Loader: OfferFastLoader

       Name: OfferFastLoader                                         [Show more]
       Type: Subroutine
   Category: Loader
    Summary: Offer the option of using the fast loader, if we haven't already,
             and set up the fast loader if it is chosen
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * Elite GMA loader (Part 2 of 4) calls OfferFastLoader


.OfferFastLoader

 LDA VIC+$11            ; Loop back to OfferFastLoader until bit 7 of VIC-II
 BPL OfferFastLoader    ; register $11 (control register 1) is set
                        ;
                        ; Bit 7 of register $11 contains the top bit of the
                        ; current raster line (which is a 9-bit value), so this
                        ; waits until the raster has reached at least line 256

 LDA #$08               ; Set the high byte of the pointer to screen memory to
 STA $0288              ; $08, so screen memory gets set to $0800

 JSR KERNALSCINIT       ; Call the Kernal's SCINIT function to initialise the
                        ; VIC-II and start using the new screen memory address

 LDA VIC+$18            ; Set bits 4-7 of VIC register $18 to %0010 to set the
 AND #%00001111         ; address of screen RAM to $0800
 ORA #%00100000
 STA VIC+$18

 LDA #2                 ; Set VIC register $20 to set the border colour to the
 STA VIC+$20            ; colour number in bits 0-3 (i.e. colour 2, red)

 STA VIC+$21            ; Set VIC register $21 to set the background colour to
                        ; the colour number in bits 0-3 (i.e. colour 2, red)

 LDX #0                 ; Print the first string from loaderScreens, which
 JSR PrintString        ; clears the screen and prints the "FAST LOADER? (Y/N)"
                        ; prompt

 TXA                    ; Store X on the stack, as it contains the offset of the
 PHA                    ; second string in loaderScreens

 LDA fastLoaderOffered  ; If fastLoaderOffered is non-zero then we have already
 BNE setf2              ; asked about the fast loader, so jump to setf2 to skip
                        ; the following and go straight to the loading screen
                        ; (so we don't ask twice)

 INC fastLoaderOffered  ; Set fastLoaderOffered to 1 to record that we have
                        ; asked about the fast loader

 LDA #$1C               ; Change the colour of the "FAST LOADER? (Y/N)" prompt
 STA promptText         ; from yellow to red to hide it, as it is on a red
                        ; background

.setf1

 JSR KERNALGETIN        ; Call the Kernal's GETIN function to fetch a key press
                        ; from the keyboard

 BEQ setf1              ; Loop back to setf1 until a key is pressed

 CMP #'N'               ; If "N" was pressed then jump to setf2 to skip the fast
 BEQ setf2              ; loader setup and stick to the standard load routines

 CMP #'Y'               ; If "Y" was not pressed then loop back to setf1 to wait
 BNE setf1              ; for another key press

                        ; If we get here then "Y" was pressed, so we need to set
                        ; up the fast loader

 JSR SetUpFastLoader    ; Call SetUpFastLoader to set up the fast loader, so
                        ; that calls to the Kernal's file functions use the fast
                        ; loader routines instead of the built-in functions

.setf2

 PLA                    ; Retrieve the value of X from the stack so it points to
 TAX                    ; the second string in loaderScreens, i.e. the "LOADING
                        ; ELITE" screen

                        ; Fall through into PrintString to display the "LOADING
                        ; ELITE" screen