I am writing an application for my own purposes that aims to get play pause events no matter what is going on in the system. I have gotten this much working
let commandCenter = MPRemoteCommandCenter.shared()
commandCenter.togglePlayPauseCommand.isEnabled = true
commandCenter.togglePlayPauseCommand.addTarget { (MPRemoteCommandEvent) -> MPRemoteCommandHandlerStatus in
print("Play Pause Command")
return .success
}
commandCenter.nextTrackCommand.isEnabled = true
commandCenter.nextTrackCommand.addTarget { (MPRemoteCommandEvent) -> MPRemoteCommandHandlerStatus in
print("NextTrackCommand")
return .success
}
commandCenter.previousTrackCommand.isEnabled = true
commandCenter.previousTrackCommand.addTarget { (MPRemoteCommandEvent) -> MPRemoteCommandHandlerStatus in
print("previousTrackCommand")
return .success
}
commandCenter.playCommand.isEnabled = true
commandCenter.playCommand.addTarget { (MPRemoteCommandEvent) -> MPRemoteCommandHandlerStatus in
print("playCommand")
return .success
}
MPNowPlayingInfoCenter.default().playbackState = .playing
Most of those methods are there because apparently you will not get any notifications without having nextTrackCommand or previousTrackCommand or playCommand implemented.
Anyways my one issue is that as soon as you open another application that uses audio these event handlers stop getting called and I cant find a way to detect and fix this.
I would normally try doing AVAudioSession things to state this as a background application however that does not seem to work. Any ideas on how I can get playpause events no matter what state the system is in?
I would like to be able to always listen for these events OR get an indication of when someone else has taken control of the audio? Perhaps even be able to re-subscribe to these play pause events.
There's an internal queue in the system which contains all the audio event subscribers. Other applications get on top of it when you start using them.
I would like to be able to always listen for these events
There's no API for that but there's a dirty workaround. If I understand your issue correctly, this snippet:
MPNowPlayingInfoCenter.default().playbackState = .paused
MPNowPlayingInfoCenter.default().playbackState = .playing
must do the trick for you if you run it in a loop somewhere in your application.
Note that this is not 100% reliable because:
If an event is generated before two subsequent playbackState state changes right after you've switched to a different application, it would still be catched by the application in the active window;
If another application is doing the same thing, there would be a constant race condition in the queue, with unpredictable outcome.
References:
Documentation for playbackState is here;
See also a similar question;
See also a bug report for mpv with a similar
issue (a pre-MPRemoteCommandCenter one, but still very valuable)
OR get an indication of when someone else has taken control of the audio
As far as I know there's no public API for this in macOS.
Related
My team is currently facing an issue in our Xamarin.Forms app across all platforms(Android, iOS, and UWP). Realm will frequently become unresponsive, where the only way to use it again is to close the app. Over the past few months it's become more frequent and easy to reproduce, yet we have not been able to determine the cause or a workaround.
We have identified a few patterns that may help identify what's happening. We've noticed that whenever something that needs information from the database, we'll see that worker thread stuck on a Realm.Write() call. This behavior seems almost as if there's a deadlock occuring within the Realm system. It's not consistent as to which Write() call it's stuck on, seeming to be random based on when the Realm fails. At that point, any other attempts to access this realm through any method, such as Find(),All(),Remove(), etc also get stuck. We've also confirmed that the code within the Write() is never being run at this point, since we can put a realm independent logging call on the first line and never see it in our logs.
Once this issue occurs, some other issues can happen in addition to this. We have two other Realms in our app that handle completely separate data, and as such have no overlapping code. These Realms are never the cause of this issue, but when the problem Realm gets stuck, it sometimes causes the other Realms to get stuck on their next calls as well. This issue also sometimes persists between uses of the app, causing the very first call to Realm to get stuck and requires a complete reinstall to fix.
Due to our app using Reactive based programming, we've had to structure how we handle our database a bit differently. For the problem Realm, we have a service that keeps a single instance active in an observable stream, which can then be subscribed to for watching changes. I've added some examples of this architecture at the end of this post. We also route all our other non-observable actions through this stream, however during debugging we've been able to move these calls to their own independent realm instances with little issue/no change to functionality.
Currently, we're thinking it's most likely an issue related either to how we're converting Realm to an observable system, or with our Realms crashing/becoming corrupted somehow.
RealmStream declaration:
_realmStream = Observable
.Start(() => Realm.GetInstance(_dbConfig), _scheduler)
.Do(_ => logger.LogTrace("Realm created"), () => logger.LogTrace("Realm stream completed"))
.Replay()
.AutoConnect();
RealmStream use example:
public IObservable<IChangeSet<TResult>> GetChangeSetStream<TSource, TResult>(Func<Realm, IQueryable<TSource>> selector, Func<TSource, TResult> transformFactory) where TSource : RealmObject
{
return _realmStream
.Select(realm =>
selector(realm)
.AsRealmCollection()
.ToObservableChangeSet<IRealmCollection<TSource>, TSource>()
.SubscribeOn(_scheduler)
.Transform(transformFactory)
.DisposeMany())
.Switch()
.Catch<IChangeSet<TResult>, Exception>(ex =>
{
_logger.LogError(ex, "Error getting property change stream");
return Observable.Return<IChangeSet<TResult>>(default);
})
.SubscribeOn(_scheduler);
}
Non-Observable realm methodss:
public async Task Run(Action<Realm> action)
{
await _realmStream
.Do(action)
.SubscribeOn(_scheduler);
}
public async Task<TResult> Run<TResult>(Func<Realm, TResult> action)
{
return await _realmStream
.Select(action)
.SubscribeOn(_scheduler);
}
So far, we've attempted the following:
Made sure Realm and Xamarin are both on the most recent versions
Reducing the number of Realm.Write()s (Minor improvement)
Moving every Realm function into our observable system (No noticable change, most of our functions already do this)
Attempted moving everything that does not require observables to using independent realm instances (increased frequency of locking)
Attempted to move everything away from our single instance of Realm. We weren't able to do this, as we could not determine how to properly handle some observable events, such as a RealmObject being deleted, without causing major performance issues
realm.Write needs to acquire a write lock and based on your description, it appears that you do get a deadlock where a thread with an open write transaction waits for another thread that is stuck on the realm.Write call. If you're able to reproduce the hand with a debugger attached, you can inspect the threads window and try to pinpoint the offending code.
This article provides some tips about debugging deadlocks. Unfortunately, without the whole project and a repro case, it'd be hard to pinpoint the cause.
I am making an addon in Firefox, so I have a ChromeWorker - which is a privileged WebWorker. This is just a thread other then the mainthread.
In here I have no code but this (modified to make it look like not js-ctypes [which is the language for addons])
On startup I run this code, conn is a global variable:
conn = xcb_connect(null, null);
Then I run this in a 200ms interval:
evt = xcb_poll_for_event(conn);
console.log('evt:', evt);
if (!evt.isNull()) {
console.log('good got an event!!');
ostypes.API('free')(evt);
}
However evt is always null, I am never getting any events. My goal is to get all events on the system.
Anyone know what can cause something so simple to not work?
I have tried
xcb_change_window_attributes (conn, screens.data->root, XCB_CW_EVENT_MASK, values);
But this didn't fix it :(
The only way I can get it to work is by doing xcb_create_window xcb_map_window but then I get ONLY the events that happen in this created window.
You don't just magically get all events by opening a connection. There's only very few messages any client will receive, such as client messages, most others will only be sent to a client if it explicitly registered itself to receive them.
And yes, that means you have to register them on each and every window, which involves both crawling the tree and listening for windows being created, mapped, unmapped and destroyed and registering on them as well.
However, I would reconsider whether
My goal is to get all events on the system.
isn't an A-B problem. Why do you "need" all events? What do you actually want to do?
I'm trying to enhance an existing Firefox extension which relies on nsIContentPolicy to detect and abort certain network loads (in order to block the resulting UI action, i.e. tab navigation). Then handle loading that resource internally. Under rare circumstances, only after handling the load, it turns out we shouldn't have interrupted the load at all, so we flag it to be ignored and re-start it.
Under e10s/multi-process, that means the parent (where the content policy is running) must send a message to the child (handling the UI for the content) to restart the load. Today, that's done by:
function findMessageManager(aContext) {
// With e10s off, context is a <browser> with a direct reference to
// the docshell loaded therein.
var docShell = aContext && aContext.docShell;
if (!docShell) {
// But with e10s on, context is a content window and we have to work hard
// to find the docshell, from which we can find the message manager.
docShell = aContext
.QueryInterface(Ci.nsIInterfaceRequestor)
.getInterface(Ci.nsIWebNavigation)
.QueryInterface(Ci.nsIDocShellTreeItem).rootTreeItem;
}
try {
return docShell
.QueryInterface(Ci.nsIInterfaceRequestor)
.getInterface(Ci.nsIContentFrameMessageManager);
} catch (e) {
return null;
}
};
Which is crazy complex, because e10s is crazy complex. But it works; it generates some object in the parent, upon which I can call .sendAsyncMessage(), and then the addMessageListener() handler in my frame/child script receives it, and does what it needs to do.
I'd like to switch from nsIContentPolicy to http-on-modify-request as it presents more information for making a better determination (block and handle this load?) earlier. Inside that observer I can do:
var browser = httpChannel
.notificationCallbacks.getInterface(Ci.nsILoadContext)
.topFrameElement;
Which gives me an object which has a .messageManager which is some kind of message manager, and which has a .sendAsyncMessage() method. But when I use that .sendAsyncMessage(), the message disappears, never to be observed by the child.
Context: https://github.com/greasemonkey/greasemonkey/issues/2280
This should work in principle, although the docshell tree traversal may do different things in e10s and non-e10s, so you have to be careful there. In e10s rootTreeItem -> nsIContentFrameMessageManager should give you the MM equivalent to a frame script and topFrameElement.frameLoader.messageManager should give you the <browser>'s MM, which pretty much is the parent side counterpart to it.
Potential sources of confusion:
e10s on vs. off
process MM vs. frame MM hierarchy
listening in the wrong frame for the message (registering in all frames might help for debugging purposes)
This is the function I use to find the content message manager:
function contentMMFromContentWindow_Method2(aContentWindow) {
if (!gCFMM) {
gCFMM = aContentWindow.QueryInterface(Ci.nsIInterfaceRequestor)
.getInterface(Ci.nsIDocShell)
.QueryInterface(Ci.nsIInterfaceRequestor)
.getInterface(Ci.nsIContentFrameMessageManager);
}
return gCFMM;
}
So maybe get the content window that triggered that request, and then use this function.
I would like to start a service that once in awhile on all platforms has checked is there a notification to appear or not. Is there any nuget to connect all platforms or some examples?
You can use the Device.StartTimer(TimeSpan minutes) method to start a background task that will repeat after the given time span. Here is a code example:
var minutes = TimeSpan.FromMinutes (3);
Device.StartTimer (minutes, () => {
// call your method to check for notifications here
// Returning true means you want to repeat this timer
return true;
});
This is included with Xamarin Forms, so you don't need any platform specific logic.
http://iosapi.xamarin.com/index.aspx?link=M%3AXamarin.Forms.Device.StartTimer(System.TimeSpan%2CSystem.Func%7BSystem.Boolean%7D)
I think that the best that you can do is following:
Unfortunately, the way that these two platforms have evolved to handle executing background code is completely different. As such, there is no way that we can abstract the backgrounding feature into the Xamarin.Forms library. Instead, we going to continue to rely on the native APIs to execute our shared background task.
Further information for this topic can be found here:
https://robgibbens.com/backgrounding-with-xamarin-forms/
Does anyone know how to detect when the user changes the current input source in OSX?
I can call TISCopyCurrentKeyboardInputSource() to find out which input source ID is being used like this:
TISInputSourceRef isource = TISCopyCurrentKeyboardInputSource();
if ( isource == NULL )
{
cerr << "Couldn't get the current input source\n.";
return -1;
}
CFStringRef id = (CFStringRef)TISGetInputSourceProperty(
isource,
kTISPropertyInputSourceID);
CFRelease(isource);
If my input source is "German", then id ends up being "com.apple.keylayout.German", which is mostly what I want. Except:
The results of TISCopyCurrentKeyboardInputSource() doesn't change once my process starts? In particular, I can call TISCopyCurrentKeyboardInputSource() in a loop and switch my input source, but TISCopyCurrentKeyboardInputSource() keeps returning the input source that my process started with.
I'd really like to be notified when the input source changes. Is there any way of doing this? To get a notification or an event of some kind telling me that the input source has been changed?
You can observe the NSTextInputContextKeyboardSelectionDidChangeNotification notification posted by NSTextInputContext to the default Cocoa notification center. Alternatively, you can observe the kTISNotifySelectedKeyboardInputSourceChanged notification delivered via the Core Foundation distributed notification center.
However, any such change starts in a system process external to your app. The system then notifies the frameworks in each app process. The frameworks can only receive such notifications when it is allowed to run its event loop. Likewise, if you're observing the distributed notification yourself, that can only happen when the event loop (or at least the main thread's run loop) is allowed to run.
So, that explains why running a loop which repeatedly checks the result of TISCopyCurrentKeyboardInputSource() doesn't work. You're not allowing the frameworks to monitor the channel over which it would be informed of the change. If, rather than a loop, you were to use a repeating timer with a low enough frequency that other stuff has a chance to run, and you returned control to the app's event loop, you would see the result of TISCopyCurrentKeyboardInputSource() changing.