From bf5c7f67ea418d4ae22925c16052646f6fe31efa Mon Sep 17 00:00:00 2001
From: Mateusz Dukat <mateusz.dukat1@gmail.com>
Date: Sun, 10 Mar 2024 16:24:17 +0100
Subject: [PATCH] [GPU] Add hard FPS limit without vsync

---
 src/xenia/gpu/gpu_flags.cc       | 7 +++++++
 src/xenia/gpu/gpu_flags.h        | 3 +++
 src/xenia/gpu/graphics_system.cc | 8 +++++++-
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/xenia/gpu/gpu_flags.cc b/src/xenia/gpu/gpu_flags.cc
index e6ae0ad69..810d9f5ee 100644
--- a/src/xenia/gpu/gpu_flags.cc
+++ b/src/xenia/gpu/gpu_flags.cc
@@ -22,6 +22,13 @@ DEFINE_bool(vsync, true, "Enable VSYNC.", "GPU");
 
 DEFINE_uint64(vsync_fps, 60, "VSYNC frames per second", "GPU");
 
+DEFINE_uint64(hard_fps, 60,
+    "Hard FPS lock, ignored when vsync is used. "
+    "Game will never exceed this value", "GPU");
+
+DEFINE_bool(hard_fps_enable, false,
+    "Enable hard FPS lock, ignored if vsync is enabled", "GPU");
+
 DEFINE_bool(
     gpu_allow_invalid_fetch_constants, true,
     "Allow texture and vertex fetch constants with invalid type - generally "
diff --git a/src/xenia/gpu/gpu_flags.h b/src/xenia/gpu/gpu_flags.h
index c5ba7fcdd..e0f97a348 100644
--- a/src/xenia/gpu/gpu_flags.h
+++ b/src/xenia/gpu/gpu_flags.h
@@ -20,6 +20,9 @@ DECLARE_bool(vsync);
 
 DECLARE_uint64(vsync_fps);
 
+DECLARE_uint64(hard_fps);
+DECLARE_bool(hard_fps_enable);
+
 DECLARE_bool(gpu_allow_invalid_fetch_constants);
 
 DECLARE_bool(half_pixel_offset);
diff --git a/src/xenia/gpu/graphics_system.cc b/src/xenia/gpu/graphics_system.cc
index cc06c1390..91c3a3139 100644
--- a/src/xenia/gpu/graphics_system.cc
+++ b/src/xenia/gpu/graphics_system.cc
@@ -133,8 +133,14 @@ X_STATUS GraphicsSystem::Setup(cpu::Processor* processor,
               threading::NanoSleep(estimated_nanoseconds);
             }
           }
+          
           if (!cvars::vsync) {
-            xe::threading::Sleep(std::chrono::milliseconds(1));
+            if (cvars::hard_fps_enable) {
+              uint64_t hard_frame_sleep_time = 1000000000 / cvars::hard_fps;
+              xe::threading::NanoSleep(hard_frame_sleep_time);
+            } else {
+              xe::threading::Sleep(std::chrono::milliseconds(1));
+            }
           }
         }
         return 0;