Minimize EditText Spans 2/N: Make stripAttributeEquivalentSpans generic

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/textinput/ReactEditText.java

@@ -585,9 +585,7 @@ public void maybeSetText(ReactTextUpdate reactTextUpdate) {
         new SpannableStringBuilder(reactTextUpdate.getText());
 
     manageSpans(spannableStringBuilder, reactTextUpdate.mContainsMultipleFragments);
-
-    // Mitigation for https://github.com/facebook/react-native/issues/35936 (S318090)
-    stripAttributeEquivalentSpans(spannableStringBuilder);
+    stripStyleEquivalentSpans(spannableStringBuilder);
 
     mContainsImages = reactTextUpdate.containsImages();
 
@@ -662,50 +660,55 @@ private void manageSpans(
     }
   }
 
-  private void stripAttributeEquivalentSpans(SpannableStringBuilder sb) {
-    // We have already set a font size on the EditText itself. We can safely remove sizing spans
-    // which are the same as the set font size, and not otherwise overlapped.
-    final int effectiveFontSize = mTextAttributes.getEffectiveFontSize();
-    ReactAbsoluteSizeSpan[] spans = sb.getSpans(0, sb.length(), ReactAbsoluteSizeSpan.class);
+  // TODO: Replace with Predicate<T> and lambdas once Java 8 builds in OSS
+  interface SpanPredicate<T> {
+    boolean test(T span);
+  }
 
-    outerLoop:
-    for (ReactAbsoluteSizeSpan span : spans) {
-      ReactAbsoluteSizeSpan[] overlappingSpans =
-          sb.getSpans(sb.getSpanStart(span), sb.getSpanEnd(span), ReactAbsoluteSizeSpan.class);
+  /**
+   * Remove spans from the SpannableStringBuilder which can be represented by TextAppearance
+   * attributes on the underlying EditText. This works around instability on Samsung devices with
+   * the presence of spans https://github.com/facebook/react-native/issues/35936 (S318090)
+   */
+  private void stripStyleEquivalentSpans(SpannableStringBuilder sb) {
+    stripSpansOfKind(
+        sb,
+        ReactAbsoluteSizeSpan.class,
+        new SpanPredicate<ReactAbsoluteSizeSpan>() {
+          @Override
+          public boolean test(ReactAbsoluteSizeSpan span) {
+            return span.getSize() == mTextAttributes.getEffectiveFontSize();
+          }
+        });
+  }
 
-      for (ReactAbsoluteSizeSpan overlappingSpan : overlappingSpans) {
-        if (span.getSize() != effectiveFontSize) {
-          continue outerLoop;
-        }
-      }
+  private <T> void stripSpansOfKind(
+      SpannableStringBuilder sb, Class<T> clazz, SpanPredicate<T> shouldStrip) {
+    T[] spans = sb.getSpans(0, sb.length(), clazz);
 
-      sb.removeSpan(span);
+    for (T span : spans) {
+      if (shouldStrip.test(span)) {
+        sb.removeSpan(span);
+      }
     }
   }
 
-  private void unstripAttributeEquivalentSpans(
-      SpannableStringBuilder workingText, Spannable originalText) {
-    // We must add spans back for Fabric to be able to measure, at lower precedence than any
-    // existing spans. Remove all spans, add the attributes, then re-add the spans over
-    workingText.append(originalText);
+  /**
+   * Copy back styles represented as attributes to the underlying span, for later measurement
+   * outside the ReactEditText.
+   */
+  private void restoreStyleEquivalentSpans(SpannableStringBuilder workingText) {
+    int spanFlags = Spannable.SPAN_INCLUSIVE_INCLUSIVE;
 
-    for (Object span : workingText.getSpans(0, workingText.length(), Object.class)) {
-      workingText.removeSpan(span);
-    }
+    // Set all bits for SPAN_PRIORITY so that this span has the highest possible priority
+    // (least precedence). This ensures the span is behind any overlapping spans.
+    spanFlags |= Spannable.SPAN_PRIORITY;
 
     workingText.setSpan(
         new ReactAbsoluteSizeSpan(mTextAttributes.getEffectiveFontSize()),
         0,
         workingText.length(),
-        Spanned.SPAN_INCLUSIVE_INCLUSIVE);
-
-    for (Object span : originalText.getSpans(0, originalText.length(), Object.class)) {
-      workingText.setSpan(
-          span,
-          originalText.getSpanStart(span),
-          originalText.getSpanEnd(span),
-          originalText.getSpanFlags(span));
-    }
+        spanFlags);
   }
 
   private static boolean sameTextForSpan(
@@ -1132,8 +1135,8 @@ private void updateCachedSpannable(boolean resetStyles) {
       // ...
       // - android.app.Activity.dispatchKeyEvent (Activity.java:3447)
       try {
-        Spannable text = (Spannable) currentText.subSequence(0, currentText.length());
-        unstripAttributeEquivalentSpans(sb, text);
+        sb.append(currentText.subSequence(0, currentText.length()));
+        restoreStyleEquivalentSpans(sb);
       } catch (IndexOutOfBoundsException e) {
         ReactSoftExceptionLogger.logSoftException(TAG, e);
       }