Persist the "Debug details" toggle in the layout .ini

The View-menu verbosity switch reset to off on every launch. Register a
custom ImGui settings handler (a [CoopUI][State] section in coop_layout.ini,
alongside the window layout) so the operator's choice survives restarts.
Toggling it marks settings dirty so ImGui's auto-save writes it back.

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

host/src/main.cpp

@@ -152,6 +152,9 @@ int run()
 	bool show_overlay = true;
 	double overlay_hidden_at = 0.0;
 	coop::UiState ui;
+	// Persist the "Debug details" verbosity in the .ini. Register before the first
+	// begin_frame() below, which is when ImGui loads the .ini and replays our handler.
+	coop::register_ui_settings(ui);
 	coop::FrameStats stats;
 
 	// Frame-sync: the hook generation we last presented (so we wait for the next one).

host/src/ui/app_chrome.cpp

@@ -2,14 +2,51 @@
 
 #include <algorithm>
 #include <cstdio>
+#include <cstdlib>
+#include <cstring>
 
 #include "imgui.h"
+#include "imgui_internal.h" // ImGuiSettingsHandler / AddSettingsHandler (custom .ini section)
 
 namespace coop
 {
 
 namespace
 {
+// --- Custom .ini persistence for the UI switches ---------------------------
+// We piggy-back on ImGui's .ini so the "Debug details" verbosity survives restarts
+// without inventing a separate settings file. The section looks like:
+//   [CoopUI][State]
+//   DebugDetails=1
+// ImGui calls ReadOpenFn once per "[CoopUI][<name>]" entry; we return the bound
+// UiState* as the entry handle so ReadLineFn can write into it.
+constexpr const char* kUiSettingsType = "CoopUI";
+
+void* ui_settings_read_open(ImGuiContext*, ImGuiSettingsHandler* handler, const char* name)
+{
+	// Only one entry ("State"); hand back the UiState* so ReadLineFn can fill it.
+	return std::strcmp(name, "State") == 0 ? handler->UserData : nullptr;
+}
+
+void ui_settings_read_line(ImGuiContext*, ImGuiSettingsHandler*, void* entry, const char* line)
+{
+	auto* ui = static_cast<UiState*>(entry);
+	// Manual parse (avoids the sscanf CRT-secure deprecation for a single int key).
+	constexpr char kKey[] = "DebugDetails=";
+	if (std::strncmp(line, kKey, sizeof(kKey) - 1) == 0)
+	{
+		ui->debug_details = std::atoi(line + sizeof(kKey) - 1) != 0;
+	}
+}
+
+void ui_settings_write_all(ImGuiContext*, ImGuiSettingsHandler* handler, ImGuiTextBuffer* buf)
+{
+	const auto* ui = static_cast<const UiState*>(handler->UserData);
+	buf->appendf("[%s][State]\n", kUiSettingsType);
+	buf->appendf("DebugDetails=%d\n", ui->debug_details ? 1 : 0);
+	buf->append("\n");
+}
+
 // Set by "View -> Reset layout"; true for the one frame in which panels re-apply
 // their default position/size, then cleared by apply_layout_end_frame().
 bool g_layout_reset = false;
@@ -22,6 +59,23 @@ int g_startup_force = 4;
 bool g_had_persisted_layout = false;
 } // namespace
 
+void register_ui_settings(UiState& ui)
+{
+	// Idempotent: don't stack a second handler if this is somehow called twice.
+	if (ImGui::FindSettingsHandler(kUiSettingsType) != nullptr)
+	{
+		return;
+	}
+	ImGuiSettingsHandler handler;
+	handler.TypeName = kUiSettingsType;
+	handler.TypeHash = ImHashStr(kUiSettingsType);
+	handler.ReadOpenFn = ui_settings_read_open;
+	handler.ReadLineFn = ui_settings_read_line;
+	handler.WriteAllFn = ui_settings_write_all;
+	handler.UserData = &ui;
+	ImGui::AddSettingsHandler(&handler); // copied into the context
+}
+
 void request_layout_reset()
 {
 	g_layout_reset = true;
@@ -123,7 +177,10 @@ float draw_main_menu_bar(UiState& ui, const FrameStats& stats)
 		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);
+		if (ImGui::MenuItem("Debug details", nullptr, &ui.debug_details))
+		{
+			ImGui::MarkIniSettingsDirty(); // persist the new verbosity to coop_layout.ini
+		}
 		if (ImGui::MenuItem("Reset layout"))
 		{
 			request_layout_reset();

host/src/ui/app_chrome.hpp

@@ -22,6 +22,13 @@ struct UiState
 	bool debug_details = false; // off = general status; on = full diagnostics
 };
 
+// Persist the verbosity-affecting UI switches (currently the "Debug details" toggle)
+// into ImGui's .ini, alongside the window layout, so the operator's choice survives
+// restarts. Registers a custom .ini settings handler bound to `ui`; call once after
+// the ImGui context exists but before the first NewFrame (which loads the .ini), and
+// keep `ui` alive for the program's lifetime (the handler stores a pointer to it).
+void register_ui_settings(UiState& ui);
+
 // The overlay panels, for the shared default layout below.
 enum class Panel
 {