On 10/9/2024 2:18 PM, Frantisek Rysanek via Freedos-user wrote:
Unfortunately I cannot find any hints that VESA VBE would have a
function to switch outputs...
That is not further surprising, as that has nothing to do with DOS in
general and VESA in particular. This is ONLY an issue with the laptop
internal circuitry and the ability of the BIOS to recognize an external
screen and how to handle this.
There is no (none, zero) option in DOS for such a switch. DOS only know,
about the BIOS Data segment, what the primary and secondary monitor is,
in case that you have one monochrome (compatible) adapter plus one
CGA/EGA/VGA adapter in your system. In that case, there are options to
determine and change which one the primary and which one the secondary
output would be. But there is no (none, zero) option to handle two
CGA/EGA/VGA adapters nor switching between physical output options of
one of those CGA/EGA/VGA adapters.
Ralf
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