContext:(CGContextRef)context {
    if (!context || !_ctFrame) {
        return;
    }

    [_lock lock];

    // Save graphics state
    CGContextSaveGState(context);

    // CoreText uses bottom-left origin, UIKit uses top-left
    // We need to flip the coordinate system
    CGContextTranslateCTM(context, 0, _frame.size.height);
    CGContextScaleCTM(context, 1.0, -1.0);

    // Draw the frame
    CTFrameDraw(_ctFrame, context);

    // Restore graphics state
    CGContextRestoreGState(context);

    [_lock unlock];
}

/**
 * Draws the layout frame with options.
 *
 * @param context The CGContext to draw into
 * @param options Drawing options dictionary
 */
- (void)drawInContext:(CGContextRef)context options:(NSDictionary *)options {
    if (!context || !_ctFrame) {
        return;
    }

    [_lock lock];

    // Save graphics state
    CGContextSaveGState(context);

    // Apply coordinate transformation
    CGContextTranslateCTM(context, 0, _frame.size.height);
    CGContextScaleCTM(context, 1.0, -1.0);

    // Check for custom drawing options
    BOOL drawImages = [options[@"drawImages"] boolValue];
    BOOL drawLinks = [options[@"drawLinks"] boolValue];
    BOOL drawSelection = [options[@"drawSelection"] boolValue];

    // Draw the frame
    CTFrameDraw(_ctFrame, context);

    // Draw images if requested
    if (drawImages) {
        [self drawImagesInContext:context options:options];
    }

    // Draw links if requested
    if (drawLinks) {
        [self drawLinksInContext:context options:options];
    }

    // Draw selection if requested
    if (drawSelection) {
        [self drawSelectionInContext:context options:options];
    }

    // Restore graphics state
    CGContextRestoreGState(context);

    [_lock unlock];
}

/**
 * Draws images in the layout frame.
 */
- (void)drawImagesInContext:(CGContextRef)context options:(NSDictionary *)options {
    // Extract image attachments from attributed string
    NSArray<DTCoreTextLayoutLine *> *allLines = [self lines];

    for (DTCoreTextLayoutLine *line in allLines) {
        NSArray<DTCoreTextGlyphRun *> *runs = [line glyphRuns];

        for (DTCoreTextGlyphRun *run in runs) {
            NSDictionary *attributes = run.attributes;

            // Check for attachment
            NSTextAttachment *attachment = attributes[@"NSAttachment"];
            if (attachment && attachment.image) {
                CGRect runFrame = run.frame;

                // Draw the image at the run's position
                CGContextDrawImage(context, runFrame, attachment.image.CGImage);
            }
        }
    }
}

/**
 * Draws link indicators.
 */
- (void)drawLinksInContext:(CGContextRef)context options:(NSDictionary *)options {
    // Draw underlines for links
    NSArray<DTCoreTextLayoutLine *> *allLines = [self lines];

    for (DTCoreTextLayoutLine *line in allLines) {
        NSArray<DTCoreTextGlyphRun *> *runs = [line glyphRuns];

        for (DTCoreTextGlyphRun *run in runs) {
            NSDictionary *attributes = run.attributes;
            NSURL *linkURL = attributes[@"NSLink"];

            if (linkURL) {
                // Draw underline for link
                CGRect runFrame = run.frame;
                CGFloat underlineY = runFrame.origin.y;

                CGContextSetStrokeColorWithColor(context, [UIColor blueColor].CGColor);
                CGContextSetLineWidth(context, 1.0);

                CGContextMoveToPoint(context, runFrame.origin.x, underlineY);
                CGContextAddLineToPoint(context, CGRectGetMaxX(runFrame), underlineY);
                CGContextStrokePath(context);
            }
        }
    }
}

/**
 * Draws selection highlight.
 */
- (void)drawSelectionInContext:(CGContextRef)context options:(NSDictionary *)options {
    NSArray *selectedRanges = options[@"selectedRanges"];
    UIColor *selectionColor = options[@"selectionColor"] ?: [UIColor colorWithRed:0.0
                                                                             green:0.47
                                                                              blue:1.0
                                                                             alpha:0.2];

    for (NSValue *rangeValue in selectedRanges) {
        NSRange range = [rangeValue rangeValue];

        // Get the rects for this range
        NSArray<NSValue *> *rects = [self rectsForRange:range];

        CGContextSetFillColorWithColor(context, selectionColor.CGColor);

        for (NSValue *rectValue in rects) {
            CGRect rect = [rectValue CGRectValue];
            CGContextFillRect(context, rect);
        }
    }
}

/**
 * Returns rects for a string range.
 */
- (NSArray<NSValue *> *)rectsForRange:(NSRange)range {
    NSMutableArray<NSValue *> *rects = [NSMutableArray array];

    NSArray<DTCoreTextLayoutLine *> *allLines = [self lines];

    for (DTCoreTextLayoutLine *line in allLines) {
        NSRange lineRange = line.stringRange;
        NSRange intersection = NSIntersectionRange(range, lineRange);

        if (intersection.length > 0) {
            // Get the x positions for the range within this line
            CGFloat startX = CTLineGetOffsetForStringIndex(
                line.ctLine, intersection.location, NULL);
            CGFloat endX = CTLineGetOffsetForStringIndex(
                line.ctLine, intersection.location + intersection.length, NULL);

            CGRect lineRect = CGRectMake(
                line.origin.x + startX,
                line.origin.y - line.descent,
                endX - startX,
                line.height
            );

            [rects addObject:[NSValue valueWithRect:lineRect]];
        }
    }

    return [rects copy];
}

#pragma mark - Hit Testing

/**
 * Returns the string index at the given point.
 *
 * Uses CTLineGetStringIndexForPosition to find which character
 * is at the given point.
 *
 * @param point The point to test
 * @return The string index, or NSNotFound
 */
- (NSUInteger)stringIndexAtPoint:(CGPoint)point {
    NSArray<DTCoreTextLayoutLine *> *allLines = [self lines];

    for (DTCoreTextLayoutLine *line in allLines) {
        // Check if the point is within this line's vertical bounds
        CGFloat lineTop = line.origin.y + line.ascent;
        CGFloat lineBottom = line.origin.y - line.descent;

        if (point.y >= lineBottom && point.y <= lineTop) {
            // Use CTLine to find the character index
            CFIndex index = CTLineGetStringIndexForPosition(line.ctLine, point);

            if (index != kCFNotFound) {
                return (NSUInteger)index;
            }
        }
    }

    return NSNotFound;
}

/**
 * Returns the rect for the given string index.
 */
- (CGRect)rectForStringIndex:(NSUInteger)index {
    NSArray<DTCoreTextLayoutLine *> *allLines = [self lines];

    for (DTCoreTextLayoutLine *line in allLines) {
        NSRange range = line.stringRange;

        if (index >= range.location && index < range.location + range.length) {
            // Get the x position for this character
            CGFloat x = CTLineGetOffsetForStringIndex(line.ctLine, index, NULL);

            return CGRectMake(line.origin.x + x,
                            line.origin.y - line.descent,
                            1,
                            line.height);
        }
    }

    return CGRectNull;
}

/**
 * Returns the cursor position for a given string index.
 */
- (CGRect)cursorRectForIndex:(NSUInteger)index {
    NSArray<DTCoreTextLayoutLine *> *allLines = [self lines];

    for (DTCoreTextLayoutLine *line in allLines) {
        NSRange range = line.stringRange;

        if (index >= range.location && index <= range.location + range.length) {
            CGFloat x = CTLineGetOffsetForStringIndex(line.ctLine, index, NULL);

            return CGRectMake(line.origin.x + x - 1,
                            line.origin.y - line.descent,
                            2,
                            line.height);
        }
    }

    return CGRectNull;
}

#pragma mark - Text Geometry

/**
 * Returns the baseline origin for a given string index.
 */
- (CGPoint)baselineOriginForStringIndex:(NSUInteger)index {
    NSArray<DTCoreTextLayoutLine *> *allLines = [self lines];

    for (DTCoreTextLayoutLine *line in allLines) {
        NSRange range = line.stringRange;

        if (index >= range.location && index < range.location + range.length) {
            CGFloat x = CTLineGetOffsetForStringIndex(line.ctLine, index, NULL);

            return CGPointMake(line.origin.x + x, line.origin.y);
        }
    }

    return CGPointZero;
}

/**
 * Returns the frame for a given string range.
 */
- (CGRect)frameForStringRange:(NSRange)range {
    NSArray<NSValue *> *rects = [self rectsForRange:range];

    if ([rects count] == 0) {
        return CGRectNull;
    }

    // Union all rects
    CGRect result = CGRectNull;
    for (NSValue *rectValue in rects) {
        result = CGRectUnion(result, [rectValue CGRectValue]);
    }

    return result;
}

/**
 * Returns the string range for a given rect.
 */
- (NSRange)stringRangeForRect:(CGRect)rect {
    NSArray<DTCoreTextLayoutLine *> *allLines = [self lines];

    NSUInteger start = NSNotFound;
    NSUInteger end = NSNotFound;

    for (DTCoreTextLayoutLine *line in allLines) {
        CGRect lineRect = CGRectMake(
            line.origin.x,
            line.origin.y - line.descent,
            line.width,
            line.height
        );

        if (CGRectIntersectsRect(rect, lineRect)) {
            if (start == NSNotFound) {
                start = line.stringRange.location;
            }
            end = line.stringRange.location + line.stringRange.length;
        }
    }

    if (start != NSNotFound && end != NSNotFound) {
        return NSMakeRange(start, end - start);
    }

    return NSMakeRange(NSNotFound, 0);
}

#pragma mark - Line Geometry

/**
 * Returns the line origins.
 */
- (NSArray<NSValue *> *)lineOrigins {
    if (_cachedLineOrigins) {
        return _cachedLineOrigins;
    }

    [_lock lock];

    NSArray<DTCoreTextLayoutLine *> *allLines = [self lines];
    NSMutableArray<NSValue *> *origins = [NSMutableArray arrayWithCapacity:[allLines count]];

    for (DTCoreTextLayoutLine *line in allLines) {
        [origins addObject:[NSValue valueWithCGPoint:line.origin]];
    }

    _cachedLineOrigins = [origins copy];

    [_lock unlock];

    return _cachedLineOrigins;
}

/**
 * Returns the line frames.
 */
- (NSArray<NSValue *> *)lineFrames {
    NSArray<DTCoreTextLayoutLine *> *allLines = [self lines];
    NSMutableArray<NSValue *> *frames = [NSMutableArray arrayWithCapacity:[allLines count]];

    for (DTCoreTextLayoutLine *line in allLines) {
        CGRect lineFrame = CGRectMake(
            line.origin.x,
            line.origin.y - line.descent,
            line.width,
            line.height
        );
        [frames addObject:[NSValue valueWithRect:lineFrame]];
    }

    return [frames copy];
}

#pragma mark - Content Height

/**
 * Returns the rendered content height.
 */
- (CGFloat)contentHeight {
    [_lock lock];

    if (_contentHeightCached) {
        [_lock unlock];
        return _cachedContentHeight;
    }

    NSArray<DTCoreTextLayoutLine *> *allLines = [self lines];

    if ([allLines count] == 0) {
        _cachedContentHeight = 0;
        _contentHeightCached = YES;
        [_lock unlock];
        return 0;
    }

    // Find the lowest point of the last line
    DTCoreTextLayoutLine *lastLine = [allLines lastObject];
    CGFloat lastLineBottom = lastLine.origin.y - lastLine.descent;

    // Content height is from top of frame to bottom of last line
    _cachedContentHeight = _frame.size.height - lastLineBottom;
    _contentHeightCached = YES;

    [_lock unlock];

    return _cachedContentHeight;
}

- (CGFloat)maximumY {
    NSArray<DTCoreTextLayoutLine *> *allLines = [self lines];

    if ([allLines count] == 0) {
        return _frame.origin.y + _frame.size.height;
    }

    DTCoreTextLayoutLine *firstLine = [allLines firstObject];
    return firstLine.origin.y + firstLine.ascent;
}

- (CGFloat)minimumY {
    NSArray<DTCoreTextLayoutLine *> *allLines = [self lines];

    if ([allLines count] == 0) {
        return _frame.origin.y;
    }

    DTCoreTextLayoutLine *lastLine = [allLines lastObject];
    return lastLine.origin.y - lastLine.descent;
}

#pragma mark - Truncation

/**
 * Returns whether the frame is truncated.
 */
- (BOOL)isTruncated {
    // Check if the attributed string extends beyond the visible range
    NSUInteger stringEnd = _range.location + _range.length;
    NSUInteger visibleEnd = _visibleStringRange.location + _visibleStringRange.length;

    return visibleEnd < stringEnd;
}

/**
 * Returns the truncation string range.
 */
- (NSRange)truncatedStringRange {
    if (![self isTruncated]) {
        return NSMakeRange(NSNotFound, 0);
    }

    NSUInteger visibleEnd = _visibleStringRange.location + _visibleStringRange.length;
    NSUInteger stringEnd = _range.location + _range.length;

    return NSMakeRange(visibleEnd, stringEnd - visibleEnd);
}

#pragma mark - Layout Updates

/**
 * Invalidates the layout, forcing recalculation on next access.
 */
- (void)invalidateLayout {
    [_lock lock];

    _linesExtracted = NO;
    _glyphRunsExtracted = NO;
    _contentHeightCached = NO;
    _cachedLines = nil;
    _cachedGlyphRuns = nil;
    _cachedLineOrigins = nil;
    _needsLayout = YES;

    [_lock unlock];
}

/**
 * Forces a layout pass.
 */
- (void)layoutIfNeeded {
    if (_needsLayout) {
        [self extractLines];
        _needsLayout = NO;
    }
}

- (NSUInteger)stringIndex {
    return _range.location + _range.length;
}

@end