Implement GlyphPathBag for caching Paths per char, after a applyTextPropertiesToPaint(paint, font)

Path glyph = bag.getOrCreateAndCache(currentChar, current);

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

@@ -0,0 +1,48 @@
+package com.horcrux.svg;
+
+import android.graphics.Paint;
+import android.graphics.Path;
+
+import java.util.ArrayList;
+
+class GlyphPathBag {
+    private ArrayList<Path> paths = new ArrayList<>();
+    private int[][] data = new int[255][];
+    Paint paint;
+
+    GlyphPathBag(Paint paint) {
+        this.paint = paint;
+        // Make indexed-by-one, to allow zero to represent non-cached
+        paths.add(new Path());
+    }
+
+    Path getOrCreateAndCache(char ch, String current) {
+        int index = getIndex(ch);
+        Path cached;
+
+        if (index != 0) {
+            cached = paths.get(index);
+        } else {
+            cached = new Path();
+            paint.getTextPath(current, 0, 1, 0, 0, cached);
+
+            int[] bin = data[ch >> 8];
+            if (bin == null) {
+                bin = data[ch >> 8] = new int[255];
+            }
+            bin[ch & 0xFF] = paths.size();
+
+            paths.add(cached);
+        }
+
+        Path glyph = new Path();
+        glyph.addPath(cached);
+        return glyph;
+    }
+
+    private int getIndex(char ch) {
+        int[] bin = data[ch >> 8];
+        if (bin == null) return 0;
+        return bin[ch & 0xFF];
+    }
+}

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

@@ -98,6 +98,7 @@ class TSpanShadowNode extends TextShadowNode {
         GlyphContext gc = getTextRootGlyphContext();
         FontData font = gc.getFont();
         applyTextPropertiesToPaint(paint, font);
+        GlyphPathBag bag = new GlyphPathBag(paint);
 
         /*
             Determine the startpoint-on-the-path for the first glyph using attribute ‘startOffset’
@@ -127,7 +128,6 @@ class TSpanShadowNode extends TextShadowNode {
 
         double distance = 0;
         PathMeasure pm = null;
-        double renderMethodScaling = 1;
         if (textPath != null) {
             pm = new PathMeasure(textPath.getPath(), false);
             distance = pm.getLength();
@@ -142,12 +142,10 @@ class TSpanShadowNode extends TextShadowNode {
                 // https://svgwg.org/svg2-draft/text.html#TextPathElementSpacingAttribute
             }
             */
-            final TextPathMethod method = textPath.getMethod();
-            if (method == TextPathMethod.stretch) {
-                renderMethodScaling = distance / textMeasure;
-            }
         }
 
+        double renderMethodScaling = getRenderMethodScaling(textMeasure, distance);
+
         /*
         *
         * Three properties affect the space between characters and words:
@@ -427,8 +425,7 @@ class TSpanShadowNode extends TextShadowNode {
 
             mid.preRotate((float) r);
 
-            Path glyph = new Path();
-            paint.getTextPath(current, 0, 1, 0, 0, glyph);
+            Path glyph = bag.getOrCreateAndCache(currentChar, current);
             glyph.transform(mid);
             path.addPath(glyph);
         }
@@ -436,6 +433,13 @@ class TSpanShadowNode extends TextShadowNode {
         return path;
     }
 
+    private double getRenderMethodScaling(double textMeasure, double distance) {
+        if (textPath != null && textPath.getMethod() == TextPathMethod.stretch) {
+            return distance / textMeasure;
+        }
+        return 1;
+    }
+
     private double getAbsoluteStartOffset(double distance, double size, String startOffset) {
         return PropHelper.fromRelative(startOffset, distance, 0, mScale, size);
     }