Add support for shadows to RCTVirtualText

Summary: React provides properties to support shadows for Text, this diff implements it for Nodes.

Reviewed By: ahmedre

Differential Revision: D2817212

ReactAndroid/src/main/java/com/facebook/react/flat/RCTVirtualText.java

@@ -16,6 +16,7 @@ import android.text.Spannable;
 import android.text.SpannableStringBuilder;
 import android.text.TextUtils;
 
+import com.facebook.react.bridge.ReadableMap;
 import com.facebook.react.uimanager.PixelUtil;
 import com.facebook.react.uimanager.annotations.ReactProp;
 import com.facebook.react.uimanager.ViewProps;
@@ -29,7 +30,13 @@ import com.facebook.react.uimanager.ViewProps;
   private static final String ITALIC = "italic";
   private static final String NORMAL = "normal";
 
+  private static final String PROP_SHADOW_OFFSET = "textShadowOffset";
+  private static final String PROP_SHADOW_RADIUS = "textShadowRadius";
+  private static final String PROP_SHADOW_COLOR = "textShadowColor";
+  private static final int DEFAULT_TEXT_SHADOW_COLOR = 0x55000000;
+
   private FontStylingSpan mFontStylingSpan = FontStylingSpan.INSTANCE;
+  private ShadowStyleSpan mShadowStyleSpan = ShadowStyleSpan.INSTANCE;
 
   @Override
   protected void performCollectText(SpannableStringBuilder builder) {
@@ -49,6 +56,16 @@ import com.facebook.react.uimanager.ViewProps;
         end,
         Spannable.SPAN_INCLUSIVE_EXCLUSIVE);
 
+    if (mShadowStyleSpan.getColor() != 0 && mShadowStyleSpan.getRadius() != 0) {
+      mShadowStyleSpan.freeze();
+
+      builder.setSpan(
+          mShadowStyleSpan,
+          begin,
+          end,
+          Spannable.SPAN_INCLUSIVE_EXCLUSIVE);
+    }
+
     for (int i = 0, childCount = getChildCount(); i < childCount; ++i) {
       FlatTextShadowNode child = (FlatTextShadowNode) getChildAt(i);
       child.applySpans(builder);
@@ -156,6 +173,42 @@ import com.facebook.react.uimanager.ViewProps;
     }
   }
 
+  @ReactProp(name = PROP_SHADOW_OFFSET)
+  public void setTextShadowOffset(@Nullable ReadableMap offsetMap) {
+    float dx = 0;
+    float dy = 0;
+    if (offsetMap != null) {
+      if (offsetMap.hasKey("width")) {
+        dx = PixelUtil.toPixelFromDIP(offsetMap.getDouble("width"));
+      }
+      if (offsetMap.hasKey("height")) {
+        dy = PixelUtil.toPixelFromDIP(offsetMap.getDouble("height"));
+      }
+    }
+
+    if (!mShadowStyleSpan.offsetMatches(dx, dy)) {
+      getShadowSpan().setOffset(dx, dy);
+      notifyChanged(false);
+    }
+  }
+
+  @ReactProp(name = PROP_SHADOW_RADIUS)
+  public void setTextShadowRadius(float textShadowRadius) {
+    textShadowRadius = PixelUtil.toPixelFromDIP(textShadowRadius);
+    if (mShadowStyleSpan.getRadius() != textShadowRadius) {
+      getShadowSpan().setRadius(textShadowRadius);
+      notifyChanged(false);
+    }
+  }
+
+  @ReactProp(name = PROP_SHADOW_COLOR, defaultInt = DEFAULT_TEXT_SHADOW_COLOR, customType = "Color")
+  public void setTextShadowColor(int textShadowColor) {
+    if (mShadowStyleSpan.getColor() != textShadowColor) {
+      getShadowSpan().setColor(textShadowColor);
+      notifyChanged(false);
+    }
+  }
+
   /**
    * Returns font size for this node.
    * When called on RCTText, this value is never -1 (unset).
@@ -179,6 +232,13 @@ import com.facebook.react.uimanager.ViewProps;
     return mFontStylingSpan;
   }
 
+  private final ShadowStyleSpan getShadowSpan() {
+    if (mShadowStyleSpan.isFrozen()) {
+      mShadowStyleSpan = mShadowStyleSpan.mutableCopy();
+    }
+    return mShadowStyleSpan;
+  }
+
   /**
    * Return -1 if the input string is not a valid numeric fontWeight (100, 200, ..., 900), otherwise
    * return the weight.

ReactAndroid/src/main/java/com/facebook/react/flat/ShadowStyleSpan.java

@@ -0,0 +1,74 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+package com.facebook.react.flat;
+
+import android.text.TextPaint;
+import android.text.style.CharacterStyle;
+
+/* package */ final class ShadowStyleSpan extends CharacterStyle {
+
+  /* package */ static final ShadowStyleSpan INSTANCE = new ShadowStyleSpan(0, 0, 0, 0, true);
+
+  private float mDx;
+  private float mDy;
+  private float mRadius;
+  private int mColor;
+  private boolean mFrozen;
+
+  private ShadowStyleSpan(float dx, float dy, float radius, int color, boolean frozen) {
+    mDx = dx;
+    mDy = dy;
+    mRadius = radius;
+    mColor = color;
+    mFrozen = frozen;
+  }
+
+  public boolean offsetMatches(float dx, float dy) {
+    return mDx == dx && mDy == dy;
+  }
+
+  public void setOffset(float dx, float dy) {
+    mDx = dx;
+    mDy = dy;
+  }
+
+  public float getRadius() {
+    return mRadius;
+  }
+
+  public void setRadius(float radius) {
+    mRadius = radius;
+  }
+
+  public int getColor() {
+    return mColor;
+  }
+
+  public void setColor(int color) {
+    mColor = color;
+  }
+
+  /* package */ ShadowStyleSpan mutableCopy() {
+    return new ShadowStyleSpan(mDx, mDy, mRadius, mColor, false);
+  }
+
+  /* package */ boolean isFrozen() {
+    return mFrozen;
+  }
+
+  /* package */ void freeze() {
+    mFrozen = true;
+  }
+
+  @Override
+  public void updateDrawState(TextPaint textPaint) {
+    textPaint.setShadowLayer(mRadius, mDx, mDy, mColor);
+  }
+}