Re: [MdeModulePkg/TerminalDxe] Why do we delay 2s for ESC being pressed?

["Zeng, Star" <star.zeng@intel.com>]

Cc Terminal expert Ray to see if any comments on this.


Thanks,
Star
-----Original Message-----
From: Heyi Guo [mailto:heyi.guo@linaro.org] 
Sent: Wednesday, November 8, 2017 3:04 PM
To: edk2-devel@lists.01.org
Cc: Zeng, Star <star.zeng@intel.com>; Dong, Eric <eric.dong@intel.com>
Subject: [MdeModulePkg/TerminalDxe] Why do we delay 2s for ESC being pressed?

Hi folks,

We found ESC key responded fairly slow on serial port terminal, and we think it might be caused by the code in UnicodeToEfiKey in TerminalConIn.c:

     if (UnicodeChar == ESC) {
       TerminalDevice->InputState = INPUT_STATE_ESC;
     }

     if (UnicodeChar == CSI) {
       TerminalDevice->InputState = INPUT_STATE_CSI;
     }

     if (TerminalDevice->InputState != INPUT_STATE_DEFAULT) {
       Status = gBS->SetTimer(
                       TerminalDevice->TwoSecondTimeOut,
                       TimerRelative,
                       (UINT64)20000000
                       );
       ASSERT_EFI_ERROR (Status);
       continue;
     }

It seems we intentionally add 2 seconds delay for ESC key press. This provides not so good user experience when we press ESC to exit or cancel some operation.

We tried reducing this timeout value to 1 second, then the experience improved much and we didn't find any issue introduced.

What's the reason for this timeout value and is there any improvement?

Thanks and regards,

Heyi