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⌂ ∞ Elite on the BBC Micro and NES

Equipment: qv

[NES version, Bank 0]

       Name: qv                                                      [Show more]
       Type: Subroutine
   Category: Equipment
    Summary: Print a popup menu of the four space views, for buying lasers

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




 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:

   X                    The chosen view number (0-3)



.qv

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

 LDA controller1Left03  ; If A button is being pressed, or the left or right
 ORA controller1Right03 ; buttons were being pressed four VBlanks ago, then
 ORA controller1A       ; loop back to qv until they are released
 BMI qv

 LDY #3                 ; We now print a popup menu showing all four views, so
                        ; set a view counter in Y, starting with view 3 (right)

.vpop1

 JSR PrintLaserView     ; Print the name of the laser view specified in Y at the
                        ; correct on-screen position for the popup menu

 DEY                    ; Decrement the view counter in Y

 BNE vpop1              ; Loop back to print the next view until we have printed
                        ; all four view names in the popup

                        ; Next, we highlight the first view (front) as by this
                        ; point Y = 0

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

 JSR PrintLaserView     ; Print the name of the laser view specified in Y at the
                        ; correct on-screen position for the popup menu

 LDA #1                 ; Set the font style to print in the normal font
 STA fontStyle

                        ; We now draw a box around the list of views to make it
                        ; look like a popup menu

 LDA #11                ; Move the text cursor to column 11
 STA XC

 STA K+2                ; Set K+2 = 11 to pass to DrawSmallBox as the text row
                        ; on which to draw the top-left corner of the small box

 LDA #7                 ; Move the text cursor to row 7
 STA YC

 STA K+3                ; Set K+3 = 7 to pass to DrawSmallBox as the text column
                        ; on which to draw the top-left corner of the small box

 LDX languageIndex      ; Set K to the correct width for the laser view popup in
 LDA popupWidth,X       ; the chosen language, to pass to DrawSmallBox as the
 STA K                  ; width of the small box

 LDA #6                 ; Set K+1 = 6 to pass to DrawSmallBox as the height of
 STA K+1                ; the small box

 JSR DrawSmallBox_b3    ; Draw a box around the popup, with the top-left corner
                        ; at (7, 11), a height of 6 rows, and the correct width
                        ; for the chosen language

 JSR DrawScreenInNMI    ; Configure the NMI handler to draw the screen, so the
                        ; screen gets updated

                        ; The popup menu is now on-screen, so now we manage the
                        ; process of making a choice

 LDY #0                 ; We use Y to keep track of the highlighted view, which
                        ; we set to the front view above, so set Y = 0 to
                        ; reflect this

.vpop2

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

 LDA controller1Up      ; If the up button is not being pressed, jump to vpop4
 BPL vpop4              ; to move on to the next button check

                        ; If we get here then we need to move the highlight up
                        ; the menu, wrapping around if we go off the top

 JSR PrintLaserView     ; Print the name of the laser view specified in Y at the
                        ; correct on-screen position for the popup menu, to
                        ; remove the highlight from the current selection

 DEY                    ; Decrement Y to move the number of the selected view up
                        ; the menu

 BPL vpop3              ; If the view number is positive when we have not gone
                        ; off the top of the menu, so jump to vpop3 to skip the
                        ; following instruction

 LDY #3                 ; We just moved past the top of the menu, so set Y to 3
                        ; to move the selection to the bottom entry in the menu
                        ; (the right view)

.vpop3

 JSR HighlightLaserView ; Highlight the Y-th entry in the popup menu, to reflect
                        ; the new choice

.vpop4

 LDA controller1Down    ; If the down button is not being pressed, jump to vpop6
 BPL vpop6              ; to move on to the next button check

                        ; If we get here then we need to move the highlight down
                        ; the menu, wrapping around if we go off the bottom

 JSR PrintLaserView     ; Print the name of the laser view specified in Y at the
                        ; correct on-screen position for the popup menu, to
                        ; remove the highlight from the current selection

 INY                    ; Increment Y to move the number of the selected view
                        ; down the menu

 CPY #4                 ; If Y is not 4 then we have not gone off the bottom of
 BNE vpop5              ; the menu, so jump to vpop5 to skip the following
                        ; instruction

 LDY #0                 ; We just moved past the bottom of the menu, so set Y to
                        ; 0 to move the selection to the top entry in the menu
                        ; (the front view)

.vpop5

 JSR HighlightLaserView ; Highlight the Y-th entry in the popup menu, to reflect
                        ; the new choice

.vpop6

 LDA controller1A       ; If the A button is being pressed, jump to vpop7 to
 BMI vpop7              ; return the highlighted view as the chosen laser view

 LDA iconBarChoice      ; If iconBarChoice = 0 then nothing has been chosen on
 BEQ vpop2              ; the icon bar (if it had, iconBarChoice would contain
                        ; the number of the chosen icon bar button), so loop
                        ; back to vpop2 to keep processing the popup keys

                        ; If we get here then either a choice has been made on
                        ; the icon bar during NMI and the number of the icon bar
                        ; button is in iconBarChoice, or the Start button has
                        ; been pressed and iconBarChoice is 80

 CMP #80                ; If iconBarChoice = 80 then the Start button has been
 BNE vpop7              ; pressed to pause the game, so if this is not the case,
                        ; then a different icon bar option has been chosen, so
                        ; jump to vpop7 to return from the subroutine and abort
                        ; the laser purchase

                        ; If we get here then iconBarChoice = 80, which means
                        ; the Start button has been pressed to pause the game

 LDA #0                 ; Set iconBarChoice = 0 to clear the pause button press
 STA iconBarChoice      ; so we don't simply re-enter the pause menu when we
                        ; resume

 JSR PauseGame_b6       ; Pause the game and process choices from the pause menu
                        ; until the game is unpaused by another press of Start

 JMP vpop2              ; Jump back to vpop2 to pick up where we left off and go
                        ; back to processing the popup choice

.vpop7

 TYA                    ; Copy the number of the highlighted laser view from Y
 TAX                    ; into X, so we can return the choice in X

 RTS                    ; Return from the subroutine