fix(UI): correct ImGui scaling for borderless mode

src/Menu/OverlayRenderer.cpp

@@ -3,6 +3,7 @@
 #include "HomePageRenderer.h"
 #include "ThemeManager.h"
 
+#include <dxgi.h>
 #include <imgui.h>
 #include <imgui_impl_dx11.h>
 #include <imgui_impl_win32.h>
@@ -117,8 +118,16 @@ void OverlayRenderer::InitializeImGuiFrame(Menu& menu)
 	// Start the Dear ImGui frame
 	ImGui_ImplDX11_NewFrame();
 	ImGui_ImplWin32_NewFrame();
-	ImGui::NewFrame();
 
+	DXGI_SWAP_CHAIN_DESC desc{};
+	globals::d3d::swapChain->GetDesc(&desc);
+
+	Util::UpdateImGuiInput(
+		desc.OutputWindow,
+		static_cast<float>(desc.BufferDesc.Width),
+		static_cast<float>(desc.BufferDesc.Height));
+
+	ImGui::NewFrame();
 	ThemeManager::SetupImGuiStyle(menu);
 }
 

src/Utils/UI.cpp

@@ -17,6 +17,7 @@
 #include <DirectXTex.h>
 #include <d3d11.h>
 #include <dinput.h>
+#include <dxgi.h>
 #include <imgui.h>
 #include <imgui_internal.h>
 #include <wrl/client.h>
@@ -45,6 +46,47 @@
 
 namespace Util
 {
+	static ImVec2 g_screenScaleRatio = { 1.0f, 1.0f };
+	static ImVec2 g_displaySize = { 0.0f, 0.0f };
+
+	static int g_lastWindowWidth = 0;
+	static int g_lastWindowHeight = 0;
+
+	void RefreshScreenScale(HWND hwnd, float bufferWidth, float bufferHeight)
+	{
+		RECT rect{};
+		if (!GetClientRect(hwnd, &rect) || rect.right <= 0 || rect.bottom <= 0)
+			return;
+
+		if (rect.right == g_lastWindowWidth && rect.bottom == g_lastWindowHeight)
+			return;
+
+		g_displaySize.x = bufferWidth;
+		g_displaySize.y = bufferHeight;
+
+		g_screenScaleRatio.x = bufferWidth / static_cast<float>(rect.right);
+		g_screenScaleRatio.y = bufferHeight / static_cast<float>(rect.bottom);
+
+		g_lastWindowWidth = rect.right;
+		g_lastWindowHeight = rect.bottom;
+	}
+
+	void UpdateImGuiInput(HWND hwnd, float bufferWidth, float bufferHeight)
+	{
+		RefreshScreenScale(hwnd, bufferWidth, bufferHeight);
+
+		auto& io = ImGui::GetIO();
+		io.DisplaySize = g_displaySize;
+
+		POINT cursorPos{};
+		if (GetCursorPos(&cursorPos) &&
+			ScreenToClient(hwnd, &cursorPos)) {
+			io.AddMousePosEvent(
+				static_cast<float>(cursorPos.x) * g_screenScaleRatio.x,
+				static_cast<float>(cursorPos.y) * g_screenScaleRatio.y);
+		}
+	}
+
 	HoverTooltipWrapper::HoverTooltipWrapper() :
 		previousFont(nullptr)
 	{

src/Utils/UI.h

@@ -49,6 +49,7 @@ class Feature;
 
 namespace Util
 {
+	void UpdateImGuiInput(HWND hwnd, float bufferWidth, float bufferHeight);
 	/**
 	 * Represents a single line and its color for any colored text rendering (tooltips, legends, etc.).
 	 */