How to adjust font size of label to fit the rectangle?
I found Niels' answer to be the best answer for this issue. However, I have a UIView that can have 100 labels where I need to fit the text, so this process was very inefficient and I could feel the hit in performance.
Here is his code modified to use a binary search instead, rather than a linear search. Now it works very efficiently.
- (NSInteger)binarySearchForFontSizeForLabel:(UILabel *)label withMinFontSize:(NSInteger)minFontSize withMaxFontSize:(NSInteger)maxFontSize withSize:(CGSize)size {
// If the sizes are incorrect, return 0, or error, or an assertion.
if (maxFontSize < minFontSize) {
return 0;
}
// Find the middle
NSInteger fontSize = (minFontSize + maxFontSize) / 2;
// Create the font
UIFont *font = [UIFont fontWithName:label.font.fontName size:fontSize];
// Create a constraint size with max height
CGSize constraintSize = CGSizeMake(size.width, MAXFLOAT);
// Find label size for current font size
CGRect rect = [label.text boundingRectWithSize:constraintSize
options:NSStringDrawingUsesLineFragmentOrigin
attributes:@{NSFontAttributeName : font}
context:nil];
CGSize labelSize = rect.size;
// EDIT: The next block is modified from the original answer posted in SO to consider the width in the decision. This works much better for certain labels that are too thin and were giving bad results.
if (labelSize.height >= (size.height + 10) && labelSize.width >= (size.width + 10) && labelSize.height <= (size.height) && labelSize.width <= (size.width)) {
return fontSize;
} else if (labelSize.height > size.height || labelSize.width > size.width) {
return [self binarySearchForFontSizeForLabel:label withMinFontSize:minFontSize withMaxFontSize:fontSize - 1 withSize:size];
} else {
return [self binarySearchForFontSizeForLabel:label withMinFontSize:fontSize + 1 withMaxFontSize:maxFontSize withSize:size];
}
}
- (void)sizeBinaryLabel:(UILabel *)label toRect:(CGRect)labelRect {
// Set the frame of the label to the targeted rectangle
label.frame = labelRect;
// Try all font sizes from largest to smallest font
int maxFontSize = 300;
int minFontSize = 5;
NSInteger size = [self binarySearchForFontSizeForLabel:label withMinFontSize:minFontSize withMaxFontSize:maxFontSize withSize:label.frame.size];
label.font = [UIFont fontWithName:label.font.fontName size:size];
}
Credit goes also to https://gist.github.com/988219
If you want to make sure the label fits in the rectangle both width and height wise you can try different font size on the label to see if one will fit.
This snippet starts at 300 pt and tries to fit the label in the targeted rectangle by reducing the font size.
- (void) sizeLabel: (UILabel *) label toRect: (CGRect) labelRect {
// Set the frame of the label to the targeted rectangle
label.frame = labelRect;
// Try all font sizes from largest to smallest font size
int fontSize = 300;
int minFontSize = 5;
// Fit label width wize
CGSize constraintSize = CGSizeMake(label.frame.size.width, MAXFLOAT);
do {
// Set current font size
label.font = [UIFont fontWithName:label.font.fontName size:fontSize];
// Find label size for current font size
CGRect textRect = [[label text] boundingRectWithSize:constraintSize
options:NSStringDrawingUsesLineFragmentOrigin
attributes:@{NSFontAttributeName: label.font}
context:nil];
CGSize labelSize = textRect.size;
// Done, if created label is within target size
if( labelSize.height <= label.frame.size.height )
break;
// Decrease the font size and try again
fontSize -= 2;
} while (fontSize > minFontSize);
}
I think the above explains what goes on. A faster implementation could use caching and argarcians binary search as follows
+ (CGFloat) fontSizeForString: (NSString*) s inRect: (CGRect) labelRect {
// Cache repeat queries
static NSMutableDictionary* mutableDict = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
mutableDict = [NSMutableDictionary dictionary];
});
NSString* key = [NSString stringWithFormat:@"%@_%d_%d", s, (int) labelRect.size.width, (int) labelRect.size.height];
NSNumber* value = [mutableDict objectForKey:key];
if (value)
return value.doubleValue;
// Set the frame of the label to the targeted rectangle
UILabel* label = [[UILabel alloc] init];
label.text = s;
label.frame = labelRect;
// Hopefully between 5 and 300
CGFloat theSize = (CGFloat) [self binarySearchForFontSizeForLabel:label withMinFontSize:5 withMaxFontSize:300 withSize:label.frame.size];
[mutableDict setObject:@(theSize) forKey:key];
return theSize;
}
+ (NSInteger)binarySearchForFontSizeForLabel:(UILabel *)label withMinFontSize:(NSInteger)minFontSize withMaxFontSize:(NSInteger)maxFontSize withSize:(CGSize)size {
// If the sizes are incorrect, return 0, or error, or an assertion.
if (maxFontSize < minFontSize) {
return maxFontSize;
}
// Find the middle
NSInteger fontSize = (minFontSize + maxFontSize) / 2;
// Create the font
UIFont *font = [UIFont fontWithName:label.font.fontName size:fontSize];
// Create a constraint size with max height
CGSize constraintSize = CGSizeMake(size.width, MAXFLOAT);
// Find label size for current font size
CGRect rect = [label.text boundingRectWithSize:constraintSize
options:NSStringDrawingUsesLineFragmentOrigin
attributes:@{NSFontAttributeName : font}
context:nil];
CGSize labelSize = rect.size;
// EDIT: The next block is modified from the original answer posted in SO to consider the width in the decision. This works much better for certain labels that are too thin and were giving bad results.
if (labelSize.height >= (size.height + 10) && labelSize.width >= (size.width + 10) && labelSize.height <= (size.height) && labelSize.width <= (size.width)) {
return fontSize;
} else if (labelSize.height > size.height || labelSize.width > size.width) {
return [self binarySearchForFontSizeForLabel:label withMinFontSize:minFontSize withMaxFontSize:fontSize - 1 withSize:size];
} else {
return [self binarySearchForFontSizeForLabel:label withMinFontSize:fontSize + 1 withMaxFontSize:maxFontSize withSize:size];
}
}
Here's Swift version according to @NielsCastle answer, using binary search
extension UILabel{
func adjustFontSizeToFitRect(rect : CGRect){
if text == nil{
return
}
frame = rect
let maxFontSize: CGFloat = 100.0
let minFontSize: CGFloat = 5.0
var q = Int(maxFontSize)
var p = Int(minFontSize)
let constraintSize = CGSize(width: rect.width, height: CGFloat.max)
while(p <= q){
let currentSize = (p + q) / 2
font = font.fontWithSize( CGFloat(currentSize) )
let text = NSAttributedString(string: self.text!, attributes: [NSFontAttributeName:font])
let textRect = text.boundingRectWithSize(constraintSize, options: .UsesLineFragmentOrigin, context: nil)
let labelSize = textRect.size
if labelSize.height < frame.height && labelSize.height >= frame.height-10 && labelSize.width < frame.width && labelSize.width >= frame.width-10 {
break
}else if labelSize.height > frame.height || labelSize.width > frame.width{
q = currentSize - 1
}else{
p = currentSize + 1
}
}
}
}
Usage
label.adjustFontSizeToFitRect(rect)
often just
label.adjustFontSizeToFitRect(rect.frame)