Implement minimumFontScale, match ios behavior

Author: janicduplessis

ReactAndroid/src/main/java/com/facebook/react/uimanager/ViewProps.java

@@ -89,6 +89,7 @@ public class ViewProps {
   public static final String NUMBER_OF_LINES = "numberOfLines";
   public static final String ELLIPSIZE_MODE = "ellipsizeMode";
   public static final String ADJUSTS_FONT_SIZE_TO_FIT = "adjustsFontSizeToFit";
+  public static final String MINIMUM_FONT_SCALE = "minimumFontScale";
   public static final String ON = "on";
   public static final String RESIZE_MODE = "resizeMode";
   public static final String RESIZE_METHOD = "resizeMethod";

ReactAndroid/src/main/java/com/facebook/react/views/text/ReactBaseTextShadowNode.java

@@ -342,6 +342,7 @@ private static int parseNumericFontWeight(String fontWeightString) {
   protected boolean mIsLineThroughTextDecorationSet = false;
   protected boolean mIncludeFontPadding = true;
   protected boolean mAdjustsFontSizeToFit = false;
+  protected float mMinimumFontScale = 0;
 
   /**
    * mFontStyle can be {@link Typeface#NORMAL} or {@link Typeface#ITALIC}. mFontWeight can be {@link
@@ -630,4 +631,12 @@ public void setAdjustFontSizeToFit(boolean adjustsFontSizeToFit) {
       markUpdated();
     }
   }
+
+  @ReactProp(name = ViewProps.MINIMUM_FONT_SCALE)
+  public void setMinimumFontScale(float minimumFontScale) {
+    if (minimumFontScale != mMinimumFontScale) {
+      mMinimumFontScale = minimumFontScale;
+      markUpdated();
+    }
+  }
 }

ReactAndroid/src/main/java/com/facebook/react/views/text/ReactTextShadowNode.java

@@ -22,6 +22,7 @@
 import com.facebook.react.bridge.WritableArray;
 import com.facebook.react.bridge.WritableMap;
 import com.facebook.react.uimanager.NativeViewHierarchyOptimizer;
+import com.facebook.react.uimanager.PixelUtil;
 import com.facebook.react.uimanager.ReactShadowNode;
 import com.facebook.react.uimanager.Spacing;
 import com.facebook.react.uimanager.UIViewOperationQueue;
@@ -161,14 +162,24 @@ public long measure(
           Layout layout = measureSpannedText(text, width, widthMode);
 
           if (mAdjustsFontSizeToFit) {
+            int initialFontSize = mTextAttributes.getEffectiveFontSize();
+            int currentFontSize = mTextAttributes.getEffectiveFontSize();
+            // Minimum font size is 4pts to match the iOS implementation.
+            int minimumFontSize = (int) Math.max(mMinimumFontScale * initialFontSize, PixelUtil.toPixelFromDIP(4));
             while (
-              mNumberOfLines != UNSET && layout.getLineCount() > mNumberOfLines ||
-              heightMode != YogaMeasureMode.UNDEFINED && layout.getHeight() > height
+              currentFontSize > minimumFontSize && (
+                mNumberOfLines != UNSET && layout.getLineCount() > mNumberOfLines ||
+                heightMode != YogaMeasureMode.UNDEFINED && layout.getHeight() > height)
             ) {
+              // TODO: We could probably use a smarter algorithm here. This will require 0(n) measurements
+              // based on the number of points the font size needs to be reduced by.
+              currentFontSize = currentFontSize - (int) PixelUtil.toPixelFromDIP(1);
+
+              float ratio = (float) currentFontSize / (float) initialFontSize;
               ReactAbsoluteSizeSpan[] sizeSpans = text.getSpans(0, text.length(), ReactAbsoluteSizeSpan.class);
               for (ReactAbsoluteSizeSpan span : sizeSpans) {
                 text.setSpan(
-                    new ReactAbsoluteSizeSpan(span.getSize() - 1),
+                    new ReactAbsoluteSizeSpan((int) Math.max((span.getSize() * ratio), minimumFontSize)),
                     text.getSpanStart(span),
                     text.getSpanEnd(span),
                     text.getSpanFlags(span));

ReactAndroid/src/main/java/com/facebook/react/views/text/ReactTextView.java

@@ -48,7 +48,7 @@ public class ReactTextView extends AppCompatTextView implements ReactCompoundVie
   private int mTextAlign = Gravity.NO_GRAVITY;
   private int mNumberOfLines = ViewDefaults.NUMBER_OF_LINES;
   private TextUtils.TruncateAt mEllipsizeLocation = TextUtils.TruncateAt.END;
-  private boolean mAdjustsFontSizeToFit;
+  private boolean mAdjustsFontSizeToFit = false;
   private int mLinkifyMaskType = 0;
   private boolean mNotifyOnInlineViewLayout;