From 14829f827ce63a9fad915e54cc18f5e4bb35a9e4 Mon Sep 17 00:00:00 2001
From: Stepanov Igor <ygrik2003@yandex.ru>
Date: Sat, 18 Oct 2025 00:43:13 +0300
Subject: [PATCH] fix fps settings

---
 src/engine/Engine.cpp           |  1 +
 src/window/detail/SDLWindow.cpp | 16 ++++++++++++++--
 src/window/detail/SDLWindow.hpp |  3 +++
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/src/engine/Engine.cpp b/src/engine/Engine.cpp
index a977f354b..71bcd580f 100644
--- a/src/engine/Engine.cpp
+++ b/src/engine/Engine.cpp
@@ -308,6 +308,7 @@ void Engine::nextFrame() {
             : settings.display.framerate.get()
     );
     window->swapBuffers();
+    // todo: process it on another thread
     input->pollEvents();
 }
 
diff --git a/src/window/detail/SDLWindow.cpp b/src/window/detail/SDLWindow.cpp
index 01be25cd9..7277c080e 100644
--- a/src/window/detail/SDLWindow.cpp
+++ b/src/window/detail/SDLWindow.cpp
@@ -18,6 +18,7 @@
 #include "graphics/core/ImageData.hpp"
 #include "graphics/core/Texture.hpp"
 #include "settings.hpp"
+#include "util/platform.hpp"
 #include "window/Window.hpp"
 #include "window/detail/SDLInput.hpp"
 
@@ -231,6 +232,17 @@ SDLWindow::~SDLWindow() {
 }
 
 void SDLWindow::swapBuffers() noexcept {
+    if (framerate > 0) {
+        auto elapsedTime = time() - prevSwap;
+        auto frameTime = 1.0 / framerate;
+        if (elapsedTime < frameTime) {
+            platform::sleep(
+                static_cast<size_t>((frameTime - elapsedTime) * 1000)
+            );
+        }
+        prevSwap = time();
+    }
+
     if (!SDL_GL_SwapWindow(window)) [[unlikely]] {  // C++20 needed
         logger.error() << "Cant swap buffer: " << SDL_GetError();
     }
@@ -425,10 +437,10 @@ double SDLWindow::time() {
 }
 
 void SDLWindow::setFramerate(int framerate) {
-    /*todo*/
-    if (!SDL_GL_SetSwapInterval(framerate)) {
+    if (!SDL_GL_SetSwapInterval(framerate == -1)) {
         logger.error() << "Failed to set framerate: " << SDL_GetError();
     }
+    this->framerate = framerate;
 }
 
 // todo: move somewhere
diff --git a/src/window/detail/SDLWindow.hpp b/src/window/detail/SDLWindow.hpp
index 8e9f23e8a..f1b32e837 100644
--- a/src/window/detail/SDLWindow.hpp
+++ b/src/window/detail/SDLWindow.hpp
@@ -47,6 +47,9 @@ private:
     bool toClose = false;
     bool fullscreen = false;
 
+    double framerate = -1;
+    double prevSwap = 0.0;
+
     SDL_Window *window = nullptr;
     SDL_Renderer *renderer = nullptr;
     SDL_Cursor *cursor = nullptr;