add event watch for window exposed

Disabled on linux since it introduces really bad flickering on resize,
and is not needed anyway since linux does not lock your main thread
while you're changing the window

Author: HeliumAnt

Source/Managers/WindowMan.cpp

@@ -1,7 +1,6 @@
 #include "WindowMan.h"
 #include "RTEError.h"
-#include "SDL3/SDL_error.h"
-#include "SDL3/SDL_video.h"
+#include "SDL3/SDL.h"
 #include "SettingsMan.h"
 #include "FrameMan.h"
 #include "ActivityMan.h"
@@ -155,6 +154,10 @@ void WindowMan::Initialize() {
 	} else {
 		SetViewportLetterboxed();
 	}
+
+#ifdef _WIN32
+	SDL_AddEventWatch((SDL_EventFilter)WindowMan::HandleWindowExposedEvent, nullptr);
+#endif
 }
 
 void WindowMan::CreatePrimaryWindow() {
@@ -674,6 +677,15 @@ void WindowMan::DisplaySwitchOut() const {
 	SDL_SetCursor(nullptr);
 }
 
+void WindowMan::HandleWindowExposedEvent(void *userdata, SDL_Event *event) {
+	if (event->type == SDL_EVENT_WINDOW_EXPOSED) {
+		g_WindowMan.SetViewportLetterboxed();
+		g_WindowMan.ClearBackbuffer(false);
+		g_WindowMan.UploadFrame();
+		g_WindowMan.Present();
+	}
+}
+
 void WindowMan::QueueWindowEvent(const SDL_Event& windowEvent) {
 	m_EventQueue.emplace_back(windowEvent);
 }
@@ -722,6 +734,7 @@ void WindowMan::Update() {
 			case SDL_EVENT_WINDOW_RESIZED:
 			case SDL_WINDOW_MAXIMIZED:
 				SetViewportLetterboxed();
+				std::cout << "resize" << std::endl;
 				break;
 			default:
 				break;

Source/Managers/WindowMan.h

@@ -168,6 +168,9 @@ namespace RTE {
 #pragma endregion
 
 #pragma region Concrete Methods
+		/// SDL_EventFilter to hadnle window exposed events for live resize.
+		static void HandleWindowExposedEvent(void* userdata, SDL_Event* event);
+
 		/// Adds an SDL_Event to the Event queue for processing on Update.
 		/// @param windowEvent The SDL window event to queue.
 		void QueueWindowEvent(const SDL_Event& windowEvent);