feat: keyboard and mouse shortcut overview window

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

src/shortcuts.cpp

@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: MIT
+#include "shortcuts.hpp"
+
+#include <gdk/gdk.h>
+
+namespace udpscope {
+namespace {
+
+/// Bare letters are toggles, Ctrl is for files and windows. Nothing here shadows a key the
+/// plot's own controller handles ('+', '-', 'f', the arrows, Escape).
+constexpr Accel kAccels[] = {
+    {GDK_KEY_space, 0, AppAction::PauseToggle, "Space", "Pause or resume the display",
+     "Acquisition"},
+    {GDK_KEY_a, 0, AppAction::TriggerArm, "A", "Arm or disarm the trigger", "Acquisition"},
+    {GDK_KEY_t, 0, AppAction::TriggerPanel, "T", "Show or hide the trigger panel",
+     "Acquisition"},
+    {GDK_KEY_c, 0, AppAction::CursorsPane, "C", "Show or hide the cursors pane",
+     "Panes and editors"},
+    {GDK_KEY_m, 0, AppAction::MeasuresPane, "M", "Show or hide the measurements pane",
+     "Panes and editors"},
+    {GDK_KEY_g, 0, AppAction::MathPane, "G", "Show or hide the math pane",
+     "Panes and editors"},
+    {GDK_KEY_l, 0, AppAction::LayoutEditor, "L", "Show or hide the layout editor",
+     "Panes and editors"},
+    {GDK_KEY_s, 0, AppAction::SidePanel, "S", "Show or hide the side panel",
+     "Panes and editors"},
+    {GDK_KEY_e, GDK_CONTROL_MASK, AppAction::Export, "Ctrl+E",
+     "Export the visible range", "Files and windows"},
+    {GDK_KEY_F1, 0, AppAction::Help, "F1", "Open the help window", "Files and windows"},
+    {GDK_KEY_slash, GDK_CONTROL_MASK, AppAction::Shortcuts, "Ctrl+/",
+     "Open this shortcut overview", "Files and windows"},
+    {GDK_KEY_q, GDK_CONTROL_MASK, AppAction::Quit, "Ctrl+Q", "Quit udpscope",
+     "Files and windows"},
+};
+constexpr int kAccelCount = static_cast<int>(sizeof(kAccels) / sizeof(kAccels[0]));
+
+/// The plot's own interactions, documentation only. The keyboard's modifiers are not the
+/// wheel's: '+' is shift+'=' on common layouts, so Shift could not mean anything there.
+constexpr Gesture kGestures[] = {
+    {"+ / -", "Zoom in or out, both axes", "Plot keyboard"},
+    {"Ctrl + / Ctrl -", "Zoom the time axis only", "Plot keyboard"},
+    {"Alt + / Alt -", "Zoom the value axis only", "Plot keyboard"},
+    {"Left / Right", "Pan along time", "Plot keyboard"},
+    {"Up / Down", "Pan along values", "Plot keyboard"},
+    {"F", "Fit the view to the data", "Plot keyboard"},
+    {"Escape", "Cancel the gesture in progress", "Plot keyboard"},
+    {"Wheel", "Zoom about the pointer, both axes", "Plot mouse"},
+    {"Shift+wheel", "Zoom the time axis only", "Plot mouse"},
+    {"Ctrl+wheel", "Zoom the value axis only", "Plot mouse"},
+    {"Drag", "Pan", "Plot mouse"},
+    {"Ctrl+drag", "Box zoom on time", "Plot mouse"},
+    {"Alt+drag", "Box zoom on values", "Plot mouse"},
+};
+constexpr int kGestureCount = static_cast<int>(sizeof(kGestures) / sizeof(kGestures[0]));
+
+/// The only modifiers a table row may require. Lock, Num-Lock and the pointer buttons all
+/// arrive in the same mask and must be masked out or no row ever matches.
+constexpr unsigned kModMask = GDK_CONTROL_MASK | GDK_SHIFT_MASK | GDK_ALT_MASK;
+
+}  // namespace
+
+const Accel* app_accels(int* count) {
+  if (count != nullptr) *count = kAccelCount;
+  return kAccels;
+}
+
+const Gesture* plot_gestures(int* count) {
+  if (count != nullptr) *count = kGestureCount;
+  return kGestures;
+}
+
+const Accel* find_accel(unsigned keyval, unsigned mods) {
+  const unsigned wanted = mods & kModMask;
+  for (const Accel& accel : kAccels) {
+    if (accel.keyval == keyval && accel.mods == wanted) return &accel;
+  }
+  return nullptr;
+}
+
+}  // namespace udpscope