How do I generate a call to the UI thread on an ETO application using C#?

Question

I want to build a cross platform GUI app for linux and windows. ETO was recommended https://github.com/picoe/Eto I'm pretty used to winforms, but I'm stuck trying to get ETO to respond to a repeated call from a timer. The examples I've found require using the winforms this.InvokeRequired, which doesn't exist under Linux.

I want a timer to start up and send a signal to update the GUI textbox every 100ms.

I have this:

// This timer needs to kick off every 100ms to update the GUI.
Timer myTimer = new Timer(TimerTick, // the callback function
new object(),
0,
100); // Every 100ms

private static void TimerTick(object state)
{
    if (ProcessTics == true)
    { Task.Factory.StartNew(CallTheBackgroundFunctions); }

}


private static void CallTheBackgroundFunctions()
{
    OtherClass.ProcessTic();
    mainTextDisplay.Text = OtherClass.GetText(); //This errors out
}

The problem is the timer is a static instance and I've written my OtherClass as a static instance. If I provide a reference to the main form, this.Invalidate(); doesn't update the gui.

I believe I need to use ETO's invoke, but I'm really struggling to make it work.

Any suggestions for a good way to have a background thread update the GUI on an ETO form? Or suggestions for another cross platform GUI framework that supports C#? This is all for a text processing project.

Thank you for your time.

Answer 1

The real trick was to properly call Application.Instance.Invoke delegate.
In case anyone else runs into a similar issue, here's how I arranged the classes to update a textbox from another thread.

public static class TextRender
{   
    public delegate void BroadCastText(object sender, EventArgs e, string message);
    public static BroadCastText Broadcasting;



    public static void ProcessTic()
    {       
        string outboundText = "";
        // do some behind the scenes work.

        if (Broadcasting != null) // Verify someone has subscribed to the event, otherwise null object error.
        {
            Broadcasting(null, EventArgs.Empty, outboundText);
        }
        else
        {
            Console.WriteLine("I'm talking but no one is listening!!");
        }
    }
}

public class MainForm : Form
{
    Timer myTimer; // High resolution timer.
    UITimer UITimerTick = new UITimer(); // Low resolution timer, but runs on the UI thread.
    TextArea mainTextDisplay = new TextArea(); // Textbox that needs to be updated in realtime.
    

    
   private static void TimerTick(object state)
   {
       TextRender.ProcessTic();
   }


   /// <summary>
   /// Takes the incoming string and uses the UI thread to update the display.
   /// </summary>
   /// <param name="sender"></param>
   /// <param name="e"></param>
   /// <param name="message"></param>
   private void WriteTextDelegate(Object sender, EventArgs e, string message)
   {
       Application.Instance.Invoke(delegate {
           mainTextDisplay.Text = message;
       });
   }

   /// <summary>
   /// Toggles a timer that performs a callback to update the UI.
   /// </summary>
   private void Timer1()
   {
       if (Timer1Active)
       {
           TextRender.Broadcasting -= WriteTextDelegate;
           myTimer.Dispose();
           Timer1Active = false;
       }
       else
       {
           myTimer = new Timer(TimerTick, // the callback function
           new object(), 
           0, // the time to wait before the timer starts it's first tick
           50); // the tick interval

           TextRender.Broadcasting += WriteTextDelegate;  //  Subscribe to the event
           Timer1Active = true;
           Console.WriteLine("Timer 1 start");
       }
   }

   /// <summary>
   /// Toggles using the UI timer solution.  This is not intended to update faster than 1 per second.  
   /// </summary>
   private void Timer2()
   {
       if (Timer2Active)
       {
           UITimerTick.Stop();
           UITimerTick.Dispose();
           Timer2Active = false;
       }
       else
       {
           UITimerTick.Interval = 0.5;  //half second refresh.  Can't go any faster without window freezing.
           UITimerTick.Elapsed += (sender, ev) =>
           {
               TextRender.ProcessTic();
               mainTextDisplay.Text = TextRender.CachedText;
           };
           
           UITimerTick.Start();
           Timer2Active = true;
           Console.WriteLine("Timer 2 start.");
       }
   }

}