I'm trying to build an NES emulator using winit, which entails building a game loop which should run exactly 60 times per second.
At first, I used std::thread to create a separate thread where the game loop would run and wait 16 milliseconds before running again. This worked quite well, until I tried to compile the program again targeting WebAssembly. I then found out that both winit::window::Window and winit::event_loop::EventLoopProxy are not Send when targeting Wasm, and that std::thread::spawn panics in Wasm.
After some struggle, I decided to try to do the same thing using task::spawn_local from one of the main asynchronous runtimes. Ultimately, I went with async_std.
I'm not used to asynchronous programming, so I'm not even sure if what I'm trying to do could work.
My idea is to do something like this:
use winit::{window::WindowBuilder, event_loop::EventLoop};
use std::time::Duration;
fn main() {
let event_loop = EventLoop::new();
let _window = WindowBuilder::new()
.build(&event_loop);
async_std::task::spawn_local(async {
// game loop goes here
loop {
// [update game state]
// [update frame buffer]
// [send render event with EventLoopProxy]
async_std::task::sleep(Duration::from_millis(16)).await;
// ^ note: I'll be using a different sleep function with Wasm
}
});
event_loop.run(move |event, _, control_flow| {
control_flow.set_wait();
match event {
// ...
_ => ()
}
});
}
The problem with this approach is that the game loop will never run. If I'm not mistaken, some asynchronous code in the main thread would need to be blocked (by calling .await) for the runtime to poll other Futures, such as the one spawned by the spawn_local function. I can't do this easily, since event_loop.run is not asynchronous.
Having time to await other events shouldn't be a problem, since the control flow is set to wait.
Testing this on native code, nothing inside the game loop ever runs. Testing this on Wasm code (with wasm_timer::Delay as the sleep function), the game loop does run, but at a very low framerate and with long intervals of halting.
Having explained my situation, I would like to ask: is it possible to do what I'm trying to do, and if it is, how would I approach it? I will also accept answers telling me how I could try to do this differently, such as by using web workers.
Thanks in advance!
I have (in the past) written cross-platform (Windows/Unix) applications which, when started from the command line, handled a user-typed Ctrl-C combination in the same way (i.e. to terminate the application cleanly).
Is it possible on Windows to send a Ctrl-C/SIGINT/equivalent to a process from another (unrelated) process to request that it terminate cleanly (giving it an opportunity to tidy up resources etc.)?
I have done some research around this topic, which turned out to be more popular than I anticipated. KindDragon's reply was one of the pivotal points.
I wrote a longer blog post on the topic and created a working demo program, which demonstrates using this type of system to close a command line application in a couple of nice fashions. That post also lists external links that I used in my research.
In short, those demo programs do the following:
Start a program with a visible window using .Net, hide with pinvoke, run for 6 seconds, show with pinvoke, stop with .Net.
Start a program without a window using .Net, run for 6 seconds, stop by attaching console and issuing ConsoleCtrlEvent
Edit: The amended solution from #KindDragon for those who are interested in the code here and now. If you plan to start other programs after stopping the first one, you should re-enable CTRL+C handling, otherwise the next process will inherit the parent's disabled state and will not respond to CTRL+C.
[DllImport("kernel32.dll", SetLastError = true)]
static extern bool AttachConsole(uint dwProcessId);
[DllImport("kernel32.dll", SetLastError = true, ExactSpelling = true)]
static extern bool FreeConsole();
[DllImport("kernel32.dll")]
static extern bool SetConsoleCtrlHandler(ConsoleCtrlDelegate HandlerRoutine, bool Add);
delegate bool ConsoleCtrlDelegate(CtrlTypes CtrlType);
// Enumerated type for the control messages sent to the handler routine
enum CtrlTypes : uint
{
CTRL_C_EVENT = 0,
CTRL_BREAK_EVENT,
CTRL_CLOSE_EVENT,
CTRL_LOGOFF_EVENT = 5,
CTRL_SHUTDOWN_EVENT
}
[DllImport("kernel32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool GenerateConsoleCtrlEvent(CtrlTypes dwCtrlEvent, uint dwProcessGroupId);
public void StopProgram(Process proc)
{
//This does not require the console window to be visible.
if (AttachConsole((uint)proc.Id))
{
// Disable Ctrl-C handling for our program
SetConsoleCtrlHandler(null, true);
GenerateConsoleCtrlEvent(CtrlTypes.CTRL_C_EVENT, 0);
//Moved this command up on suggestion from Timothy Jannace (see comments below)
FreeConsole();
// Must wait here. If we don't and re-enable Ctrl-C
// handling below too fast, we might terminate ourselves.
proc.WaitForExit(2000);
//Re-enable Ctrl-C handling or any subsequently started
//programs will inherit the disabled state.
SetConsoleCtrlHandler(null, false);
}
}
Also, plan for a contingency solution if AttachConsole() or the sent signal should fail, for instance sleeping then this:
if (!proc.HasExited)
{
try
{
proc.Kill();
}
catch (InvalidOperationException e){}
}
The closest that I've come to a solution is the SendSignal 3rd party app. The author lists source code and an executable. I've verified that it works under 64-bit windows (running as a 32-bit program, killing another 32-bit program), but I've not figured out how to embed the code into a windows program (either 32-bit or 64-bit).
How it works:
After much digging around in the debugger I discovered that the entry point that actually does the behavior associated with a signal like ctrl-break is kernel32!CtrlRoutine. The function had the same prototype as ThreadProc, so it can be used with CreateRemoteThread directly, without having to inject code. However, that's not an exported symbol! It's at different addresses (and even has different names) on different versions of Windows. What to do?
Here is the solution I finally came up with. I install a console ctrl handler for my app, then generate a ctrl-break signal for my app. When my handler gets called, I look back at the top of the stack to find out the parameters passed to kernel32!BaseThreadStart. I grab the first param, which is the desired start address of the thread, which is the address of kernel32!CtrlRoutine. Then I return from my handler, indicating that I have handled the signal and my app should not be terminated. Back in the main thread, I wait until the address of kernel32!CtrlRoutine has been retrieved. Once I've got it, I create a remote thread in the target process with the discovered start address. This causes the ctrl handlers in the target process to be evaluated as if ctrl-break had been pressed!
The nice thing is that only the target process is affected, and any process (even a windowed process) can be targeted. One downside is that my little app can't be used in a batch file, since it will kill it when it sends the ctrl-break event in order to discover the address of kernel32!CtrlRoutine.
(Precede it with start if running it in a batch file.)
I guess I'm a bit late on this question but I'll write something anyway for anyone having the same problem.
This is the same answer as I gave to this question.
My problem was that I'd like my application to be a GUI application but the processes executed should be run in the background without any interactive console window attached. I think this solution should also work when the parent process is a console process. You may have to remove the "CREATE_NO_WINDOW" flag though.
I managed to solve this using GenerateConsoleCtrlEvent() with a wrapper app. The tricky part is just that the documentation is not really clear on exactly how it can be used and the pitfalls with it.
My solution is based on what is described here. But that didn't really explain all the details either and with an error, so here is the details on how to get it working.
Create a new helper application "Helper.exe". This application will sit between your application (parent) and the child process you want to be able to close. It will also create the actual child process. You must have this "middle man" process or GenerateConsoleCtrlEvent() will fail.
Use some kind of IPC mechanism to communicate from the parent to the helper process that the helper should close the child process. When the helper get this event it calls "GenerateConsoleCtrlEvent(CTRL_BREAK, 0)" which closes down itself and the child process. I used an event object for this myself which the parent completes when it wants to cancel the child process.
To create your Helper.exe create it with CREATE_NO_WINDOW and CREATE_NEW_PROCESS_GROUP. And when creating the child process create it with no flags (0) meaning it will derive the console from its parent. Failing to do this will cause it to ignore the event.
It is very important that each step is done like this. I've been trying all different kinds of combinations but this combination is the only one that works. You can't send a CTRL_C event. It will return success but will be ignored by the process. CTRL_BREAK is the only one that works. Doesn't really matter since they will both call ExitProcess() in the end.
You also can't call GenerateConsoleCtrlEvent() with a process groupd id of the child process id directly allowing the helper process to continue living. This will fail as well.
I spent a whole day trying to get this working. This solution works for me but if anyone has anything else to add please do. I went all over the net finding lots of people with similar problems but no definite solution to the problem. How GenerateConsoleCtrlEvent() works is also a bit weird so if anyone knows more details on it please share.
Somehow GenerateConsoleCtrlEvent() return error if you call it for another process, but you can attach to another console application and send event to all child processes.
void SendControlC(int pid)
{
AttachConsole(pid); // attach to process console
SetConsoleCtrlHandler(NULL, TRUE); // disable Control+C handling for our app
GenerateConsoleCtrlEvent(CTRL_C_EVENT, 0); // generate Control+C event
}
Edit:
For a GUI App, the "normal" way to handle this in Windows development would be to send a WM_CLOSE message to the process's main window.
For a console app, you need to use SetConsoleCtrlHandler to add a CTRL_C_EVENT.
If the application doesn't honor that, you could call TerminateProcess.
Here is the code I use in my C++ app.
Positive points :
Works from console app
Works from Windows service
No delay required
Does not close the current app
Negative points :
The main console is lost and a new one is created (see FreeConsole)
The console switching give strange results...
// Inspired from http://stackoverflow.com/a/15281070/1529139
// and http://stackoverflow.com/q/40059902/1529139
bool signalCtrl(DWORD dwProcessId, DWORD dwCtrlEvent)
{
bool success = false;
DWORD thisConsoleId = GetCurrentProcessId();
// Leave current console if it exists
// (otherwise AttachConsole will return ERROR_ACCESS_DENIED)
bool consoleDetached = (FreeConsole() != FALSE);
if (AttachConsole(dwProcessId) != FALSE)
{
// Add a fake Ctrl-C handler for avoid instant kill is this console
// WARNING: do not revert it or current program will be also killed
SetConsoleCtrlHandler(nullptr, true);
success = (GenerateConsoleCtrlEvent(dwCtrlEvent, 0) != FALSE);
FreeConsole();
}
if (consoleDetached)
{
// Create a new console if previous was deleted by OS
if (AttachConsole(thisConsoleId) == FALSE)
{
int errorCode = GetLastError();
if (errorCode == 31) // 31=ERROR_GEN_FAILURE
{
AllocConsole();
}
}
}
return success;
}
Usage example :
DWORD dwProcessId = ...;
if (signalCtrl(dwProcessId, CTRL_C_EVENT))
{
cout << "Signal sent" << endl;
}
A solution that I have found from here is pretty simple if you have python 3.x available in your command line. First, save a file (ctrl_c.py) with the contents:
import ctypes
import sys
kernel = ctypes.windll.kernel32
pid = int(sys.argv[1])
kernel.FreeConsole()
kernel.AttachConsole(pid)
kernel.SetConsoleCtrlHandler(None, 1)
kernel.GenerateConsoleCtrlEvent(0, 0)
sys.exit(0)
Then call:
python ctrl_c.py 12345
If that doesn't work, I recommend trying out the windows-kill project:
Choco: https://github.com/ElyDotDev/windows-kill
Node: https://github.com/ElyDotDev/node-windows-kill
void SendSIGINT( HANDLE hProcess )
{
DWORD pid = GetProcessId(hProcess);
FreeConsole();
if (AttachConsole(pid))
{
// Disable Ctrl-C handling for our program
SetConsoleCtrlHandler(NULL, true);
GenerateConsoleCtrlEvent(CTRL_C_EVENT, 0); // SIGINT
//Re-enable Ctrl-C handling or any subsequently started
//programs will inherit the disabled state.
SetConsoleCtrlHandler(NULL, false);
WaitForSingleObject(hProcess, 10000);
}
}
Thanks to jimhark's answer and other answers here, I found a way to do it in PowerShell:
$ProcessID = 1234
$MemberDefinition = '
[DllImport("kernel32.dll")]public static extern bool FreeConsole();
[DllImport("kernel32.dll")]public static extern bool AttachConsole(uint p);
[DllImport("kernel32.dll")]public static extern bool GenerateConsoleCtrlEvent(uint e, uint p);
public static void SendCtrlC(uint p) {
FreeConsole();
if (AttachConsole(p)) {
GenerateConsoleCtrlEvent(0, p);
FreeConsole();
}
AttachConsole(uint.MaxValue);
}'
Add-Type -Name 'dummyName' -Namespace 'dummyNamespace' -MemberDefinition $MemberDefinition
[dummyNamespace.dummyName]::SendCtrlC($ProcessID)
What made things work was sending the GenerateConsoleCtrlEvent to the desired process group instead of sending it to all processes that share the console of the calling process and then AttachConsole back to the current process' parent's console.
Yes. The https://github.com/ElyDotDev/windows-kill project does exactly what you want:
windows-kill -SIGINT 1234
It should be made crystal clear because at the moment it isn't.
There is a modified and compiled version of SendSignal to send Ctrl-C (by default it only sends Ctrl+Break). Here are some binaries:
(2014-3-7) : I built both 32-bit and 64-bit version with Ctrl-C, it's called SendSignalCtrlC.exe and you can download it at: https://dl.dropboxusercontent.com/u/49065779/sendsignalctrlc/x86/SendSignalCtrlC.exe https://dl.dropboxusercontent.com/u/49065779/sendsignalctrlc/x86_64/SendSignalCtrlC.exe -- Juraj Michalak
I have also mirrored those files just in case:
32-bit version: https://www.dropbox.com/s/r96jxglhkm4sjz2/SendSignalCtrlC.exe?dl=0
64-bit version: https://www.dropbox.com/s/hhe0io7mcgcle1c/SendSignalCtrlC64.exe?dl=0
Disclaimer: I didn't build those files. No modification was made to the compiled
original files. The only platform tested is the 64-bit Windows 7. It is recommended to adapt the source available at http://www.latenighthacking.com/projects/2003/sendSignal/ and compile it yourself.
In Java, using JNA with the Kernel32.dll library, similar to a C++ solution. Runs the CtrlCSender main method as a Process which just gets the console of the process to send the Ctrl+C event to and generates the event. As it runs separately without a console the Ctrl+C event does not need to be disabled and enabled again.
CtrlCSender.java - Based on Nemo1024's and KindDragon's answers.
Given a known process ID, this consoless application will attach the console of targeted process and generate a CTRL+C Event on it.
import com.sun.jna.platform.win32.Kernel32;
public class CtrlCSender {
public static void main(String args[]) {
int processId = Integer.parseInt(args[0]);
Kernel32.INSTANCE.AttachConsole(processId);
Kernel32.INSTANCE.GenerateConsoleCtrlEvent(Kernel32.CTRL_C_EVENT, 0);
}
}
Main Application - Runs CtrlCSender as a separate consoless process
ProcessBuilder pb = new ProcessBuilder();
pb.command("javaw", "-cp", System.getProperty("java.class.path", "."), CtrlCSender.class.getName(), processId);
pb.redirectErrorStream();
pb.redirectOutput(ProcessBuilder.Redirect.INHERIT);
pb.redirectError(ProcessBuilder.Redirect.INHERIT);
Process ctrlCProcess = pb.start();
ctrlCProcess.waitFor();
I found all this too complicated and used SendKeys to send a CTRL-C keystroke to the command line window (i.e. cmd.exe window) as a workaround.
A friend of mine suggested a complete different way of solving the problem and it worked for me. Use a vbscript like below. It starts and application, let it run for 7 seconds and close it using ctrl+c.
'VBScript Example
Set WshShell = WScript.CreateObject("WScript.Shell")
WshShell.Run "notepad.exe"
WshShell.AppActivate "notepad"
WScript.Sleep 7000
WshShell.SendKeys "^C"
// Send [CTRL-C] to interrupt a batch file running in a Command Prompt window, even if the Command Prompt window is not visible,
// without bringing the Command Prompt window into focus.
// [CTRL-C] will have an effect on the batch file, but not on the Command Prompt window itself -- in other words,
// [CTRL-C] will not have the same visible effect on a Command Prompt window that isn't running a batch file at the moment
// as bringing a Command Prompt window that isn't running a batch file into focus and pressing [CTRL-C] on the keyboard.
ulong ulProcessId = 0UL;
// hwC = Find Command Prompt window HWND
GetWindowThreadProcessId (hwC, (LPDWORD) &ulProcessId);
AttachConsole ((DWORD) ulProcessId);
SetConsoleCtrlHandler (NULL, TRUE);
GenerateConsoleCtrlEvent (CTRL_C_EVENT, 0UL);
SetConsoleCtrlHandler (NULL, FALSE);
FreeConsole ();
SIGINT can be send to program using windows-kill, by syntax windows-kill -SIGINT PID, where PID can be obtained by Microsoft's pslist.
Regarding catching SIGINTs, if your program is in Python then you can implement SIGINT processing/catching like in this solution.
Based on process id, we can send the signal to process to terminate forcefully or gracefully or any other signal.
List all process :
C:\>tasklist
To kill the process:
C:\>Taskkill /IM firefox.exe /F
or
C:\>Taskkill /PID 26356 /F
Details:
http://tweaks.com/windows/39559/kill-processes-from-command-prompt/
How I can write data in serial port, with delay between send's messages?
This is my code:
void MainWindow::on_pushButton_Done_clicked()
{
if(sport->isOpen()){
sport->clear();
QString cmd = Phase+Mode;
//Write Stop
sport->write("stop!", 5);
//Write Mode
sport->write(cmd.toStdString().c_str(), cmd.toStdString().length());
//Write Speed
sport->write(Speed.toStdString().c_str(), Speed.toStdString().length());
//Write Direction
sport->write(Direction.toStdString().c_str(), Direction.toStdString().length());
//Run
sport->write("start!", 6);
}
}
My device receives an error message when I call this function.
Thank you.
2 options:
use waitForBytesWritten to ensure the bytes are written and then a short sleep
however this will block the thread and will block the gui
the other is using a QTimer to trigger another slot a few times and a field that will indicate what needs to be sent
Looks like you are trying to program some step motor controller or something similar.
Usually in such controllers you should wait for controller response to verify that command was processed properly.
It looks like that your design of code is very bad. Move everything related with this controller to separate class, which has set of slots, something like: starRotateLeftWithSpeed(double). Code will be cleaner and it will be easy to use thread if you decide to use methods like waitForBytesWritten proposed in another answer.
Definitely you should read controller manual more carefully.
Well i've been looking how to do an auto updater on google, however no success.
What i would plan is to create an updater (ANother exe called by QProcess though the principal exe) but here ihave some questions:
How do i make the QProcess silent?
If there's a new version, how do i show a notification on the window from where the process has been started (I meant i've create the process in Game.exe, i want to send a notification to Game.exe from Updater.exe that there's a new version available.)
Thanks for the answers.
First, I've never encountered a need to create anything other than a QThread to handle my update needs. The QProcess would be helpful if, once the user updates, you want to download, install, and relaunch the program while the user continues with the main program. (But this can all be achieved with a shell script, python script, even BAT file)
When you use QProcess, you will have to rely on the signals readyReadStandardError() and readyReadStandardOutput(). Then the application that your process is calling should send its output to stderr or stdout. Updater.exe should write to either of these files.
I would imagine your Updater to make use of QNetworkAccessManager::finished(QNetworkReply *reply). When this slot is called, please do something nicer than this:
void Updater::replyFinished(QNetworkReply *reply){
QString r(reply->readAll());
if(r.contains(SERVER_REPLY_UPDATE_AVAILABLE)){
qDebug() << "yes";
}else{
qDebug() << "no";
QApplication::quit();
}
}
If Updater.exe is going to be a full blown GUI application, do not call the show() method unless it's needed and it should appear to run in the background. I would prefer a script, but you know me.
Then your Game.exe will set up a QProcess. You can pass arguments to the process within the QProcess::start() function.
Good arguments that will help direct your update process would be:
Game.exe version number
"check_for_updates"
"ignore_updates"
"download_update"
finally, in Game.exe:
...
connect(process,SIGNAL(readyReadStandardError()),this,SLOT(readProcessReply()));
...
void Game::readProcessReply(){
QString r(process->readAllStandardError());
if(r.contains("yes")){
//show your dialog here
}else{
//do nothing
}
}
I've got a QT problem.
I want to make my program stop at place where I define, let`s say for 3 seconds. I couldn't manage to do that. I need that because earler my program generates file and it is used by a program which I call a bit later. Problem is, that file doesn't seem have enough time to create. My code looks like this:
void MainWindow::buttonHandler()
{
QFile ..... (creating a text file);
//Making a stream and writing something to a file
//A place where program should pause for 3 seconds
system("call another.exe"); //Calling another executable, which needs the created text file, but the file doesn`t seem to be created and fully written yet;
}
Thanks in advance.
Some possibilities:
1) Use another slot for the things to do after the sleep:
QTimer::singleShot(3000, this, SLOT(anotherSlot());
...
void MyClass::anotherSlot() {
system(...);
}
2) Without another slot, using a local event loop:
//write file
QEventLoop loop;
QTimer::singleShot(3000, &loop, SLOT(quit()) );
loop.exec();
//do more stuff
I would avoid local event loop and prefer 1) though, local event loops can cause a plethora of subtle bugs (During the loop.exec(), anything can happen).
Try void QTest::qSleep ( int ms ) or void QTest::qWait ( int ms )
Looking into the source of these functions is also useful if you do not want the overhead of QTest.
More info at http://doc.qt.io/qt-5/qtest.html#qSleep
Maybe you just need to close the written file before you call the other program:
QFile f;
...
f.close();
(This also flushes internal buffers so that they are written to disk)