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⌂ ∞ ▽ Elite on the 6502

Drawing lines: NLIN2

[NES version, Bank 7]

       Name: NLIN2                                                   [Show more]
       Type: Subroutine
   Category: Drawing lines
    Summary: Draw a horizontal line on tile row 2 to box in a title

    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * NLIN4 calls NLIN2
             * TT22 calls NLIN2




.NLIN2

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

 LDY #1                 ; We now draw a horizontal line into the nametable
                        ; buffer starting at column 1, so set Y as a counter for
                        ; the column number

 LDA #3                 ; Set A to tile 3 so we draw the line as a horizontal
                        ; line that's three pixels thick

.nlin1

 STA nameBuffer0+2*32,Y ; Set the Y-th tile on row 2 of nametable buffer 0 to
                        ; to tile 3

 INY                    ; Increment the column counter

 CPY #32                ; Keep drawing tile 3 along row 2 until we have drawn
 BNE nlin1              ; column 31

 RTS                    ; Return from the subroutine