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.
Related
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.
I'm writing a small accessibility app which simulates certain keyboard gestures, such as volume up\down.
The goal is to send a single command.
In practice, the volume goes all the way up to 100%, as if user pressed a button for couple seconds or as if the message was dispatched multiple times.
This behavior is the same with both PostMessage and SendMessage, in both C and C# (using PInvoke)
C:
PostMessage(0xffff, 0x0319, 0, 0xa0000)
C#:
PostMessage(new IntPtr(0xffff), WindowMessage.WM_APPCOMMAND, (void*)0, (void*)0xa0000);
The meaning of parameters: send to all windows, message, no source, volume up
Question: How do I issue a command which would result in Windows adjusting volume by the smallest increment?
Additionally, I attempted using WP_KEYUP and WP_KEYDOWN, without success
// dispatch to all apps, message, wparam: virtual key, lparam: repeat count = 1
User32.PostMessage(new IntPtr(0xffff), User32.WindowMessage.WM_KEYDOWN, new IntPtr(0xaf000), new IntPtr(1));
User32.PostMessage(new IntPtr(0xffff), User32.WindowMessage.WM_KEYUP, new IntPtr(0xaf000), new IntPtr(1));
The reason why the command is sent multiple times is, as pointed by Hans in the comment, I broadcasted it to all windows using 0xffff as first parameter. Every window handled it by increasing volume by a notch.
The solution to sending multiple messages is to send the message to either
The shell handle GetShellWindow()
The foreground window handle GetForegroundWindow()
Both handles adjusted the volume by one notch. GetDesktopWindow() did not work, though.
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 need to perform data analysis on files in a directory as they come in.
I'd like to know, if it is better,
to implement an event listener on the directory, and start the analysis process when activated. Then having the program go into sleep forever: while(true), sleep(1e10), end
or to have a loop polling for changes and reacting.
I personally prefer the listeners way, as one is able to start the analysis twice on two new files coming in NEARLY the same time but resulting in two events. While the other solution might just handle the first one and after that finds the second new data.
Additional idea for option 1: Hiding the matlab GUI by calling frames=java.awt.Frame.getFrames and setting frames(index).setVisible(0) on the index matching the com.mathworks.mde.desk.MLMainFrame-frame. (This idea is taken from Yair Altman)
Are there other ways to realize such things?
In this case, (if you are using Windows), the best way is to use the power of .NET.
fileObj = System.IO.FileSystemWatcher('c:\work\temp');
fileObj.Filter = '*.txt';
fileObj.EnableRaisingEvents = true;
addlistener(fileObj,'Changed',#eventhandlerChanged);
There are different event types, you can use the same callback for them, or different ones:
addlistener(fileObj, 'Changed', #eventhandlerChanged );
addlistener(fileObj, 'Deleted', #eventhandlerChanged );
addlistener(fileObj, 'Created', #eventhandlerChanged );
addlistener(fileObj, 'Renamed', #eventhandlerChanged );
Where eventhandlerChanged is your callback function.
function eventhandlerChanged(source,arg)
disp('TXT file changed')
end
There is no need to use sleep or polling. If your program is UI based, then there is nothing else to do, when the user closes the figure, the program has ended. The event callbacks are executed exactly like button clicks. If your program is script-like, you can use an infinite loop.
More info in here: http://www.mathworks.com/help/matlab/matlab_external/working-with-net-events-in-matlab.html
This is a Windows Forms application. I have a function which captures some mouse events modally till a condition is met. For example, I would like to wait for the user to select a point in the window's client area (or optionally cancel the operation using the Escape key) before the function returns. I am using the following structure:
Application::AddMessageFilter(someFilter);
while(someFilter->HasUserSelectedAPoint_Or_HitEscapeKey()){
Application::DoEvents();
}
Application::RemoveMessageFilter(someFilter);
This works quite nicely except for taking up nearly 100% CPU usage when control enters the while loop. I am looking for an alternative similar to what is shown below:
Application::AddMessageFilter(someFilter);
while(someFilter->HasUserSelectedAPoint_Or_HitEscapeKey()){
// Assuming that ManagedGetMessage() below is a blocking
// call which yields control to the OS
if(ManagedGetMessage())
Application::DoEvents();
}
Application::RemoveMessageFilter(someFilter);
What is the right way to use IMessageFilter and DoEvents? How do I surrender control to the OS till a message is received? Any GetMessage equivalent in the managed world?
You could sleep the thread for 500ms or so between DoEvents() calls. Experiment with different values to see what feels right.