SD_CLEAR/IOW_CLRA & SD_CLRTP/IOW_CLRT & SD_CLRBT/IOW_CLRB & SD_CLRLN/IOW_CLRL & SD_CLRRT/IOW_CLRR

These traps clear the whole of a window or parts of it.

• All registers not shown above are not used on entry and are preserved on exit.
• When only a part of the window is to be cleared the part is defined by reference to the position of the cursor. The top of the window consists of all lines above the cursor line. The bottom of the window consists of all lines below the cursor line. When only a line is cleared it is the line on which the cursor lies. When only part of a line is cleared it is all positions to the end of the line including the cursor's position.

The example below shows the use of this trap call to clear a window. It is assumed that the channel ID is in A0.L.

clear   moveq   #SD_CLEAR,d0    ; $20
        moveq   #-1,d3          ; Timeout
        trap    #3              ; Clear window
        tst.l   d0              ; OK? . .
        bne     error           ; . . no!