Drawing lines: HLOIN

       Name: HLOIN                                                   [Show more]
       Type: Subroutine
   Category: Drawing lines
    Summary: Draw a horizontal line from (X1, Y1) to (X2, Y1)
  Deep dive: Drawing monochrome pixels on the BBC Micro
    Context: See this subroutine in context in the source code
 Variations: See code variations for this subroutine in the different versions
 References: This subroutine is called as follows:
             * TT15 calls HLOIN
             * TTX66 calls HLOIN


 We do not draw a pixel at the right end of the line.


 Returns:

   Y                    Y is preserved


.HLOIN

 LDX Y1                 \ Set Y2 = Y1, so we can use the normal line-drawing
 STX Y2                 \ routine to draw a horizontal line

.HL1

 JMP LL30               \ Draw a line from (X1, Y1) to (X2, Y2), which will be
                        \ horizontal because we set Y2 to Y1 above