[glass] DataSource: Add spinlock to protect value (#4771)

A lock is needed here due to HAL async callbacks.

glass/src/lib/native/include/glass/DataSource.h

@@ -11,6 +11,7 @@
 
 #include <imgui.h>
 #include <wpi/Signal.h>
+#include <wpi/spinlock.h>
 
 namespace glass {
 
@@ -37,12 +38,21 @@ class DataSource {
   bool IsDigital() const { return m_digital; }
 
   void SetValue(double value, int64_t time = 0) {
+    std::scoped_lock lock{m_valueMutex};
     m_value = value;
     m_valueTime = time;
     valueChanged(value, time);
   }
-  double GetValue() const { return m_value; }
-  int64_t GetValueTime() const { return m_valueTime; }
+
+  double GetValue() const {
+    std::scoped_lock lock{m_valueMutex};
+    return m_value;
+  }
+
+  int64_t GetValueTime() const {
+    std::scoped_lock lock{m_valueMutex};
+    return m_valueTime;
+  }
 
   // drag source helpers
   void LabelText(const char* label, const char* fmt, ...) const IM_FMTARGS(3);
@@ -59,7 +69,7 @@ class DataSource {
                 ImGuiInputTextFlags flags = 0) const;
   void EmitDrag(ImGuiDragDropFlags flags = 0) const;
 
-  wpi::sig::Signal<double, int64_t> valueChanged;
+  wpi::sig::SignalBase<wpi::spinlock, double, int64_t> valueChanged;
 
   static DataSource* Find(std::string_view id);
 
@@ -69,6 +79,7 @@ class DataSource {
   std::string m_id;
   std::string& m_name;
   bool m_digital = false;
+  mutable wpi::spinlock m_valueMutex;
   double m_value = 0;
   int64_t m_valueTime = 0;
 };