CoopAllTheThings/hook/src/focus_spoof.cpp

#include "focus_spoof.hpp"

#include <vector>

#include <windows.h>

#include <safetyhook.hpp>

#include "find_window.hpp"
#include "hook_guard.hpp"
#include "hook_install.hpp"
#include "hook_registry.hpp"

namespace coop::hook {

namespace {

DetourGate g_gate; // drains in-flight focus / WNDPROC detours before remove nulls their state

HWND g_game_hwnd = nullptr;
WNDPROC g_orig_proc = nullptr;
bool g_unicode = true;
std::vector<safetyhook::InlineHook> g_focus_hooks;
IpcClient* g_focus_ipc = nullptr;

int g_id_foreground = -1;
int g_id_active = -1;
int g_id_focus = -1;
int g_id_wndproc = -1;
int g_id_clipcursor = -1;
int g_id_setcursorpos = -1;

// Cursor-release hooks kept separately so their trampolines can be called.
safetyhook::InlineHook g_hk_clipcursor;
safetyhook::InlineHook g_hk_setcursorpos;

// Replacement window procedure: convince the game it is never deactivated.
LRESULT CALLBACK subclass_proc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
{
	DetourGate::Guard guard(g_gate); // keep g_orig_proc / g_unicode valid for this whole dispatch
	switch (msg) {
	case WM_ACTIVATE:
		if (LOWORD(wparam) == WA_INACTIVE) {
			wparam = MAKEWPARAM(WA_ACTIVE, HIWORD(wparam));
			hook_note_call(g_id_wndproc);
		}
		break;
	case WM_ACTIVATEAPP:
		wparam = TRUE; // app is "still active"
		hook_note_call(g_id_wndproc);
		break;
	case WM_NCACTIVATE:
		wparam = TRUE; // keep the active (non-greyed) appearance
		hook_note_call(g_id_wndproc);
		break;
	case WM_KILLFOCUS:
		hook_note_call(g_id_wndproc);
		return 0; // swallow: never tell the game it lost keyboard focus
	default:
		break;
	}
	// Read g_orig_proc once; if the subclass is live but the original isn't published yet (the tiny
	// install/remove window), fall back to DefWindowProc rather than call through a null pointer.
	const WNDPROC orig = g_orig_proc;
	if (orig == nullptr) {
		return g_unicode ? DefWindowProcW(hwnd, msg, wparam, lparam) : DefWindowProcA(hwnd, msg, wparam, lparam);
	}
	return g_unicode ? CallWindowProcW(orig, hwnd, msg, wparam, lparam)
	                 : CallWindowProcA(orig, hwnd, msg, wparam, lparam);
}

HWND WINAPI hk_GetForegroundWindow()
{
	DetourGate::Guard guard(g_gate);
	hook_note_call(g_id_foreground);
	if (g_focus_ipc != nullptr) {
		g_focus_ipc->note_focus_query(FocusApi_Foreground);
	}
	return g_game_hwnd;
}

HWND WINAPI hk_GetActiveWindow()
{
	DetourGate::Guard guard(g_gate);
	hook_note_call(g_id_active);
	if (g_focus_ipc != nullptr) {
		g_focus_ipc->note_focus_query(FocusApi_Active);
	}
	return g_game_hwnd;
}

HWND WINAPI hk_GetFocus()
{
	DetourGate::Guard guard(g_gate);
	hook_note_call(g_id_focus);
	if (g_focus_ipc != nullptr) {
		g_focus_ipc->note_focus_query(FocusApi_Focus);
	}
	return g_game_hwnd;
}

// When cursor release is requested (the default), free any clip the game asks for so
// the operator's mouse isn't trapped; otherwise honor the game's clip.
BOOL WINAPI hk_ClipCursor(const RECT* rect)
{
	DetourGate::Guard guard(g_gate);
	hook_note_call(g_id_clipcursor);
	const bool allow = g_focus_ipc != nullptr && g_focus_ipc->cursor_clip_allowed();
	return g_hk_clipcursor.stdcall<BOOL>(allow ? rect : nullptr);
}

// Swallow the game's per-frame cursor re-centering while releasing, so the operator's
// mouse can move freely (e.g. to reach the overlay); pass it through when clipping.
BOOL WINAPI hk_SetCursorPos(int x, int y)
{
	DetourGate::Guard guard(g_gate);
	hook_note_call(g_id_setcursorpos);
	const bool allow = g_focus_ipc != nullptr && g_focus_ipc->cursor_clip_allowed();
	if (!allow) {
		return TRUE;
	}
	return g_hk_setcursorpos.stdcall<BOOL>(x, y);
}

void hook_export(HMODULE module, const char* name, void* detour, int registry_id)
{
	if (void* target = reinterpret_cast<void*>(GetProcAddress(module, name))) {
		g_focus_hooks.emplace_back();
		install_inline(g_focus_hooks.back(), target, detour); // assign-then-enable (no install race)
		hook_set_installed(registry_id, true);
	}
}

} // namespace

bool install_focus_spoof(IpcClient& ipc)
{
	g_focus_ipc = &ipc;
	if (g_game_hwnd != nullptr) {
		return true; // already active
	}

	g_id_foreground = hook_register("GetForegroundWindow", HookSubsys_Focus);
	g_id_active = hook_register("GetActiveWindow", HookSubsys_Focus);
	g_id_focus = hook_register("GetFocus", HookSubsys_Focus);
	g_id_wndproc = hook_register("WndProc (deactivation guard)", HookSubsys_Focus);
	g_id_clipcursor = hook_register("ClipCursor (cursor release)", HookSubsys_Focus);
	g_id_setcursorpos = hook_register("SetCursorPos (cursor release)", HookSubsys_Focus);

	HWND hwnd = find_main_window(GetCurrentProcessId());
	if (hwnd == nullptr) {
		return false; // window not created yet; caller retries
	}

	g_game_hwnd = hwnd;
	g_unicode = IsWindowUnicode(hwnd) != FALSE;

	// Publish g_orig_proc BEFORE activating the subclass, so a message that dispatches the instant the
	// subclass goes live finds a valid original (not the null/stale value from a prior install cycle)
	// -- the WNDPROC analogue of the inline-hook install race. Replacing GWLP_WNDPROC from another
	// thread is safe (the new proc runs on the window's own thread); match A/W for CallWindowProc.
	g_orig_proc = g_unicode ? reinterpret_cast<WNDPROC>(GetWindowLongPtrW(hwnd, GWLP_WNDPROC))
	                        : reinterpret_cast<WNDPROC>(GetWindowLongPtrA(hwnd, GWLP_WNDPROC));
	if (g_unicode) {
		SetWindowLongPtrW(hwnd, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(&subclass_proc));
	} else {
		SetWindowLongPtrA(hwnd, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(&subclass_proc));
	}
	hook_set_installed(g_id_wndproc, true);

	if (HMODULE user32 = GetModuleHandleW(L"user32.dll")) {
		hook_export(user32, "GetForegroundWindow", reinterpret_cast<void*>(&hk_GetForegroundWindow), g_id_foreground);
		hook_export(user32, "GetActiveWindow", reinterpret_cast<void*>(&hk_GetActiveWindow), g_id_active);
		hook_export(user32, "GetFocus", reinterpret_cast<void*>(&hk_GetFocus), g_id_focus);

		if (void* clip = reinterpret_cast<void*>(GetProcAddress(user32, "ClipCursor"))) {
			install_inline(g_hk_clipcursor, clip, &hk_ClipCursor);
			hook_set_installed(g_id_clipcursor, static_cast<bool>(g_hk_clipcursor));
		}
		if (void* setpos = reinterpret_cast<void*>(GetProcAddress(user32, "SetCursorPos"))) {
			install_inline(g_hk_setcursorpos, setpos, &hk_SetCursorPos);
			hook_set_installed(g_id_setcursorpos, static_cast<bool>(g_hk_setcursorpos));
		}
	}

	// Free any clip the game already set, so release takes effect immediately.
	if (!ipc.cursor_clip_allowed()) {
		ClipCursor(nullptr);
	}

	ipc.mark_focus_spoof(true, reinterpret_cast<std::uint64_t>(hwnd));
	return true;
}

void update_input_diagnostics(IpcClient& ipc)
{
	// Inspect how the game currently reads input, to find a focus-gated path that
	// would explain a controller working only when the game has true focus.
	bool raw_registered = false;
	bool raw_gamepad = false;
	bool raw_gamepad_sink = false;

	UINT count = 0;
	if (GetRegisteredRawInputDevices(nullptr, &count, sizeof(RAWINPUTDEVICE)) == 0 && count > 0) {
		std::vector<RAWINPUTDEVICE> devices(count);
		const UINT got = GetRegisteredRawInputDevices(devices.data(), &count, sizeof(RAWINPUTDEVICE));
		if (got != static_cast<UINT>(-1)) {
			raw_registered = got > 0;
			for (UINT i = 0; i < got; ++i) {
				// Generic Desktop (0x01) joystick (0x04) / gamepad (0x05).
				const bool is_pad =
				    devices[i].usUsagePage == 0x01 && (devices[i].usUsage == 0x04 || devices[i].usUsage == 0x05);
				if (is_pad) {
					raw_gamepad = true;
					raw_gamepad_sink = (devices[i].dwFlags & RIDEV_INPUTSINK) != 0;
				}
			}
		}
	}

	const bool dinput = GetModuleHandleW(L"dinput8.dll") != nullptr || GetModuleHandleW(L"dinput.dll") != nullptr;
	ipc.set_input_diagnostics(raw_registered, raw_gamepad, raw_gamepad_sink, dinput);
}

void release_cursor_tick()
{
	if (g_focus_ipc != nullptr && g_game_hwnd != nullptr && !g_focus_ipc->cursor_clip_allowed()) {
		ClipCursor(nullptr); // routes through hk_ClipCursor -> frees the cursor
	}
}

void remove_focus_spoof()
{
	if (g_game_hwnd != nullptr && g_orig_proc != nullptr) {
		if (g_unicode) {
			SetWindowLongPtrW(g_game_hwnd, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(g_orig_proc));
		} else {
			SetWindowLongPtrA(g_game_hwnd, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(g_orig_proc));
		}
	}
	// Disable the inline focus hooks in REVERSE install order. GetForegroundWindow/GetActiveWindow
	// share user32 code (the real GetForegroundWindow's path runs through GetActiveWindow's body), so
	// GetActiveWindow's inline patch corrupts that shared code. GetForegroundWindow is installed
	// first, so disabling in reverse unhooks GetActiveWindow (restoring the shared bytes) while
	// GetForegroundWindow is still hooked -- its detour returns g_game_hwnd and never reaches the
	// patched bytes. The reverse of the enable order (GFW first) keeps the invariant "GetActiveWindow
	// hooked => GetForegroundWindow hooked" across the whole install/remove cycle, so a call never
	// lands in a half-patched shared region.
	for (auto it = g_focus_hooks.rbegin(); it != g_focus_hooks.rend(); ++it) {
		disable_for_removal(*it);
	}
	disable_for_removal(g_hk_clipcursor);
	disable_for_removal(g_hk_setcursorpos);
	ClipCursor(nullptr); // leave the cursor free when the spoof is removed
	hook_set_installed(g_id_foreground, false);
	hook_set_installed(g_id_active, false);
	hook_set_installed(g_id_focus, false);
	hook_set_installed(g_id_wndproc, false);
	hook_set_installed(g_id_clipcursor, false);
	hook_set_installed(g_id_setcursorpos, false);
	// The WNDPROC is restored and the inline hooks disabled above, so no NEW detour can start. Drain
	// any focus / WNDPROC detour still in-flight on the game's window thread before nulling the
	// state they read (g_orig_proc / g_game_hwnd / g_focus_ipc) -- otherwise a dispatch mid-flight
	// could call a null original WNDPROC or a dangling IPC pointer.
	g_gate.drain();
	// The focus-query hooks (GetForegroundWindow/GetActiveWindow/GetFocus) return g_game_hwnd and
	// never call the trampoline, so destroying them is safe; recreate on re-install. The cursor hooks
	// DO call the trampoline, so keep them ALIVE (disabled) -- persistent, re-enabled on re-install
	// (see hook_install.hpp) -- so a stale detour never hits a freed trampoline.
	g_focus_hooks.clear();
	if (g_focus_ipc != nullptr) {
		g_focus_ipc->mark_focus_spoof(false, 0);
	}
	g_game_hwnd = nullptr;
	g_orig_proc = nullptr;
	g_focus_ipc = nullptr;
}

} // namespace coop::hook