QDOS Internals

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====== SD_SCROL/IOW_SCRA etc ======


These traps scroll all or part of a window.
^Trap^Value in D0.B^Action^
|SD_SCROL/IOW_SCRA|$18|Scroll all of window|
|SD_SCRTP/IOW_SCRT|$19|Scroll top of window|
|SD_SCRBT/IOW_SCRB|$1A|Scroll bottom of window|

^Call Parameters^^Return Parameters^^
|D0.B|See above|D0.L|Error return.|
|D1.W|Distance to scroll |D1.L|Corrupted.|
|D3.W|Timeout |D3.L|Preserved.|
|A0.L|Channel ID |A0.L|Preserved.|

===== Errors =====


|ERR_NC|Not complete.|
|ERR_NO|Channel not open.|


===== Notes =====
  * All registers not shown above are not used on entry and are preserved on exit.
  * Scrolling means that the area selected will be moved up or down by an integral number of pixels. A positive number in D1.W will cause a downward movement. The vacated rows of pixels will be filled with paper colour.
  * The top of a window is defined as all the rows above the line on which the cursor lies (the cursor line).
  * The bottom of the window is defined as all the rows below the cursor line.
===== Example =====
The example below shows the use of this trap call to scroll text up by one line. It is assumed that A0 contains the correct channel ID.

<code>
scroll  moveq   #sd_scrol,d0    ; $18
        moveq   #-10,d1         ; Up one line
        moveq   #-1,d3          ; Timeout
        trap    #3              ; Scroll up a line
        tst.l   d0              ; OK? . .
        bne     error           ; . . no!
</code>

QDOS Internals

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