main.cpp

int main(int, char**)
{
    // Create application window
    WNDCLASSEX wc = { sizeof(WNDCLASSEX), CS_CLASSDC, WndProc, 0L, 0L, GetModuleHandle(NULL), NULL, LoadCursor(NULL, IDC_ARROW), NULL, NULL, _T("ImGui Example"), NULL };
    RegisterClassEx(&wc);
    HWND hwnd = CreateWindow(_T("ImGui Example"), _T("ImGui DirectX11 Example"), WS_POPUP, 100, 100, 1280, 800, NULL, NULL, wc.hInstance, NULL);

    // Initialize Direct3D
    if (CreateDeviceD3D(hwnd) < 0)
    {
        CleanupDeviceD3D();
        UnregisterClass(_T("ImGui Example"), wc.hInstance);
        return 1;
    }

    // Show the window
    ShowWindow(hwnd, SW_SHOWDEFAULT);
    UpdateWindow(hwnd);

    // Setup ImGui binding
    ImGui_ImplDX11_Init(hwnd, g_pd3dDevice, g_pd3dDeviceContext);

    bool show_another_window = true;
    ImVec4 clear_col = ImColor(114, 144, 154);

	int moveOffsetX = 0;
	int moveOffsetY = 0;

    // Main loop
    MSG msg;
    ZeroMemory(&msg, sizeof(msg));
    while (msg.message != WM_QUIT)
    {
        if (PeekMessage(&msg, NULL, 0U, 0U, PM_REMOVE))
        {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
            continue;
        }
        ImGui_ImplDX11_NewFrame();

		if (ImGui::IsMouseClicked(0))
		{
			POINT point;
			RECT rect;

			GetCursorPos(&point);
			GetWindowRect(hwnd, &rect);

			// Calculate the difference between the cursor pos and window pos
			moveOffsetX = point.x - rect.left;
			moveOffsetY = point.y - rect.top;
		}

		// 2. Show another simple window, this time using an explicit Begin/End pair
		ImGui::Begin("Another Window", &show_another_window, ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoCollapse);
		{
			ImGui::SetWindowPos(ImVec2(0, 0), ImGuiSetCond_Once);
			ImGui::SetWindowSize(ImVec2(1280, 800), ImGuiSetCond_Once);
			ImGui::Text("Hello");

			if ((moveOffsetY >= 0 && moveOffsetY <= 22) &&	// Cursor must be *on* the titlebar
				ImGui::IsMouseDragging())					// User must drag mouse (hold LMB)
			{
				POINT point;
				GetCursorPos(&point);

				SetWindowPos(hwnd, nullptr, point.x - moveOffsetX, point.y - moveOffsetY, 0, 0, SWP_NOSIZE | SWP_NOZORDER);
			}
		}
		ImGui::End();

        // Rendering
        g_pd3dDeviceContext->ClearRenderTargetView(g_mainRenderTargetView, (float*)&clear_col);
        ImGui::Render();
        g_pSwapChain->Present(0, 0);
    }

    ImGui_ImplDX11_Shutdown();
    CleanupDeviceD3D();
    UnregisterClass(_T("ImGui Example"), wc.hInstance);

    return 0;
}