Merge commit 'refs/review/20261014/pr661' into integrate/pr658plus-regressions-20261014

runtime/CMakeLists.txt

@@ -1821,6 +1821,9 @@ if(BUILD_TESTING)
                              --cc ${CMAKE_C_COMPILER})
         endif()
         add_test(NAME fntrace_c_linkage_test COMMAND ${Python3_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/tests/test_fntrace_c_linkage.py)
+        add_test(NAME depth24_present_hold_vblank_test
+                 COMMAND ${Python3_EXECUTABLE}
+                         ${CMAKE_CURRENT_SOURCE_DIR}/tests/test_depth24_present_hold_vblank.py)
         add_test(NAME netplay_load_apply_flow_test
                  COMMAND ${Python3_EXECUTABLE}
                          ${CMAKE_CURRENT_SOURCE_DIR}/tests/test_netplay_load_apply_flow.py)

runtime/src/gpu.c

@@ -3408,6 +3408,12 @@ static uint16_t vram_write_pixels[1024 * 512];
  * gpu_depth24_rgb_limit — declared early so gpu_reset_state can clear it. */
 static uint32_t s_d24_upload_x1 = 0;
 static int      s_d24_present_hold = 0; /* vblanks to skip Swap after GP1(07h) */
+/* Host side of the hold: whether the present after the latest guest VBlank
+ * skips its Swap. The count itself is guest state (in the GPU snap) and moves
+ * only at guest VBlank, so a live run, a rollback replay and a headless run
+ * all hold the same span (#636: a present-ticked hold stuck at 3 in headless
+ * live play and was zeroed by a rollback load, so replay != live). */
+static int      s_d24_present_skip = 0;
 static uint32_t s_d24_prev_disp_h = 0;  /* last GP1(07h) band height */
 static void depth24_note_upload(uint32_t x, uint32_t w);
 
@@ -3880,6 +3886,7 @@ static void gpu_reset_state(int clear_vram) {
     ws_scene_hold_reset(&s_ws_scene_hold);
     s_d24_upload_x1 = 0;
     s_d24_present_hold = 0;
+    s_d24_present_skip = 0;
     s_d24_prev_disp_h = 0;
 }
 
@@ -4145,6 +4152,9 @@ void gpu_vblank_tick(void) {
      * poll first became reachable in this runtime. */
     if (vertical_interlace)
         interlace_field = (lcf ^ 1) & 1;
+    s_d24_present_skip = s_d24_present_hold > 0;
+    if (s_d24_present_hold > 0)
+        s_d24_present_hold--;
     /* snapshot per-frame draw-offset-Y range for the strobe instrumentation */
     if (g_doff_cnt_this) {
         g_doff_min_last = g_doff_min_this;
@@ -4232,15 +4242,16 @@ void gpu_depth24_upload_span_reset(void) {
 }
 
 int gpu_depth24_present_hold_tick(void) {
-    if (s_d24_present_hold <= 0) return 0;
-    s_d24_present_hold--;
-    return 1;
+    int skip = s_d24_present_skip;
+    s_d24_present_skip = 0; /* one skipped Swap per guest VBlank */
+    return skip;
 }
 
 void gpu_depth24_on_savestate_loaded(void) {
     /* Hold skips Swap — after restore we want the restored VRAM visible now.
      * Upload span / prev_h were restored from the GPU snap. */
     s_d24_present_hold = 0;
+    s_d24_present_skip = 0;
 }
 
 /* ---- Present-time screen-colour LUT (verified-enhancement, opt-in) -------

runtime/src/main.cpp

@@ -1122,7 +1122,9 @@ extern "C" void psx_frontend_on_rb_snap_loaded(void) {
     const int media = gpu_display_is_depth24() || mdec_recently_active(8) ||
                       cdrom_fmv_stream_pending() || cdrom_xa_stream_active();
     g_audio_cycle_resync = 1;
-    gpu_depth24_on_savestate_loaded();
+    /* The depth24 present hold came back with the GPU snap and is guest state
+     * now (ticked at guest VBlank): keep it, so the replay matches the live
+     * run of the same ticks. */
     s_d24_cutover_blank = 0;
     if (media) {
         s_d24_saw_gap = 0;
@@ -9034,9 +9036,8 @@ static NetplayVblankEpilogue sdl_vblank_present_body(void) {
 
     /* Depth24 GP1(07h) retarget (MotK intro→crawl): keep the prior Swap for a
      * few vblanks so stale trailing VRAM never flashes on the right edge.
-     * Must tick every present — gpu.c arms s_d24_present_hold and also
-     * freezes upload-span tracking while hold > 0; without this call the hold
-     * sticks and depth24_fix_trailing_margin blanks the whole FMV forever. */
+     * gpu.c counts the hold down at guest VBlank (it also freezes upload-span
+     * tracking while > 0); this skips the Swap of each held VBlank. */
     if (gpu_depth24_present_hold_tick())
         return ep;
 

runtime/tests/test_depth24_present_hold_vblank.py

@@ -0,0 +1,32 @@
+#!/usr/bin/env python3
+"""The depth24 present hold is guest state, counted down at guest VBlank.
+
+GP1(07h) arms s_d24_present_hold (skip a few Swaps after a depth24 band
+retarget). It is in the GPU snap. It used to count down only at host present,
+so a headless run never moved it, and a rollback snap load zeroed it: the
+replayed save of a tick differed from the live save in the GPU section
+(psxrecomp #636). Guards: gpu_vblank_tick counts it down, the present-side
+query never touches it, and a rollback snap load keeps the restored value.
+"""
+from pathlib import Path
+
+from test_netplay_load_apply_flow import function_body
+
+SRC = Path(__file__).resolve().parents[1] / "src"
+
+
+def main():
+    gpu = (SRC / "gpu.c").read_text()
+    vblank = function_body(gpu, "void gpu_vblank_tick(void)")
+    assert "s_d24_present_hold--" in vblank
+    tick = function_body(gpu, "int gpu_depth24_present_hold_tick(void)")
+    assert "s_d24_present_hold" not in tick, "the hold must not move at host present"
+
+    main_cpp = (SRC / "main.cpp").read_text()
+    rb_loaded = function_body(main_cpp, 'extern "C" void psx_frontend_on_rb_snap_loaded(void)')
+    assert "gpu_depth24_on_savestate_loaded" not in rb_loaded
+    print("depth24 present hold: ok")
+
+
+if __name__ == "__main__":
+    main()