refactor(screenshot): Per-call MaskRenderer, main-thread VH capture, and don't leak unmasked screenshots

- Use per-call MaskRenderer via try-with-resources instead of shared instance
- Remove Closeable from ScreenshotEventProcessor (nothing to clean up)
- Capture view hierarchy on main thread via runOnUiThread + CountDownLatch
- Apply masking on the calling thread (only VH traversal needs main thread)
- Return null on masking failure to avoid sending unmasked screenshots
- Fix setMaskViewContainerClass to not trigger trackCustomMasking

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: romtsn

sentry-android-core/api/sentry-android-core.api

@@ -325,9 +325,8 @@ public final class io/sentry/android/core/NetworkBreadcrumbsIntegration : io/sen
 	public fun register (Lio/sentry/IScopes;Lio/sentry/SentryOptions;)V
 }
 
-public final class io/sentry/android/core/ScreenshotEventProcessor : io/sentry/EventProcessor, java/io/Closeable {
+public final class io/sentry/android/core/ScreenshotEventProcessor : io/sentry/EventProcessor {
 	public fun <init> (Lio/sentry/android/core/SentryAndroidOptions;Lio/sentry/android/core/BuildInfoProvider;Z)V
-	public fun close ()V
 	public fun getOrder ()Ljava/lang/Long;
 	public fun process (Lio/sentry/SentryEvent;Lio/sentry/Hint;)Lio/sentry/SentryEvent;
 	public fun process (Lio/sentry/protocol/SentryTransaction;Lio/sentry/Hint;)Lio/sentry/protocol/SentryTransaction;

sentry-android-core/src/main/java/io/sentry/android/core/ScreenshotEventProcessor.java

@@ -21,8 +21,9 @@
 import io.sentry.protocol.SentryTransaction;
 import io.sentry.util.HintUtils;
 import io.sentry.util.Objects;
-import java.io.Closeable;
-import java.io.IOException;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicReference;
 import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -32,16 +33,17 @@
  * captured.
  */
 @ApiStatus.Internal
-public final class ScreenshotEventProcessor implements EventProcessor, Closeable {
+public final class ScreenshotEventProcessor implements EventProcessor {
 
   private final @NotNull SentryAndroidOptions options;
   private final @NotNull BuildInfoProvider buildInfoProvider;
 
   private final @NotNull Debouncer debouncer;
   private static final long DEBOUNCE_WAIT_TIME_MS = 2000;
   private static final int DEBOUNCE_MAX_EXECUTIONS = 3;
+  private static final long MASKING_TIMEOUT_MS = 2000;
 
-  private @Nullable MaskRenderer maskRenderer = null;
+  private final boolean isReplayAvailable;
 
   public ScreenshotEventProcessor(
       final @NotNull SentryAndroidOptions options,
@@ -56,9 +58,7 @@ public ScreenshotEventProcessor(
             DEBOUNCE_WAIT_TIME_MS,
             DEBOUNCE_MAX_EXECUTIONS);
 
-    if (isReplayAvailable) {
-      maskRenderer = new MaskRenderer();
-    }
+    this.isReplayAvailable = isReplayAvailable;
 
     if (options.isAttachScreenshot()) {
       addIntegrationToSdkVersion("Screenshot");
@@ -69,7 +69,7 @@ private boolean isMaskingEnabled() {
     if (options.getScreenshotOptions().getMaskViewClasses().isEmpty()) {
       return false;
     }
-    if (maskRenderer == null) {
+    if (!isReplayAvailable) {
       options
           .getLogger()
           .log(SentryLevel.WARNING, "Screenshot masking requires sentry-android-replay module");
@@ -124,14 +124,13 @@ private boolean isMaskingEnabled() {
 
     // Apply masking if enabled and replay module is available
     if (isMaskingEnabled()) {
-      final @Nullable View rootView =
-          activity.getWindow() != null
-                  && activity.getWindow().peekDecorView() != null
-                  && activity.getWindow().peekDecorView().getRootView() != null
-              ? activity.getWindow().peekDecorView().getRootView()
-              : null;
-      if (rootView != null) {
-        screenshot = applyMasking(screenshot, rootView);
+      final @Nullable ViewHierarchyNode rootNode = captureViewHierarchy(activity);
+      if (rootNode == null) {
+        return event;
+      }
+      screenshot = applyMasking(screenshot, rootNode);
+      if (screenshot == null) {
+        return event;
       }
     }
 
@@ -146,11 +145,65 @@ private boolean isMaskingEnabled() {
     return event;
   }
 
-  private @NotNull Bitmap applyMasking(
-      final @NotNull Bitmap screenshot, final @NotNull View rootView) {
+  /**
+   * Captures the view hierarchy on the main thread, since view traversal requires it. If already on
+   * the main thread, captures directly; otherwise posts to the main thread and waits.
+   */
+  private @Nullable ViewHierarchyNode captureViewHierarchy(final @NotNull Activity activity) {
+    if (options.getThreadChecker().isMainThread()) {
+      return buildViewHierarchy(activity);
+    }
+
+    final AtomicReference<ViewHierarchyNode> result = new AtomicReference<>(null);
+    final CountDownLatch latch = new CountDownLatch(1);
+
+    activity.runOnUiThread(
+        () -> {
+          try {
+            result.set(buildViewHierarchy(activity));
+          } finally {
+            latch.countDown();
+          }
+        });
+
+    try {
+      if (!latch.await(MASKING_TIMEOUT_MS, TimeUnit.MILLISECONDS)) {
+        options
+            .getLogger()
+            .log(
+                SentryLevel.WARNING, "Timed out waiting for view hierarchy capture on main thread");
+        return null;
+      }
+    } catch (Throwable e) {
+      options.getLogger().log(SentryLevel.ERROR, "Failed to capture view hierarchy", e);
+      return null;
+    }
+
+    return result.get();
+  }
+
+  private @Nullable ViewHierarchyNode buildViewHierarchy(final @NotNull Activity activity) {
+    final @Nullable View rootView =
+        activity.getWindow() != null
+                && activity.getWindow().peekDecorView() != null
+                && activity.getWindow().peekDecorView().getRootView() != null
+            ? activity.getWindow().peekDecorView().getRootView()
+            : null;
+    if (rootView == null) {
+      return null;
+    }
+
+    final ViewHierarchyNode rootNode =
+        ViewHierarchyNode.Companion.fromView(rootView, null, 0, options.getScreenshotOptions());
+    ViewsKt.traverse(rootView, rootNode, options.getScreenshotOptions(), options.getLogger());
+    return rootNode;
+  }
+
+  private @Nullable Bitmap applyMasking(
+      final @NotNull Bitmap screenshot, final @NotNull ViewHierarchyNode rootNode) {
     Bitmap mutableBitmap = screenshot;
     boolean createdCopy = false;
-    try {
+    try (final MaskRenderer maskRenderer = new MaskRenderer()) {
       // Make bitmap mutable if needed
       if (!screenshot.isMutable()) {
         mutableBitmap = screenshot.copy(Bitmap.Config.ARGB_8888, true);
@@ -160,16 +213,7 @@ private boolean isMaskingEnabled() {
         createdCopy = true;
       }
 
-      // we can access it here, since it's "internal" only for Kotlin
-
-      // Build view hierarchy and apply masks
-      final ViewHierarchyNode rootNode =
-          ViewHierarchyNode.Companion.fromView(rootView, null, 0, options.getScreenshotOptions());
-      ViewsKt.traverse(rootView, rootNode, options.getScreenshotOptions(), options.getLogger());
-
-      if (maskRenderer != null) {
-        maskRenderer.renderMasks(mutableBitmap, rootNode, null);
-      }
+      maskRenderer.renderMasks(mutableBitmap, rootNode, null);
 
       // Recycle original if we created a copy
       if (createdCopy && !screenshot.isRecycled()) {
@@ -183,19 +227,13 @@ private boolean isMaskingEnabled() {
       if (createdCopy && !mutableBitmap.isRecycled()) {
         mutableBitmap.recycle();
       }
-      return screenshot;
+      // Don't return unmasked screenshot when masking is configured
+      return null;
     }
   }
 
   @Override
   public @Nullable Long getOrder() {
     return 10000L;
   }
-
-  @Override
-  public void close() throws IOException {
-    if (maskRenderer != null) {
-      maskRenderer.close();
-    }
-  }
 }

sentry-android-core/src/test/java/io/sentry/android/core/ScreenshotEventProcessorTest.kt

@@ -323,6 +323,51 @@ class ScreenshotEventProcessorTest {
     assertNotNull(hint.screenshot)
   }
 
+  @Test
+  fun `when masking is configured and VH capture fails, no screenshot is attached`() {
+    val sut = fixture.getSut(attachScreenshot = true, isReplayAvailable = true)
+    fixture.options.screenshotOptions.setMaskAllText(true)
+    val hint = Hint()
+
+    // No activity set, so VH capture will return null (no rootView)
+    CurrentActivityHolder.getInstance().clearActivity()
+
+    val event = fixture.mainProcessor.process(getEvent(), hint)
+    sut.process(event, hint)
+
+    assertNull(hint.screenshot)
+  }
+
+  @Test
+  fun `when masking is configured but replay is not available, screenshot is still captured without masking`() {
+    val sut = fixture.getSut(attachScreenshot = true, isReplayAvailable = false)
+    fixture.options.screenshotOptions.setMaskAllText(true)
+    val hint = Hint()
+
+    CurrentActivityHolder.getInstance().setActivity(fixture.activity)
+
+    val event = fixture.mainProcessor.process(getEvent(), hint)
+    sut.process(event, hint)
+
+    assertNotNull(hint.screenshot)
+  }
+
+  @Test
+  fun `when masking is configured from background thread, VH is captured on main thread`() {
+    fixture.options.screenshotOptions.setMaskAllText(true)
+    val sut = fixture.getSut(attachScreenshot = true, isReplayAvailable = true)
+    whenever(fixture.threadChecker.isMainThread).thenReturn(false)
+
+    CurrentActivityHolder.getInstance().setActivity(fixture.activity)
+
+    val hint = Hint()
+    val event = fixture.mainProcessor.process(getEvent(), hint)
+    sut.process(event, hint)
+
+    shadowOf(Looper.getMainLooper()).idle()
+    assertNotNull(hint.screenshot)
+  }
+
   // region Snapshot Tests
 
   @Test

sentry/src/main/java/io/sentry/SentryMaskingOptions.java

@@ -109,7 +109,7 @@ public void addUnmaskViewClass(final @NotNull String className) {
   }
 
   public void setMaskViewContainerClass(@NotNull String containerClass) {
-    addMaskViewClass(containerClass);
+    maskViewClasses.add(containerClass);
     maskViewContainerClass = containerClass;
   }