Odd characters generated by mouse movement on Raspbian

[fizzikzz]

I made a dotnet console application using the ReactiveUI example as a template. Mouse movement over the window area generates these strange characters in the top left of the screen under the menubar:

[BDisp]

Do you are using the nuget package or the current main branch?

[fizzikzz]

It's main branch, not nuget.

[BDisp]

Ok and what driver do you are using, CursesDriver or NetDriver? Do you are also using the Process class?

[fizzikzz]

It's the CursesDriver. I'm not sure about the process class...I dont think so. I copy and pasted the terminalscheduler.cs from the Reactive example and all this app is using so far is a menubar, a statusbar, labels, and lineviews.

[BDisp]

I don't have Raspbian. Can you try first on another Linux version, like Ubuntu, to see if that happens, please?

[fizzikzz]

Okay, so I had a datetime statusbar item that was being updated via an observable every second:

which was updating the statusbar item this way:

And when I commented out that observable, the behaviour stopped. What would be the proper way of binding the statusbar item to the whenAny?

[tznind]

Can you try updating the UI using Application.MainLoop.Invoke. Typically you don't want to update UI components from another Thread.

So something like:

Application.MainLoop.Invoke(()=>{
dateTimeStatusItem.Text = time;
});

[fizzikzz]

I was under the impression that observing on the RxApp.MainThreadScheduler would ensure things happened on the UI thread?

[BDisp]

Perhaps is not ensuring, because it don't know how to deal with the Terminal.Gui threads.

[fizzikzz]

I tried replace the code with Application.MainLoop.Invoke...

The issue remains

[tznind]

Can you try running the following in a new console app on your OS. It should replicate what you are trying to do (I think). And narrow down whether it is an issue with the Environment or with the code:

using System;
using System.Threading;
using System.Threading.Tasks;
using Terminal.Gui;

namespace repro
{
    class Program
    {
        static void Main(string[] args)
        {
            Application.Init();

            var bar = new StatusBar();
            var item = new StatusItem(Key.D0,"fff",()=>{});
            bar.AddItemAt(0,item);

            Task.Run(()=>{

                while(true)
                {
                    Thread.Sleep(100);
                    Application.MainLoop.Invoke(()=>{               
                        item.Title = DateTime.Now.ToString();
                        bar.SetNeedsDisplay(); 
                    });
                }
            });

            Application.Top.Add(bar);

            Application.Run();
        }
    }
}

[BDisp]

It's not there where you have to place the Application.MainLoop.Invoke, but where you call DateTimeStatusItem.

[fizzikzz]

In my MainView, which is analogous to the "LoginView" of the React example. I init the status bar in the Program.cs and pass it into the constructor of the MainView where I add the DateTimeStatusBarItem and bind it to the Observable interval in the MainViewModel (which is analogous to the "LoginViewModel" in the React example)

[fizzikzz]

I've tried taking out the observe on and invoking the way that tznind suggested:

but the issue remains unless I tell the driver to stop listening to mouse events after I Application.Init()

[BDisp]

The LoginViewModel doesn't have any binding to an Observable that call the UI thread in a determined interval. It only have events that causes the UI been refreshed by the MainLoop. With tasks running on the background the calling to the UI thread must be do through the Application.MainLoop.Invoke.

[tznind]

How often do change events come in? is it possible they are millions of times a second or something?

If you are able to run the demo code I linked that would help rule out any Environment related issue.

[fizzikzz]

I tried that out by changing the subscription of the Observable:

Its just once a second, very tame.

[fizzikzz]

It didn't resolve by moving the MainLoop.Invoke() to the MainViewModel instead

[fizzikzz]

It appears to be caused by mouse-movements over the window, during the window updates, no matter how quick or slow the interval of the observable.

[tznind]

Can you try changing GetWifiInformation to the time string or a fixed value? Is it possible that is spawning a subprocess?

[fizzikzz]

I commented it right out, but the issue remains :(

[tznind]

Is there any other part of your program that could be spawning a sub-process in the background attached to the same console?

For reference I can get the following:

By changing my example code to:

            Task.Run(()=>{

                while(true)
                {
                    Thread.Sleep(500);

                    Process.Start("echo"," ");

                    Application.MainLoop.Invoke(()=>{               
                        item.Title = DateTime.Now.ToString();
                        bar.SetNeedsDisplay(); 
                    });
                }
            });

[fizzikzz]

Definitely!

[fizzikzz]

That's definitely it

[fizzikzz]

Is there a way around it?

[BDisp]

Can you try on another Linux version to exclude a version issue?

[fizzikzz]

I don't have another version of linux to exclude version issues, but it appears tznind found out how to trigger it on his own version

[BDisp]

This is why I mentioned the Process class before. Using it it's needed to redirect the output and error to another way, other than the console.

[fizzikzz]

So how can I invoke commands without interfering with the currently displayed console?

[BDisp]

Read this #1501

[fizzikzz]

So just waiting for repo-update to get the fixed code?

[BDisp]

So just waiting for repo-update to get the fixed code?

No, that was already merged into main branch.

[BDisp]

I don't have another version of linux to exclude version issues, but it appears tznind found out how to trigger it on his own version

@tznind only proves that using the Process class causes this issue and may have some sub-process in the React library at RxApp.MainThreadScheduler which may call some sub-process.

[tznind]

Also just to check that there is no kind of Console logging going on in your ReactiveUI app? or use of Console.Write...

[fizzikzz]

It's definitely process that also uses a terminal. I invoke a command to the shell the get the current wlan0 information. If the mouse is moving around the window while it does that, you see the odd characters

[tznind]

Great, seems like we are getting to the bottom of this. Please can you try changing your Process starting code to be something like this:

var startInfo = new ProcessStartInfo
{
    FileName = "echo",
    Arguments = " ",
    UseShellExecute = false,
    RedirectStandardOutput = true,
    RedirectStandardInput = true,
    CreateNoWindow = true,
    RedirectStandardError = true,
};

var process = new Process();
process.StartInfo = startInfo;
process.Start();

while (!process.StandardOutput.EndOfStream)
{
    process.StandardOutput.ReadLine().Trim();
}

[fizzikzz]

unfortunately my shell invoking is being done through Dein Toolbox because it's a crossplatform application :(.

I think I'll have to pull down a copy of Dein's repo instead of using the nuget so I can get into the process behavior

[BDisp]

The problem is that the input, output and error is redirect to the console while the process occurs. Moving the mouse is like an input of characters and the process is redirecting to the console. If redirecting these output and error to the process events which is writing to a variable, this output on the console doesn't occurs.

[tznind]

If redirecting these output and error to the process events which is writing to a variable, this output on the console doesn't occurs.

@BDisp does this mean that the input events don't go to Terminal.Gui for the lifetime of the process?

So you couldn't for example have 1 button to start a long running process and another button to terminate it (because while it was running you wouldn't be able to hit Tab and Enter to switch to the other button).

Is there any way around this? e.g. to explicitly redirect the standard input back to Terminal.Gui after starting the process?

[BDisp]

This is only a CursesDriver issue and only with mouse. With the others drivers this doesn't happens, I think.

[fizzikzz]

I can confirm, the same cross-platform program, running on windows, doesn't have the same behaviour. Are there any plans to address it? I wasn't able to resolve the issue aside from setting up a screen-refreshing loop if the CursesDriver is detected, but that seems sloppy.

[tznind]

So I decided to do a little digging. I was able to have a process running for a long time (sleep command below) and still interact with Terminal.Gui to e.g. stop the process early.

But you still need all the extra process start info stuff.

using System;
using System.Diagnostics;
using System.IO;
using System.Threading;
using System.Threading.Tasks;
using Terminal.Gui;

namespace repro
{
    class Program
    {
        static void Main(string[] args)
        {
            Application.Init();

            Process process = null;

            var label = new Label("Exe Status:");
            var btnStart = new Button("Start"){Y=1};
            var btnStop = new Button("Stop"){Y=2};

            btnStart.Clicked += ()=>{
                try{
                    process = StartProcess();
                }catch(Exception ex)
                {
                    MessageBox.ErrorQuery("Error starting process",ex.Message,"Ok");
                }
            };

            btnStop.Clicked += ()=>{
                process?.Kill();
            };

            Application.MainLoop.AddTimeout(TimeSpan.FromMilliseconds(100),

            (m)=> {
                label.Text = "Is Running:" + (process == null ? "Not Started" : (!process.HasExited).ToString());
                return true;
            });

            Application.Top.Add(label);
            Application.Top.Add(btnStart);
            Application.Top.Add(btnStop);

            Application.Run();
            Application.Shutdown();
        }

        private static Process StartProcess()
        {
            var startInfo = new ProcessStartInfo
            {
                FileName = "sleep",
                Arguments = "5",
                UseShellExecute = false,
                RedirectStandardOutput = true,
                RedirectStandardInput = true,
                RedirectStandardError = true,
                CreateNoWindow = true,
            };

            var process = new Process();
            process.StartInfo = startInfo;
            process.Start();

            return process;
        }

        private static Process StartProcessBlind()
        {
            return Process.Start("sleep","5");
        }
    }
}

[BDisp]

This sample doesn't do the mouse issue behavior. Can you confirm, please?

    Application.Init ();

    var output = new Label ();
    var error = new Label (0, 1, "");
    var tv = new TextView () {
        X = Pos.Center (),
        Y = Pos.Center (),
        Width = Dim.Percent (70f),
        Height = Dim.Percent (60f),
        Text = "Typing while the task is running...",
        SelectionStartColumn = 0,
        SelectionStartRow = 0,
        CursorPosition = new Point(35, 0)
    };
    var bar = new StatusBar ();
    var item = new StatusItem (Key.D0, "fff", () => { });
    bar.AddItemAt (0, item);

    var running = true;

    Task.Run (() => {

        while (true) {
            Thread.Sleep (500);

            var date = DateTime.Now.ToString ();
            var strOutput = "";
            var strError = "";
            var startInfo = new ProcessStartInfo {
                FileName = "echo",
                Arguments = date,
                UseShellExecute = false,
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                RedirectStandardInput = true,
                CreateNoWindow = true
            };

            var process = new Process {
                StartInfo = startInfo,
                EnableRaisingEvents = true,
            };
            process.OutputDataReceived += (sender, args) => {
                strOutput = args.Data ?? date;
            };
            process.ErrorDataReceived += (sender, args) => {
                strError = args.Data ?? "";
            };
            process.Start ();
            process.BeginOutputReadLine ();
            process.BeginErrorReadLine ();
            process.WaitForExit ();
            process.CancelOutputRead ();

            if (!running) {
                break;
            }
            Application.MainLoop.Invoke (() => {
                item.Title = date;
                bar.SetNeedsDisplay ();
                output.Text = strOutput;
                error.Text = strError;
            });
        }
    });

    Application.Top.Add (bar, output, error, tv);

    Application.Run ();

    running = false;

[tznind]

I think the critical bit is this:

RedirectStandardOutput = true,
RedirectStandardError = true,
RedirectStandardInput = true,

There is a use case where the Process creation is handled by an external dependency that the programmer doesn't have control of and it doesnt use all/any of those 3 properties.

I'd be interested if there is a way to suppress or prevent the behaviour manifesting when just using the vanilla Process.Start("exe","args") code (I have a feeling the answer is no - at least not with a lot of digging in ncurses)

[BDisp]

I already made a google search about the mouse behavior issue on ncurses without success to find something useful. I'm also very interested on the resolution of this, but if it it's some ncurses issue I can't managed it.