Initial implementation of adjustsFontSizeToFit.

Summary: Closes https://github.com/facebook/react-native/pull/4026

Differential Revision: D2678492

Pulled By: nicklockwood

fbshipit-source-id: 0467814f810fee997ac50960ffb1daa74d52acba

Examples/UIExplorer/js/TextExample.ios.js

@@ -29,6 +29,7 @@ var {
   StyleSheet,
   Text,
   View,
+  LayoutAnimation,
 } = ReactNative;
 
 class Entity extends React.Component {
@@ -81,6 +82,86 @@ class AttributeToggler extends React.Component {
   }
 }
 
+var AdjustingFontSize = React.createClass({
+  getInitialState: function() {
+    return {dynamicText:'', shouldRender: true,};
+  },
+  reset: function() {
+    LayoutAnimation.easeInEaseOut();
+    this.setState({
+      shouldRender: false,
+    });
+    setTimeout(()=>{
+      LayoutAnimation.easeInEaseOut();
+      this.setState({
+        dynamicText: '',
+        shouldRender: true,
+      });
+    }, 300);
+  },
+  addText: function() {
+    this.setState({
+      dynamicText: this.state.dynamicText + (Math.floor((Math.random() * 10) % 2) ? ' foo' : ' bar'),
+    });
+  },
+  removeText: function() {
+    this.setState({
+      dynamicText: this.state.dynamicText.slice(0, this.state.dynamicText.length - 4),
+    });
+  },
+  render: function() {
+
+    if (!this.state.shouldRender) {
+      return (<View/>);
+    }
+    return (
+      <View>
+        <Text lineBreakMode="tail" numberOfLines={1} style={{fontSize: 36, marginVertical:6}}>
+          Truncated text is baaaaad.
+        </Text>
+        <Text numberOfLines={1} adjustsFontSizeToFit={true} style={{fontSize: 40, marginVertical:6}}>
+          Shrinking to fit available space is much better!
+        </Text>
+
+        <Text adjustsFontSizeToFit={true} numberOfLines={1} style={{fontSize:30, marginVertical:6}}>
+        {'Add text to me to watch me shrink!' + ' ' + this.state.dynamicText}
+        </Text>
+
+        <Text adjustsFontSizeToFit={true} numberOfLines={4} style={{fontSize:20, marginVertical:6}}>
+        {'Multiline text component shrinking is supported, watch as this reeeeaaaally loooooong teeeeeeext grooooows and then shriiiinks as you add text to me! ioahsdia soady auydoa aoisyd aosdy ' + ' ' + this.state.dynamicText}
+        </Text>
+
+        <Text adjustsFontSizeToFit={true} numberOfLines={1} style={{marginVertical:6}}>
+          <Text style={{fontSize:14}}>
+            {'Differently sized nested elements will shrink together. '}
+          </Text>
+          <Text style={{fontSize:20}}>
+            {'LARGE TEXT! ' + this.state.dynamicText}
+          </Text>
+        </Text>
+
+        <View style={{flexDirection:'row', justifyContent:'space-around', marginTop: 5, marginVertical:6}}>
+          <Text
+            style={{backgroundColor: '#ffaaaa'}}
+            onPress={this.reset}>
+            Reset
+          </Text>
+          <Text
+            style={{backgroundColor: '#aaaaff'}}
+            onPress={this.removeText}>
+            Remove Text
+          </Text>
+          <Text
+            style={{backgroundColor: '#aaffaa'}}
+            onPress={this.addText}>
+            Add Text
+          </Text>
+        </View>
+      </View>
+    );
+  }
+});
+
 exports.title = '<Text>';
 exports.description = 'Base component for rendering styled text.';
 exports.displayName = 'TextExample';
@@ -492,6 +573,11 @@ exports.examples = [
       </View>
     );
   },
+}, {
+  title: 'Dynamic Font Size Adjustment',
+  render: function(): ReactElement<any> {
+    return <AdjustingFontSize />;
+  },
 }];
 
 var styles = StyleSheet.create({

Libraries/Text/RCTShadowText.h

@@ -10,6 +10,14 @@
 #import "RCTShadowView.h"
 #import "RCTTextDecorationLineType.h"
 
+typedef NS_ENUM(NSInteger, RCTSizeComparison)
+{
+  RCTSizeTooLarge,
+  RCTSizeTooSmall,
+  RCTSizeWithinRange,
+};
+
+
 extern NSString *const RCTIsHighlightedAttributeName;
 extern NSString *const RCTReactTagAttributeName;
 
@@ -38,6 +46,8 @@ extern NSString *const RCTReactTagAttributeName;
 @property (nonatomic, assign) CGSize textShadowOffset;
 @property (nonatomic, assign) CGFloat textShadowRadius;
 @property (nonatomic, strong) UIColor *textShadowColor;
+@property (nonatomic, assign) BOOL adjustsFontSizeToFit;
+@property (nonatomic, assign) CGFloat minimumFontScale;
 
 - (void)recomputeText;
 

Libraries/Text/RCTShadowText.m

@@ -24,6 +24,11 @@ NSString *const RCTShadowViewAttributeName = @"RCTShadowViewAttributeName";
 NSString *const RCTIsHighlightedAttributeName = @"IsHighlightedAttributeName";
 NSString *const RCTReactTagAttributeName = @"ReactTagAttributeName";
 
+CGFloat const RCTTextAutoSizeDefaultMinimumFontScale       = 0.5f;
+CGFloat const RCTTextAutoSizeWidthErrorMargin              = 0.05f;
+CGFloat const RCTTextAutoSizeHeightErrorMargin             = 0.025f;
+CGFloat const RCTTextAutoSizeGranularity                   = 0.001f;
+
 @implementation RCTShadowText
 {
   NSTextStorage *_cachedTextStorage;
@@ -37,6 +42,7 @@ static CSSSize RCTMeasure(void *context, float width, CSSMeasureMode widthMode,
 {
   RCTShadowText *shadowText = (__bridge RCTShadowText *)context;
   NSTextStorage *textStorage = [shadowText buildTextStorageForWidth:width widthMode:widthMode];
+  [shadowText calculateTextFrame:textStorage];
   NSLayoutManager *layoutManager = textStorage.layoutManagers.firstObject;
   NSTextContainer *textContainer = layoutManager.textContainers.firstObject;
   CGSize computedSize = [layoutManager usedRectForTextContainer:textContainer].size;
@@ -105,10 +111,13 @@ static CSSSize RCTMeasure(void *context, float width, CSSMeasureMode widthMode,
   UIEdgeInsets padding = self.paddingAsInsets;
   CGFloat width = self.frame.size.width - (padding.left + padding.right);
 
+
   NSNumber *parentTag = [[self reactSuperview] reactTag];
   NSTextStorage *textStorage = [self buildTextStorageForWidth:width widthMode:CSSMeasureModeExactly];
+  CGRect textFrame = [self calculateTextFrame:textStorage];
   [applierBlocks addObject:^(NSDictionary<NSNumber *, UIView *> *viewRegistry) {
     RCTText *view = (RCTText *)viewRegistry[self.reactTag];
+    view.textFrame = textFrame;
     view.textStorage = textStorage;
 
     /**
@@ -452,6 +461,155 @@ static CSSSize RCTMeasure(void *context, float width, CSSMeasureMode widthMode,
   }
 }
 
+#pragma mark Autosizing
+
+- (CGRect)calculateTextFrame:(NSTextStorage *)textStorage
+{
+  CGRect textFrame = UIEdgeInsetsInsetRect((CGRect){CGPointZero, self.frame.size},
+                                           self.paddingAsInsets);
+  
+
+  if (_adjustsFontSizeToFit) {
+    textFrame = [self updateStorage:textStorage toFitFrame:textFrame];
+  }
+
+  return textFrame;
+}
+
+- (CGRect)updateStorage:(NSTextStorage *)textStorage toFitFrame:(CGRect)frame
+{
+
+  BOOL fits = [self attemptScale:1.0f
+                       inStorage:textStorage
+                        forFrame:frame];
+  CGSize requiredSize;
+  if (!fits) {
+    requiredSize = [self calculateOptimumScaleInFrame:frame
+                                           forStorage:textStorage
+                                             minScale:self.minimumFontScale
+                                             maxScale:1.0
+                                              prevMid:INT_MAX];
+  } else {
+    requiredSize = [self calculateSize:textStorage];
+  }
+
+  //Vertically center draw position for new text sizing.
+  frame.origin.y = self.paddingAsInsets.top + RCTRoundPixelValue((CGRectGetHeight(frame) - requiredSize.height) / 2.0f);
+  return frame;
+}
+
+- (CGSize)calculateOptimumScaleInFrame:(CGRect)frame
+                            forStorage:(NSTextStorage *)textStorage
+                              minScale:(CGFloat)minScale
+                              maxScale:(CGFloat)maxScale
+                               prevMid:(CGFloat)prevMid
+{
+  CGFloat midScale = (minScale + maxScale) / 2.0f;
+  if (round((prevMid / RCTTextAutoSizeGranularity)) == round((midScale / RCTTextAutoSizeGranularity))) {
+    //Bail because we can't meet error margin.
+    return [self calculateSize:textStorage];
+  } else {
+    RCTSizeComparison comparison = [self attemptScale:midScale
+                                            inStorage:textStorage
+                                             forFrame:frame];
+    if (comparison == RCTSizeWithinRange) {
+      return [self calculateSize:textStorage];
+    } else if (comparison == RCTSizeTooLarge) {
+      return [self calculateOptimumScaleInFrame:frame
+                                     forStorage:textStorage
+                                       minScale:minScale
+                                       maxScale:midScale - RCTTextAutoSizeGranularity
+                                        prevMid:midScale];
+    } else {
+      return [self calculateOptimumScaleInFrame:frame
+                                     forStorage:textStorage
+                                       minScale:midScale + RCTTextAutoSizeGranularity
+                                       maxScale:maxScale
+                                        prevMid:midScale];
+    }
+  }
+}
+
+- (RCTSizeComparison)attemptScale:(CGFloat)scale
+                        inStorage:(NSTextStorage *)textStorage
+                         forFrame:(CGRect)frame
+{
+  NSLayoutManager *layoutManager = [textStorage.layoutManagers firstObject];
+  NSTextContainer *textContainer = [layoutManager.textContainers firstObject];
+
+  NSRange glyphRange = NSMakeRange(0, textStorage.length);
+  [textStorage beginEditing];
+  [textStorage enumerateAttribute:NSFontAttributeName
+                           inRange:glyphRange
+                           options:0
+                        usingBlock:^(UIFont *font, NSRange range, BOOL *stop)
+   {
+     if (font) {
+       UIFont *originalFont = [self.attributedString attribute:NSFontAttributeName
+                                                       atIndex:range.location
+                                                effectiveRange:&range];
+       UIFont *newFont = [font fontWithSize:originalFont.pointSize * scale];
+       [textStorage removeAttribute:NSFontAttributeName range:range];
+       [textStorage addAttribute:NSFontAttributeName value:newFont range:range];
+     }
+   }];
+
+  [textStorage endEditing];
+
+  NSInteger linesRequired = [self numberOfLinesRequired:[textStorage.layoutManagers firstObject]];
+  CGSize requiredSize = [self calculateSize:textStorage];
+
+  BOOL fitSize = requiredSize.height <= CGRectGetHeight(frame) &&
+  requiredSize.width <= CGRectGetWidth(frame);
+
+  BOOL fitLines = linesRequired <= textContainer.maximumNumberOfLines ||
+  textContainer.maximumNumberOfLines == 0;
+
+  if (fitLines && fitSize) {
+    if ((requiredSize.width + (CGRectGetWidth(frame) * RCTTextAutoSizeWidthErrorMargin)) > CGRectGetWidth(frame) &&
+        (requiredSize.height + (CGRectGetHeight(frame) * RCTTextAutoSizeHeightErrorMargin)) > CGRectGetHeight(frame))
+    {
+      return RCTSizeWithinRange;
+    } else {
+      return RCTSizeTooSmall;
+    }
+  } else {
+    return RCTSizeTooLarge;
+  }
+}
+
+// Via Apple Text Layout Programming Guide
+// https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/TextLayout/Tasks/CountLines.html
+- (NSInteger)numberOfLinesRequired:(NSLayoutManager *)layoutManager
+{
+  NSInteger numberOfLines, index, numberOfGlyphs = [layoutManager numberOfGlyphs];
+  NSRange lineRange;
+  for (numberOfLines = 0, index = 0; index < numberOfGlyphs; numberOfLines++){
+    (void) [layoutManager lineFragmentRectForGlyphAtIndex:index
+                                           effectiveRange:&lineRange];
+    index = NSMaxRange(lineRange);
+  }
+
+  return numberOfLines;
+}
+
+// Via Apple Text Layout Programming Guide
+//https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/TextLayout/Tasks/StringHeight.html
+- (CGSize)calculateSize:(NSTextStorage *)storage
+{
+  NSLayoutManager *layoutManager = [storage.layoutManagers firstObject];
+  NSTextContainer *textContainer = [layoutManager.textContainers firstObject];
+
+  [textContainer setLineBreakMode:NSLineBreakByWordWrapping];
+  NSInteger maxLines = [textContainer maximumNumberOfLines];
+  [textContainer setMaximumNumberOfLines:0];
+  (void) [layoutManager glyphRangeForTextContainer:textContainer];
+  CGSize requiredSize = [layoutManager usedRectForTextContainer:textContainer].size;
+  [textContainer setMaximumNumberOfLines:maxLines];
+
+  return requiredSize;
+}
+
 - (void)setBackgroundColor:(UIColor *)backgroundColor
 {
   super.backgroundColor = backgroundColor;
@@ -465,6 +623,7 @@ static CSSSize RCTMeasure(void *context, float width, CSSMeasureMode widthMode,
   [self dirtyText];                            \
 }
 
+RCT_TEXT_PROPERTY(AdjustsFontSizeToFit, _adjustsFontSizeToFit, BOOL)
 RCT_TEXT_PROPERTY(Color, _color, UIColor *)
 RCT_TEXT_PROPERTY(FontFamily, _fontFamily, NSString *)
 RCT_TEXT_PROPERTY(FontSize, _fontSize, CGFloat)
@@ -512,4 +671,12 @@ RCT_TEXT_PROPERTY(TextShadowColor, _textShadowColor, UIColor *);
   [self dirtyText];
 }
 
+- (void)setMinimumFontScale:(CGFloat)minimumFontScale
+{
+  if (minimumFontScale >= 0.01) {
+    _minimumFontScale = minimumFontScale;
+  }
+  [self dirtyText];
+}
+
 @end

Libraries/Text/RCTText.h

@@ -13,5 +13,7 @@
 
 @property (nonatomic, assign) UIEdgeInsets contentInset;
 @property (nonatomic, strong) NSTextStorage *textStorage;
+@property (nonatomic, assign) CGRect textFrame;
+
 
 @end

Libraries/Text/RCTText.m

@@ -34,7 +34,6 @@ static void collectNonTextDescendants(RCTText *view, NSMutableArray *nonTextDesc
 {
   if ((self = [super initWithFrame:frame])) {
     _textStorage = [NSTextStorage new];
-
     self.isAccessibilityElement = YES;
     self.accessibilityTraits |= UIAccessibilityTraitStaticText;
 
@@ -97,11 +96,11 @@ static void collectNonTextDescendants(RCTText *view, NSMutableArray *nonTextDesc
 
 - (void)drawRect:(CGRect)rect
 {
-  NSLayoutManager *layoutManager = _textStorage.layoutManagers.firstObject;
+  NSLayoutManager *layoutManager = [_textStorage.layoutManagers firstObject];
-  NSTextContainer *textContainer = layoutManager.textContainers.firstObject;
+  NSTextContainer *textContainer = [layoutManager.textContainers firstObject];
-  CGRect textFrame = UIEdgeInsetsInsetRect(self.bounds, _contentInset);
-  NSRange glyphRange = [layoutManager glyphRangeForTextContainer:textContainer];
 
+  NSRange glyphRange = [layoutManager glyphRangeForTextContainer:textContainer];
+  CGRect textFrame = self.textFrame;
   [layoutManager drawBackgroundForGlyphRange:glyphRange atPoint:textFrame.origin];
   [layoutManager drawGlyphsForGlyphRange:glyphRange atPoint:textFrame.origin];
 
@@ -170,6 +169,7 @@ static void collectNonTextDescendants(RCTText *view, NSMutableArray *nonTextDesc
   }
 }
 
+
 #pragma mark - Accessibility
 
 - (NSString *)accessibilityLabel

Libraries/Text/RCTTextManager.m

@@ -76,6 +76,8 @@ RCT_EXPORT_SHADOW_PROPERTY(opacity, CGFloat)
 RCT_EXPORT_SHADOW_PROPERTY(textShadowOffset, CGSize)
 RCT_EXPORT_SHADOW_PROPERTY(textShadowRadius, CGFloat)
 RCT_EXPORT_SHADOW_PROPERTY(textShadowColor, UIColor)
+RCT_EXPORT_SHADOW_PROPERTY(adjustsFontSizeToFit, BOOL)
+RCT_EXPORT_SHADOW_PROPERTY(minimumFontScale, CGFloat)
 
 - (RCTViewManagerUIBlock)uiBlockToAmendWithShadowViewRegistry:(NSDictionary<NSNumber *, RCTShadowView *> *)shadowViewRegistry
 {

Libraries/Text/Text.js

@@ -32,6 +32,8 @@ const viewConfig = {
     ellipsizeMode: true,
     allowFontScaling: true,
     selectable: true,
+    adjustsFontSizeToFit: true,
+    minimumFontScale: true,
   }),
   uiViewClassName: 'RCTText',
 };
@@ -166,7 +168,18 @@ const Text = React.createClass({
      * [Accessibility guide](/react-native/docs/accessibility.html#accessible-ios-android)
      * for more information.
      */
-     accessible: React.PropTypes.bool,
+    accessible: React.PropTypes.bool,
+    /**
+     * Specifies whether font should be scaled down automatically to fit given style constraints.
+     * @platform ios
+     */
+    adjustsFontSizeToFit: React.PropTypes.bool,
+
+    /**
+     * Specifies smallest possible scale a font can reach when adjustsFontSizeToFit is enabled. (values 0.01-1.0).
+     * @platform ios
+     */
+    minimumFontScale: React.PropTypes.number,
   },
   getDefaultProps(): Object {
     return {