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| author | user <user@clank> | 2026-07-18 21:56:21 +0200 |
|---|---|---|
| committer | user <user@clank> | 2026-07-18 21:56:21 +0200 |
| commit | bea52bc8f99ee6dbcc8154a366560fc18e7b24c8 (patch) | |
| tree | 0772b5d9e98de7f6c495198844c230537c7fb9d6 /include | |
| parent | term: SCY ring-scroll - scroll writes ONE map row; OSK toggle is 212 cycles (diff) | |
| download | gbos-bea52bc8f99ee6dbcc8154a366560fc18e7b24c8.tar.gz gbos-bea52bc8f99ee6dbcc8154a366560fc18e7b24c8.tar.xz gbos-bea52bc8f99ee6dbcc8154a366560fc18e7b24c8.zip | |
term: latch SCY in VBlank - fix ring-scroll shear on live displays
The ring-scroll wrote SCY mid-frame; SCY is sampled per scanline (on
hardware and in sl0pboy's PPU), so a scroll landing mid-frame rendered
the top of the frame at the old offset and the bottom at the new one -
a one-frame shear, invisible in frame-sampled GIF captures but ugly on
a live sixel view.
term_view_update now writes hSCY (HRAM) and a transparent VBlank ISR
(push af / apply / pop af / reti, same profile as TimerISR) copies it
to rSCY, so the view only ever moves at frame boundaries. The scroll's
tile+map writes stay immediate: the new map row is invisible at the
old SCY by construction (it's the ring row one past the visible 18).
Diffstat (limited to '')
| -rw-r--r-- | include/gbos.inc | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/include/gbos.inc b/include/gbos.inc index be6009f..cbd2670 100644 --- a/include/gbos.inc +++ b/include/gbos.inc @@ -13,7 +13,8 @@ DEF rIE EQU $FFFF ; interrupt enable DEF rTIMA EQU $FF05 ; timer counter DEF rTMA EQU $FF06 ; timer modulo (reload) DEF rTAC EQU $FF07 ; timer control (bit2 = enable, bits1-0 = clock) -DEF IEF_TIMER EQU %00000100 +DEF IEF_TIMER EQU %00000100 +DEF IEF_VBLANK EQU %00000001 DEF rDIV EQU $FF04 ; divider register: free-running 8-bit @ 16384 Hz DEF rSVBK EQU $FF70 ; CGB WRAM bank select ($D000-$DFFF): 1..7 DEF wCurMask EQU $D589 ; term/osk: cursor underline bits OR'd into a tile's last row |