Controllers: YESNO

       Name: YESNO                                                   [Show more]
       Type: Subroutine
   Category: Controllers
    Summary: Display "YES" or "NO" and wait until one is chosen
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * TBRIEF calls YESNO


 This routine does a similar job to the routine of the same name in the BBC
 Master version of Elite, but the code is significantly different.


 Returns:

   A                    The result:

                          * 1 if "YES" was chosen

                          * 2 if "NO" was chosen


.YESNO

 LDA fontStyle          ; Store the current font style on the stack, so we can
 PHA                    ; restore it when we return from the subroutine

 LDA #2                 ; Set the font style to print in the highlight font
 STA fontStyle

 LDA #1                 ; Push a value of 1 onto the stack, so the following
 PHA                    ; prints extended token 1 ("YES")

.yeno1

 JSR CLYNS              ; Clear the bottom two text rows of the upper screen,
                        ; and move the text cursor to the first cleared row

 LDA #15                ; Move the text cursor to column 15
 STA XC

 PLA                    ; Print the extended token whose number is on the stack,
 PHA                    ; so this will be "YES" (token 1) or "NO" (token 2)
 JSR DETOK_b2

 JSR DrawMessageInNMI   ; Configure the NMI to display the YES/NO message that
                        ; we just printed

 LDA controller1A       ; If the A button is being pressed on the controller,
 BMI yeno3              ; jump to yeno3 to record the choice

 LDA controller1Up      ; If neither the up nor down arrow is being pressed on
 ORA controller1Down    ; the controller, jump to yeno2 to pause and loop back
 BPL yeno2              ; to keep waiting for a choice to be made

                        ; If we get here then either the up or down arrow is
                        ; being pressed, so we toggle the on-screen choice
                        ; between "YES" and "NO"

 PLA                    ; Flip the value on the top of the stack between 1 and 2
 EOR #3                 ; by EOR'ing with 3, which toggles the token between
 PHA                    ; "YES" and "NO"

.yeno2

 LDY #8                 ; Wait until eight NMI interrupts have passed (i.e. the
 JSR DELAY              ; next eight VBlanks)

 JMP yeno1              ; Loop back to print "YES" or NO" and wait for a choice

.yeno3

 LDA #0                 ; Reset the key logger entry for the icon bar button
 STA iconBarKeyPress    ; choice to clear any icon bar choices that might have
                        ; been processed in the background (via the pause menu,
                        ; for example)

 STA controller1A       ; Reset the key logger for the A button as we have
                        ; consumed the button press

 PLA                    ; Set X to the value from the top of the stack, which
 TAX                    ; will be 1 for "YES" or 2 for "NO", giving us our
                        ; result to return

 PLA                    ; Restore the font style that we stored on the stack
 STA fontStyle          ; so it's unchanged by the routine

 TXA                    ; Copy X to A, so we return the result in both A and X

 RTS                    ; Return from the subroutine