[MDCSnackbar] Add snackbarIsPresenting to MDCSnackbarManagerDelegate.

PiperOrigin-RevId: 312316674

components/Snackbar/src/MDCSnackbarManager.m

@@ -270,6 +270,10 @@ - (void)displaySnackbarViewForMessage:(MDCSnackbarMessage *)message {
                 });
               }
             }];
+
+  if ([self.delegate respondsToSelector:@selector(isPresentingSnackbarWithMessageView:)]) {
+    [self.delegate isPresentingSnackbarWithMessageView:snackbarView];
+  }
 }
 
 - (MDCSnackbarOverlayView *)overlayView {

components/Snackbar/src/MDCSnackbarManagerDelegate.h

@@ -36,4 +36,12 @@
  */
 - (void)snackbarDidDisappear;
 
+/**
+ This method is called after the snackbar begins presenting (and is laid out),
+ but before the animiation is finished.
+
+ @param messageView The messageView of the snackbar that was just presented.
+ */
+- (void)isPresentingSnackbarWithMessageView:(nullable MDCSnackbarMessageView *)messageView;
+
 @end

components/Snackbar/tests/unit/MDCSnackbarMessageViewTests.m

@@ -624,10 +624,20 @@ - (void)testNotDismissedOnScreenTap {
 
   // Then
   [NSThread sleepForTimeInterval:0.5];
-  // Unfortunately, there is no way to to assert an expectation  has *not* fired after a time
+  // Unfortunately, there is no way to to assert an expectation has *not* fired after a time
   // interval. Instead we rely on 'internalManager.currentSnackbar' to be nil iff the snackbar is
   // dismissed.
   XCTAssertNotNil(self.manager.internalManager.currentSnackbar);
 }
 
+- (void)testsnackbarIsPresentingDelegateCalled {
+  // Given
+  self.delegate.willPresentExpectation = [self expectationWithDescription:@"willPresent"];
+  self.delegate.isPresentingExpectation = [self expectationWithDescription:@"isPresenting"];
+  // When
+  [self.manager showMessage:self.message];
+  // Then
+  [self waitForExpectationsWithTimeout:0.2 handler:nil];
+}
+
 @end

components/Snackbar/tests/unit/supplemental/MDCFakeMDCSnackbarManagerDelegate.h

@@ -22,7 +22,6 @@
 @property(nonatomic, assign) BOOL shouldSetSnackbarViewAccessibilityViewIsModal;
 @property(nonatomic, assign) XCTestExpectation *disappearExpectation;
 @property(nonatomic, assign) XCTestExpectation *willPresentExpectation;
-
-- (void)willPresentSnackbarWithMessageView:(MDCSnackbarMessageView *)messageView;
+@property(nonatomic, assign) XCTestExpectation *isPresentingExpectation;
 
 @end

components/Snackbar/tests/unit/supplemental/MDCFakeMDCSnackbarManagerDelegate.m

@@ -28,4 +28,8 @@ - (void)snackbarDidDisappear {
   [self.disappearExpectation fulfill];
 }
 
+- (void)isPresentingSnackbarWithMessageView:(nullable MDCSnackbarMessageView *)messageView {
+  [self.isPresentingExpectation fulfill];
+}
+
 @end