Yes, I was in general talking about cannonical input mode processing in
a kernel's line discipline terminal module and in the kernel module,
again, yes, the erase is usually done by as you mentioned, i.e., by using
'\b' and also writing necessary amount of ' 's (0x20 characters) to kind of
"erase".
With regards,
Ienup
PS. Some terminals/terminal emulators do maintain line buffer for some
additional processings as I mentioned.
] Date: Fri, 26 Jan 2001 23:51:43 +0100 (CET)
] From: Bruno Haible <[EMAIL PROTECTED]>
] Subject: Re: backspace, erase modes
] To: [EMAIL PROTECTED]
] MIME-version: 1.0
] Content-transfer-encoding: 7bit
]
] Ienup Sung writes:
]
] > - Display cell erase mode:
] > ...
] > In this erase mode, no matter how many characters are in a display cell,
] > the display cell will be erase and thus all characters in the display cell
] > will also be erased from the line buffer. For instance,
] > if we have A, a combinging diacritical mark accute, and a combining
] > diacritical mark breve in a single column display cell and also in
] > a line buffer, a backspace operation will erase all the characters in
] > the display cell from the screen and also the line buffer.
] >
] > - Character/character element erase mode:
] > In this erase mode, the last character in the current display cell will be
] > erased and depending on the context, the display cell could be erased (if
] > the character erased is the last remaining one in the display cell) or
] > that particular character only will be erased while the other characters
in
] > the display cell still show up in the display cell. For instance,
] > if we have A, a combinging diacritical mark accute, and a combining
] > diacritical mark breve in a single column display cell and also in
] > a line buffer, a backspace operation will erase only the combining
] > diacritical mark breve and thus the display cell will be re-displayed with
] > the A with the combining diacritical mark accute only.
]
] You mention a "line buffer". A terminal emulator has no line buffer.
] It has only a screen contents and a cursor position. Therefore I think
] you are talking about line editing facilities, not about terminal
] emulators.
]
] I agree with you that a line editing facility, e.g. readline, could
] provide both modes.
]
] How about a third mode, let me call it "emacs erase mode":
] - If, since the last character was input, no other keystroke has
] been entered and the cursor has not been moved, the last character
] element is erased. Otherwise, the entire last display cell is
] erased.
]
] This is what the user sees. However, the primitive cursor positioning
] operation (echo '\b') must be "move left by one column". The line
] editor's three erase modes can be implemented on top of that (assuming
] a consistent wcwidth()). OTOH, if the terminal would be doing more
] complicated things than simple cursor positioning, it would be very
] hard or impossible to implement a reliable ncurses library.
]
] Bruno
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