Capturing escape key during a command

[misterblobby]

Hi all,

I have a vb.net Autocad add-in which runs an iterative routine with a while..wend loop that often takes a few minutes to finish.

The routine is very stable and always restores user control eventually, but if the user hits the escape key while it is running, a fatal error occurs in acad.exe.

Does anyone know if there is a way to detect that the escape key has been pressed so the routine is exited?

[SENL1362]

bool EscapePressed=false;

//before your while loop

Autodesk.AutoCAD.ApplicationServices.Application.PreTranslateMessage += new PreTranslateMessageEventHandler(myEscWatcher);

while(true)

{

    //do your work

   if (EscapePressed)

       break;

}

const int KEYDOWN= 0x0100;

void myEscWatcher(object sender, PreTranslateMessageEventArgs messageDetails)
{
if (messageDetails.Message.message == KEYDOWN && ((Keys)(int)messageDetails.Message.wParam & Keys.KeyCode) == Keys.Escape)
{
    //do something when ESCAPE has been pressed, for example

   EscapePressed=true;
}

[augusto.goncalves · Accepted solution]

Hi,

AutoCAD has a property to determine whenever the ESCAPE was pressed, check the posts below:

http://adndevblog.typepad.com/autocad/2013/02/return-to-command-prompt-when-escape-is-pressed-using-...

http://adndevblog.typepad.com/autocad/2012/07/allowing-users-to-escape-from-long-operations-in-autoc...

[misterblobby]

Thanks guys,

Easy as that!

Just for convenience, below is the relevant piece of code from the first link above in VB. I had to place it in a few different places to catch the keypress reliably, but it works well if in the right spot.

If HostApplicationServices.Current.UserBreak = True Then
           Throw New Autodesk.AutoCAD.Runtime.Exception(ErrorStatus.UserBreak, "Escape pressed")
            Exit Sub

End If

[FRFR1426]

It looks like it's not working anymore since AutoCAD 2015.

[ActivistInvestor]

---

@FRFR1426 wrote:

It looks like it's not working anymore since AutoCAD 2015.

---

If you're calling UserBreak() from a non-interactive process, it will not work because it requires AutoCAD to process windows messages in order to detect the ESC keypress. While a non-interactive process is underway, AutoCAD normally doesn't process windows messages until the process returns control to it.

In that circumstance, the native, undocumented acedUsrBrkWithMessagePump() API has always been required, but this was never exposed to managed code.

acedUsrBrkWithMessagePump() is essentially nothing more than this:

   public static class HostApplicationServicesExtensions
   {
      public static bool UserBreakWithMessagePump(this HostApplicationServices hostapp)
      {
         System.Windows.Forms.Application.DoEvents();
         return hostapp.UserBreak();
      }
   }

[FRFR1426]

I'm pretty sure I've tried with a DoEvents.

[ActivistInvestor]

---

@FRFR1426 wrote:

I'm pretty sure I've tried with a DoEvents.

---

It works here (in-use on AutoCAD 2013-2017).

It's also used extensively to force AutoCAD to refresh the display after calls to Editor.WriteMessage() so they appear immediately.