movePlayerDownOrScrollUp

procedure movePlayerDownOrScrollUp();
// player moving down
begin
  if viewRowEnd = mapEnd then begin
  // at bottom of map so don't scroll screen up
  // and move normally
    player.yPos := player.yPos + player.yVel;
    Exit;
  end;

  if player.ty < VIEW_THRESHOLD_B then begin
    // don't scroll yet, not low enough down the screen
    // move normally
    player.yPos := player.yPos + player.yVel;
    Exit;
  end;

  vic_waitForRaster(IRQ_BLANK_LINE);

  // change scroll reg by y-vel (max 2 per frame)
  Inc(scrollY,2);//abs8(player.yVel.b1));

  if scrollY >= 8 then begin
  // wrap around and do hardscroll
    scrollY := scrollY and 7;

    asm
      .for(var y = VIEW_ROW_OFFSET+1; y < SCREEN_HEIGHT; y++) {
        ldx #MAP_WIDTH-1
      !:
        lda SCREEN0_ADDRESS + (y + 0) * SCREEN_WIDTH,x
        sta SCREEN0_ADDRESS + (y - 1) * SCREEN_WIDTH,x
        lda COLOR_ADDRESS + (y + 0) * SCREEN_WIDTH,x
        sta COLOR_ADDRESS + (y - 1) * SCREEN_WIDTH,x
        dex
        bpl !-
      }
    end;

    // move view down in map
    Inc(viewRowStart);
    Inc(viewRowEnd);

    // fill bottom row with level data
    addressPntr1 := levelRowOffset[viewRowEnd];
    addressPntr2 := screenRowOffset[SCREEN_HEIGHT-1];

    asm
      clc
      lda addressPntr2 + 0
      adc #<(COLOR_ADDRESS-SCREEN0_ADDRESS)
      sta addressPntr3 + 0
      lda addressPntr2 + 1
      adc #>(COLOR_ADDRESS-SCREEN0_ADDRESS)
      sta addressPntr3 + 1

      ldy #MAP_WIDTH-1
    !:
      lda (addressPntr1),y
      // store level char for color attrib later
      pha
      sta (addressPntr2),y
      // restore level char for color attrib
      pla
      tax
      lda charAttribs,x
      sta (addressPntr3),y
      dey
      bpl !-
    end;
  end;

//  vic_set_scrolly(scrollY);
end;