This SMSQ/E trap sets the wallpaper.

• All registers not shown above are not used on entry and are probably preserved on exit.
• The code in D1.L has the following meanings:
  • -1 if the background colour is not to be changed.
  • 0 for a black background.
  • 1-255 for a stippled QL colour background.
  • n*256 for a 24 bit true colour background.
• The code in D2.L is -1 for no background image and 0 for an image.
• The address in A1 is only needed when D2 = 0. In this case the image to which A1 points must be a snapshot of the screen in the current mode and resolution.

The example below shows the use of this trap call to set a QL colour background. It is assumed that A0 contains the ID of a valid screen channel.

wallp   moveq   #-1,d3          ; Timeout
        moveq   #119,d1         ; A QL stipple colour
        moveq   #-1,d2          ; No image
        moveq   #iop_wpap,d0    ; $6B
        trap    #3              ; Set the background colour
        tst.l   d0              ; OK? . .
        bne     error           ; . . no!