WiiTASInputWindow: Update controls when attachment changes

Change the displayed controls in the TAS Input window when the
controller's extension (including MotionPlus) is changed.

This previously required restarting Dolphin after the attachment was
changed, as the controls were never updated after the WiiTASInputWindow
was created at Dolphin startup.

Source/Core/InputCommon/ControllerEmu/Setting/NumericSetting.h

@@ -3,8 +3,13 @@
 
 #pragma once
 
+#include <algorithm>
 #include <atomic>
+#include <functional>
+#include <mutex>
 #include <string>
+#include <utility>
+#include <vector>
 
 #include "Common/CommonTypes.h"
 #include "Common/IniFile.h"
@@ -173,7 +178,9 @@ class SettingValue
   friend class NumericSetting<T>;
 
 public:
-  ValueType GetValue() const
+  virtual ~SettingValue() = default;
+
+  virtual ValueType GetValue() const
   {
     // Only update dynamic values when the input gate is enabled.
     // Otherwise settings will all change to 0 when window focus is lost.
@@ -184,9 +191,11 @@ public:
     return m_value;
   }
 
+  ValueType GetCachedValue() const { return m_value; }
+
   bool IsSimpleValue() const { return m_input.GetExpression().empty(); }
 
-  void SetValue(ValueType value)
+  virtual void SetValue(const ValueType value)
   {
     m_value = value;
 
@@ -202,4 +211,78 @@ private:
   mutable InputReference m_input;
 };
 
+template <typename ValueType>
+class SubscribableSettingValue final : public SettingValue<ValueType>
+{
+public:
+  using Base = SettingValue<ValueType>;
+
+  ValueType GetValue() const override
+  {
+    const ValueType cached_value = GetCachedValue();
+    if (IsSimpleValue())
+      return cached_value;
+
+    const ValueType updated_value = Base::GetValue();
+    if (updated_value != cached_value)
+      TriggerCallbacks();
+
+    return updated_value;
+  }
+
+  void SetValue(const ValueType value) override
+  {
+    if (value != GetCachedValue())
+    {
+      Base::SetValue(value);
+      TriggerCallbacks();
+    }
+    else if (!IsSimpleValue())
+    {
+      // The setting has an expression with a cached value equal to the one currently being set.
+      // Don't trigger the callbacks (since the value didn't change), but clear the expression and
+      // make the setting a simple value instead.
+      Base::SetValue(value);
+    }
+  }
+
+  ValueType GetCachedValue() const { return Base::GetCachedValue(); }
+  bool IsSimpleValue() const { return Base::IsSimpleValue(); }
+
+  using SettingChangedCallback = std::function<void(ValueType)>;
+
+  int AddCallback(const SettingChangedCallback& callback)
+  {
+    std::lock_guard lock(m_mutex);
+    const int callback_id = m_next_callback_id;
+    ++m_next_callback_id;
+    m_callback_pairs.emplace_back(callback_id, callback);
+
+    return callback_id;
+  }
+
+  void RemoveCallback(const int id)
+  {
+    std::lock_guard lock(m_mutex);
+    const auto iter = std::ranges::find(m_callback_pairs, id, &IDCallbackPair::first);
+    if (iter != m_callback_pairs.end())
+      m_callback_pairs.erase(iter);
+  }
+
+private:
+  void TriggerCallbacks() const
+  {
+    std::lock_guard lock(m_mutex);
+    const ValueType value = Base::GetValue();
+    for (const auto& pair : m_callback_pairs)
+      pair.second(value);
+  }
+
+  using IDCallbackPair = std::pair<int, SettingChangedCallback>;
+  std::vector<IDCallbackPair> m_callback_pairs;
+  int m_next_callback_id = 0;
+
+  mutable std::mutex m_mutex;
+};
+
 }  // namespace ControllerEmu