diff options
Diffstat (limited to 'scroll/include/background.s')
| -rw-r--r-- | scroll/include/background.s | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/scroll/include/background.s b/scroll/include/background.s index f392792..69725fd 100644 --- a/scroll/include/background.s +++ b/scroll/include/background.s @@ -27,6 +27,15 @@ DISABLED_BACKGROUND_CYCLE = $FE BACKGROUND_CYCLE_MAX = $02 + ;; The offset for metatile rows. That is, from where should the engine start + ;; counting rows of metatiles. By default it's 0, but it could be set to + ;; something else to reserve so top space for a HUD or something similar. + ;; + ;; NOTE: configurable. + .ifndef BACKGROUND_ROW_OFFSET + BACKGROUND_ROW_OFFSET = 0 + .endif + ;; Current column (or the next to be loaded by functions like ;; `load_column`). zp_cur_column = $75 @@ -51,9 +60,11 @@ lda #$00 sta zp_scroll sta Buffer::zp_vram_idx - sta zp_cur_row sta zp_cur_column + lda #BACKGROUND_ROW_OFFSET + sta zp_cur_row + rts .endproc @@ -112,7 +123,7 @@ ;; Increase the column being used and loop if we are not at the end of ;; the screen yet. - lda #0 + lda #BACKGROUND_ROW_OFFSET sta zp_cur_row inc zp_cur_column lda zp_cur_column @@ -418,7 +429,7 @@ ;; screen/level by poking the right flags. .proc prepare_next_column ;; The row index always has to be set to zero. - lda #0 + lda #BACKGROUND_ROW_OFFSET sta zp_cur_row ;; Is this the last column? If not, just quit. |