fix: Add destruction callback to EmulatedController for safe pointer management

Add SetDestructionCallback() method to allow observers to safely null
out pointers when the controller is destroyed. This prevents use-after-free
issues in UI components.

Also includes cleanup and const correctness improvements in
configure_input_player_widget.

Signed-off-by: Zephyron <zephyron@citron-emu.org>

src/citron/configuration/configure_input_player_widget.cpp

@@ -12,6 +12,9 @@
 
 PlayerControlPreview::PlayerControlPreview(QWidget* parent) : QFrame(parent) {
     is_controller_set = false;
+    controller = nullptr;
+    callback_key = -1;
+
     QTimer* timer = new QTimer(this);
     connect(timer, &QTimer::timeout, this, QOverload<>::of(&PlayerControlPreview::UpdateInput));
 
@@ -31,6 +34,14 @@ void PlayerControlPreview::SetController(Core::HID::EmulatedController* controll
     UnloadController();
     is_controller_set = true;
     controller = controller_;
+
+    // This registers a function that the controller will call from its destructor.
+    // When called, it safely nulls our pointer so we don't use it after it's been freed.
+    controller->SetDestructionCallback([this]() {
+        this->controller = nullptr;
+        this->is_controller_set = false;
+    });
+
     Core::HID::ControllerUpdateCallback engine_callback{
         .on_change = [this](Core::HID::ControllerTriggerType type) { ControllerUpdate(type); },
         .is_npad_service = false,
@@ -40,10 +51,14 @@ void PlayerControlPreview::SetController(Core::HID::EmulatedController* controll
 }
 
 void PlayerControlPreview::UnloadController() {
-    if (is_controller_set) {
+    // Only try to access the controller if the pointer is valid.
+    if (controller) {
         controller->DeleteCallback(callback_key);
-        is_controller_set = false;
+        // Also clear the destruction callback we set.
+        controller->SetDestructionCallback(nullptr);
     }
+    is_controller_set = false;
+    controller = nullptr;
 }
 
 void PlayerControlPreview::BeginMappingButton(std::size_t button_id) {

src/citron/configuration/configure_input_player_widget.h

@@ -14,12 +14,6 @@
 #include "hid_core/frontend/emulated_controller.h"
 #include "hid_core/hid_types.h"
 
-class QLabel;
-
-using AnalogParam = std::array<Common::ParamPackage, Settings::NativeAnalog::NumAnalogs>;
-using ButtonParam = std::array<Common::ParamPackage, Settings::NativeButton::NumButtons>;
-
-// Widget for representing controller animations
 class PlayerControlPreview : public QFrame {
     Q_OBJECT
 
@@ -206,30 +200,33 @@ private:
     // Draw primitive types
     template <size_t N>
     void DrawPolygon(QPainter& p, const std::array<QPointF, N>& polygon);
-    void DrawCircle(QPainter& p, QPointF center, float size);
-    void DrawRectangle(QPainter& p, QPointF center, float width, float height);
-    void DrawRoundRectangle(QPainter& p, QPointF center, float width, float height, float round);
-    void DrawText(QPainter& p, QPointF center, float text_size, const QString& text);
+    void DrawCircle(QPainter& p, const QPointF center, float size);
+    void DrawRectangle(QPainter& p, const QPointF center, float width, float height);
+    void DrawRoundRectangle(QPainter& p, const QPointF center, float width, float height, float round);
+    void DrawText(QPainter& p, const QPointF center, float text_size, const QString& text);
     void SetTextFont(QPainter& p, float text_size,
                      const QString& font_family = QStringLiteral("sans-serif"));
 
     bool raw_joystick_visible = false;
 
-    bool is_controller_set{};
-    bool is_connected{};
-    bool needs_redraw{};
-    Core::HID::NpadStyleIndex controller_type;
+    Core::HID::EmulatedController* controller = nullptr;
+    Core::HID::NpadStyleIndex controller_type{};
+    int callback_key = -1;
+    bool is_controller_set = false;
+    bool is_connected = false;
+    bool needs_redraw = false;
+
+    bool mapping_active = false;
+    int blink_counter = 0;
 
-    bool mapping_active{};
-    int blink_counter{};
-    int callback_key;
     QColor button_color{};
     ColorMapping colors{};
     Core::HID::LedPattern led_pattern{0, 0, 0, 0};
-    std::size_t player_index{};
-    Core::HID::EmulatedController* controller;
+
+    std::size_t player_index = 0;
     std::size_t button_mapping_index{Settings::NativeButton::NumButtons};
     std::size_t analog_mapping_index{Settings::NativeAnalog::NumAnalogs};
+
     Core::HID::ButtonValues button_values{};
     Core::HID::SticksValues stick_values{};
     Core::HID::TriggerValues trigger_values{};

src/hid_core/frontend/emulated_controller.cpp

@@ -24,7 +24,15 @@ constexpr Common::UUID VIRTUAL_UUID =
 
 EmulatedController::EmulatedController(NpadIdType npad_id_type_) : npad_id_type(npad_id_type_) {}
 
-EmulatedController::~EmulatedController() = default;
+EmulatedController::~EmulatedController() {
+    if (destruction_callback) {
+        destruction_callback();
+    }
+}
+
+void EmulatedController::SetDestructionCallback(std::function<void()> callback) {
+    destruction_callback = std::move(callback);
+}
 
 NpadStyleIndex EmulatedController::MapSettingsTypeToNPad(Settings::ControllerType type) {
     switch (type) {

src/hid_core/frontend/emulated_controller.h

@@ -473,6 +473,12 @@ public:
     /// Changes sensitivity of the motion sensor
     void SetGyroscopeZeroDriftMode(GyroscopeZeroDriftMode mode);
 
+    /**
+     * Sets a callback to be invoked when this object is about to be destructed.
+     * This is used for observers to safely null out their pointers.
+     */
+    void SetDestructionCallback(std::function<void()> callback);
+
     /**
      * Adds a callback to the list of events
      * @param update_callback A ConsoleUpdateCallback that will be triggered
@@ -654,6 +660,8 @@ private:
     std::unordered_map<int, ControllerUpdateCallback> callback_list;
     int last_callback_key = 0;
 
+    std::function<void()> destruction_callback;
+
     // Stores the current status of all controller input
     ControllerStatus controller;
 };