Drawing the screen: wantdials

       Name: wantdials                                               [Show more]
       Type: Subroutine
   Category: Drawing the screen
    Summary: Show the dashboard on-screen
  Deep dive: The split-screen mode in Commodore 64 Elite
             Colouring the Commodore 64 bitmap screen
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * TTX66K calls wantdials


.wantdials

 JSR BOX2               ; Draw a border box around the space view

 LDA #$91               ; Set abraxas = $91, so the colour of the lower part of
 STA abraxas            ; the screen is determined by screen RAM at $6400
                        ; (i.e. for when the dashboard is being shown)

 LDA #%11010000         ; Set bit 4 of caravanserai so that the lower part of
 STA caravanserai       ; the screen (the dashboard) is shown in multicolour
                        ; bitmap mode

 LDA DFLAG              ; If DFLAG is non-zero then the dashboard is already
 BNE nearlyxmas         ; being shown on-screen, so jump to nearlyxmas to skip
                        ; displaying the dashboard on-screen

                        ; We now copy the dashboard bitmap from the copy at
                        ; DSTORE% into the screen bitmap, so the dashboard
                        ; appears on-screen
                        ;
                        ; The bitmap is seven character rows in size, which is
                        ; 7 * 40 * 7 = $8C0 bytes, so we need to copy this many
                        ; bytes from DSTORE% to the screen bitmap address of the
                        ; dashboard at DLOC%

 LDX #8                 ; Set X = 8 so we copy the first eight pages of the
                        ; dashboard bitmap from DSTORE% to screen memory

 LDA #LO(DSTORE%)       ; Set V(1 0) = DSTORE%
 STA V                  ;
 LDA #HI(DSTORE%)       ; So V(1 0) points to the copy of the dashboard image
 STA V+1                ; and colour data at DSTORE%

 LDA #LO(DLOC%)         ; Set SC(1 0) = DLOC%
 STA SC                 ;
 LDA #HI(DLOC%)         ; So SC(1 0) points to the address in the screen bitmap
 STA SC+1               ; of the start of the dashboard at DLOC%

 JSR mvblockK           ; Copy X pages from V(1 0) to SC(1 0), which copies all
                        ; eight pages of the dashboard bitmap from the copy at
                        ; DSTORE% into the screen bitmap

                        ; We have copied $800 bytes, so now for the other $C0
                        ; bytes

 LDY #$C0               ; Set Y = $C0 so we copy this many bytes

 LDX #1                 ; Set X = 1 so we copy this many bytes within just one
                        ; page

 JSR mvbllop            ; Copy Y bytes from V(1 0) to SC(1 0), so this copies
                        ; the rest of the dashboard bitmap to the screen

 JSR zonkscanners       ; Hide all ships on the scanner

 JSR DIALS              ; Call DIALS to update the dashboard

.nearlyxmas

 JSR BLUEBAND           ; Clear the borders along the edges of the space view,
                        ; to hide any sprites that might be lurking there

 JSR NOSPRITES          ; Call NOSPRITES to disable all sprites and remove them
                        ; from the screen

 LDA #$FF               ; Set DFLAG to $FF to indicate that the dashboard is now
 STA DFLAG              ; being shown on-screen

 RTS                    ; Return from the subroutine