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@ -98,3 +98,61 @@ If you want to compile st for OpenBSD you have to remove -lrt from config.mk, an |
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st will compile without any loss of functionality, because all the functions are |
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included in libc on this platform. |
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## Backspace key does not work |
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This is an issue that was discussed in suckless mailing list |
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<http://lists.suckless.org/dev/1404/20697.html>: |
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Well, I am going to comment why I want to change the behaviour |
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of this key. When ascii was defined in 1968 communication |
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with computers were done using punched cards, or hardcopy |
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terminals (basically a typewritter machine connected with |
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the computer using a serial port). Due to this, ascii defines |
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DELETE as 7F, because in the puched cards, it means all the |
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holes of the card punched, so it is a kind of 'phisical |
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delete'. In the same way, BACKSPACE key was a non destructive |
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back space, as in typewriter machines. So, if you wanted |
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to delete a character, you had to BACKSPACE and then DELETE. |
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Other use of BACKSPACE was accented characters, for example |
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'a BACKSPACE `'. The VT100 had no BACKSPACE key, it was |
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generated using the CONTROL key as another control character |
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(CONTROL key sets to 0 b7 b6 b5, so it converts H (code |
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0x48) into BACKSPACE (code 0x08)), but it had a DELETE key |
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in a similar position where BACKSPACE key is located today |
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in common PC keyboards. All the terminal emulators emulated |
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correctly the difference between these keys, and backspace |
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key generated a BACKSPACE (^H) and delete key generated a |
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DELETE (^?). |
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But the problem arised when Linus Torvald wrote Linux, and |
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he did that the virtual terminal (the terminal emulator |
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integrated in the kernel) returns a DELETE when backspace |
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was pressed, due to the fact of the key in that position |
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in VT100 was a delete key. This created a lot of problems |
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(you can see it in [1] and [2]), and how Linux became the |
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king, a lot of terminal emulators today generate a DELETE |
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when backspace key is pressed in order to avoid problems |
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with linux. It causes that the only way of generating a |
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BACKSPACE in these systems is using CONTROL + H. I also |
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think that emacs had an important point here because CONTROL |
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+ H prefix is used in emacs in some commands (help commands). |
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From point of view of the kernel, you can change the key |
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for deleting a previous character with stty erase. When you |
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connect a real terminal into a machine you describe the |
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type of terminal, so getty configure the correct value of |
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stty erase for this terminal, but in the case of terminal |
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emulators you don't have any getty that can set the correct |
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value of stty erase, so you always get the default value. |
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So it means that in case of changing the value of the |
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backspace keyboard, you have to add a 'stty erase ^H' into |
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your profile. Of course, other solution can be that st |
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itself modify the value of stty erase. I have usually the |
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inverse problem, when I connect with non Unix machines, and |
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I have to press control + h to get a BACKSPACE, or the |
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inverse, when a user connects to my unix machines from a |
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different system with a correct backspace key. |
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[1] http://www.ibb.net/~anne/keyboard.html |
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[2] http://www.tldp.org/HOWTO/Keyboard-and-Console-HOWTO-5.html |
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Roberto E. Vargas Caballero
10 years ago