feat: add FlagsEnum::isEmpty for checking if a FlagsEnum is empty (#5550)

CHANGELOG.md

@@ -64,6 +64,7 @@
 - Dev: Cleanly exit on shutdown. (#5537)
 - Dev: Renamed threads created by Chatterino on Linux and Windows. (#5538, #5539, #5544)
 - Dev: Refactored a few `#define`s into `const(expr)` and cleaned includes. (#5527)
+- Dev: Added `FlagsEnum::isEmpty`. (#5550)
 - Dev: Prepared for Qt 6.8 by addressing some deprecations. (#5529)
 
 ## 2.5.1

src/common/FlagsEnum.hpp

@@ -132,6 +132,12 @@ public:
         return this->hasNone(FlagsEnum{flags...});
     }
 
+    /// Returns true if the enum has no flag set (i.e. its underlying value is 0)
+    constexpr bool isEmpty() const noexcept
+    {
+        return static_cast<Int>(this->value_) == 0;
+    }
+
     constexpr T value() const noexcept
     {
         return this->value_;

tests/src/FlagsEnum.cpp

@@ -326,6 +326,23 @@ TEST(FlagsEnum, hasNone)
     testHasNone<BasicUnscoped>();
 }
 
+template <typename E>
+consteval void testIsEmpty()
+{
+    using FE = FlagsEnum<E>;
+
+    static_assert(FE{}.isEmpty());
+    static_assert(!FE{E::Foo}.isEmpty());
+    static_assert(FE{E::None}.isEmpty());
+    static_assert(!FE{E::Foo, E::Waldo}.isEmpty());
+}
+
+TEST(FlagsEnum, isEmpty)
+{
+    testIsEmpty<BasicScoped>();
+    testIsEmpty<BasicUnscoped>();
+}
+
 template <typename T>
 constexpr inline auto CONSTRUCTION_VALID = requires() { FlagsEnum<T>{}; };