Drawing lines: DrawClippedLine (Part 6 of 6)

       Name: DrawClippedLine (Part 6 of 6)                           [Show more]
       Type: Subroutine
   Category: Drawing lines
    Summary: Add the clipped line to the line buffer and draw it
    Context: See this subroutine in context in the source code
 References: No direct references to this subroutine in this source file


 LDA colourCycle        \ If bit 7 of colourCycle is set, i.e. %11110000, jump
 BMI draw23             \ down to draw23 to add a line to buffer 1

 LDX lineBuffer2Count   \ If lineBuffer2Count <> 95, line buffer 2 is not full,
 CPX #95                \ so jump down to draw22 to add a new line to the buffer
 BNE draw22

 RTS                    \ Return from the subroutine

.draw22

 INX                    \ Increment the value in lineBuffer2Count as we are
 STX lineBuffer2Count   \ about to add a new line to line buffer 2

 JMP draw25             \ Jump down to draw25 to buffer the line and draw it

.draw23

 LDX lineBuffer1Count   \ If lineBuffer1Count <> 47, line buffer 1 is not full,
 CPX #47                \ so jump down to draw24 to add a new line to the buffer
 BNE draw24

 RTS                    \ Return from the subroutine

.draw24

 INX                    \ Increment the value in lineBuffer1Count as we are
 STX lineBuffer1Count   \ about to add a new line to line buffer 1

.draw25

 LDA R                  \ Save the start x-coordinate in lineBufferR
 STA lineBufferR,X

 LDA W                  \ Save the max/min x-coordinate in lineBufferW
 STA lineBufferW,X

 LDA S                  \ Save the start y-coordinate in lineBufferS
 STA lineBufferS,X

 LDA G                  \ Save the max/min y-coordinate in lineBufferG
 STA lineBufferG,X

 LDA T                  \ Save the |x-delta| in lineBufferT
 STA lineBufferT,X

 LDA U                  \ Save the |y-delta| in lineBufferU
 STA lineBufferU,X

 LDA V                  \ Save the direction in lineBufferV
 STA lineBufferV,X

                        \ Fall through into DrawCanopyLine to draw the line