Fix case where WindowFilter could deadlock upon injection

CMakeLists.txt

@@ -876,6 +876,7 @@ list(APPEND ue4poc_SOURCES
 	"src/Main.cpp"
 	"src/Mod.cpp"
 	"src/Mods.cpp"
+	"src/WindowFilter.cpp"
 	"src/hooks/D3D11Hook.cpp"
 	"src/hooks/D3D12Hook.cpp"
 	"src/hooks/WindowsMessageHook.cpp"
@@ -1029,6 +1030,7 @@ list(APPEND ue4poc-nolog_SOURCES
 	"src/Main.cpp"
 	"src/Mod.cpp"
 	"src/Mods.cpp"
+	"src/WindowFilter.cpp"
 	"src/hooks/D3D11Hook.cpp"
 	"src/hooks/D3D12Hook.cpp"
 	"src/hooks/WindowsMessageHook.cpp"

src/WindowFilter.cpp

@@ -0,0 +1,81 @@
+#include "WindowFilter.hpp"
+
+// To prevent usage of statics (TLS breaks the present thread...?)
+WindowFilter g_window_filter{};
+
+WindowFilter& WindowFilter::get() {
+    return g_window_filter;
+}
+
+WindowFilter::WindowFilter() {
+    // We create a job thread because GetWindowTextA can actually deadlock inside
+    // the present thread...
+    m_job_thread = std::make_unique<std::jthread>([this](std::stop_token s){
+        while (!s.stop_requested()) {
+            std::this_thread::sleep_for(std::chrono::milliseconds{100});
+
+            if (m_window_jobs.empty()) {
+                return;
+            }
+
+            std::vector<HWND> window_jobs{};
+
+            {
+                std::scoped_lock _{m_mutex};
+                window_jobs = std::move(m_window_jobs);
+            }
+
+            for (const auto hwnd : window_jobs) {
+                if (is_filtered_nocache(hwnd)) {
+                    filter_window(hwnd);
+                }
+            }
+        }
+    });
+}
+
+WindowFilter::~WindowFilter() {
+    m_job_thread->request_stop();
+    m_job_thread->join();
+}
+
+bool WindowFilter::is_filtered(HWND hwnd) {
+    if (hwnd == nullptr) {
+        return true;
+    }
+
+    std::scoped_lock _{m_mutex};
+
+    if (m_filtered_windows.find(hwnd) != m_filtered_windows.end()) {
+        return true;
+    }
+
+    // if we havent even seen this window yet, add it to the job queue
+    // and return true;
+    if (m_seen_windows.find(hwnd) == m_seen_windows.end()) {
+        m_seen_windows.insert(hwnd);
+        m_window_jobs.push_back(hwnd);
+        return true;
+    }
+
+    return false;
+}
+
+bool WindowFilter::is_filtered_nocache(HWND hwnd) {
+    // get window name
+    char window_name[256]{};
+    GetWindowTextA(hwnd, window_name, sizeof(window_name));
+
+    const auto sv = std::string_view{window_name};
+
+    if (sv.find("UE4SS") != std::string_view::npos) {
+        return true;
+    }
+
+    if (sv.find("PimaxXR") != std::string_view::npos) {
+        return true;
+    }
+
+    // TODO: more problematic windows
+    return false;
+}

src/WindowFilter.hpp

@@ -4,61 +4,31 @@
 
 #include <string_view>
 #include <unordered_set>
+#include <thread>
+#include <vector>
+#include <mutex>
 
 class WindowFilter {
 public:
-    static WindowFilter& get() {
-        static WindowFilter instance{};
-        return instance;
-    }
+    static WindowFilter& get();
 
 public:
-    bool is_filtered(HWND hwnd) {
-        if (hwnd == nullptr) {
-            return true;
-        }
-
-        if (m_filtered_windows.find(hwnd) != m_filtered_windows.end()) {
-            return true;
-        }
-
-        if (m_seen_windows.find(hwnd) != m_seen_windows.end()) {
-            return false;
-        }
-
-        m_seen_windows.insert(hwnd);
-
-        if (is_filtered_nocache(hwnd)) {
-            filter_window(hwnd);
-            return true;
-        }
+    WindowFilter();
+    virtual ~WindowFilter();
 
-        return false;
-    }
+    bool is_filtered(HWND hwnd);
 
     void filter_window(HWND hwnd) {
+        std::scoped_lock _{m_mutex};
         m_filtered_windows.insert(hwnd);
     }
 
 private:
-    bool is_filtered_nocache(HWND hwnd) {
-        // get window name
-        char window_name[256]{};
-        GetWindowTextA(hwnd, window_name, sizeof(window_name));
-
-        const auto sv = std::string_view{window_name};
-
-        if (sv.find("UE4SS") != std::string_view::npos) {
-            return true;
-        }
+    bool is_filtered_nocache(HWND hwnd);
 
-        if (sv.find("PimaxXR") != std::string_view::npos) {
-            return true;
-        }
-
-        // TODO: more problematic windows
-        return false;
-    }
+    std::recursive_mutex m_mutex{};
+    std::vector<HWND> m_window_jobs{};
+    std::unique_ptr<std::jthread> m_job_thread{};
 
     std::unordered_set<HWND> m_seen_windows{};
     std::unordered_set<HWND> m_filtered_windows{};