Create EnumFormatter

Source/Core/Common/EnumFormatter.h

@@ -0,0 +1,91 @@
+// Copyright 2021 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <array>
+#include <fmt/format.h>
+#include <type_traits>
+
+/*
+ * Helper for using enums with fmt.
+ *
+ * Usage example:
+ *
+ * enum class Foo
+ * {
+ *   A = 0,
+ *   B = 1,
+ *   C = 2,
+ * };
+ *
+ * template <>
+ * struct fmt::formatter<Foo> : EnumFormatter<Foo::C>
+ * {
+ *   formatter() : EnumFormatter({"A", "B", "C"}) {}
+ * };
+ *
+ * enum class Bar
+ * {
+ *   D = 0,
+ *   E = 1,
+ *   F = 3,
+ * };
+ *
+ * template <>
+ * struct fmt::formatter<Bar> : EnumFormatter<Bar::F>
+ * {
+ *   // using std::array here fails due to nullptr not being const char*, at least in MSVC
+ *   // (but only when a field is used; directly in the constructor is OK)
+ *   static constexpr array_type names = {"D", "E", nullptr, "F"};
+ *   formatter() : EnumFormatter(names) {}
+ * };
+ */
+template <auto last_member, typename T = decltype(last_member),
+          size_t size = static_cast<size_t>(last_member) + 1,
+          std::enable_if_t<std::is_enum_v<T>, bool> = true>
+class EnumFormatter
+{
+public:
+  constexpr auto parse(fmt::format_parse_context& ctx)
+  {
+    auto it = ctx.begin(), end = ctx.end();
+    // 'u' for user display, 's' for shader generation
+    if (it != end && (*it == 'u' || *it == 's'))
+      formatting_for_shader = (*it++ == 's');
+    return it;
+  }
+
+  template <typename FormatContext>
+  auto format(const T& e, FormatContext& ctx)
+  {
+    const auto value = static_cast<std::underlying_type_t<T>>(e);
+
+    if (!formatting_for_shader)
+    {
+      if (value >= 0 && value < size && m_names[value] != nullptr)
+        return fmt::format_to(ctx.out(), "{} ({})", m_names[value], value);
+      else
+        return fmt::format_to(ctx.out(), "Invalid ({})", value);
+    }
+    else
+    {
+      if (value >= 0 && value < size && m_names[value] != nullptr)
+        return fmt::format_to(ctx.out(), "{:#x}u /* {} */", value, m_names[value]);
+      else
+        return fmt::format_to(ctx.out(), "{:#x}u /* Invalid */",
+                              static_cast<std::make_unsigned_t<T>>(value));
+    }
+  }
+
+protected:
+  // This is needed because std::array deduces incorrectly if nullptr is included in the list
+  using array_type = std::array<const char*, size>;
+
+  constexpr explicit EnumFormatter(const array_type names) : m_names(std::move(names)) {}
+
+private:
+  const array_type m_names;
+  bool formatting_for_shader = false;
+};