Log window: stream the hook's logs over IPC into an in-app Log panel

Add a shared log ring (common/coop/log_ring.hpp): a lossy multi-producer /
single-consumer ring named coop_log_<pid>. The hook logs from several threads,
so producers claim a slot with fetch_add and publish each record with a
release store of its sequence; the consumer reads in order and tolerates
losing the oldest lines if it falls a whole ring behind.

The DLL's logf() now formats once and pushes every line to the ring (the file
trace stays as an opt-in mirror); the worker attaches the ring right after IPC
connect so bring-up is captured. The host (IpcServer) creates the ring at
injection time and exposes drain_logs(); a new LogPanel pulls new lines each
frame into a bounded rolling buffer and renders them with auto-scroll, a
filter, and clear. Added to the View menu (and UiState.show_log).

Verified against Phantom Brave via coop_audio_probe, which now also creates the
ring and drains it: the full hook bring-up trace streamed over IPC. All four
tests pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

host/src/injection_panel.hpp

@@ -42,6 +42,13 @@ public:
 		return server_.hook_status();
 	}
 
+	// Drain log lines the hook streamed (for the Log window). No-op if not active.
+	template <typename F>
+	void drain_logs(F&& emit)
+	{
+		server_.drain_logs(std::forward<F>(emit));
+	}
+
 private:
 	void refresh_processes();
 	void inject_selected();

host/src/ipc/ipc_server.cpp

@@ -22,6 +22,15 @@ bool IpcServer::start(unsigned long target_pid)
 
 	block_ = block;
 	target_pid_ = target_pid;
+
+	// Log ring: the injected hook opens this and streams its log lines back for the
+	// Log window. Best-effort -- the rest of the tool works without it.
+	if (log_shm_.create(log_ring_name(target_pid), log_ring_total_size(kLogCapacity)))
+	{
+		log_ring_ = log_shm_.as<LogRing>();
+		log_ring_init(*log_ring_, kLogCapacity);
+		log_cursor_ = 0;
+	}
 	return true;
 }
 
@@ -96,6 +105,9 @@ void IpcServer::stop()
 		block_ = nullptr;
 	}
 	shm_.reset();
+	log_ring_ = nullptr;
+	log_shm_.reset();
+	log_cursor_ = 0;
 	target_pid_ = 0;
 }
 

host/src/ipc/ipc_server.hpp

@@ -5,6 +5,7 @@
 #include <array>
 #include <cstdint>
 
+#include "coop/log_ring.hpp"
 #include "coop/protocol.hpp"
 #include "coop/shared_memory.hpp"
 #include "input/input_source.hpp"
@@ -56,6 +57,17 @@ public:
 	// reconciles on its next tick. No-op if not started.
 	void set_subsystem_enabled(std::uint32_t subsystem, bool enabled);
 
+	// Drain new log lines streamed by the hook, calling `emit(const LogRecord&)`
+	// for each. No-op if not started. Header-only so the callback can stay generic.
+	template <typename F>
+	void drain_logs(F&& emit)
+	{
+		if (log_ring_ != nullptr)
+		{
+			log_ring_drain(*log_ring_, log_cursor_, emit);
+		}
+	}
+
 	[[nodiscard]] bool running() const
 	{
 		return block_ != nullptr;
@@ -69,6 +81,10 @@ private:
 	SharedMemory shm_;
 	SharedBlock* block_ = nullptr;
 	unsigned long target_pid_ = 0;
+
+	SharedMemory log_shm_;          // shared log ring (named coop_log_<pid>)
+	LogRing* log_ring_ = nullptr;
+	std::uint64_t log_cursor_ = 0;  // consumer position into the log ring
 };
 
 } // namespace coop

host/src/log_panel.cpp

@@ -0,0 +1,75 @@
+#include "log_panel.hpp"
+
+#include <cstdio>
+#include <cstring>
+
+#include "imgui.h"
+
+#include "injection_panel.hpp"
+
+namespace coop
+{
+
+void LogPanel::add_line(const LogRecord& rec)
+{
+	if (first_millis_ == 0)
+	{
+		first_millis_ = rec.millis;
+	}
+	const double secs = static_cast<double>(rec.millis - first_millis_) / 1000.0;
+
+	char buf[256];
+	std::snprintf(buf, sizeof(buf), "[%8.3f] %s", secs, rec.text);
+	lines_.emplace_back(buf);
+	while (lines_.size() > kMaxLines)
+	{
+		lines_.pop_front();
+	}
+}
+
+void LogPanel::pull(InjectionPanel& injection)
+{
+	injection.drain_logs([this](const LogRecord& rec) { add_line(rec); });
+}
+
+void LogPanel::draw()
+{
+	ImGui::SetNextWindowPos(ImVec2(24, 760), ImGuiCond_FirstUseEver);
+	ImGui::SetNextWindowSize(ImVec2(720, 240), ImGuiCond_FirstUseEver);
+	ImGui::Begin("Log");
+
+	if (ImGui::Button("Clear"))
+	{
+		lines_.clear();
+		first_millis_ = 0;
+	}
+	ImGui::SameLine();
+	ImGui::Checkbox("Auto-scroll", &autoscroll_);
+	ImGui::SameLine();
+	ImGui::SetNextItemWidth(-1.0f);
+	ImGui::InputTextWithHint("##logfilter", "filter...", filter_, sizeof(filter_));
+
+	ImGui::Separator();
+	if (ImGui::BeginChild("loglines", ImVec2(0, 0), ImGuiChildFlags_None, ImGuiWindowFlags_HorizontalScrollbar))
+	{
+		const bool has_filter = filter_[0] != '\0';
+		for (const std::string& line : lines_)
+		{
+			if (has_filter && line.find(filter_) == std::string::npos)
+			{
+				continue;
+			}
+			ImGui::TextUnformatted(line.c_str());
+		}
+		// Stick to the bottom while new lines arrive (unless the user scrolled up).
+		if (autoscroll_ && ImGui::GetScrollY() >= ImGui::GetScrollMaxY() - 1.0f)
+		{
+			ImGui::SetScrollHereY(1.0f);
+		}
+	}
+	ImGui::EndChild();
+
+	ImGui::End();
+}
+
+} // namespace coop

host/src/log_panel.hpp

@@ -0,0 +1,36 @@
+// Log window: shows the log lines the injected hook streams over the shared log
+// ring (see coop/log_ring.hpp). Pull new lines each frame from the IPC server,
+// keep a bounded rolling history, and render them with autoscroll + a filter.
+#pragma once
+
+#include <cstdint>
+#include <deque>
+#include <string>
+
+#include "coop/log_ring.hpp"
+
+namespace coop
+{
+
+class InjectionPanel;
+
+class LogPanel
+{
+public:
+	// Pull any new lines the hook emitted (call once per frame before draw()).
+	void pull(InjectionPanel& injection);
+
+	void draw();
+
+private:
+	void add_line(const LogRecord& rec);
+
+	std::deque<std::string> lines_;
+	char filter_[96] = {};
+	bool autoscroll_ = true;
+	std::uint64_t first_millis_ = 0; // hook clock at the first line, for relative timestamps
+
+	static constexpr std::size_t kMaxLines = 2000;
+};
+
+} // namespace coop

host/src/main.cpp

@@ -20,6 +20,7 @@
 #include "imgui_layer.hpp"
 #include "injection_panel.hpp"
 #include "input/xinput_source.hpp"
+#include "log_panel.hpp"
 #include "ui/app_chrome.hpp"
 
 namespace
@@ -68,6 +69,7 @@ int run()
 	coop::InjectionPanel injection;
 	coop::AudioPanel audio;
 	coop::CapturePanel capture;
+	coop::LogPanel log;
 	if (!capture.init(window.device()))
 	{
 		MessageBoxW(nullptr, L"Failed to initialize the video mirror.", L"CoopAllTheThings", MB_ICONERROR);
@@ -91,6 +93,7 @@ int run()
 
 		imgui.begin_frame();
 		stats.tick(ImGui::GetIO().DeltaTime * 1000.0f);
+		log.pull(injection); // drain hook log lines even while the Log window is hidden
 
 		if (ImGui::IsKeyPressed(ImGuiKey_F1, false))
 		{
@@ -120,6 +123,10 @@ int run()
 			{
 				capture.draw_ui(stats);
 			}
+			if (ui.show_log)
+			{
+				log.draw();
+			}
 		}
 		else
 		{

host/src/ui/app_chrome.cpp

@@ -24,6 +24,7 @@ float draw_main_menu_bar(UiState& ui, const FrameStats& stats)
 		ImGui::MenuItem("Injection", nullptr, &ui.show_injection);
 		ImGui::MenuItem("Video mirror", nullptr, &ui.show_video);
 		ImGui::MenuItem("Audio mirror", nullptr, &ui.show_audio);
+		ImGui::MenuItem("Log", nullptr, &ui.show_log);
 		ImGui::Separator();
 		ImGui::MenuItem("Debug details", nullptr, &ui.debug_details);
 		ImGui::EndMenu();

host/src/ui/app_chrome.hpp

@@ -18,6 +18,7 @@ struct UiState
 	bool show_injection = true;
 	bool show_video = true;
 	bool show_audio = true;
+	bool show_log = true;
 	bool debug_details = false; // off = general status; on = full diagnostics
 };