TextureTools: add a NoCreate AtlasLandfill constructor.

src/Magnum/TextureTools/Atlas.cpp

@@ -214,6 +214,8 @@ AtlasLandfill::AtlasLandfill(const Vector3i& size):_state{InPlaceInit} {
 
 AtlasLandfill::AtlasLandfill(const Vector2i& size): AtlasLandfill{{size, 1}} {}
 
+AtlasLandfill::AtlasLandfill(NoCreateT) noexcept {}
+
 AtlasLandfill::AtlasLandfill(AtlasLandfill&&) noexcept = default;
 
 AtlasLandfill::~AtlasLandfill() = default;

src/Magnum/TextureTools/Atlas.h

@@ -226,6 +226,20 @@ class MAGNUM_TEXTURETOOLS_EXPORT AtlasLandfill {
          */
         explicit AtlasLandfill(const Vector2i& size);
 
+        /**
+         * @brief Construct without creating the internal state
+         * @m_since_latest
+         *
+         * The constructed instance is equivalent to moved-from state, i.e. no
+         * APIs can be safely called on the object. Useful in cases where you
+         * will overwrite the instance later anyway. Move another object over
+         * it to make it useful.
+         *
+         * Note that this is a low-level and a potentially dangerous API, see
+         * the documentation of @ref NoCreate for alternatives.
+         */
+        explicit AtlasLandfill(NoCreateT) noexcept;
+
         /** @brief Copying is not allowed */
         AtlasLandfill(const AtlasLandfill&) = delete;
 

src/Magnum/TextureTools/Test/AtlasTest.cpp

@@ -53,6 +53,7 @@ struct AtlasTest: TestSuite::Tester {
 
     void landfillConstruct();
     void landfillConstructInvalidSize();
+    void landfillConstructNoCreate();
     void landfillConstructCopy();
     void landfillConstructMove();
 
@@ -504,6 +505,7 @@ AtlasTest::AtlasTest() {
 
               &AtlasTest::landfillConstruct,
               &AtlasTest::landfillConstructInvalidSize,
+              &AtlasTest::landfillConstructNoCreate,
               &AtlasTest::landfillConstructCopy,
               &AtlasTest::landfillConstructMove,
 
@@ -614,6 +616,16 @@ void AtlasTest::landfillConstructInvalidSize() {
         TestSuite::Compare::String);
 }
 
+void AtlasTest::landfillConstructNoCreate() {
+    AtlasLandfill a{NoCreate};
+
+    /* Shouldn't crash */
+    CORRADE_VERIFY(true);
+
+    /* Implicit construction is not allowed */
+    CORRADE_VERIFY(!std::is_convertible<NoCreateT, AtlasLandfill>::value);
+}
+
 void AtlasTest::landfillConstructCopy() {
     CORRADE_VERIFY(!std::is_copy_constructible<AtlasLandfill>{});
     CORRADE_VERIFY(!std::is_copy_assignable<AtlasLandfill>{});