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⌂ ∞ ▽ Elite on the 6502

Save and load: MoveInLeftColumn

[NES version, Bank 6]

       Name: MoveInLeftColumn                                        [Show more]
       Type: Subroutine
   Category: Save and load
    Summary: Process moving the highlight when it's in the left column (the
             current commander)

    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * MoveToLeftColumn calls MoveInLeftColumn




 Arguments:

   A                    Must be set to 9, as that represents the slot number of
                        the left column containing the current commander



.MoveInLeftColumn

 JSR SetupPPUForIconBar ; If the PPU has started drawing the icon bar, configure
                        ; the PPU to use nametable 0 and pattern table 0

 LDX controller1Left03  ; If the left button on controller 1 was not being held
 BPL mlef3              ; down four VBlanks ago or for the three VBlanks before
                        ; that, jump to mlef3 to check the right button

                        ; If we get here then the left button is being pressed,
                        ; so we need to move the highlight left from its current
                        ; position (which is given in A and is always 9) to the
                        ; right column

 JSR PrintSaveName      ; Print the name of the commander file in its current
                        ; position in A, to remove the highlight

 CMP #9                 ; If A = 9 then we have pressed the left button while
 BEQ mlef1              ; highlighting the current commander name on the left
                        ; of the screen, so we need to move the highlight to the
                        ; right column, so jump to mlef1 to do this
                        ;
                        ; This will always be the case as this routine is only
                        ; called with A = 9 (as that's the slot number we use
                        ; to represent the current commander in the left
                        ; column), so presumably this logic is left over from a
                        ; time when this routine was a bit more generic

 LDA #0                 ; Otherwise the highlight must currently be in either
                        ; the middle or right column, so set A = 0 so the
                        ; highlight moves to the top of the new column (though
                        ; again, this will never happen)

 JMP mlef2              ; Jump to mlef2 to move the highlight to the right
                        ; column

.mlef1

                        ; If we get here then we have pressed the left button
                        ; while highlighting the current commander name on the
                        ; left of the screen

 LDA #4                 ; Set A = 4 so the call to MoveInRightColumn moves the
                        ; highlight to slot 4 in the right column, which is at
                        ; the same vertical position as the current commander
                        ; name on the left

.mlef2

 JMP MoveInRightColumn  ; Move the highlight left to the specified slot number
                        ; in the right column and process any further button
                        ; presses accordingly

.mlef3

 LDX controller1Right03 ; If the right button on controller 1 was not being held
 BPL mlef6              ; down four VBlanks ago or for the three VBlanks before
                        ; that, jump to mlef6 to check the icon bar buttons

                        ; If we get here then the right button is being pressed,
                        ; so we need to move the highlight right from its
                        ; current position (which is given in A and is always 9)
                        ; to the middle column

 JSR PrintSaveName      ; Print the name of the commander file in its current
                        ; position in A, to remove the highlight

 CMP #9                 ; If A = 9 then we have pressed the right button while
 BEQ mlef4              ; highlighting the current commander name on the left of
                        ; the screen, so we need to move the highlight to the
                        ; middle column, so jump to mlef4 to do this
                        ;
                        ; This will always be the case as this routine is only
                        ; called with A = 9 (as that's the slot number we use
                        ; to represent the current commander in the left
                        ; column), so presumably this logic is left over from a
                        ; time when this routine was a bit more generic

 LDA #0                 ; Otherwise the highlight must currently be in either
                        ; the middle or right column, so set A = 0 so the
                        ; highlight moves to the top of the new column (though
                        ; again, this will never happen)

 JMP mlef5              ; Jump to mlef5 to move the highlight to the middle
                        ; column

.mlef4

                        ; If we get here then we have pressed the right button
                        ; while highlighting the current commander name on the
                        ; left of the screen

 LDA #4                 ; Set A = 4 so the call to MoveInMiddleColumn moves the
                        ; highlight to slot 4 in the middle column, which is at
                        ; the same vertical position as the current commander
                        ; name on the left

.mlef5

 JMP MoveInMiddleColumn ; Move the highlight left to the specified slot number
                        ; in the middle column and process any further button
                        ; presses accordingly

.mlef6

                        ; If we get here then neither of the left or right
                        ; buttons have been pressed, so we move on to checking
                        ; the icon bar buttons

 JSR CheckSaveLoadBar   ; Check the icon bar buttons to see if any of them have
                        ; been chosen

 BCS MoveInLeftColumn   ; The C flag will be set if we are to resume what we
                        ; were doing (so we pick up where we left off after
                        ; processing the pause menu, for example), so loop back
                        ; to the start of the routine to keep checking for left
                        ; and right button presses

                        ; If we get here then the C flag is clear and we need to
                        ; return from the SVE routine and go back to the icon
                        ; bar processing routine in TT102

 RTS                    ; Return from the subroutine