From 7d1fadb07c99e1929743816bd1c54f20e4d2d949 Mon Sep 17 00:00:00 2001
From: Matthew Stanley <1379tech@gmail.com>
Date: Tue, 14 Jul 2026 10:08:54 -0700
Subject: [PATCH] runtime: report simulated-vblank FPS telemetry

Adapted from NyperYuhgard's PR #13.

Co-authored-by: NyperYuhgard <93950153+NyperYuhgard@users.noreply.github.com>
---
 docs/internal/upstream/pr13-fps-telemetry.md |  9 ++++++
 runtime/src/main.cpp                         | 34 ++++++++++++++++++++
 2 files changed, 43 insertions(+)
 create mode 100644 docs/internal/upstream/pr13-fps-telemetry.md

diff --git a/docs/internal/upstream/pr13-fps-telemetry.md b/docs/internal/upstream/pr13-fps-telemetry.md
new file mode 100644
index 000000000..2ae437d11
--- /dev/null
+++ b/docs/internal/upstream/pr13-fps-telemetry.md
@@ -0,0 +1,9 @@
+# PR #13 FPS telemetry provenance
+
+Parked from NyperYuhgard's PSXrecomp PR #13, commit
+[`b49548e7b8f494c9584eb09039a8c325d7375b46`](https://github.com/mstan/psxrecomp/commit/b49548e7b8f494c9584eb09039a8c325d7375b46).
+
+This branch retains only the title-neutral simulated-vblank FPS and realtime-speed
+telemetry. It was adapted to current master and guards window-title access in
+headless/windowless operation. The overlay-cache inventory from the same upstream
+commit is parked separately.
diff --git a/runtime/src/main.cpp b/runtime/src/main.cpp
index 6b0418b86..994cb69b5 100644
--- a/runtime/src/main.cpp
+++ b/runtime/src/main.cpp
@@ -2045,6 +2045,40 @@ static void sdl_vblank_present(void) {
 
     runtime_perf_diag_tick();
 
+    /* Lightweight frontend telemetry from PR #13. Count simulated vblanks rather
+     * than presents so turbo and skipped-frame modes still report game speed. */
+    {
+        static Uint64 fps_last_time = 0;
+        static uint64_t fps_last_frame = 0;
+        static std::string fps_base_title;
+        extern uint64_t s_frame_count;
+        const Uint64 now = SDL_GetPerformanceCounter();
+        const Uint64 frequency = SDL_GetPerformanceFrequency();
+        if (!fps_last_time) {
+            fps_last_time = now;
+            fps_last_frame = s_frame_count;
+            if (sdl_window) {
+                const char *title = SDL_GetWindowTitle(sdl_window);
+                if (title) fps_base_title = title;
+            }
+        } else if (frequency && now - fps_last_time >= frequency) {
+            const double seconds = (double)(now - fps_last_time) / (double)frequency;
+            const double fps = (double)(s_frame_count - fps_last_frame) / seconds;
+            const double speed = fps / 59.94;
+            if (!g_headless && sdl_window) {
+                char title[256];
+                snprintf(title, sizeof(title), "%s  [%.0f fps %.2fx]",
+                         fps_base_title.c_str(), fps, speed);
+                SDL_SetWindowTitle(sdl_window, title);
+            }
+            std::fprintf(stderr, "[FPS] game: %.1f fps (%.2fx) | frames: %llu\n",
+                         fps, speed, (unsigned long long)s_frame_count);
+            std::fflush(stderr);
+            fps_last_time = now;
+            fps_last_frame = s_frame_count;
+        }
+    }
+
     /* Host-stack-usage profile sample — frame counter is now current, and we are
      * on the guest fiber (see §17 block above). BEFORE the turbo/fast-boot early
      * returns so the curve is captured even when presents are skipped. */