[Android] Attempt to fix text-anchor subtree advance/extent calculation

Related to
https://github.com/react-native-community/react-native-svg/issues/600
https://github.com/react-native-community/react-native-svg/issues/570

android/src/main/java/com/horcrux/svg/TSpanView.java

@@ -21,6 +21,7 @@ import android.graphics.Rect;
 import android.graphics.RectF;
 import android.graphics.Typeface;
 import android.os.Build;
+import android.view.View;
 import android.view.ViewParent;
 
 import com.facebook.react.bridge.ReactContext;
@@ -106,6 +107,50 @@ class TSpanView extends TextView {
         return mPath;
     }
 
+    double getSubtreeTextChunksTotalAdvance(Paint paint) {
+        double advance = 0;
+
+        if (mContent == null) {
+            for (int i = 0; i < getChildCount(); i++) {
+                View child = getChildAt(i);
+                if (child instanceof TextView) {
+                    TextView text = (TextView)child;
+                    advance += text.getSubtreeTextChunksTotalAdvance(paint);
+                }
+            }
+            return advance;
+        }
+
+        String line = mContent;
+        final int length = line.length();
+
+        if (length == 0) {
+            return advance;
+        }
+
+        GlyphContext gc = getTextRootGlyphContext();
+        FontData font = gc.getFont();
+        applyTextPropertiesToPaint(paint, font);
+
+        double letterSpacing = font.letterSpacing;
+        final boolean allowOptionalLigatures = letterSpacing == 0 &&
+                font.fontVariantLigatures == FontVariantLigatures.normal;
+
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+            String required = "'rlig', 'liga', 'clig', 'calt', 'locl', 'ccmp', 'mark', 'mkmk',";
+            String defaultFeatures = required + "'kern', ";
+            if (allowOptionalLigatures) {
+                String additionalLigatures = "'hlig', 'cala', ";
+                paint.setFontFeatureSettings(defaultFeatures + additionalLigatures + font.fontFeatureSettings);
+            } else {
+                String disableDiscretionaryLigatures = "'liga' 0, 'clig' 0, 'dlig' 0, 'hlig' 0, 'cala' 0, ";
+                paint.setFontFeatureSettings(defaultFeatures + disableDiscretionaryLigatures + font.fontFeatureSettings);
+            }
+        }
+
+        return paint.measureText(line);
+    }
+
     @SuppressWarnings("ConstantConditions")
     private Path getLinePath(String line, Paint paint, Canvas canvas) {
         final int length = line.length();
@@ -311,8 +356,10 @@ class TSpanView extends TextView {
             attributes, such as a ‘dx’ attribute value on a ‘tspan’ element.
          */
         final TextAnchor textAnchor = font.textAnchor;
-        final double textMeasure = paint.measureText(line);
+        TextView anchorRoot = getTextAnchorRoot();
+        final double textMeasure = anchorRoot.getSubtreeTextChunksTotalAdvance(paint);
         double offset = getTextAnchorOffset(textAnchor, textMeasure);
+        applyTextPropertiesToPaint(paint, font);
 
         int side = 1;
         double startOfRendering = 0;

android/src/main/java/com/horcrux/svg/TextView.java

@@ -14,6 +14,7 @@ import android.graphics.Canvas;
 import android.graphics.Paint;
 import android.graphics.Path;
 import android.graphics.Region;
+import android.view.View;
 import android.view.ViewParent;
 
 import com.facebook.react.bridge.Dynamic;
@@ -38,6 +39,7 @@ class TextView extends GroupView {
     @Nullable ArrayList<SVGLength> mRotate;
     @Nullable ArrayList<SVGLength> mDeltaX;
     @Nullable ArrayList<SVGLength> mDeltaY;
+    double cachedAdvance = Double.NaN;
 
     public TextView(ReactContext reactContext) {
         super(reactContext);
@@ -48,6 +50,7 @@ class TextView extends GroupView {
         if (mPath == null) {
             return;
         }
+        cachedAdvance = Double.NaN;
         super.invalidate();
         clearChildCache();
     }
@@ -207,4 +210,42 @@ class TextView extends GroupView {
         boolean isTextNode = !(this instanceof TextPathView) && !(this instanceof TSpanView);
         getTextRootGlyphContext().pushContext(isTextNode, this, mFont, mPositionX, mPositionY, mDeltaX, mDeltaY, mRotate);
     }
+
+    TextView getTextAnchorRoot() {
+        GlyphContext gc = getTextRootGlyphContext();
+        FontData font = gc.getFont();
+        TextProperties.TextAnchor textAnchor = font.textAnchor;
+        if (textAnchor == TextProperties.TextAnchor.start) {
+            return this;
+        }
+        ViewParent parent = this.getParent();
+        if (parent instanceof TextView) {
+            TextView parentText = (TextView)parent;
+            GlyphContext parentGc = parentText.getGlyphContext();
+            FontData parentFont = parentGc.getFont();
+            if (parentFont.textAnchor == TextProperties.TextAnchor.start) {
+                return this;
+            } else {
+                return parentText.getTextAnchorRoot();
+            }
+        }
+        return this;
+    }
+
+    double getSubtreeTextChunksTotalAdvance(Paint paint) {
+        if (!Double.isNaN(cachedAdvance)) {
+            return cachedAdvance;
+        }
+        double advance = 0;
+        for (int i = 0; i < getChildCount(); i++) {
+            View child = getChildAt(i);
+            if (child instanceof TextView) {
+                TextView text = (TextView)child;
+                advance += text.getSubtreeTextChunksTotalAdvance(paint);
+            }
+        }
+        cachedAdvance = advance;
+        return advance;
+    }
+
 }