Keyboard: TT102

       Name: TT102                                                   [Show more]
       Type: Subroutine
   Category: Keyboard
    Summary: Process number key, save key, hyperspace and chart key presses
             and update the hyperspace counter
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * Main game loop (Part 6 of 6) calls TT102
             * HME2 calls via T95


 Process number key presses, plus "I" (save commander), "H" (hyperspace), "G"
 (galactic hyperspace), "D" (show distance to system) and "O" (move chart
 cursor back to current system). We can also pass cursor position deltas in X
 and Y to indicate that the cursor keys or joystick have been used (i.e. the
 values that are returned by routine TT17).

 This routine also checks for the "F" key press (search for a system), which
 applies to enhanced versions only.


 Arguments:

   A                    The key number of the key pressed

   X                    The amount to move the crosshairs in the x-axis

   Y                    The amount to move the crosshairs in the y-axis


 Other entry points:

   T95                  Print the distance to the selected system


.TT102

 CMP #f8                ; If key "8" was pressed, jump to STATUS to show the
 BNE P%+5               ; Status Mode screen, returning from the subroutine
 JMP STATUS             ; using a tail call

 CMP #f4                ; If key "4" was pressed, jump to TT22 to show the
 BNE P%+5               ; Long-range Chart, returning from the subroutine using
 JMP TT22               ; a tail call

 CMP #f5                ; If key "5" was pressed, jump to TT23 to show the
 BNE P%+5               ; Short-range Chart, returning from the subroutine using
 JMP TT23               ; a tail call

 CMP #f6                ; If key "6" was pressed, call TT111 to select the
 BNE TT92               ; system nearest to galactic coordinates (QQ9, QQ10)
 JSR TT111              ; (the location of the chart crosshairs) and set ZZ to
 JMP TT25               ; the system number, and then jump to TT25 to show the
                        ; Data on System screen (along with an extended system
                        ; description for the system in ZZ if we're docked),
                        ; returning from the subroutine using a tail call

.TT92

 CMP #f9                ; If key "9" was pressed, jump to TT213 to show the
 BNE P%+5               ; Inventory screen, returning from the subroutine
 JMP TT213              ; using a tail call

 CMP #f7                ; If key "7" was pressed, jump to TT167 to show the
 BNE P%+5               ; Market Price screen, returning from the subroutine
 JMP TT167              ; using a tail call

 CMP #f0                ; If key "1" was pressed, jump to TT110 to launch our
 BNE fvw                ; ship (if docked), returning from the subroutine using
 JMP TT110              ; a tail call

.fvw

 BIT QQ12               ; If bit 7 of QQ12 is clear (i.e. we are not docked, but
 BPL INSP               ; in space), jump to INSP to skip the following checks
                        ; for f1-f3 and "@" (save commander file) key presses

 CMP #f3                ; If key "3" was pressed, jump to EQSHP to show the
 BNE P%+5               ; Equip Ship screen, returning from the subroutine using
 JMP EQSHP              ; a tail call

 CMP #f1                ; If key "1" was pressed, jump to TT219 to show the
 BNE P%+5               ; Buy Cargo screen, returning from the subroutine using
 JMP TT219              ; a tail call

 CMP #'I'               ; If "I" was not pressed, skip to nosave
 BNE nosave

 JSR SVE                ; "@" was pressed, so call SVE to show the disk access
                        ; menu

 BCC P%+5               ; If the C flag was set by SVE, then we loaded a new
 JMP QU5                ; commander file, so jump to QU5 to restart the game
                        ; with the newly loaded commander

 JMP BAY                ; Otherwise the C flag was clear, so jump to BAY to go
                        ; to the docking bay (i.e. show the Status Mode screen)

.nosave

 CMP #f2                ; If key "2" was pressed, jump to TT208 to show the
 BNE LABEL_3            ; Sell Cargo screen, returning from the subroutine using
 JMP TT208              ; a tail call

.INSP

 CMP #f12               ; If key "2" was pressed, jump to chview1
 BEQ chview1

 CMP #f22               ; If key "3" was pressed, jump to chview2
 BEQ chview2

 CMP #f32               ; If key "4" was not pressed, jump to LABEL_3 to keep
 BNE LABEL_3            ; checking for which key was pressed

 LDX #3                 ; Key "4" was pressed, so set the view number in X to
                        ; 3 for the right view

 EQUB $2C               ; Skip the next instruction by turning it into
                        ; $2C $A2 $02, or BIT $02A2, which does nothing apart
                        ; from affect the flags

.chview2

 LDX #2                 ; If we jump to here, key "3" was pressed, so set the
                        ; view number in X to 2 for the left view

 EQUB $2C               ; Skip the next instruction by turning it into
                        ; $2C $A2 $01, or BIT $02A2, which does nothing apart
                        ; from affect the flags

.chview1

 LDX #1                 ; If we jump to here, key "2" was pressed, so set the
                        ; view number in X to 1 for the rear view

 JMP LOOK1              ; Jump to LOOK1 to switch to view X (rear, left or
                        ; right), returning from the subroutine using a tail
                        ; call

.LABEL_3

 LDA KL                 ; If "H" was not pressed, skip the following instruction
 CMP #'H'
 BNE P%+5

 JMP hyp                ; Jump to hyp to do a hyperspace jump (if we are in
                        ; space), returning from the subroutine using a tail
                        ; call

 CMP #'G'               ; If "G" was not pressed, skip the following instruction
 BNE P%+5

 JMP hyp                ; Jump to hyp to do a galactic hyperspace jump (if we
                        ; are in space), returning from the subroutine using a
                        ; tail call

.NWDAV5

 CMP #'D'               ; If "D" was pressed, jump to T95 to print the distance
 BEQ T95                ; to a system (if we are in one of the chart screens)

 CMP #'F'               ; If "F" was not pressed, jump down to HME1, otherwise
 BNE HME1               ; keep going to process searching for systems

 LDA QQ12               ; If QQ12 = 0 (we are not docked), we can't search for
 BEQ t95                ; systems, so return from the subroutine (as t95
                        ; contains an RTS)

 LDA QQ11               ; If the current view is a chart (QQ11 = 64 or 128),
 AND #%11000000         ; keep going, otherwise return from the subroutine (as
 BEQ t95                ; t95 contains an RTS)

 JMP HME2               ; Jump to HME2 to let us search for a system, returning
                        ; from the subroutine using a tail call

.HME1

 STA T1                 ; Store A (the key that's been pressed) in T1

 LDA QQ11               ; If the current view is a chart (QQ11 = 64 or 128),
 AND #%11000000         ; keep going, otherwise jump down to TT107 to skip the
 BEQ TT107              ; following

 LDA QQ22+1             ; If the on-screen hyperspace counter is non-zero,
 BNE TT107              ; then we are already counting down, so jump to TT107
                        ; to skip the following

 LDA T1                 ; Restore the original value of A (the key that's been
                        ; pressed) from T1

 CMP #'O'               ; If "O" was pressed, do the following three jumps,
 BNE ee2                ; otherwise skip to ee2 to continue

 JSR TT103              ; Draw small crosshairs at coordinates (QQ9, QQ10),
                        ; which will erase the crosshairs currently there

 JSR ping               ; Set the target system to the current system (which
                        ; will move the location in (QQ9, QQ10) to the current
                        ; home system

 JMP TT103              ; Draw small crosshairs at coordinates (QQ9, QQ10),
                        ; which will draw the crosshairs at our current home
                        ; system, and return from the subroutine using a tail
                        ; call

.ee2

 JSR TT16               ; Call TT16 to move the crosshairs by the amount in X
                        ; and Y, which were passed to this subroutine as
                        ; arguments

.TT107

 LDA QQ22+1             ; If the on-screen hyperspace counter is zero, return
 BEQ t95                ; from the subroutine (as t95 contains an RTS), as we
                        ; are not currently counting down to a hyperspace jump

 DEC QQ22               ; Decrement the internal hyperspace counter

 BNE t95                ; If the internal hyperspace counter is still non-zero,
                        ; then we are still counting down, so return from the
                        ; subroutine (as t95 contains an RTS)

                        ; If we get here then the internal hyperspace counter
                        ; has just reached zero and it wasn't zero before, so
                        ; we need to reduce the on-screen counter and update
                        ; the screen. We do this by first printing the next
                        ; number in the countdown sequence, and then printing
                        ; the old number, which will erase the old number
                        ; and display the new one because printing uses EOR
                        ; logic

 LDX QQ22+1             ; Set X = the on-screen hyperspace counter - 1
 DEX                    ; (i.e. the next number in the sequence)

 JSR ee3                ; Print the 8-bit number in X at text location (0, 1)

 LDA #5                 ; Reset the internal hyperspace counter to 5
 STA QQ22

 LDX QQ22+1             ; Set X = the on-screen hyperspace counter (i.e. the
                        ; current number in the sequence, which is already
                        ; shown on-screen)

 JSR ee3                ; Print the 8-bit number in X at text location (0, 1),
                        ; i.e. print the hyperspace countdown in the top-left
                        ; corner

 DEC QQ22+1             ; Decrement the on-screen hyperspace countdown

 BNE t95                ; If the countdown is not yet at zero, return from the
                        ; subroutine (as t95 contains an RTS)

 JMP TT18               ; Otherwise the countdown has finished, so jump to TT18
                        ; to do a hyperspace jump, returning from the subroutine
                        ; using a tail call

.t95

 RTS                    ; Return from the subroutine

.T95

                        ; If we get here, "D" was pressed, so we need to show
                        ; the distance to the selected system (if we are in a
                        ; chart view)

 LDA QQ11               ; If the current view is a chart (QQ11 = 64 or 128),
 AND #%11000000         ; keep going, otherwise return from the subroutine (as
 BEQ t95                ; t95 contains an RTS)

 JSR hm                 ; Call hm to move the crosshairs to the target system
                        ; in (QQ9, QQ10), returning with A = 0

;STA QQ17               ; This instruction is commented out in the original
                        ; source

 JSR cpl                ; Print control code 3 (the selected system name)

 LDA #%10000000         ; Set bit 7 of QQ17 to switch to Sentence Case, with the
 STA QQ17               ; next letter in capitals

 LDA #12                ; Print a line feed to move the text cursor down a line
 JSR TT26

 JMP TT146              ; Print the distance to the selected system and return
                        ; from the subroutine using a tail call