feat: keyboard and mouse shortcut overview window

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

src/help_window.cpp

@@ -6,6 +6,7 @@
 
 #include "build_info.hpp"
 #include "layout_store.hpp"
+#include "shortcuts.hpp"
 
 namespace udpscope {
 namespace {
@@ -14,6 +15,7 @@ namespace {
 /// One pointer per window, file-scope because there is one application.
 GtkWidget* g_about = nullptr;
 GtkWidget* g_help = nullptr;
+GtkWidget* g_shortcuts = nullptr;
 
 gboolean on_window_close(GtkWindow* window, gpointer slot) {
   (void)window;
@@ -212,9 +214,93 @@ void show_help(GtkWindow* parent) {
   gtk_window_present(GTK_WINDOW(window));
 }
 
+namespace {
+
+/// One `accel  description` pair appended to `grid` at `row`. The accel column is
+/// monospaced and right-aligned so the descriptions line up down the window.
+void append_shortcut_row(GtkWidget* grid, int row, const char* accel_text,
+                         const char* description) {
+  GtkWidget* keys = gtk_label_new(nullptr);
+  char markup[256];
+  std::snprintf(markup, sizeof(markup), "<tt>%s</tt>", accel_text);
+  gtk_label_set_markup(GTK_LABEL(keys), markup);
+  gtk_label_set_xalign(GTK_LABEL(keys), 1.0f);
+  gtk_widget_set_margin_end(keys, 14);
+  gtk_grid_attach(GTK_GRID(grid), keys, 0, row, 1, 1);
+
+  GtkWidget* what = gtk_label_new(description);
+  gtk_label_set_xalign(GTK_LABEL(what), 0.0f);
+  gtk_grid_attach(GTK_GRID(grid), what, 1, row, 1, 1);
+}
+
+/// A section heading spanning both columns.
+void append_shortcut_heading(GtkWidget* grid, int row, const char* section) {
+  GtkWidget* heading = gtk_label_new(nullptr);
+  char markup[128];
+  std::snprintf(markup, sizeof(markup), "<b>%s</b>", section);
+  gtk_label_set_markup(GTK_LABEL(heading), markup);
+  gtk_label_set_xalign(GTK_LABEL(heading), 0.0f);
+  gtk_widget_set_margin_top(heading, row == 0 ? 0 : 14);
+  gtk_widget_set_margin_bottom(heading, 4);
+  gtk_grid_attach(GTK_GRID(grid), heading, 0, row, 2, 1);
+}
+
+}  // namespace
+
+void show_shortcuts(GtkWindow* parent) {
+  if (g_shortcuts != nullptr) {
+    gtk_window_present(GTK_WINDOW(g_shortcuts));
+    return;
+  }
+
+  GtkWidget* window = gtk_window_new();
+  g_shortcuts = window;
+  gtk_window_set_title(GTK_WINDOW(window), "Keyboard and mouse shortcuts");
+  gtk_window_set_default_size(GTK_WINDOW(window), 560, 680);
+  gtk_window_set_transient_for(GTK_WINDOW(window), parent);
+
+  GtkWidget* grid = gtk_grid_new();
+  gtk_grid_set_row_spacing(GTK_GRID(grid), 2);
+  gtk_widget_set_margin_start(grid, 20);
+  gtk_widget_set_margin_end(grid, 20);
+  gtk_widget_set_margin_top(grid, 16);
+  gtk_widget_set_margin_bottom(grid, 16);
+
+  int row = 0;
+  const char* section = nullptr;
+  int accel_count = 0;
+  const Accel* accels = app_accels(&accel_count);
+  for (int i = 0; i < accel_count; ++i) {
+    if (section == nullptr || std::string(section) != accels[i].section) {
+      section = accels[i].section;
+      append_shortcut_heading(grid, row++, section);
+    }
+    append_shortcut_row(grid, row++, accels[i].accel_text, accels[i].description);
+  }
+  int gesture_count = 0;
+  const Gesture* gestures = plot_gestures(&gesture_count);
+  for (int i = 0; i < gesture_count; ++i) {
+    if (section == nullptr || std::string(section) != gestures[i].section) {
+      section = gestures[i].section;
+      append_shortcut_heading(grid, row++, section);
+    }
+    append_shortcut_row(grid, row++, gestures[i].accel_text, gestures[i].description);
+  }
+
+  GtkWidget* scroll = gtk_scrolled_window_new();
+  gtk_scrolled_window_set_policy(GTK_SCROLLED_WINDOW(scroll), GTK_POLICY_NEVER,
+                                 GTK_POLICY_AUTOMATIC);
+  gtk_scrolled_window_set_child(GTK_SCROLLED_WINDOW(scroll), grid);
+  gtk_window_set_child(GTK_WINDOW(window), scroll);
+
+  g_signal_connect(window, "close-request", G_CALLBACK(on_window_close), &g_shortcuts);
+  gtk_window_present(GTK_WINDOW(window));
+}
+
 void close_help_windows() {
   if (g_help != nullptr) gtk_window_close(GTK_WINDOW(g_help));
   if (g_about != nullptr) gtk_window_close(GTK_WINDOW(g_about));
+  if (g_shortcuts != nullptr) gtk_window_close(GTK_WINDOW(g_shortcuts));
 }
 
 }  // namespace udpscope