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     File: SimpleCoreTextView.m
 Abstract: 
 A view that draws text, reasons about layout, and manages a selection over its text range.
 IMPORTANT: Its use of CoreText is naive and inefficient, it deals only with
 left-to-right text layout, and it is by no means a good template for any text
 editor.  It is a toy implementation included only to illustrate how to bind
 the system keyboard to some pre-existing text editor.
  Version: 1.0
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 redistribute this Apple software.
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 license, under Apple's copyrights in this original Apple software (the
 "Apple Software"), to use, reproduce, modify and redistribute the Apple
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 Neither the name, trademarks, service marks or logos of Apple Inc. may
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 without specific prior written permission from Apple.  Except as
 expressly stated in this notice, no other rights or licenses, express or
 implied, are granted by Apple herein, including but not limited to any
 patent rights that may be infringed by your derivative works or by other
 works in which the Apple Software may be incorporated.
 The Apple Software is provided by Apple on an "AS IS" basis.  APPLE
 MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION
 THE IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS
 FOR A PARTICULAR PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND
 OPERATION ALONE OR IN COMBINATION WITH YOUR PRODUCTS.
 IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL
 OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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#import "SimpleCoreTextView.h"
#import <QuartzCore/CALayer.h>
#pragma mark SimpleCoreTextView class extension
@interface SimpleCoreTextView ()
@property (nonatomic, retain) NSDictionary *attributes;
- (void)clearPreviousLayoutInformation;
- (void)textChanged;
// Note that for this sample for simplicity, the selection color and
// insertion point "caret" color are fixed and cannot be changed.
+ (UIColor *)selectionColor;
+ (UIColor *)caretColor;
#pragma mark SimpleCaretView definition
// SimpleCaretView draws a basic text "caret", used as an insertion point
// cursor in SimpleCoreTextView
@interface SimpleCaretView : UIView {
    NSTimer *_blinkTimer;
- (void)delayBlink;
#pragma mark SimpleCoreTextView implementation
@implementation SimpleCoreTextView
@synthesize text = _text;
@synthesize font = _font;
@synthesize editing = _editing;
@synthesize markedTextRange = _markedTextRange;
@synthesize selectedTextRange = _selectedTextRange;
@synthesize attributes = _attributes;
- (id)initWithFrame:(CGRect)frame {
    if ((self = [super initWithFrame:frame])) {
        self.layer.geometryFlipped = YES;  // For ease of interaction with the CoreText coordinate system.
        self.text = @"";        
        self.font = [UIFont systemFontOfSize:18];
        self.backgroundColor = [UIColor clearColor];
        _caretView = [[SimpleCaretView alloc] initWithFrame:CGRectZero];
    return self;
- (void)dealloc
    self.text = nil;
    self.font = nil;
    self.attributes = nil;
    [_caretView release];
    [super dealloc];
// Helper method to release our cached Core Text framesetter and frame
- (void)clearPreviousLayoutInformation
    if (_framesetter != NULL) {
        CFRelease(_framesetter);
        _framesetter = NULL;
    if (_frame != NULL) {
        CFRelease(_frame);
        _frame = NULL;
// font property setter override - we need to additionally create and set the Core Text
// font object that corresponds to the UIFont being set.
- (void)setFont:(UIFont *)font
    UIFont *oldFont = _font;
    _font = [font retain];
	// Find matching CTFont via name and size
    CTFontRef ctFont = CTFontCreateWithName((CFStringRef) self.font.fontName, self.font.pointSize, NULL);        
	// Set CTFont instance in our attributes dictionary, to be set on our attributed string
    self.attributes = [[NSDictionary dictionaryWithObject:(id)ctFont forKey:(NSString *)kCTFontAttributeName] retain];
    CFRelease(ctFont);        
    [self textChanged];
    [oldFont release];
// Helper method to update our text storage when the text content has changed
- (void)textChanged
    [self setNeedsDisplay];    
    [self clearPreviousLayoutInformation];
	// Build the attributed string from our text data and string attribute data
    NSAttributedString *attributedString = [[NSAttributedString alloc] initWithString:self.text attributes:self.attributes];    
	// Create the Core Text framesetter using the attributed string
    _framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attributedString);
	// Create the Core Text frame using our current view rect bounds
    UIBezierPath *path = [UIBezierPath bezierPathWithRect:self.bounds];
    _frame =  CTFramesetterCreateFrame(_framesetter, CFRangeMake(0, 0), [path CGPath], NULL);
    [attributedString release];
// text property accessor overrides
- (NSString *)text {
    return _text;
- (void)setText:(NSString *)text
    NSString *oldText = _text;
    _text = [text copy];
    [oldText release];
	// We need to call textChanged after setting the new property text to update layout
    [self textChanged];
// Helper method for obtaining the intersection of two ranges (for handling
// selection range across multiple line ranges in drawRangeAsSelection below)
- (NSRange)RangeIntersection:(NSRange)first withSecond:(NSRange)second
    NSRange result = NSMakeRange(NSNotFound, 0);
	// Ensure first range does not start after second range
    if (first.location > second.location) {
        NSRange tmp = first;
        first = second;
        second = tmp;
	// Find the overlap intersection range between first and second
    if (second.location < first.location + first.length) {
        result.location = second.location;
        NSUInteger end = MIN(first.location + first.length, second.location + second.length);
        result.length = end - result.location;
    return result;    
// Helper method for drawing the current selection range (as a simple filled rect)
- (void)drawRangeAsSelection:(NSRange)selectionRange
	// If not in editing mode, we do not draw selection rects
    if (!self.editing)
        return;
    // If selection range empty, do not draw
    if (selectionRange.length == 0 || selectionRange.location == NSNotFound)
        return;
	// set the fill color to the selection color
    [[SimpleCoreTextView selectionColor] setFill];
	// Iterate over the lines in our CTFrame, looking for lines that intersect
	// with the given selection range, and draw a selection rect for each intersection
    NSArray *lines = (NSArray *) CTFrameGetLines(_frame);
    for (int i = 0; i < [lines count]; i++) {
        CTLineRef line = (CTLineRef) [lines objectAtIndex:i];
        CFRange lineRange = CTLineGetStringRange(line);
        NSRange range = NSMakeRange(lineRange.location, lineRange.length);
        NSRange intersection = [self RangeIntersection:range withSecond:selectionRange];
        if (intersection.location != NSNotFound && intersection.length > 0) {
			// The text range for this line intersects our selection range
            CGFloat xStart = CTLineGetOffsetForStringIndex(line, intersection.location, NULL);
            CGFloat xEnd = CTLineGetOffsetForStringIndex(line, intersection.location + intersection.length, NULL);
            CGPoint origin;
			// Get coordinate and bounds information for the intersection text range
            CTFrameGetLineOrigins(_frame, CFRangeMake(i, 0), &origin);
            CGFloat ascent, descent;
            CTLineGetTypographicBounds(line, &ascent, &descent, NULL);
			// Create a rect for the intersection and draw it with selection color
            CGRect selectionRect = CGRectMake(xStart, origin.y - descent, xEnd - xStart, ascent + descent);
            UIRectFill(selectionRect);
// Standard UIView drawRect override that uses Core Text to draw our text contents
- (void)drawRect:(CGRect)rect
    // First draw selection / marked text, then draw text
    [self drawRangeAsSelection:_selectedTextRange];
    [self drawRangeAsSelection:_markedTextRange];
    CTFrameDraw(_frame, UIGraphicsGetCurrentContext());    
// Public method to find the text range index for a given CGPoint
- (NSInteger)closestIndexToPoint:(CGPoint)point
	// Use Core Text to find the text index for a given CGPoint by
	// iterating over the y-origin points for each line, finding the closest
	// line, and finding the closest index within that line.
    NSArray *lines = (NSArray *) CTFrameGetLines(_frame);
    CGPoint origins[lines.count];
    CTFrameGetLineOrigins(_frame, CFRangeMake(0, lines.count), origins);
    for (int i = 0; i < lines.count; i++) {
        if (point.y > origins[i].y) {
			// This line origin is closest to the y-coordinate of our point,
			// now look for the closest string index in this line.
            CTLineRef line = (CTLineRef) [lines objectAtIndex:i];
            return CTLineGetStringIndexForPosition(line, point);
    return  _text.length;
// Public method to determine the CGRect for the insertion point or selection, used
// when creating or updating our SimpleCaretView instance
- (CGRect)caretRectForIndex:(int)index
    NSArray *lines = (NSArray *) CTFrameGetLines(_frame);
    // Special case, no text
    if (_text.length == 0) {
        CGPoint origin = CGPointMake(CGRectGetMinX(self.bounds), CGRectGetMaxY(self.bounds) - self.font.leading);
		// Note: using fabs() for typically negative descender from fonts
        return CGRectMake(origin.x, origin.y - fabs(self.font.descender), 3, self.font.ascender + fabs(self.font.descender));
    // Special case, insertion point at final position in text after newline
    if (index == _text.length && [_text characterAtIndex:(index - 1)] == '\n') {
        CTLineRef line = (CTLineRef) [lines lastObject];
        CFRange range = CTLineGetStringRange(line);
        CGFloat xPos = CTLineGetOffsetForStringIndex(line, range.location, NULL);
        CGPoint origin;
        CGFloat ascent, descent;
        CTLineGetTypographicBounds(line, &ascent, &descent, NULL);
        CTFrameGetLineOrigins(_frame, CFRangeMake(lines.count - 1, 0), &origin); 
		// Place point after last line, including any font leading spacing if applicable
        origin.y -= self.font.leading;
        return CGRectMake(xPos, origin.y - descent, 3, ascent + descent);        
    // Regular case, caret somewhere within our text content range
    for (int i = 0; i < [lines count]; i++) {
        CTLineRef line = (CTLineRef) [lines objectAtIndex:i];
        CFRange range = CTLineGetStringRange(line);
        NSInteger localIndex = index - range.location;
        if (localIndex >= 0 && localIndex <= range.length) {
			// index is in the range for this line
            CGFloat xPos = CTLineGetOffsetForStringIndex(line, index, NULL);
            CGPoint origin;
            CGFloat ascent, descent;
            CTLineGetTypographicBounds(line, &ascent, &descent, NULL);
            CTFrameGetLineOrigins(_frame, CFRangeMake(i, 0), &origin);
			// Make a small "caret" rect at the index position
            return CGRectMake(xPos, origin.y - descent, 3, ascent + descent);
    return CGRectNull;
// Public method to create a rect for a given range in the text contents
// Called by our EditableTextRange to implement the required 
// UITextInput:firstRectForRange method
- (CGRect)firstRectForNSRange:(NSRange)range;
    NSInteger index = range.location;
	// Iterate over our CTLines, looking for the line that encompasses the given range
    NSArray *lines = (NSArray *) CTFrameGetLines(_frame);
    for (int i = 0; i < [lines count]; i++) {
        CTLineRef line = (CTLineRef) [lines objectAtIndex:i];
        CFRange lineRange = CTLineGetStringRange(line);
        NSInteger localIndex = index - lineRange.location;
        if (localIndex >= 0 && localIndex < lineRange.length) {
			// For this sample, we use just the first line that intersects range
            NSInteger finalIndex = MIN(lineRange.location + lineRange.length, range.location + range.length);
			// Create a rect for the given range within this line
            CGFloat xStart = CTLineGetOffsetForStringIndex(line, index, NULL);
            CGFloat xEnd = CTLineGetOffsetForStringIndex(line, finalIndex, NULL);
            CGPoint origin;			
            CTFrameGetLineOrigins(_frame, CFRangeMake(i, 0), &origin);
            CGFloat ascent, descent;
            CTLineGetTypographicBounds(line, &ascent, &descent, NULL);
            return CGRectMake(xStart, origin.y - descent, xEnd - xStart, ascent + descent);
    return CGRectNull;
// Helper method to update caretView when insertion point/selection changes
- (void)selectionChanged
	// If not in editing mode, we don't show the caret
    if (!self.editing) {
        [_caretView removeFromSuperview];
        return;
	// If there is no selection range (always true for this sample), find the
	// insert point rect and create a caretView to draw the caret at this position
    if (self.selectedTextRange.length == 0) {
        _caretView.frame = [self caretRectForIndex:self.selectedTextRange.location];
        if (!_caretView.superview) {
            [self addSubview:_caretView];
            [self setNeedsDisplay];            
        // Set up a timer to "blink" the caret
        [_caretView delayBlink];
    } else {
		// If there is an actual selection, don't draw the insertion caret too
        [_caretView removeFromSuperview];
        [self setNeedsDisplay];
    if (self.markedTextRange.location != NSNotFound) {
        [self setNeedsDisplay];
// markedTextRange property accessor overrides 
- (NSRange)markedTextRange
    return _markedTextRange;
- (void)setMarkedTextRange:(NSRange)range
    _markedTextRange = range;
	// Call selectionChanged to update view if necessary	
    [self selectionChanged];
// selectedTextRange property accessor overrides 
- (NSRange)selectedTextRange
    return _selectedTextRange;
- (void)setSelectedTextRange:(NSRange)range
    _selectedTextRange = range;
	// Call selectionChanged to update view if necessary	
    [self selectionChanged];
// editing property accessor overrides
- (BOOL)isEditing
    return _editing;
- (void)setEditing:(BOOL)editing
    _editing = editing;
	// Call selectionChanged to update view if necessary	
    [self selectionChanged];
// Class method that returns current selection color (note that in this sample,
// the color cannot be changed)
+ (UIColor *)selectionColor
    static UIColor *color = nil;
    if (color == nil) {
        color = [[UIColor alloc] initWithRed:0.25 green:0.50 blue:1.0 alpha:0.50];    
    return color;
// Class method that returns current caret color (note that in this sample,
// the color cannot be changed)
+ (UIColor *)caretColor
    static UIColor *color = nil;
    if (color == nil) {
        color = [[UIColor alloc] initWithRed:0.25 green:0.50 blue:1.0 alpha:1.0];
    return color;
#pragma mark SimpleCaretView implementation
@implementation SimpleCaretView
static const NSTimeInterval InitialBlinkDelay = 0.7;
static const NSTimeInterval BlinkRate = 0.5;
- (id)initWithFrame:(CGRect)frame {
    if ((self = [super initWithFrame:frame])) {
        self.backgroundColor = [SimpleCoreTextView caretColor];
    return self;
// Helper method to toggle hidden state of caret view
- (void)blink
    self.hidden = !self.hidden;
// UIView didMoveToSuperview override to set up blink timers after caret view created in superview
- (void)didMoveToSuperview
    self.hidden = NO;
    if (self.superview) {
        _blinkTimer = [[NSTimer scheduledTimerWithTimeInterval:BlinkRate target:self selector:@selector(blink) userInfo:nil repeats:YES] retain];
        [self delayBlink];
    } else {
        [_blinkTimer invalidate];
        [_blinkTimer release];
        _blinkTimer = nil;        
- (void)dealloc
    [_blinkTimer invalidate];
    [_blinkTimer release];
    [super dealloc];
// Helper method to set an initial blink delay
- (void)delayBlink
    self.hidden = NO;
    [_blinkTimer setFireDate:[NSDate dateWithTimeIntervalSinceNow:InitialBlinkDelay]];
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