From 9b813f2a0eb8626f84489de0f55dc6da2ed22420 Mon Sep 17 00:00:00 2001
From: user <user@clank>
Date: Sat, 18 Jul 2026 21:50:22 +0200
Subject: term: SCY ring-scroll - scroll writes ONE map row; OSK toggle is 212
 cycles

The BG map's 32 rows become a ring: logical row L always lives at map
row (wMapTop + L) & 31, and SCY = (wMapTop + wViewTop)*8 places the
view. Scrolling bumps wMapTop, rebuilds the one new bottom line and
writes its single map row (map_row_one); the other 17 rows move for
free. The whole OSK view dance - shift the cursor above the keys,
restore the backlog on hide - is now term_view_update: one SCY write,
no map rewrite at all.

OSK safety: the keyboard lives on the WINDOW layer, which SCY never
moves. Stale ring rows can only appear under it: wViewTop = max(0,
wCurRow-14) <= 3 is nonzero only while the OSK is visible, and the
window covers exactly those bottom 3 rows (WX=7, WY=120). Verified:
scroll + view shift + scroll-while-OSK-up + backlog restore all
pixel-correct via VRAM screenshots; full README demo passes.

term_scroll: 78.5k -> 35.6k T-cycles (857k pre-optimization: 24x).
OSK toggle: 45k tilemap rewrite -> 212 cycles.
Regenerated demo/gbos-demo.gif on the new renderer.
---
 src/osk.asm | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'src/osk.asm')

diff --git a/src/osk.asm b/src/osk.asm
index d5edad7..0f188eb 100644
--- a/src/osk.asm
+++ b/src/osk.asm
@@ -247,12 +247,12 @@ osk_toggle::
     ld a, [rLCDC]
     or %00100000
     ld [rLCDC], a
-    jp term_write_tilemap
+    jp term_view_update         ; SCY-only now: the map ring is untouched
 .hide
     ld a, [rLCDC]
     and %11011111
     ld [rLCDC], a
-    jp term_write_tilemap       ; offset recomputes to 0 -> full backlog
+    jp term_view_update         ; offset recomputes to 0 -> full backlog
 
 ; movement with wrap-around; each moves the highlight
 osk_up:
-- 
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