From 66c3bc21126b7e961226dbc89d8ef58ac99898da Mon Sep 17 00:00:00 2001
From: pajlada <rasmus.karlsson@pajlada.com>
Date: Sun, 18 Aug 2024 12:22:41 +0200
Subject: [PATCH] feat: add `FlagsEnum::isEmpty` for checking if a FlagsEnum is
 empty (#5550)

---
 CHANGELOG.md             |  1 +
 src/common/FlagsEnum.hpp |  6 ++++++
 tests/src/FlagsEnum.cpp  | 17 +++++++++++++++++
 3 files changed, 24 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7d4c7ffcc..3afc6f95a 100644
--- a/CHANGELOG.md
+++ b/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
diff --git a/src/common/FlagsEnum.hpp b/src/common/FlagsEnum.hpp
index e49c30aa6..d2ae4ebf7 100644
--- a/src/common/FlagsEnum.hpp
+++ b/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_;
diff --git a/tests/src/FlagsEnum.cpp b/tests/src/FlagsEnum.cpp
index 4b3e94ba5..0d165c9f0 100644
--- a/tests/src/FlagsEnum.cpp
+++ b/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>{}; };