Text: add a NoCreate constructor to [DistanceField]GlyphCache.

Want to construct them without a GL context present, and Optional is too
wasteful. Also adding it to the AbstractGlyphCache base, where it skips
also allocating the internal PIMPL state, because it's not going to get
used for anything in a NoCreate'd instance anyway.

doc/changelog.dox

@@ -809,6 +809,9 @@ See also:
     missing before, and @ref Text::Alignment::TopCenterIntegral, which is also
     needed in order to prevent aligning pixel-perfect fonts to fractional
     positions.
+-   Added a @ref Text::GlyphCache::GlyphCache(NoCreateT) and
+    @ref Text::DistanceFieldGlyphCache::DistanceFieldGlyphCache(NoCreateT)
+    constructor allowing to construct the object without a GL context present
 
 @subsubsection changelog-latest-changes-texturetools TextureTools library
 

src/Magnum/Text/AbstractGlyphCache.cpp

@@ -144,6 +144,8 @@ AbstractGlyphCache::AbstractGlyphCache(const Vector2i& size, const Vector2i& pad
 AbstractGlyphCache::AbstractGlyphCache(const Vector2i& size): AbstractGlyphCache{PixelFormat::R8Unorm, size, {}} {}
 #endif
 
+AbstractGlyphCache::AbstractGlyphCache(NoCreateT) noexcept {}
+
 AbstractGlyphCache::AbstractGlyphCache(AbstractGlyphCache&&) noexcept = default;
 
 AbstractGlyphCache::~AbstractGlyphCache() = default;

src/Magnum/Text/AbstractGlyphCache.h

@@ -317,6 +317,20 @@ class MAGNUM_TEXT_EXPORT AbstractGlyphCache {
         #endif
         #endif
 
+        /**
+         * @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 AbstractGlyphCache(NoCreateT) noexcept;
+
         /** @brief Copying is not allowed */
         AbstractGlyphCache(const AbstractGlyphCache&) = delete;
 

src/Magnum/Text/DistanceFieldGlyphCache.cpp

@@ -69,6 +69,8 @@ DistanceFieldGlyphCache::DistanceFieldGlyphCache(const Vector2i& sourceSize, con
     #endif
 }
 
+DistanceFieldGlyphCache::DistanceFieldGlyphCache(NoCreateT) noexcept: GlyphCache{NoCreate}, _distanceField{NoCreate} {}
+
 GlyphCacheFeatures DistanceFieldGlyphCache::doFeatures() const {
     return GlyphCacheFeature::ImageProcessing
         #ifndef MAGNUM_TARGET_GLES

src/Magnum/Text/DistanceFieldGlyphCache.h

@@ -100,6 +100,22 @@ class MAGNUM_TEXT_EXPORT DistanceFieldGlyphCache: public GlyphCache {
          */
         explicit DistanceFieldGlyphCache(const Vector2i& sourceSize, const Vector2i& size, UnsignedInt radius);
 
+        /**
+         * @brief Construct without creating the internal state and the OpenGL texture object
+         * @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.
+         *
+         * This function can be safely used for constructing (and later
+         * destructing) objects even without any OpenGL context being active.
+         * However note that this is a low-level and a potentially dangerous
+         * API, see the documentation of @ref NoCreate for alternatives.
+         */
+        explicit DistanceFieldGlyphCache(NoCreateT) noexcept;
+
         /**
          * @brief Distance field texture size
          *

src/Magnum/Text/GlyphCache.cpp

@@ -63,6 +63,8 @@ GlyphCache::GlyphCache(const Vector2i& originalSize, const Vector2i& size, const
     #endif
 }
 
+GlyphCache::GlyphCache(NoCreateT) noexcept: AbstractGlyphCache{NoCreate}, _texture{NoCreate} {}
+
 GlyphCacheFeatures GlyphCache::doFeatures() const { return {}; }
 
 void GlyphCache::doSetImage(const Vector2i& offset, const ImageView2D& image) {

src/Magnum/Text/GlyphCache.h

@@ -107,6 +107,22 @@ class MAGNUM_TEXT_EXPORT GlyphCache: public AbstractGlyphCache {
          */
         explicit GlyphCache(const Vector2i& size, const Vector2i& padding = {});
 
+        /**
+         * @brief Construct without creating the internal state and the OpenGL texture object
+         * @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.
+         *
+         * This function can be safely used for constructing (and later
+         * destructing) objects even without any OpenGL context being active.
+         * However note that this is a low-level and a potentially dangerous
+         * API, see the documentation of @ref NoCreate for alternatives.
+         */
+        explicit GlyphCache(NoCreateT) noexcept;
+
         /** @brief Cache texture */
         GL::Texture2D& texture() { return _texture; }
 

src/Magnum/Text/Test/AbstractGlyphCacheTest.cpp

@@ -66,6 +66,7 @@ struct AbstractGlyphCacheTest: TestSuite::Tester {
     #endif
     void constructImageRowPadding();
     void constructZeroSize();
+    void constructNoCreate();
 
     void constructCopy();
     void constructMove();
@@ -162,6 +163,7 @@ AbstractGlyphCacheTest::AbstractGlyphCacheTest() {
               #endif
               &AbstractGlyphCacheTest::constructImageRowPadding,
               &AbstractGlyphCacheTest::constructZeroSize,
+              &AbstractGlyphCacheTest::constructNoCreate,
 
               &AbstractGlyphCacheTest::constructCopy,
               &AbstractGlyphCacheTest::constructMove,
@@ -446,6 +448,16 @@ void AbstractGlyphCacheTest::constructZeroSize() {
         "Text::AbstractGlyphCache: expected non-zero size, got {0, 2, 1}\n");
 }
 
+void AbstractGlyphCacheTest::constructNoCreate() {
+    DummyGlyphCache cache{NoCreate};
+
+    /* Shouldn't crash */
+    CORRADE_VERIFY(true);
+
+    /* Implicit construction is not allowed */
+    CORRADE_VERIFY(!std::is_convertible<NoCreateT, DummyGlyphCache>::value);
+}
+
 void AbstractGlyphCacheTest::constructCopy() {
     CORRADE_VERIFY(!std::is_copy_constructible<DummyGlyphCache>{});
     CORRADE_VERIFY(!std::is_copy_assignable<DummyGlyphCache>{});

src/Magnum/Text/Test/CMakeLists.txt

@@ -83,40 +83,45 @@ corrade_add_test(TextFeatureTest FeatureTest.cpp LIBRARIES MagnumTextTestLib)
 corrade_add_test(TextRendererTest RendererTest.cpp LIBRARIES MagnumTextTestLib)
 corrade_add_test(TextScriptTest ScriptTest.cpp LIBRARIES MagnumTextTestLib)
 
-if(MAGNUM_TARGET_GL AND MAGNUM_BUILD_GL_TESTS)
-    corrade_add_test(TextDistanceFieldGlyphCacheGLTest DistanceFieldGlyphCacheGLTest.cpp
-        LIBRARIES
-            MagnumTextTestLib
-            MagnumOpenGLTester
-            MagnumDebugTools
-        FILES
-            ${PROJECT_SOURCE_DIR}/src/Magnum/TextureTools/Test/DistanceFieldGLTestFiles/input.tga
-            ${PROJECT_SOURCE_DIR}/src/Magnum/TextureTools/Test/DistanceFieldGLTestFiles/output.tga)
-    target_include_directories(TextDistanceFieldGlyphCacheGLTest PRIVATE ${CMAKE_CURRENT_BINARY_DIR}/$<CONFIG>)
-    if(MAGNUM_BUILD_PLUGINS_STATIC)
-        if(MAGNUM_WITH_ANYIMAGEIMPORTER)
-            target_link_libraries(TextDistanceFieldGlyphCacheGLTest PRIVATE AnyImageImporter)
-        endif()
-        if(MAGNUM_WITH_TGAIMPORTER)
-            target_link_libraries(TextDistanceFieldGlyphCacheGLTest PRIVATE TgaImporter)
-        endif()
-    else()
-        # So the plugins get properly built when building the test
-        if(MAGNUM_WITH_ANYIMAGEIMPORTER)
-            add_dependencies(TextDistanceFieldGlyphCacheGLTest AnyImageImporter)
-        endif()
-        if(MAGNUM_WITH_TGAIMPORTER)
-            add_dependencies(TextDistanceFieldGlyphCacheGLTest TgaImporter)
+if(MAGNUM_TARGET_GL)
+    corrade_add_test(TextGlyphCacheTest GlyphCacheTest.cpp LIBRARIES MagnumText)
+    corrade_add_test(TextDistanceFieldGlyphCacheTest DistanceFieldGlyphCacheTest.cpp LIBRARIES MagnumText)
+
+    if(MAGNUM_BUILD_GL_TESTS)
+        corrade_add_test(TextDistanceFieldGlyphCacheGLTest DistanceFieldGlyphCacheGLTest.cpp
+            LIBRARIES
+                MagnumTextTestLib
+                MagnumOpenGLTester
+                MagnumDebugTools
+            FILES
+                ${PROJECT_SOURCE_DIR}/src/Magnum/TextureTools/Test/DistanceFieldGLTestFiles/input.tga
+                ${PROJECT_SOURCE_DIR}/src/Magnum/TextureTools/Test/DistanceFieldGLTestFiles/output.tga)
+        target_include_directories(TextDistanceFieldGlyphCacheGLTest PRIVATE ${CMAKE_CURRENT_BINARY_DIR}/$<CONFIG>)
+        if(MAGNUM_BUILD_PLUGINS_STATIC)
+            if(MAGNUM_WITH_ANYIMAGEIMPORTER)
+                target_link_libraries(TextDistanceFieldGlyphCacheGLTest PRIVATE AnyImageImporter)
+            endif()
+            if(MAGNUM_WITH_TGAIMPORTER)
+                target_link_libraries(TextDistanceFieldGlyphCacheGLTest PRIVATE TgaImporter)
+            endif()
+        else()
+            # So the plugins get properly built when building the test
+            if(MAGNUM_WITH_ANYIMAGEIMPORTER)
+                add_dependencies(TextDistanceFieldGlyphCacheGLTest AnyImageImporter)
+            endif()
+            if(MAGNUM_WITH_TGAIMPORTER)
+                add_dependencies(TextDistanceFieldGlyphCacheGLTest TgaImporter)
+            endif()
         endif()
-    endif()
 
-    corrade_add_test(TextGlyphCacheGLTest GlyphCacheGLTest.cpp
-        LIBRARIES
-            MagnumText
-            MagnumOpenGLTester
-            MagnumDebugTools)
-    corrade_add_test(TextRendererGLTest RendererGLTest.cpp
-        LIBRARIES
-            MagnumTextTestLib
-            MagnumOpenGLTester)
+        corrade_add_test(TextGlyphCacheGLTest GlyphCacheGLTest.cpp
+            LIBRARIES
+                MagnumText
+                MagnumOpenGLTester
+                MagnumDebugTools)
+        corrade_add_test(TextRendererGLTest RendererGLTest.cpp
+            LIBRARIES
+                MagnumTextTestLib
+                MagnumOpenGLTester)
+    endif()
 endif()

src/Magnum/Text/Test/DistanceFieldGlyphCacheTest.cpp

@@ -0,0 +1,54 @@
+/*
+    This file is part of Magnum.
+
+    Copyright © 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019,
+                2020, 2021, 2022, 2023 Vladimír Vondruš <mosra@centrum.cz>
+
+    Permission is hereby granted, free of charge, to any person obtaining a
+    copy of this software and associated documentation files (the "Software"),
+    to deal in the Software without restriction, including without limitation
+    the rights to use, copy, modify, merge, publish, distribute, sublicense,
+    and/or sell copies of the Software, and to permit persons to whom the
+    Software is furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included
+    in all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+    DEALINGS IN THE SOFTWARE.
+*/
+
+#include <Corrade/TestSuite/Tester.h>
+
+#include "Magnum/Text/DistanceFieldGlyphCache.h"
+
+namespace Magnum { namespace Text { namespace Test { namespace {
+
+struct DistanceFieldGlyphCacheTest: TestSuite::Tester {
+    explicit DistanceFieldGlyphCacheTest();
+
+    void constructNoCreate();
+};
+
+DistanceFieldGlyphCacheTest::DistanceFieldGlyphCacheTest() {
+    addTests({&DistanceFieldGlyphCacheTest::constructNoCreate});
+}
+
+void DistanceFieldGlyphCacheTest::constructNoCreate() {
+    DistanceFieldGlyphCache cache{NoCreate};
+
+    /* Shouldn't crash or try to acces GL */
+    CORRADE_VERIFY(true);
+
+    /* Implicit construction is not allowed */
+    CORRADE_VERIFY(!std::is_convertible<NoCreateT, DistanceFieldGlyphCache>::value);
+}
+
+}}}}
+
+CORRADE_TEST_MAIN(Magnum::Text::Test::DistanceFieldGlyphCacheTest)

src/Magnum/Text/Test/GlyphCacheTest.cpp

@@ -0,0 +1,54 @@
+/*
+    This file is part of Magnum.
+
+    Copyright © 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019,
+                2020, 2021, 2022, 2023 Vladimír Vondruš <mosra@centrum.cz>
+
+    Permission is hereby granted, free of charge, to any person obtaining a
+    copy of this software and associated documentation files (the "Software"),
+    to deal in the Software without restriction, including without limitation
+    the rights to use, copy, modify, merge, publish, distribute, sublicense,
+    and/or sell copies of the Software, and to permit persons to whom the
+    Software is furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included
+    in all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+    DEALINGS IN THE SOFTWARE.
+*/
+
+#include <Corrade/TestSuite/Tester.h>
+
+#include "Magnum/Text/GlyphCache.h"
+
+namespace Magnum { namespace Text { namespace Test { namespace {
+
+struct GlyphCacheTest: TestSuite::Tester {
+    explicit GlyphCacheTest();
+
+    void constructNoCreate();
+};
+
+GlyphCacheTest::GlyphCacheTest() {
+    addTests({&GlyphCacheTest::constructNoCreate});
+}
+
+void GlyphCacheTest::constructNoCreate() {
+    GlyphCache cache{NoCreate};
+
+    /* Shouldn't crash or try to acces GL */
+    CORRADE_VERIFY(true);
+
+    /* Implicit construction is not allowed */
+    CORRADE_VERIFY(!std::is_convertible<NoCreateT, GlyphCache>::value);
+}
+
+}}}}
+
+CORRADE_TEST_MAIN(Magnum::Text::Test::GlyphCacheTest)