`base-line` metric exposure for <TextInput>

Summary:
Now <TextInput> (both bersions) exposes base-line metric to Yoga.
Before:
https://cl.ly/0G1Q29450O0y
After:
https://cl.ly/2X103V3O0322

Reviewed By: yungsters

Differential Revision: D6957054

fbshipit-source-id: d76d96f56720d710a4230c53beafdb0b2521e8a9

Libraries/Text/TextInput/RCTBaseTextInputShadowView.m

@@ -37,6 +37,7 @@
     _needsUpdateView = YES;
 
     YGNodeSetMeasureFunc(self.yogaNode, RCTBaseTextInputShadowViewMeasure);
+    YGNodeSetBaselineFunc(self.yogaNode, RCTTextInputShadowViewBaseline);
   }
 
   return self;
@@ -167,7 +168,7 @@
 
 #pragma mark -
 
-- (CGSize)sizeThatFitsMinimumSize:(CGSize)minimumSize maximumSize:(CGSize)maximumSize
+- (NSAttributedString *)measurableAttributedText
 {
   // Only for the very first render when we don't have `_localAttributedText`,
   // we use value directly from the property and/or nested content.
@@ -187,6 +188,13 @@
     attributedText = [[NSAttributedString alloc] initWithString:text attributes:self.textAttributes.effectiveTextAttributes];
   }
 
+  return attributedText;
+}
+
+- (CGSize)sizeThatFitsMinimumSize:(CGSize)minimumSize maximumSize:(CGSize)maximumSize
+{
+  NSAttributedString *attributedText = [self measurableAttributedText];
+
   if (!_textStorage) {
     _textContainer = [NSTextContainer new];
     _textContainer.lineFragmentPadding = 0.0; // Note, the default value is 5.
@@ -209,6 +217,26 @@
   };
 }
 
+- (CGFloat)lastBaselineForSize:(CGSize)size
+{
+  NSAttributedString *attributedText = [self measurableAttributedText];
+
+  __block CGFloat maximumDescender = 0.0;
+
+  [attributedText enumerateAttribute:NSFontAttributeName
+                             inRange:NSMakeRange(0, attributedText.length)
+                             options:NSAttributedStringEnumerationLongestEffectiveRangeNotRequired
+                          usingBlock:
+    ^(UIFont *font, NSRange range, __unused BOOL *stop) {
+      if (maximumDescender > font.descender) {
+        maximumDescender = font.descender;
+      }
+    }
+  ];
+
+  return size.height + maximumDescender;
+}
+
 static YGSize RCTBaseTextInputShadowViewMeasure(YGNodeRef node, float width, YGMeasureMode widthMode, float height, YGMeasureMode heightMode)
 {
   RCTShadowView *shadowView = (__bridge RCTShadowView *)YGNodeGetContext(node);
@@ -253,4 +281,18 @@ static YGSize RCTBaseTextInputShadowViewMeasure(YGNodeRef node, float width, YGM
   };
 }
 
+static float RCTTextInputShadowViewBaseline(YGNodeRef node, const float width, const float height)
+{
+  RCTBaseTextInputShadowView *shadowTextView = (__bridge RCTBaseTextInputShadowView *)YGNodeGetContext(node);
+
+  CGSize size = (CGSize){
+    RCTCoreGraphicsFloatFromYogaFloat(width),
+    RCTCoreGraphicsFloatFromYogaFloat(height)
+  };
+
+  CGFloat lastBaseline = [shadowTextView lastBaselineForSize:size];
+
+  return RCTYogaFloatFromCoreGraphicsFloat(lastBaseline);
+}
+
 @end