Drawing objects: DrawCars

       Name: DrawCars                                                [Show more]
       Type: Subroutine
   Category: Drawing objects
    Summary: Draw all the car objects, with four objects for the closest car in
             front of us
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * MoveAndDrawCars calls DrawCars


.DrawCars

 LDX currentPosition    \ Set X to the current player's position, so we work our
                        \ way backwards through the pack, starting with the car
                        \ behind the current player, and wrapping round to the
                        \ cars in front, working our way towards the player's
                        \ car in the order in which they should be drawn (with
                        \ distant cars first)

 BPL cars2              \ If X is positive, jump to cars2 to skip the following
                        \ instruction

.cars1

 JSR DrawCarInPosition  \ Draw the car in position X

.cars2

 JSR GetPositionBehind  \ Set X to the number of the position behind position X,
                        \ so we work our way back through the pack

 CPX positionAhead      \ Loop back to cars1 until we have reached the position
 BNE cars1              \ ahead of the current player

                        \ We now draw the car that's just in front of us, which
                        \ is made up of four objects that can be skewed to make
                        \ it look like the car is steering

 LDX #22                \ The four objects are the front tyres, body, rear tyres
                        \ and rear wing, so set up a counter in X to work
                        \ through the first three in the order 22, 21 and 20, to
                        \ pass to DrawCarOrSign in turn so they get drawn in
                        \ that order: front tyres, body/helmet and rear tyres

.cars3

 STX xStoreDraw         \ Store X in xStoreDraw so it gets preserved through
                        \ the call to DrawCarOrSign

 JSR DrawCarOrSign      \ Draw the specified part of the four-object car just
                        \ in front of us

 DEX                    \ Decrement the object counter

 CPX #20                \ Loop back until we have drawn all three objects
 BCS cars3

 LDX positionAhead      \ Set X to the position ahead of the current player

 JSR DrawCarInPosition  \ Draw the car in position X, which draws the rear wing
                        \ as the last (and closest) of the four objects

 RTS                    \ Return from the subroutine