Improve Text on a path layout rules conformance.

Correct glyph point and delta x / y calculation and context handling.
Remove incorrect whitespace from getLinePath method call.
Correct the y coordinate of the text's origin when rendering glyphs into paths using getTextPath.
Remove strange postTranslate transform.

https://www.w3.org/TR/SVG11/text.html#TextOnAPath

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

@@ -25,6 +25,7 @@ public class GlyphContext {
 
     private ArrayList<ReadableMap> mFontContext;
     private ArrayList<PointF> mLocationContext;
+    private ArrayList<PointF> mDeltaContext;
     private ArrayList<ArrayList<Float>> mDeltaXContext;
     private ArrayList<ArrayList<Float>> mDeltaYContext;
     private ArrayList<Float> mXContext;
@@ -42,6 +43,7 @@ public class GlyphContext {
         mCurrentLocation = new PointF();
         mFontContext = new ArrayList<>();
         mLocationContext = new ArrayList<>();
+        mDeltaContext = new ArrayList<>();
         mDeltaXContext = new ArrayList<>();
         mDeltaYContext = new ArrayList<>();
         mXContext = new ArrayList<>();
@@ -59,6 +61,7 @@ public class GlyphContext {
         }
 
         mLocationContext.add(location);
+        mDeltaContext.add(new PointF(0, 0));
         mFontContext.add(font);
         mDeltaXContext.add(getFloatArrayListFromReadableArray(deltaX));
         mDeltaYContext.add(getFloatArrayListFromReadableArray(deltaY));
@@ -72,6 +75,7 @@ public class GlyphContext {
         float x = mXContext.get(mContextLength - 1);
         mFontContext.remove(mContextLength - 1);
         mLocationContext.remove(mContextLength - 1);
+        mDeltaContext.remove(mContextLength - 1);
         mDeltaXContext.remove(mContextLength - 1);
         mDeltaYContext.remove(mContextLength - 1);
         mXContext.remove(mContextLength - 1);
@@ -87,23 +91,28 @@ public class GlyphContext {
     }
 
     public PointF getNextGlyphPoint(float offset, float glyphWidth) {
-        float dx = getNextDelta(mDeltaXContext);
-        mCurrentLocation.x += dx;
-
-        float dy = getNextDelta(mDeltaYContext);
-        mCurrentLocation.y += dy;
-
-        for (PointF point: mLocationContext) {
-            point.x += dx;
-            point.y += dy;
-        }
-
         mXContext.set(mXContext.size() - 1, mCurrentLocation.x + offset + glyphWidth);
 
         return new PointF(mCurrentLocation.x + offset, mCurrentLocation.y);
 
     }
 
+    public PointF getNextGlyphDelta() {
+        float dx = getNextDelta(mDeltaXContext);
+        float dy = getNextDelta(mDeltaYContext);
+
+        if (mContextLength > 0) {
+            for (PointF point: mDeltaContext) {
+                point.x += dx;
+                point.y += dy;
+            }
+
+            return mDeltaContext.get(mContextLength - 1);
+        }
+
+        return new PointF(dx, dy);
+    }
+
     private float getNextDelta(ArrayList<ArrayList<Float>> deltaContext) {
         float value = 0;
         boolean valueSet = false;

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

@@ -78,7 +78,7 @@ public class TSpanShadowNode extends TextShadowNode {
 
         pushGlyphContext();
         applyTextPropertiesToPaint(paint);
-        getLinePath(mContent + " ", paint, path);
+        getLinePath(mContent + "", paint, path);
 
         mCache = path;
         popGlyphContext();
@@ -99,13 +99,14 @@ public class TSpanShadowNode extends TextShadowNode {
             Path glyph = new Path();
             float width = widths[index];
 
-            paint.getTextPath(letter, 0, 1, 0, -paint.ascent(), glyph);
+            paint.getTextPath(letter, 0, 1, 0, 0, glyph);
+            PointF glyphDelta = getGlyphDeltaFromContext();
             PointF glyphPoint = getGlyphPointFromContext(glyphPosition, width);
             glyphPosition += width;
             Matrix matrix = new Matrix();
 
             if (mBezierTransformer != null) {
-                matrix = mBezierTransformer.getTransformAtDistance(glyphPoint.x);
+                matrix = mBezierTransformer.getTransformAtDistance(glyphPoint.x + glyphDelta.x);
 
                 if (textPathHasReachedEnd()) {
                     break;
@@ -113,22 +114,16 @@ public class TSpanShadowNode extends TextShadowNode {
                     continue;
                 }
 
+                matrix.preTranslate(0, glyphDelta.y);
                 matrix.postTranslate(0, glyphPoint.y);
             } else {
-                matrix.setTranslate(glyphPoint.x, glyphPoint.y);
+                matrix.setTranslate(glyphPoint.x + glyphDelta.x, glyphPoint.y + glyphDelta.y);
             }
 
-
             glyph.transform(matrix);
             path.addPath(glyph);
         }
 
-        if (mBezierTransformer != null) {
-            Matrix matrix = new Matrix();
-            matrix.postTranslate(0, paint.ascent() * 1.1f);
-            path.transform(matrix);
-        }
-
         return path;
     }
 

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

@@ -200,6 +200,10 @@ public class TextShadowNode extends GroupShadowNode {
         return  getTextRoot().getGlyphContext().getNextGlyphPoint(offset, glyphWidth);
     }
 
+    protected PointF getGlyphDeltaFromContext() {
+        return  getTextRoot().getGlyphContext().getNextGlyphDelta();
+    }
+
     private Matrix getAlignMatrix(Path path) {
         RectF box = new RectF();
         path.computeBounds(box, true);