[wpilib] Improve Color.toString (#4450)

wpilibc/src/main/native/cpp/smartdashboard/Mechanism2d.cpp

@@ -34,8 +34,7 @@ MechanismRoot2d* Mechanism2d::GetRoot(std::string_view name, double x,
 }
 
 void Mechanism2d::SetBackgroundColor(const Color8Bit& color) {
-  std::snprintf(m_color, sizeof(m_color), "#%02X%02X%02X", color.red,
-                color.green, color.blue);
+  m_color = color.HexString();
   if (m_table) {
     m_table->GetEntry(kBackgroundColor).SetString(m_color);
   }

wpilibc/src/main/native/cpp/util/Color.cpp

@@ -0,0 +1,15 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include "frc/util/Color.h"
+
+#include <fmt/format.h>
+
+using namespace frc;
+
+std::string Color::HexString() const {
+  return fmt::format("#{:02X}{:02X}{:02X}", static_cast<int>(255.0 * red),
+                     static_cast<int>(255.0 * green),
+                     static_cast<int>(255.0 * blue));
+}

wpilibc/src/main/native/cpp/util/Color8Bit.cpp

@@ -0,0 +1,13 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include "frc/util/Color8Bit.h"
+
+#include <fmt/format.h>
+
+using namespace frc;
+
+std::string Color8Bit::HexString() const {
+  return fmt::format("#{:02X}{:02X}{:02X}", red, green, blue);
+}