Re: [Freedos-devel] FreeCOM CLS suggestions (vs. CTTY?)
Dear Mr. Auer,
Mr. Ehlert is in France this week but he will be back at the weekend.
He will answer your questions as soon as possible.
Thanks,
i.A. L. Tartan
Sunday, June 13, 2004, 5:01:20 AM, you wrote:
Hi, I wondered what CLS should do while CTTY points to not CON.
Any ideas? I could not find it by Googling, so I assume that people
will simply not try using CLS over a serial terminal... Or if they
do
- the CLEAR / HOME ANSI escape sequence or
- a bunch for linefeeds or
- a formfeed
should do the trick. As CTTY targets can only be CON, NUL and serial
ports (parallel ports would not make much sense) or other bidirectional
char devices, I think one of the above choices should be okay. Alternatively,
even just always clear the local display even during CTTY non-CON should
work just great for everyday CTTY / CLS users.
Instead of using the CRT unit function, which never updates the screen
size stuff as it seems, CLS for CON can best be implemented as:
AH=0f int 10 returns: AH=columns AL=mode BH=page
read byte 40[84] = max row number on screen
AH=06 (scroll) AL=0 (zero lines of scrolling, only clear) BH=07 (color,
for blank lines, should not be zero) CX=0 (upper left corner) DH=40[84]
DL=the_AH_from_int_10_function_0f int 10 (might destroy BP register but
has no return values otherwise... Trident VGA might destroy DS register
in SVGA modes...)
And finally, not to forget, AH=02
BH=the_BH_from_int_10_function_0f DX=0
(top left) int 10, which moves the cursor to home position.
The int 10.0f can be replaced by 40[...] reading, too. Combined, you
will have a TINY and RELIABLE (flexible, for different screen sizes, see
Bugzilla entry number 1687, CLS Assumes 25 Screen Lines) implementation
of CLS which does not use the CRT library of the C compiler (and therefore
the whole CRT library would no longer be used by FreeCOM anymore AFAIK).
The above { get mode by int 10.0f, get rows from RAM, clear by int 10.06,
home by int 10.02 } should be put after a check for CTTY-non-CON which
would send one of the 3 suggested strings either instead of doing the
int 10 stuff or after it to the current CTTY device unless it is CON/NUL.
Let us know if you have some experience or opinion about what should
happen for CLS in combination with CTTY to AUX or NUL or Thanks.
Eric
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Re: [Freedos-devel] FreeCOM CLS suggestions (vs. CTTY?)
The way MS-DOS dealt wit this was if the display device was not the DOS
console the CLS command should return an ANSI escape to clear the screen.
A very, very old standalone version of FreeDOS CLS did this.
-jh
Eric Auer wrote:
Hi, I wondered what CLS should do while CTTY points to not CON.
Any ideas? I could not find it by Googling, so I assume that people
will simply not try using CLS over a serial terminal... Or if they
do
- the CLEAR / HOME ANSI escape sequence or
- a bunch for linefeeds or
- a formfeed
should do the trick. As CTTY targets can only be CON, NUL and serial
ports (parallel ports would not make much sense) or other bidirectional
char devices, I think one of the above choices should be okay. Alternatively,
even just always clear the local display even during CTTY non-CON should
work just great for everyday CTTY / CLS users.
Instead of using the CRT unit function, which never updates the screen
size stuff as it seems, CLS for CON can best be implemented as:
AH=0f int 10 returns: AH=columns AL=mode BH=page
read byte 40[84] = max row number on screen
AH=06 (scroll) AL=0 (zero lines of scrolling, only clear) BH=07 (color,
for blank lines, should not be zero) CX=0 (upper left corner) DH=40[84]
DL=the_AH_from_int_10_function_0f int 10 (might destroy BP register but
has no return values otherwise... Trident VGA might destroy DS register
in SVGA modes...)
And finally, not to forget, AH=02 BH=the_BH_from_int_10_function_0f DX=0
(top left) int 10, which moves the cursor to home position.
The int 10.0f can be replaced by 40[...] reading, too. Combined, you
will have a TINY and RELIABLE (flexible, for different screen sizes, see
Bugzilla entry number 1687, CLS Assumes 25 Screen Lines) implementation
of CLS which does not use the CRT library of the C compiler (and therefore
the whole CRT library would no longer be used by FreeCOM anymore AFAIK).
The above { get mode by int 10.0f, get rows from RAM, clear by int 10.06,
home by int 10.02 } should be put after a check for CTTY-non-CON which
would send one of the 3 suggested strings either instead of doing the
int 10 stuff or after it to the current CTTY device unless it is CON/NUL.
Let us know if you have some experience or opinion about what should
happen for CLS in combination with CTTY to AUX or NUL or Thanks.
Eric
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[Freedos-devel] FreeCOM CLS suggestions (vs. CTTY?)
Hi, I wondered what CLS should do while CTTY points to not CON.
Any ideas? I could not find it by Googling, so I assume that people
will simply not try using CLS over a serial terminal... Or if they
do
- the CLEAR / HOME ANSI escape sequence or
- a bunch for linefeeds or
- a formfeed
should do the trick. As CTTY targets can only be CON, NUL and serial
ports (parallel ports would not make much sense) or other bidirectional
char devices, I think one of the above choices should be okay. Alternatively,
even just always clear the local display even during CTTY non-CON should
work just great for everyday CTTY / CLS users.
Instead of using the CRT unit function, which never updates the screen
size stuff as it seems, CLS for CON can best be implemented as:
AH=0f int 10 returns: AH=columns AL=mode BH=page
read byte 40[84] = max row number on screen
AH=06 (scroll) AL=0 (zero lines of scrolling, only clear) BH=07 (color,
for blank lines, should not be zero) CX=0 (upper left corner) DH=40[84]
DL=the_AH_from_int_10_function_0f int 10 (might destroy BP register but
has no return values otherwise... Trident VGA might destroy DS register
in SVGA modes...)
And finally, not to forget, AH=02 BH=the_BH_from_int_10_function_0f DX=0
(top left) int 10, which moves the cursor to home position.
The int 10.0f can be replaced by 40[...] reading, too. Combined, you
will have a TINY and RELIABLE (flexible, for different screen sizes, see
Bugzilla entry number 1687, CLS Assumes 25 Screen Lines) implementation
of CLS which does not use the CRT library of the C compiler (and therefore
the whole CRT library would no longer be used by FreeCOM anymore AFAIK).
The above { get mode by int 10.0f, get rows from RAM, clear by int 10.06,
home by int 10.02 } should be put after a check for CTTY-non-CON which
would send one of the 3 suggested strings either instead of doing the
int 10 stuff or after it to the current CTTY device unless it is CON/NUL.
Let us know if you have some experience or opinion about what should
happen for CLS in combination with CTTY to AUX or NUL or Thanks.
Eric
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