Cancel keys still down when hold-keys mode flips

The surface cancels its fingers under the old rules before the switch, so
a release no longer reaches the other mode (a stuck repeater or held
modifier one way, a second copy of the character the other). Sticky
modifiers, shift and dead keys start over.

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

src/input/KeyboardController.cpp

@@ -200,8 +200,15 @@ void KeyboardController::setContext(const TextContext &context)
 
 void KeyboardController::setOptions(const TypingOptions &options)
 {
-    if (m_options.holdKeys && !options.holdKeys)
+    if (options.holdKeys != m_options.holdKeys) {
+        Q_EMIT holdKeysAboutToChange();
         m_hardware.releaseAll();
+        m_backspaceRepeater.stop();
+        m_keysymRepeater.stop();
+        m_deadKeys.cancel();
+        m_modifiers.clear();
+        m_shift = {};
+    }
     m_options = options;
     m_model.setShiftLevel(shiftLevel());
     Q_EMIT shiftChanged();

src/input/KeyboardController.h

@@ -68,6 +68,9 @@ Q_SIGNALS:
     void modifiersChanged();
     void dismissRequested();
     void nextLayoutRequested(); // the globe key: switching is the system's job
+    // Hold-keys mode is about to flip: keys still down must be cancelled now,
+    // under the rules they were pressed with.
+    void holdKeysAboutToChange();
 
 private:
     void typeCharacter(const KeyDef &key, KeyOutput output, const QString &alternate);

src/input/KeyboardSurface.cpp

@@ -44,7 +44,11 @@ void KeyboardSurface::setController(KeyboardController *controller)
     if (controller == m_controller)
         return;
     cancelAll();
+    if (m_controller)
+        disconnect(m_controller, nullptr, this, nullptr);
     m_controller = controller;
+    if (m_controller)
+        connect(m_controller, &KeyboardController::holdKeysAboutToChange, this, &KeyboardSurface::cancelAll);
     Q_EMIT controllerChanged();
 }