Default to low-priority announcements

PiperOrigin-RevId: 562794503

components/Snackbar/src/MDCSnackbarMessage.m

@@ -13,8 +13,9 @@
 // limitations under the License.
 
 #import "MDCSnackbarMessage.h"
-#import "MDCSnackbarMessageView.h"
 #import "private/MDCSnackbarMessageInternal.h"
+#import "MDCAvailability.h"
+#import "MDCSnackbarMessageView.h"
 
 static const NSTimeInterval kDefaultDuration = 4;
 
@@ -108,7 +109,17 @@ - (NSString *)description {
 #pragma mark Text
 
 - (void)setText:(NSString *)text {
-  self.attributedText = [[NSAttributedString alloc] initWithString:[text copy]];
+  NSDictionary *attributes = @{};
+
+  // TODO(b/298435271): Remove the #if check below once all users are building with Xcode 15.
+#if MDC_AVAILABLE_SDK_IOS(17_0)
+  if (@available(iOS 17.0, *)) {
+    // Default to low-priority announcements.
+    attributes = @{UIAccessibilitySpeechAttributeAnnouncementPriority : UIAccessibilityPriorityLow};
+  }
+#endif
+  self.attributedText = [[NSAttributedString alloc] initWithString:[text copy]
+                                                        attributes:attributes];
 }
 
 - (NSString *)text {
@@ -130,8 +141,18 @@ - (void)setAccessibilityLabel:(NSString *)accessibilityLabel {
   if (accessibilityLabel == nil) {
     self.attributedAccessibilityLabel = nil;
   } else {
+    NSDictionary *attributes = @{};
+
+    // TODO(b/298435271): Remove the #if check below once all users are building with Xcode 15.
+#if MDC_AVAILABLE_SDK_IOS(17_0)
+    if (@available(iOS 17.0, *)) {
+      // Default to low-priority announcements.
+      attributes =
+          @{UIAccessibilitySpeechAttributeAnnouncementPriority : UIAccessibilityPriorityLow};
+    }
+#endif
     self.attributedAccessibilityLabel =
-        [[NSAttributedString alloc] initWithString:[accessibilityLabel copy]];
+        [[NSAttributedString alloc] initWithString:[accessibilityLabel copy] attributes:attributes];
   }
 }