Add equality ops to for Color and Brush

include/esc/brush.hpp

@@ -14,5 +14,20 @@ struct Brush {
     Traits traits    = Traits{Trait::None};
 };
 
+/// Returns true if the two Brushes have the same background, foreground, and
+/// traits.
+[[nodiscard]] inline auto operator==(Brush const& lhs, Brush const& rhs) -> bool
+{
+    return lhs.background == rhs.background &&
+           lhs.foreground == rhs.foreground && lhs.traits == rhs.traits;
+}
+
+/// Returns true if the two Brushes do not have the same background, foreground,
+/// and traits.
+[[nodiscard]] inline auto operator!=(Brush const& lhs, Brush const& rhs) -> bool
+{
+    return !(lhs == rhs);
+}
+
 }  // namespace esc
 #endif  // ESC_BRUSH_HPP

include/esc/default_color.hpp

@@ -5,6 +5,18 @@ namespace esc {
 /// Default Color of the terminal.
 struct Default_color {};
 
+/// Checks for equality, always returns true.
+[[nodiscard]] constexpr auto operator==(Default_color, Default_color) -> bool
+{
+    return true;
+}
+
+/// Checks for inequality, always returns false.
+[[nodiscard]] constexpr auto operator!=(Default_color, Default_color) -> bool
+{
+    return false;
+}
+
 /// Tag type for terminal default color background.
 struct BG_Default_color {};
 

include/esc/true_color.hpp

@@ -132,6 +132,20 @@ class True_color {
     constexpr True_color(HSL x) : True_color{hsl_to_rgb(x)} {}
 };
 
+/// Returns true if the two True_colors are the same.
+[[nodiscard]] inline auto operator==(True_color const& lhs,
+                                     True_color const& rhs) -> bool
+{
+    return lhs.red == rhs.red && lhs.green == rhs.green && lhs.blue == rhs.blue;
+}
+
+/// Returns true if the two True_colors are not the same.
+[[nodiscard]] inline auto operator!=(True_color const& lhs,
+                                     True_color const& rhs) -> bool
+{
+    return !(lhs == rhs);
+}
+
 /// Tag type for True_color that is used as a background.
 struct BG_True_color {
     True_color value;