From e2b931d6d82f08298746b2707fd599f2e5a2834c Mon Sep 17 00:00:00 2001
From: Kawe Mazidjatari <48657826+Mauler125@users.noreply.github.com>
Date: Fri, 15 Nov 2024 20:33:57 +0100
Subject: [PATCH] ImguiSystem: perform atomic exchange before acquiring
 snapshot lock

Significantly improves performance when none of the imgui surfaces are being drawn.
---
 src/gameui/imgui_system.cpp | 5 ++---
 src/gameui/imgui_system.h   | 2 +-
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/src/gameui/imgui_system.cpp b/src/gameui/imgui_system.cpp
index cbc480c6..2d5d4bd0 100644
--- a/src/gameui/imgui_system.cpp
+++ b/src/gameui/imgui_system.cpp
@@ -155,13 +155,12 @@ void CImguiSystem::SwapBuffers()
 void CImguiSystem::RenderFrame()
 {
 	Assert(IsInitialized());
-	AUTO_LOCK(m_snapshotBufferMutex);
 
-	if (!m_hasNewFrame)
+	if (!m_hasNewFrame.exchange(false))
 		return;
 
+	AUTO_LOCK(m_snapshotBufferMutex);
 	ImGui_ImplDX11_RenderDrawData(&m_snapshotData.DrawData);
-	m_hasNewFrame = false;
 }
 
 //-----------------------------------------------------------------------------
diff --git a/src/gameui/imgui_system.h b/src/gameui/imgui_system.h
index 7759b86f..ddc7fd74 100644
--- a/src/gameui/imgui_system.h
+++ b/src/gameui/imgui_system.h
@@ -46,7 +46,7 @@ private:
 	mutable CThreadMutex m_inputEventQueueMutex;
 
 	bool m_initialized;
-	bool m_hasNewFrame;
+	std::atomic_bool m_hasNewFrame;
 };
 
 CImguiSystem* ImguiSystem();