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Subject: |
Re: Serial Line boot may not properly clear the screen |
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Date: |
Mon, 21 Jan 2002 16:54:34 +0100 (MET) |
>>>>> Yoshinori K Okuji <address@hidden> writes:
> At Sat, 19 Jan 2002 22:40:19 +0100 (MET),
> Klaus Reichl wrote:
>> If we do a `grub_print_esc' instead of `grub_printf' for ESC
>> sequences, assuming that the terminal will swallow the sequence, and
>> bypassing auto_fill, the auto_fill logic stays intact. Is this idea
>> to simplistic?
> I considered a similar approach, but it is not the Right Thing. What's
> wrong about that is that GRUB doesn't track the cursor position
> correctly. I now believe AUTO_FILL is the evil. As GRUB controls the
> terminal completely (except when a dumb terminal is in use), GRUB
> should always be able to know where the cursor is thereotically.
> Therefore, I'm going to rewrite the terminal code radically, so that
> each terminal driver (console, hercules, and serial) deals with the
> cursor position, and remove AUTO_FILL. Perhaps the new code will have
> a filesystem-like structure, like this:
> struct terminal
> {
> /* The terminal name. */
> const char *name;
> /* Put one character. */
> void (*putchar) (int c);
> /* Check is any input is available. */
> int (*checkkey) (void);
> /* Get one character. */
> int (*getkey) (void);
> /* Get the cursor position. */
> int (*getxy) (void);
> /* Go to the specified position. */
> void (*gotoxy) (int x, int y);
> /* Clear the screen. */
> void (*cls) (void);
> /* Set the attribution of characters. */
> void (*set_attrib) (int attr);
> /* Forward the cursor by N characters. */
> void (*forward) (int n);
> };
> And, higher-level functions (such as get_cmdline) won't print any
> escape sequences explicitly. This change will simplify the
> implementation.
Great.
Do you think it is possible than to code like:
if (term->gotoxy /* or term->getxy */)
algorithm for terminals with positioning
else
algorithm for DUMB like terminals
instead of term (terminal & TERMINAL_DUMB)?
>> If the terminal is dumb:
>> prompt only with PROMPT and not with the original line
>> read in keys until RET (no line editing at all, handling of BS
>> though is debatable)
>> this could easily be achieved by turning off readline in case of
>> dumb terminal and handling the output of the original line
>> otherwise
>> normal (positioning) `get_cmdline'
> I like this approach.
Me too, however, maybe this behaviour should be on another switch to
terminal.
e.g. terminal --dumb => no ANSI positioning
terminal --no-line-edit => not even line editing
> Also, I think it would be helpful to display "The original line is
> ..." before the prompt, if non-empty CMDLINE is passed.
> Another thing I'm thinking of is echo-back. When the terminal echoes
> back inputs itself, it is just annoying that GRUB echoes back inputs
> again. This is good in the batch mode of the grub shell, as the user
> can see what command is executed currently, but no good in the
> interactive mode, since you know what you type already. So it might be
> useful to disable echo-back in a dumb terminal, except for the case of
> the batch mode.
like above:
terminal --no-echo => don't echo back
> [Oh, how many problems!]
Well, you know ...
* I do think, that your proposed terminal ops would make the code much
clearer.
* The 2nd thing (no-line-edit, no-echo) should be rather simple (I'm
on the road for some days but afterwards I will look at these).
> Thanks,
> Okuji
Thanks,
Klaus
PS: In my first mail (Sat, 19 Jan 2002 22:40:19 +0100 (MET)), I forgot
to CC bug-grub. This was not on purpose. Should we add this
discussion to bug-grub or make a proposal first?
--
Klaus Reichl voice: +43 (1) 27722 / 3884
Alcatel Austria AG/RTPT fax: +43 (1) 27722 / 3955
Scheydgasse 41 inet: address@hidden
A-1210 Wien, Austria/Europe
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