From 846e402b9812e2f45f13fa905e98e09b895e47f2 Mon Sep 17 00:00:00 2001
From: Matthew Stanley <1379tech@gmail.com>
Date: Thu, 11 Jun 2026 15:17:22 -0700
Subject: [PATCH] gl-renderer: fix double-applied draw offset dropping terrain
 layers
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gpu.c applies draw_offset_x/y to every primitive's coordinates before
calling the gr_* facade (see gp0_exec_* — triangles, rects, sprites,
lines all pre-offset), and the software raster consumes them directly
(g_offset_x is never read during rasterization). The GPU triangle paths
were adding s_off again, double-applying the offset.

At the logos the offset is 0 so it was invisible, but in the scrolling
overworld it displaced every GPU-rendered triangle by 2x the scroll,
pushing the background/foreground terrain quads off-screen while
sprites (drawn as rects -> software, single offset) stayed put. Net
effect: "the entire overworld is gone" — only sprites survived.

Drop the s_off addition in gpu_triangle/gpu_textured_triangle. Verified:
the attract-demo overworld now renders full terrain (grass, mushrooms,
cliffs, signpost, coins) instead of sprites on an empty gradient.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 runtime/src/gpu_gl_renderer.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/runtime/src/gpu_gl_renderer.c b/runtime/src/gpu_gl_renderer.c
index 5350264f..7e7dea5a 100644
--- a/runtime/src/gpu_gl_renderer.c
+++ b/runtime/src/gpu_gl_renderer.c
@@ -347,8 +347,10 @@ static void gpu_triangle(int x0,int y0,uint16_t c0, int x1,int y1,uint16_t c1,
                          int x2,int y2,uint16_t c2, int semi) {
     ensure_gpu();
     float verts[3*6];
-    int xs[3] = {x0+s_off_x, x1+s_off_x, x2+s_off_x};
-    int ys[3] = {y0+s_off_y, y1+s_off_y, y2+s_off_y};
+    /* gpu.c already applied the draw offset before calling the gr_* facade
+     * (see gp0_exec_* in gpu.c); coords arrive in final VRAM space. */
+    int xs[3] = {x0, x1, x2};
+    int ys[3] = {y0, y1, y2};
     uint16_t cs[3] = {c0,c1,c2};
     for (int i = 0; i < 3; i++) {
         verts[i*6+0] = (float)xs[i];
@@ -389,8 +391,9 @@ static void gpu_textured_triangle(const int *xs, const int *ys,
     ensure_gpu();
     float verts[3 * 8];
     for (int i = 0; i < 3; i++) {
-        verts[i*8+0] = (float)(xs[i] + s_off_x);
-        verts[i*8+1] = (float)(ys[i] + s_off_y);
+        /* coords already offset by gpu.c — do not re-apply s_off here */
+        verts[i*8+0] = (float)xs[i];
+        verts[i*8+1] = (float)ys[i];
         verts[i*8+2] = (float)us[i];
         verts[i*8+3] = (float)vs[i];
         verts[i*8+4] = col[i*3+0];