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fix: cover the delayed Screen Broadcasting alert's full appearance window #26

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Merged
Timo972 merged 1 commit into from
Aug 25, 2026
Merged

fix: cover the delayed Screen Broadcasting alert's full appearance window #26

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137 changes: 97 additions & 40 deletions WebDriverAgentLib/Utilities/FBBroadcastManager.m
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Original file line number Diff line number Diff line change
Expand Up @@ -35,9 +35,13 @@
// active, so it is re-fired periodically until the confirmation sheet shows up.
static const uint64_t PICKER_RETRIGGER_INTERVAL_MS = 2000;
// How long the post-stop sweep waits for the delayed "Screen Broadcasting" alert to appear
// before giving up on it, and the overall cap on the sweep (appearance wait plus dismissal).
static const NSTimeInterval ALERT_APPEARANCE_GRACE_SEC = 2.0;
static const NSTimeInterval ALERT_SWEEP_TIMEOUT_SEC = 5.0;
// before giving up on it. SpringBoard publishes the alert well after the extension socket
// closes, and the delay varies by device and iOS version: ~5s observed on iOS 26, and ~10s
// (up to ~12s) on iOS 18 hardware.
static const NSTimeInterval ALERT_APPEARANCE_GRACE_SEC = 15.0;
// Additional budget, on top of the appearance wait, for the dismissal tap(s) to land and the
// alert to be observed gone.
static const NSTimeInterval ALERT_DISMISSAL_BUDGET_SEC = 5.0;

static uint64_t FBBroadcastNowMs(void)
{
Expand Down Expand Up @@ -114,6 +118,16 @@ - (nullable XCUIElement *)matchingDismissButtonForAlertWithDismissLabels:(NSArra
// above: applies the re-attempt cooldown, verifies the button's frame, and dispatches the tap.
- (BOOL)dismissBroadcastStoppedAlertWithLabels:(NSArray<NSString *> *)labels
goToApplicationLabels:(NSArray<NSString *> *)goToApplicationLabels;
// Clears the "Screen Broadcasting" alert end to end: waits up to appearanceGraceSec for it to
// appear at all, then keeps re-dispatching the dismissal tap until the alert is observed gone,
// bounded overall by appearanceGraceSec plus ALERT_DISMISSAL_BUDGET_SEC. Pass 0 for
// appearanceGraceSec to only act on an alert that is already on screen (a single existence
// probe when there is none). Returns YES when an alert was seen during the sweep - regardless
// of whether dismissing it succeeded. logContext prefixes the log lines, e.g. "broadcast/stop".
- (BOOL)sweepBroadcastStoppedAlertWithDismissLabels:(NSArray<NSString *> *)dismissLabels
goToApplicationLabels:(NSArray<NSString *> *)goToAppLabels
appearanceGraceSec:(NSTimeInterval)appearanceGraceSec
logContext:(NSString *)logContext;
#endif

@end
Expand Down Expand Up @@ -309,6 +323,13 @@ - (BOOL)performBroadcastStartWithTimeout:(NSTimeInterval)timeout
// runner from inside itself blocks on a self-quiescence wait that can only ever time out:
// the waiting thread is the very main thread whose idleness is being awaited.
if (!runnerIsActive) {
// A stale "Screen Broadcasting" alert blocks LaunchServices and XCTest foregrounding alike,
// so it must be cleared before the attempts, not discovered after they both time out. With
// no alert on screen this costs a single existence probe.
[self sweepBroadcastStoppedAlertWithDismissLabels:dismissLabels
goToApplicationLabels:goToAppLabels
appearanceGraceSec:0
logContext:@"broadcast/start"];
BOOL launched = [FBUnattachedAppLauncher launchAppWithBundleId:(NSString *)NSBundle.mainBundle.bundleIdentifier];
BOOL foregrounded = launched && [[[[FBRunLoopSpinner new] timeout:2.0] interval:0.05] spinUntilTrue:^BOOL{
return UIApplication.sharedApplication.applicationState == UIApplicationStateActive;
Expand All @@ -321,6 +342,22 @@ - (BOOL)performBroadcastStartWithTimeout:(NSTimeInterval)timeout
return UIApplication.sharedApplication.applicationState == UIApplicationStateActive;
}];
}
if (!foregrounded) {
// The delayed "Screen Broadcasting" alert of a recently ended broadcast can also land
// right in the middle of the dance and swallow the activation. When that - and only
// that - is what happened, clearing the alert and re-activating recovers the start.
BOOL alertWasBlocking = [self sweepBroadcastStoppedAlertWithDismissLabels:dismissLabels
goToApplicationLabels:goToAppLabels
appearanceGraceSec:0
logContext:@"broadcast/start"];
if (alertWasBlocking) {
[FBLogger log:@"broadcast/start: retrying the activation now that the Screen Broadcasting alert is cleared"];
[runner activate];
foregrounded = [[[[FBRunLoopSpinner new] timeout:FOREGROUND_TIMEOUT] interval:0.05] spinUntilTrue:^BOOL{
return UIApplication.sharedApplication.applicationState == UIApplicationStateActive;
}];
}
}
if (!foregrounded) {
if (error) {
*error = [NSError errorWithDomain:FBBroadcastManagerErrorDomain
Expand Down Expand Up @@ -495,6 +532,42 @@ - (BOOL)dismissBroadcastStoppedAlertWithLabels:(NSArray<NSString *> *)labels
self.lastAlertDismissalAttemptMs = FBBroadcastNowMs();
return FBBroadcastTapFrameCenter(XCUIApplication.fb_systemApplication, frame, NO, nil);
}

// Survives both known failure modes: exiting once a dismissal tap is merely dispatched
// (FBBroadcastTapFrameCenter's waitForAck:NO tap is fire-and-forget and can be shed by the
// system, so the sweep must keep spinning on the matcher's OBSERVED state, not on the dispatch
// call succeeding), and exiting before the alert - which SpringBoard publishes with a delay
// AFTER the extension socket closes - has appeared at all. So: once the alert has been seen,
// declare success only when it is next observed gone (retrying the dismissal tap in between,
// paced by the 1s cooldown inside dismissBroadcastStoppedAlertWithLabels:goToApplicationLabels:);
// until it has been seen, keep waiting out the appearance grace period rather than exiting on
// the first (empty) read.
- (BOOL)sweepBroadcastStoppedAlertWithDismissLabels:(NSArray<NSString *> *)dismissLabels
goToApplicationLabels:(NSArray<NSString *> *)goToAppLabels
appearanceGraceSec:(NSTimeInterval)appearanceGraceSec
logContext:(NSString *)logContext
{
uint64_t sweepStartedMs = FBBroadcastNowMs();
__block BOOL alertSeen = NO;
[[[[FBRunLoopSpinner new] timeout:(appearanceGraceSec + ALERT_DISMISSAL_BUDGET_SEC)] interval:0.25] spinUntilTrue:^BOOL{
XCUIElement *dismissButton = [self matchingDismissButtonForAlertWithDismissLabels:dismissLabels goToApplicationLabels:goToAppLabels];
if (nil != dismissButton) {
if (!alertSeen) {
alertSeen = YES;
[FBLogger logFmt:@"%@: the Screen Broadcasting alert appeared %llums into the sweep", logContext, FBBroadcastNowMs() - sweepStartedMs];
}
if ([self dismissBroadcastStoppedAlertWithLabels:dismissLabels goToApplicationLabels:goToAppLabels]) {
[FBLogger logFmt:@"%@: dispatched a dismissal tap for the Screen Broadcasting alert", logContext];
}
return NO;
}
if (alertSeen) {
return YES;
}
return (FBBroadcastNowMs() - sweepStartedMs) >= (uint64_t)(appearanceGraceSec * 1000);
}];
return alertSeen;
}
#endif

- (BOOL)stopBroadcastWithError:(NSError **)error
Expand All @@ -506,7 +579,20 @@ - (BOOL)stopBroadcastWithDismissButtonLabels:(NSArray<NSString *> *)dismissButto
goToApplicationButtonLabels:(NSArray<NSString *> *)goToApplicationButtonLabels
error:(NSError **)error
{
#if !TARGET_OS_SIMULATOR && !TARGET_OS_TV
NSArray<NSString *> *dismissLabels = dismissButtonLabels.count > 0 ? dismissButtonLabels : @[@"OK"];
NSArray<NSString *> *goToAppLabels = goToApplicationButtonLabels.count > 0 ? goToApplicationButtonLabels : @[@"Go to Application"];
#endif
if (!self.isExtensionConnected) {
#if !TARGET_OS_SIMULATOR && !TARGET_OS_TV
// Nothing to stop, but a previous broadcast that ended without a stop call (a crash, or the
// runner being relaunched) can have left its alert on screen; clear it when it is there
// right now. Grace 0 keeps the idempotent-stop case a single existence probe.
[self sweepBroadcastStoppedAlertWithDismissLabels:dismissLabels
goToApplicationLabels:goToAppLabels
appearanceGraceSec:0
logContext:@"broadcast/stop"];
#endif
return YES;
}
[self.controlServer sendStopBroadcast];
Expand All @@ -522,43 +608,14 @@ - (BOOL)stopBroadcastWithDismissButtonLabels:(NSArray<NSString *> *)dismissButto
return NO;
}
#if !TARGET_OS_SIMULATOR && !TARGET_OS_TV
// The delayed "Screen Broadcasting" alert is an iOS 26 behavior; on older iOS the sweep below
// would only add stop latency waiting for an alert that never appears, so gate it here - the
// start dance's own dismissal (see performBroadcastStartWithTimeout:...) remains the safety
// net on every iOS version.
if (@available(iOS 26.0, *)) {
// Best-effort: a broadcast stop almost always leaves the stale "Screen Broadcasting" alert
// behind, so proactively clear it here instead of waiting for the next start dance to hit it.
// This never affects the return value below.
NSArray<NSString *> *dismissLabels = dismissButtonLabels.count > 0 ? dismissButtonLabels : @[@"OK"];
NSArray<NSString *> *goToAppLabels = goToApplicationButtonLabels.count > 0 ? goToApplicationButtonLabels : @[@"Go to Application"];
uint64_t sweepStartedMs = FBBroadcastNowMs();
__block BOOL alertSeen = NO;
// Survives both failure modes seen in review: exiting once a dismissal tap is merely
// dispatched (FBBroadcastTapFrameCenter's waitForAck:NO tap is fire-and-forget and can be
// shed by the system, so the sweep must keep spinning on the matcher's OBSERVED state, not
// on the dispatch call succeeding), and exiting before the alert - which SpringBoard
// publishes with a delay AFTER the extension socket closes - has appeared at all. So: once
// the alert has been seen, declare success only when it is next observed gone (retrying the
// dismissal tap in between, paced by the 1s cooldown inside
// dismissBroadcastStoppedAlertWithLabels:goToApplicationLabels:); until it has been seen,
// keep waiting out the appearance grace period rather than exiting on the first (empty)
// read.
[[[[FBRunLoopSpinner new] timeout:ALERT_SWEEP_TIMEOUT_SEC] interval:0.25] spinUntilTrue:^BOOL{
XCUIElement *dismissButton = [self matchingDismissButtonForAlertWithDismissLabels:dismissLabels goToApplicationLabels:goToAppLabels];
if (nil != dismissButton) {
alertSeen = YES;
if ([self dismissBroadcastStoppedAlertWithLabels:dismissLabels goToApplicationLabels:goToAppLabels]) {
[FBLogger log:@"broadcast/stop: dispatched a dismissal tap for the Screen Broadcasting alert"];
}
return NO;
}
if (alertSeen) {
return YES;
}
return (FBBroadcastNowMs() - sweepStartedMs) >= (uint64_t)(ALERT_APPEARANCE_GRACE_SEC * 1000);
}];
}
// Best-effort: a broadcast stop almost always leaves the stale "Screen Broadcasting" alert
// behind, so proactively clear it here instead of waiting for the next start dance to hit it.
// Not gated by iOS version: the delayed alert has been observed on iOS 18 (~10s, up to ~12s
// after the stop) and iOS 26 (~5s) alike. This never affects the return value below.
[self sweepBroadcastStoppedAlertWithDismissLabels:dismissLabels
goToApplicationLabels:goToAppLabels
appearanceGraceSec:ALERT_APPEARANCE_GRACE_SEC
logContext:@"broadcast/stop"];
#endif
return YES;
}
Expand Down
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