feat: About dialog with version, commit, build time and settings path

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/build_info.hpp

@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: MIT
+#pragma once
+
+namespace udpscope::build_info {
+
+/// The CMake project version, e.g. "0.1.0".
+extern const char* const kVersion;
+/// `git describe --always --dirty` at build time, or "unknown" if git was not available.
+extern const char* const kCommit;
+/// When the binary was configured/built, as "YYYY-MM-DD HH:MM UTC".
+extern const char* const kTimestamp;
+
+}  // namespace udpscope::build_info

src/help_window.cpp

@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: MIT
+#include "help_window.hpp"
+
+#include <cstdio>
+
+#include "build_info.hpp"
+#include "layout_store.hpp"
+
+namespace udpscope {
+namespace {
+
+/// Nulled by the `close-request` handler so a second open cannot present a dead widget.
+/// One pointer per window, file-scope because there is one application.
+GtkWidget* g_about = nullptr;
+
+gboolean on_window_close(GtkWindow* window, gpointer slot) {
+  (void)window;
+  *static_cast<GtkWidget**>(slot) = nullptr;
+  return FALSE;  // let the default handler destroy it
+}
+
+}  // namespace
+
+void show_about(GtkWindow* parent, const std::string& session_path) {
+  if (g_about != nullptr) {
+    gtk_window_present(GTK_WINDOW(g_about));
+    return;
+  }
+
+  // GtkAboutDialog is not deprecated in GTK 4 (unlike GtkShortcutsWindow), so the
+  // stock dialog is used here and the overview is hand-rolled.
+  GtkWidget* dialog = gtk_about_dialog_new();
+  g_about = dialog;
+  GtkAboutDialog* about = GTK_ABOUT_DIALOG(dialog);
+  gtk_about_dialog_set_program_name(about, "udpscope");
+  gtk_about_dialog_set_version(about, build_info::kVersion);
+  gtk_about_dialog_set_comments(about, "An oscilloscope for UDPStreamer sources.");
+  gtk_about_dialog_set_license_type(about, GTK_LICENSE_MIT_X11);
+
+  char details[1024];
+  std::snprintf(details, sizeof(details),
+                "Commit: %s\nBuilt: %s\nSettings: %s\nSession file: %s",
+                build_info::kCommit, build_info::kTimestamp, config_dir().c_str(),
+                session_path.c_str());
+  gtk_about_dialog_set_system_information(about, details);
+
+  gtk_window_set_transient_for(GTK_WINDOW(dialog), parent);
+  gtk_window_set_modal(GTK_WINDOW(dialog), TRUE);
+  g_signal_connect(dialog, "close-request", G_CALLBACK(on_window_close), &g_about);
+  gtk_window_present(GTK_WINDOW(dialog));
+}
+
+}  // namespace udpscope

src/help_window.hpp

@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: MIT
+#pragma once
+
+#include <gtk/gtk.h>
+
+#include <string>
+
+namespace udpscope {
+
+/// The About dialog: version, commit, build timestamp and where the session files live.
+/// Modal on `parent`. `session_path` is this run's own session file.
+void show_about(GtkWindow* parent, const std::string& session_path);
+
+}  // namespace udpscope

src/layout_store.cpp

@@ -31,14 +31,6 @@ std::string sanitize(const std::string& host) {
   return out.empty() ? "_" : out;
 }
 
-std::string config_dir() {
-  const char* xdg = std::getenv("XDG_CONFIG_HOME");
-  if (xdg != nullptr && xdg[0] != '\0') return std::string(xdg) + "/udpscope";
-  const char* home = std::getenv("HOME");
-  if (home == nullptr || home[0] == '\0') return "/tmp/udpscope-config";
-  return std::string(home) + "/.config/udpscope";
-}
-
 void mkdirs(const std::string& path) {
   // **Every** component, the last one included. The condition used to be "the path has a trailing
   // slash", so the final directory was never created: `~/.config/udpscope` did not exist, the
@@ -114,6 +106,14 @@ bool parse_string_array(const std::string& in, std::vector<std::string>& out) {
 
 }  // namespace
 
+std::string config_dir() {
+  const char* xdg = std::getenv("XDG_CONFIG_HOME");
+  if (xdg != nullptr && xdg[0] != '\0') return std::string(xdg) + "/udpscope";
+  const char* home = std::getenv("HOME");
+  if (home == nullptr || home[0] == '\0') return "/tmp/udpscope-config";
+  return std::string(home) + "/.config/udpscope";
+}
+
 std::string layout_path(const std::string& host, std::uint16_t port) {
   const std::string dir = config_dir();
   mkdirs(dir);

src/layout_store.hpp

@@ -81,6 +81,10 @@ bool forget_source(const KnownSource& src);
 std::string math_node_text(const MathNode& node);
 bool math_node_from_text(const std::string& text, MathNode& out);
 
+/// The directory session files live in: $XDG_CONFIG_HOME/udpscope, else
+/// ~/.config/udpscope, else /tmp/udpscope-config. Not created by this call.
+std::string config_dir();
+
 /// `~/.config/udpscope/<host>_<port>.toml`, with the directory created.
 /// Characters unsafe in a filename are replaced in the host part.
 std::string layout_path(const std::string& host, std::uint16_t port);

src/ui.cpp

@@ -17,6 +17,7 @@
 #include "acquisition.hpp"
 #include "config.hpp"
 #include "export.hpp"
+#include "help_window.hpp"
 #include "layout_store.hpp"
 #include "measure.hpp"
 #include "model.hpp"
@@ -4083,6 +4084,16 @@ void on_export_clicked(GtkButton*, gpointer user) {
   g_object_unref(dialog);
 }
 
+void on_about_clicked(GtkButton*, gpointer user) {
+  App* app = static_cast<App*>(user);
+  if (app->menu_button != nullptr) {
+    GtkPopover* popover = gtk_menu_button_get_popover(GTK_MENU_BUTTON(app->menu_button));
+    if (popover != nullptr) gtk_popover_popdown(popover);
+  }
+  show_about(GTK_WINDOW(app->window),
+             layout_path(app->model->config().server, app->model->config().port));
+}
+
 // --- right-click menu -------------------------------------------------------
 
 void on_y_auto_clicked(GtkButton* button, gpointer user) {
@@ -5542,6 +5553,13 @@ GtkWidget* build_toolbar(App& app) {
   g_signal_connect(app.signal_toggle, "toggled", G_CALLBACK(on_signals_toggled), &app);
   gtk_box_append(GTK_BOX(menu_box), app.signal_toggle);
 
+  gtk_box_append(GTK_BOX(menu_box), gtk_separator_new(GTK_ORIENTATION_HORIZONTAL));
+
+  GtkWidget* about_item = gtk_button_new_with_label("About udpscope");
+  gtk_widget_set_tooltip_text(about_item, "version, build timestamp and settings paths");
+  g_signal_connect(about_item, "clicked", G_CALLBACK(on_about_clicked), &app);
+  gtk_box_append(GTK_BOX(menu_box), about_item);
+
   GtkWidget* popover = gtk_popover_new();
   gtk_popover_set_child(GTK_POPOVER(popover), menu_box);
   app.menu_button = gtk_menu_button_new();