Phase 0: donor-launch spike foundation

Scaffold CoopAllTheThings: Remote Play Together for any XInput game via a
mirror app under a donor appid (real game keeps its own appid, so DRM,
achievements, and playtime stay intact).

- Build: CMake skeleton, ImGui + SafetyHook submodules (no vcpkg)
- common/: host<->hook IPC contract (seqlock pad state, shared-memory RAII)
- host/: borderless D3D11 window + ImGui overlay listing visible XInput pads,
  behind an InputSource interface (Steam Input slots in later)
- README documents the Phase 0 donor-launch validation procedure, anti-cheat
  limitation, and XInput/bitness constraints

Phase 0 validates the riskiest assumption (Steam RPT streams an arbitrary
window under a donor appid and routes guest input to it) before capture and
injection are built.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
2026-06-18 22:48:31 +02:00
commit cf058aecfa
23 changed files with 1129 additions and 0 deletions

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host/src/d3d11_window.cpp Normal file
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#include "d3d11_window.hpp"
#include <imgui_impl_win32.h>
// Forward declared in the ImGui Win32 backend; lets ImGui consume input first.
extern IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandler(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam);
using Microsoft::WRL::ComPtr;
namespace coop
{
namespace
{
constexpr wchar_t kWindowClass[] = L"CoopAllTheThingsWindow";
}
D3D11Window::~D3D11Window()
{
release_render_target();
if (hwnd_ != nullptr)
{
DestroyWindow(hwnd_);
hwnd_ = nullptr;
}
UnregisterClassW(kWindowClass, GetModuleHandleW(nullptr));
}
bool D3D11Window::create(const wchar_t* title)
{
const HINSTANCE instance = GetModuleHandleW(nullptr);
WNDCLASSEXW wc = {};
wc.cbSize = sizeof(wc);
wc.style = CS_HREDRAW | CS_VREDRAW;
wc.lpfnWndProc = &D3D11Window::wnd_proc;
wc.hInstance = instance;
wc.hCursor = LoadCursorW(nullptr, IDC_ARROW);
wc.lpszClassName = kWindowClass;
if (RegisterClassExW(&wc) == 0)
{
return false;
}
// Borderless popup covering the primary monitor. Steam RPT only streams the
// focused window, and exclusive-fullscreen swap chains can't be captured, so
// a plain WS_POPUP is exactly what we want.
const int width = GetSystemMetrics(SM_CXSCREEN);
const int height = GetSystemMetrics(SM_CYSCREEN);
hwnd_ = CreateWindowExW(0, kWindowClass, title, WS_POPUP, 0, 0, width, height, nullptr, nullptr, instance, this);
if (hwnd_ == nullptr)
{
return false;
}
if (!create_device())
{
return false;
}
ShowWindow(hwnd_, SW_SHOW);
UpdateWindow(hwnd_);
SetForegroundWindow(hwnd_);
return true;
}
bool D3D11Window::create_device()
{
DXGI_SWAP_CHAIN_DESC1 desc = {};
desc.Width = 0; // derive from the window client area
desc.Height = 0;
desc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
desc.SampleDesc.Count = 1;
desc.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;
desc.BufferCount = 2;
desc.Scaling = DXGI_SCALING_STRETCH;
desc.SwapEffect = DXGI_SWAP_EFFECT_FLIP_DISCARD;
desc.AlphaMode = DXGI_ALPHA_MODE_IGNORE;
UINT flags = 0;
#ifdef _DEBUG
flags |= D3D11_CREATE_DEVICE_DEBUG;
#endif
const D3D_FEATURE_LEVEL levels[] = {D3D_FEATURE_LEVEL_11_1, D3D_FEATURE_LEVEL_11_0};
if (FAILED(D3D11CreateDevice(nullptr, D3D_DRIVER_TYPE_HARDWARE, nullptr, flags, levels, _countof(levels),
D3D11_SDK_VERSION, device_.GetAddressOf(), nullptr, context_.GetAddressOf())))
{
return false;
}
ComPtr<IDXGIDevice> dxgi_device;
if (FAILED(device_.As(&dxgi_device)))
{
return false;
}
ComPtr<IDXGIAdapter> adapter;
if (FAILED(dxgi_device->GetAdapter(adapter.GetAddressOf())))
{
return false;
}
ComPtr<IDXGIFactory2> factory;
if (FAILED(adapter->GetParent(IID_PPV_ARGS(factory.GetAddressOf()))))
{
return false;
}
if (FAILED(factory->CreateSwapChainForHwnd(device_.Get(), hwnd_, &desc, nullptr, nullptr,
swap_chain_.GetAddressOf())))
{
return false;
}
// Don't let DXGI swallow Alt+Enter into an exclusive-fullscreen transition.
factory->MakeWindowAssociation(hwnd_, DXGI_MWA_NO_ALT_ENTER);
create_render_target();
return true;
}
void D3D11Window::create_render_target()
{
ComPtr<ID3D11Texture2D> back_buffer;
if (SUCCEEDED(swap_chain_->GetBuffer(0, IID_PPV_ARGS(back_buffer.GetAddressOf()))))
{
device_->CreateRenderTargetView(back_buffer.Get(), nullptr, rtv_.ReleaseAndGetAddressOf());
}
}
void D3D11Window::release_render_target()
{
rtv_.Reset();
}
void D3D11Window::handle_resize(UINT width, UINT height)
{
if (swap_chain_ == nullptr || width == 0 || height == 0)
{
return;
}
release_render_target();
swap_chain_->ResizeBuffers(0, width, height, DXGI_FORMAT_UNKNOWN, 0);
create_render_target();
}
bool D3D11Window::pump_messages()
{
MSG msg;
while (PeekMessageW(&msg, nullptr, 0, 0, PM_REMOVE))
{
if (msg.message == WM_QUIT)
{
return false;
}
TranslateMessage(&msg);
DispatchMessageW(&msg);
}
if (resize_pending_)
{
handle_resize(resize_width_, resize_height_);
resize_pending_ = false;
}
return true;
}
void D3D11Window::render_frame(const RenderCallback& render)
{
const float clear[4] = {0.06f, 0.06f, 0.08f, 1.0f};
context_->OMSetRenderTargets(1, rtv_.GetAddressOf(), nullptr);
context_->ClearRenderTargetView(rtv_.Get(), clear);
if (render)
{
render();
}
// vsync on: matches the captured stream cadence and avoids a busy spin.
swap_chain_->Present(1, 0);
}
LRESULT CALLBACK D3D11Window::wnd_proc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
{
if (msg == WM_NCCREATE)
{
auto* create = reinterpret_cast<CREATESTRUCTW*>(lparam);
SetWindowLongPtrW(hwnd, GWLP_USERDATA, reinterpret_cast<LONG_PTR>(create->lpCreateParams));
}
if (ImGui_ImplWin32_WndProcHandler(hwnd, msg, wparam, lparam))
{
return true;
}
auto* self = reinterpret_cast<D3D11Window*>(GetWindowLongPtrW(hwnd, GWLP_USERDATA));
switch (msg)
{
case WM_SIZE:
if (self != nullptr && wparam != SIZE_MINIMIZED)
{
self->resize_pending_ = true;
self->resize_width_ = LOWORD(lparam);
self->resize_height_ = HIWORD(lparam);
}
return 0;
case WM_KEYDOWN:
// Spike convenience: Esc quits so we aren't stuck in a borderless window.
if (wparam == VK_ESCAPE)
{
PostQuitMessage(0);
}
return 0;
case WM_DESTROY:
PostQuitMessage(0);
return 0;
default:
break;
}
return DefWindowProcW(hwnd, msg, wparam, lparam);
}
} // namespace coop