On Fri, May 8, 2015 at 2:50 AM, Laszlo Ersek lersek@redhat.com wrote:
On 05/08/15 04:26, Roy Franz wrote:
On Thu, May 7, 2015 at 7:03 PM, Kinney, Michael D michael.d.kinney@intel.com 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.
I think this email provides good background:
https://lists.debian.org/debian-i18n/1998/04/msg00015.html
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?)
Please make this configurable with a fixed PCD or feature PCD.
The key in the upper right corner on my PC keyboard, labeled
<- Backspace
emits keysim BackSpace, and XLookupString gives 0x08, according to "xev".
The key labeled
Delete
emits keysim Delete, and XLookupString gives 0x7F, according to "xev".
xev reports the same for me.
Both keys work as expected in all the applications I use, both on the character console and under X (ie. the former key removes the previous character, the latter key removes the next character).
This holds for the UEFI shell as well, when it runs as part of OVMF or ArmVirtualizationQemu, and is accessed over the QEMU serial console, from xterm.
Have you you changed any terminal/keyboard settings? What distro do you use? Your experience of working backspace of the QEMU serial port is the first report of this working I have had - it has always been broken for me and everyone I have asked about it.
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.
Most Linux distributions' default settings are horribly broken in this area.
Yeah, this was my first real trip down into the terminal rabbit hole, and it does seem to be a mess.
<rant> The fact that most applications *agree* on those broken settings doesn't make them less broken.
The obsession on Linux with VT100/VT220 is ridiculous. I was born in the seventies and have never seen a VT100/VT220 keyboard. It's 2015 and we use PC keyboards. Hence, since 1998, I've been doing my part to bludgeon all my applications and remote Linux accounts to do the right thing. Backspace is ^H, Delete is ^?; I own a PC, not some kind of electronic relic.
</rant>
I have a feeling that 'proper' VTXXX terminal emulation discussions bring out all the pedants :)
So, please make this change dependent on a feature PCD, and the default behavior shouldn't change.
Thanks! Laszlo
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:roy.franz@linaro.org] Sent: Thursday, May 07, 2015 4:33 PM To: edk2-devel@lists.sourceforge.net; linaro-uefi@lists.linaro.org; 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 roy.franz@linaro.org
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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