🚀 go-pugleaf

In article <1992Oct7.182116.15067@cs.nott.ac.uk> smb@cs.nott.ac.uk (Simon Burrows) writes:

>In article <1992Oct7.134701.24557@aisb.ed.ac.uk> ainsjc@aisb.ed.ac.uk (Steffan) writes:
>>In article <1992Oct7.161818.11278@waikato.ac.nz> bwc@waikato.ac.nz (Ug!) writes:
>>>Hi!  Could someone tell me what the FX call is to write the CMOS-RAM bit
>>>to turn the icon-dragging on?  (Assuming it still works in RiscOS 3.1)
>
>The easiest way (although it is cheating somewhat) is to type
>*FX 162,28,3. This enables solid icon drags with shadows.

Without wishing to sound too critical, this is not a good way to do it,
since you are also altering the state of seven other bits which control
other aspects of FileSwitch and the Wimp. A better way is to read the byte,
set bit 1, and then write it back. This is the program that I use:

   REM Toggle state of DragASprite bit in CMOS

   REM Read byte
   SYS "OS_Byte",161,&1C TO ,,byte%
   REM EOR byte with mask for bit 1
   byte% = byte% EOR 1<<1
   REM Write byte back again
   SYS "OS_Byte",162,&1C,byte%
   END

You *must* use the OS_Byte calls, otherwise the checksum byte will become
incorrect. This byte is calculated on a power-on reset, and then maintained
by the OS_Byte calls (in other words, they don't recalculate it, but merely
update it in a manner that is appropriate to the changes made).

The other thing to note is that you *must* do a power-on reset when
upgrading from RISC OS 2 to RISC OS 3, not just to initialise the checksum,
but more importantly  because the CMOS usage differs between the versions.

- Michael J Hardy

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