Rebuild the TextView Layout before drawing text effects on Android

ReactTextView.onDraw paints CanvasEffectSpans (underline, strikethrough) only when
getLayout() is non-null. TextView drops its Layout in setText and rebuilds it in
onMeasure, and Fabric measures a view only when its frame changed, so a text state
update that keeps the frame (a decoration or color change on a text of the same
size) reaches onDraw with no Layout and the decorations are skipped until something
else re-measures the view. Rebuild the Layout at the current size before painting;
TextView.onDraw would build one for the plain text anyway.

Author: MatiPl01

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

@@ -257,6 +257,17 @@ protected void onDraw(Canvas canvas) {
 
       if (spanned != null) {
         Layout layout = getLayout();
+        if (layout == null && getWidth() > 0 && getHeight() > 0) {
+          // TextView drops its Layout in setText and rebuilds it in onMeasure, and Fabric measures
+          // a view only when its frame changed. A text update that keeps the frame (a color or
+          // decoration change, e.g. driven by an animation) therefore gets here with no Layout,
+          // and the CanvasEffectSpans below would be skipped for that frame. Rebuild the Layout
+          // at the current size first; TextView.onDraw would build one for the text anyway.
+          measure(
+              MeasureSpec.makeMeasureSpec(getWidth(), MeasureSpec.EXACTLY),
+              MeasureSpec.makeMeasureSpec(getHeight(), MeasureSpec.EXACTLY));
+          layout = getLayout();
+        }
         if (layout != null) {
           CanvasEffectSpan[] drawSpans =
               spanned.getSpans(0, spanned.length(), CanvasEffectSpan.class);