On Thu, May 7, 2015 at 7:03 PM, Kinney, Michael D
<[email protected]> wrote:
> Roy,
>
> Did you try the command line at the UEFI Shell prompt through a serial
> terminal? There is line editing available, where backspace and delete keys
> perform different actions. I think your change prevents a user from ever
> getting the delete key behavior. Same would be true for the UEFI Shell
> command EDIT that provides a text file editor.
Hi Mike,
I did do my testing at the UEFI shell prompt with line editing.
While my patch does remove the use of the ASCII DEL character, there
are 3 other terminal escape sequences that are also used for delete.
In terraterm over serial, the delete key still works as expected, so
it is using an escape sequence. For hyperterm, delete doesn't work
before or after my change. For the Linux terminal cases, delete
doesn't work at all, as they all use a 3 character VT220 escape "[3~"
for delete which EDK2 does not accept. So this certainly will
negatively affect terminals that send ASCII DEL (0x7f), but I was not
able to find one that did.
If this change isn't globally acceptable, I'm fine with restricting
this to a terminal type, or making this otherwise configurable (maybe
with a fixed PCD?) This fixes a longstanding annoyance (ie backspace
key not working) on Linux platforms, which I would like to get fixed,
whether via this patch or a similar one.
As an aside, while reviewing the DEL escape codes, I see a simpler way
to do this patch, so the current version should not be used.
Thanks,
Roy
>
> Thanks,
>
> Mike
>
> -----Original Message-----
> From: Roy Franz [mailto:[email protected]]
> Sent: Thursday, May 07, 2015 4:33 PM
> To: [email protected]; [email protected]; Tian, Feng
> Subject: [edk2] [PATCH] Treat ASCII DEL (0x7f) as backspace
>
> Most Linux terminal emulators use ASCII 0x7f (^?) for backspace,
> rather than 0x08 (^H) since ^H is used by some programs for other
> purposes, such as help menus. This results in backspace not working
> in most Linux environments, particularly in emulated environments
> such as QEMU where telnet or xterm may be used to connect to
> the emulated UART. While in some cases this can be configured in the
> terminal emulator, it must be done on every connection, as if
> permently configured this will break all other uses of the terminal.
>
> This change causes both ASCII 0x08 and 0x7F to be treated as
> backspace. This provides a working backspace when tested with
> minicom, screen, telnet, and xterm under Linux. I also tested
> teraterm and hyperterm under Windows connecting via rs232, and
> saw no regressions. (The delete key doesn't work on hyperterm
> both before and after the change)
>
> This change removes the ASCII encoding for delete, however
> this did not cause regressions on any tested terminal emulators
> as they do not use the ASCII encoding for the delete key.
>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Roy Franz <[email protected]>
> ---
> MdeModulePkg/Universal/Console/TerminalDxe/TerminalConIn.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/MdeModulePkg/Universal/Console/TerminalDxe/TerminalConIn.c
> b/MdeModulePkg/Universal/Console/TerminalDxe/TerminalConIn.c
> index 4a008c9..c92d3d4 100644
> --- a/MdeModulePkg/Universal/Console/TerminalDxe/TerminalConIn.c
> +++ b/MdeModulePkg/Universal/Console/TerminalDxe/TerminalConIn.c
> @@ -1212,6 +1212,14 @@ UnicodeToEfiKey (
> switch (TerminalDevice->InputState) {
> case INPUT_STATE_DEFAULT:
>
> + switch (UnicodeChar) {
> + case 0x7f:
> + UnicodeChar = CHAR_BACKSPACE;
> + break;
> + default :
> + break;
> + }
> +
> break;
>
> case INPUT_STATE_ESC:
> --
> 1.9.1
>
>
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