add ASTextKitFontSizeAdjuster

AsyncDisplayKit/TextKit/ASTextKitFontSizeAdjuster.m

@@ -0,0 +1,100 @@
+//
+//  ASTextKitFontSizeAdjuster.m
+//  AsyncDisplayKit
+//
+//  Created by Luke on 1/20/16.
+//  Copyright © 2016 Facebook. All rights reserved.
+//
+
+#import "ASTextKitContext.h"
+#import "ASTextKitFontSizeAdjuster.h"
+
+@implementation ASTextKitFontSizeAdjuster
+{
+  __weak ASTextKitContext *_context;
+  CGFloat _minimumScaleFactor;
+  CGSize _constrainedSize;
+}
+
+- (instancetype)initWithContext:(ASTextKitContext *)context
+             minimumScaleFactor:(CGFloat)minimumScaleFactor
+                constrainedSize:(CGSize)constrainedSize
+{
+  if (self = [super init]) {
+    _context = context;
+    _minimumScaleFactor = minimumScaleFactor;
+    _constrainedSize = constrainedSize;
+  }
+  return self;
+}
+
+
+- (CGSize)sizeForAttributedString:(NSAttributedString *)attrString
+{
+  return [attrString boundingRectWithSize:CGSizeMake(CGFLOAT_MAX, CGFLOAT_MAX)
+                                  options:NSStringDrawingUsesLineFragmentOrigin
+                                  context:nil].size;
+}
+
+
+- (void) adjustFontSizeForAttributeString:(NSMutableAttributedString *)attrString withScaleFactor:(CGFloat)scaleFactor
+{
+  {
+    [attrString beginEditing];
+
+    [attrString enumerateAttribute:NSFontAttributeName inRange:NSMakeRange(0, attrString.length) options:0 usingBlock:^(id value, NSRange range, BOOL *stop) {
+
+      UIFont* font = value;
+      font = [font fontWithSize:font.pointSize * scaleFactor];
+
+      [attrString removeAttribute:NSFontAttributeName range:range];
+      [attrString addAttribute:NSFontAttributeName value:font range:range];
+    }];
+
+    [attrString endEditing];
+  }
+}
+
+
+- (void)adjustFontSize
+{
+  if (_minimumScaleFactor <= 0 || _minimumScaleFactor >= 1) {
+    return;
+  }
+  [_context performBlockWithLockedTextKitComponents:^(NSLayoutManager *layoutManager, NSTextStorage *textStorage, NSTextContainer *textContainer) {
+    NSString *str = textStorage.string;
+    NSArray *words = [str componentsSeparatedByCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
+    NSString *longestWordNeedingResize = @"";
+    for (NSString *word in words) {
+      if ([word length] > [longestWordNeedingResize length]) {
+        longestWordNeedingResize = word;
+      }
+    }
+
+    if ([longestWordNeedingResize length] == 0) {
+      return;
+    }
+
+    NSRange range = [str rangeOfString:longestWordNeedingResize];
+    NSMutableAttributedString *attrString = [textStorage attributedSubstringFromRange:range].mutableCopy;
+    CGSize defaultSize = [self sizeForAttributedString:attrString];
+
+    if (defaultSize.width > _constrainedSize.width) {
+      [attrString removeAttribute:NSParagraphStyleAttributeName range:NSMakeRange(0, [attrString length])];
+      NSStringDrawingContext *context = [[NSStringDrawingContext alloc] init];
+      context.minimumScaleFactor = _minimumScaleFactor;
+      [attrString boundingRectWithSize:CGSizeMake(_constrainedSize.width, defaultSize.height)
+                               options:NSStringDrawingUsesLineFragmentOrigin
+                               context:context];
+
+      [self adjustFontSizeForAttributeString:attrString withScaleFactor:context.actualScaleFactor];
+
+      if ([self sizeForAttributedString:attrString].width <= _constrainedSize.width) {
+        [self adjustFontSizeForAttributeString:textStorage withScaleFactor:context.actualScaleFactor];
+        NSLog(@"ASTextKitFontSizeAdjuster : adjusted \"%@\"to fontsize actualScaleFactor:%f", longestWordNeedingResize, context.actualScaleFactor);
+      }
+    }
+  }];
+}
+
+@end