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⌂ ∞ Aviator on the BBC Micro

Drawing lines: SwapLinePoints

       Name: SwapLinePoints                                          [Show more]
       Type: Subroutine
   Category: Drawing lines
    Summary: Copy an end point into a start point

    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * ClipBestEndOfLine calls SwapLinePoints
             * DrawClippedLine (Part 4 of 6) calls SwapLinePoints




 Arguments:

   (QQ W)               The x-coordinate of the line's end point

   (H G)                The y-coordinate of the line's end point

   UU                   The clipping requirements for the end point



 Returns:

   (RR R)               Gets set to the x-coordinate above

   (SS S)               Gets set to the y-coordinate above

   TT                   Gets set to the clipping requirements above



.SwapLinePoints

 LDA W                  \ Set (RR R) = (QQ W)
 STA R
 LDA QQ
 STA RR

 LDA G                  \ Set (SS S) = (H G)
 STA S
 LDA H
 STA SS

 LDA UU                 \ Set TT = UU
 STA TT

 RTS                    \ Return from the subroutine