Optional PC key blocks: function row, navigation, numeric keypad

- Template sections placed above or to the right of the typing keys;
  the user picks any mix in settings, typing keys included
- keysym keys send XKB keysyms on press, optionally repeating
- Geometry lays blocks side by side with one key unit; stretch keys are
  resolved at layout time so composed blocks line up
- Toggling a block resizes the window so keys keep their size

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/input/KeyboardController.cpp

@@ -14,14 +14,18 @@ static_assert(int(KeyboardController::ShiftMode::Locked) == int(ShiftState::Mode
 namespace {
 // Enough history for the text rules; fields may report megabytes.
 constexpr qsizetype MaxTextBefore = 256;
+// Like a hardware key: no word mode, a faster rate than Backspace.
+constexpr KeyRepeater::Timing KeysymRepeat{.intervalMs = 50, .wordModeAfterMs = std::numeric_limits<int>::max()};
 }
 
 KeyboardController::KeyboardController(InputEngine &engine, LayoutModel &model, QObject *parent)
     : QObject(parent)
     , m_engine(engine)
     , m_model(model)
+    , m_keysymRepeater(KeysymRepeat)
 {
     connect(&m_backspaceRepeater, &KeyRepeater::repeat, this, &KeyboardController::deleteBackward);
+    connect(&m_keysymRepeater, &KeyRepeater::repeat, this, &KeyboardController::sendRepeatedKeysym);
 }
 
 KeyboardController::ShiftMode KeyboardController::shiftMode() const
@@ -43,6 +47,13 @@ void KeyboardController::keyDown(const KeyDef &key, qint64 timeMs)
         m_layerBeforeSwitch = m_model.layerName();
         m_model.setLayer(key.target);
         break;
+    case KeyType::Keysym:
+        m_engine.sendKeysym(key.keysym);
+        if (key.repeat) {
+            m_repeatingKeysym = key.keysym;
+            m_keysymRepeater.start();
+        }
+        break;
     default:
         break; // everything else acts on release
     }
@@ -57,6 +68,9 @@ void KeyboardController::keyUp(const KeyDef &key, KeyOutput output, const QStrin
     case KeyType::Backspace:
         m_backspaceRepeater.stop();
         break;
+    case KeyType::Keysym:
+        stopRepeating(key);
+        break;
     case KeyType::Character:
         if (output == KeyOutput::Alternate && !alternate.isEmpty())
             typeText(alternate);
@@ -90,6 +104,8 @@ void KeyboardController::keyCancelled(const KeyDef &key)
         changeShift([&] { m_shift.release(); });
     else if (key.type == KeyType::Backspace)
         m_backspaceRepeater.stop();
+    else if (key.type == KeyType::Keysym)
+        stopRepeating(key);
 }
 
 void KeyboardController::slideReleased(const KeyDef &target, qint64 timeMs)
@@ -156,6 +172,18 @@ void KeyboardController::deleteBackward(bool wholeWord)
     autoCapitalize();
 }
 
+// Only the key that started the repeat stops it; another finger's key doesn't.
+void KeyboardController::stopRepeating(const KeyDef &key)
+{
+    if (key.keysym == m_repeatingKeysym)
+        m_keysymRepeater.stop();
+}
+
+void KeyboardController::sendRepeatedKeysym()
+{
+    m_engine.sendKeysym(m_repeatingKeysym);
+}
+
 void KeyboardController::autoCapitalize()
 {
     const bool capitalize = m_options.autoCapitalize && m_context.allowsAutoCapitalization()