GL: ... and neither Optional has to be in Context.h.

All that work to reduce header dependencies and yet here it's full of
them, somehow.

Well, given the fallout in various GL tests now I wonder if I should
just chuck the rest along with the state allocation as a PIMPL.

src/Magnum/GL/Context.h

@@ -34,7 +34,6 @@
 #include <Corrade/Containers/Array.h>
 #include <Corrade/Containers/ArrayTuple.h>
 #include <Corrade/Containers/EnumSet.h>
-#include <Corrade/Containers/Optional.h>
 
 #include "Magnum/Magnum.h"
 #include "Magnum/Math/BitVector.h"
@@ -928,7 +927,8 @@ class MAGNUM_GL_EXPORT Context {
         Containers::ArrayTuple _stateData;
         Implementation::State* _state;
 
-        Containers::Optional<DetectedDrivers> _detectedDrivers;
+        /* ~DetectedDrivers{} means the value is not initialized yet */
+        DetectedDrivers _detectedDrivers = ~DetectedDrivers{};
 
         /** @todo these are all needed only until the state gets created and
             then can be discarded -- what to do? we could avoid including

src/Magnum/GL/Implementation/driverSpecific.cpp

@@ -527,8 +527,9 @@ Containers::StringView findWorkaround(Containers::StringView workaround) {
 }
 
 auto Context::detectedDriver() -> DetectedDrivers {
-    if(_detectedDrivers)
-        return *_detectedDrivers;
+    /* ~DetectedDrivers{} means the value is not initialized yet */
+    if(_detectedDrivers != ~DetectedDrivers{})
+        return _detectedDrivers;
 
     _detectedDrivers = DetectedDrivers{};
 
@@ -563,12 +564,12 @@ auto Context::detectedDriver() -> DetectedDrivers {
     #ifndef CORRADE_TARGET_APPLE
     /* AMD binary desktop drivers */
     if(vendor.contains("ATI Technologies Inc."_s))
-        *_detectedDrivers |= DetectedDriver::Amd;
+        _detectedDrivers |= DetectedDriver::Amd;
 
     #ifdef CORRADE_TARGET_WINDOWS
     /* Intel Windows drivers */
     if(vendor.contains("Intel"_s))
-        *_detectedDrivers |= DetectedDriver::IntelWindows;
+        _detectedDrivers |= DetectedDriver::IntelWindows;
     #endif
 
     /* Mesa drivers.
@@ -587,21 +588,21 @@ auto Context::detectedDriver() -> DetectedDrivers {
         || version.contains("Mesa"_s)
         #endif
     ) {
-        *_detectedDrivers |= DetectedDriver::Mesa;
+        _detectedDrivers |= DetectedDriver::Mesa;
 
         if(renderer.contains("SVGA3D"_s))
-            *_detectedDrivers |= DetectedDriver::Svga3D;
+            _detectedDrivers |= DetectedDriver::Svga3D;
     }
 
     if(vendor.contains("NVIDIA Corporation"_s))
-        *_detectedDrivers |= DetectedDriver::NVidia;
+        _detectedDrivers |= DetectedDriver::NVidia;
     #endif
 
     #ifdef MAGNUM_TARGET_GLES
     /* ANGLE. On WebGL only if we are so lucky and have access to the unmasked
        renderer string. */
     if(renderer.contains("ANGLE"_s))
-        *_detectedDrivers |= DetectedDriver::Angle;
+        _detectedDrivers |= DetectedDriver::Angle;
     #ifdef MAGNUM_TARGET_WEBGL
     /* If the unmasked renderer string is not available, try other means */
     /** @todo this (and below) incorrectly detects ANGLE on FF 92+, as it has
@@ -620,7 +621,7 @@ auto Context::detectedDriver() -> DetectedDrivers {
         #else
         if(isExtensionSupported<Extensions::WEBGL::multi_draw>())
         #endif
-            *_detectedDrivers |= DetectedDriver::Angle;
+            _detectedDrivers |= DetectedDriver::Angle;
         /* Otherwise try to detect a D3D ANGLE backend by querying line width.
            It's always exactly just 1 on D3D, usually (but not always) more on
            GL, not sure about Metal. So this is not a 100% match. Sources:
@@ -629,7 +630,7 @@ auto Context::detectedDriver() -> DetectedDrivers {
             Range1Di range;
             glGetIntegerv(GL_ALIASED_LINE_WIDTH_RANGE, range.data());
             if(range.min() == 1 && range.max() == 1 && vendor != "Internet Explorer"_s) {
-                *_detectedDrivers |= DetectedDriver::Angle;
+                _detectedDrivers |= DetectedDriver::Angle;
             }
         }
     }
@@ -637,20 +638,20 @@ auto Context::detectedDriver() -> DetectedDrivers {
 
     /* SwiftShader */
     if(renderer.contains("SwiftShader"_s))
-        *_detectedDrivers |= DetectedDriver::SwiftShader;
+        _detectedDrivers |= DetectedDriver::SwiftShader;
     #endif
 
     #ifdef CORRADE_TARGET_ANDROID
     if(vendor.contains("ARM"_s) && renderer.contains("Mali"_s))
-        *_detectedDrivers |= DetectedDriver::ArmMali;
+        _detectedDrivers |= DetectedDriver::ArmMali;
     #endif
 
     #if defined(MAGNUM_TARGET_GLES) && !defined(CORRADE_TARGET_APPLE)
     if(vendor.contains("Qualcomm"_s) && renderer.contains("Adreno"_s))
-        *_detectedDrivers |= DetectedDriver::QualcommAdreno;
+        _detectedDrivers |= DetectedDriver::QualcommAdreno;
     #endif
 
-    return *_detectedDrivers;
+    return _detectedDrivers;
 }
 
 void Context::disableDriverWorkaround(const Containers::StringView workaround) {

src/Magnum/GL/Shader.cpp

@@ -29,6 +29,7 @@
 
 #include <Corrade/Containers/Array.h>
 #include <Corrade/Containers/GrowableArray.h>
+#include <Corrade/Containers/Optional.h>
 #ifdef MAGNUM_BUILD_DEPRECATED
 #include <Corrade/Containers/Reference.h>
 #endif

src/Magnum/GL/Test/ContextGLTest.cpp

@@ -25,6 +25,7 @@
 */
 
 #include <algorithm> /* std::find() */
+#include <Corrade/Containers/Optional.h>
 #include <Corrade/Containers/ScopeGuard.h>
 #include <Corrade/Containers/StringIterable.h>
 #include <Corrade/Containers/StringStl.h> /** @todo remove once Debug is stream-free */

src/Magnum/GL/Test/RendererGLTest.cpp

@@ -31,6 +31,7 @@
 #include <Corrade/Utility/Path.h>
 
 #ifdef CORRADE_TARGET_APPLE
+#include <Corrade/Containers/Optional.h>
 #include <Corrade/Containers/Pair.h>
 #include <Corrade/Utility/System.h> /* isSandboxed() */
 #endif

src/Magnum/MeshTools/Test/CompileGLTest.cpp

@@ -27,6 +27,7 @@
 
 #include <Corrade/Containers/EnumSet.h>
 #include <Corrade/Containers/GrowableArray.h>
+#include <Corrade/Containers/Optional.h>
 #include <Corrade/Containers/Pair.h>
 #include <Corrade/Containers/String.h>
 #include <Corrade/Containers/StringIterable.h>

src/Magnum/Shaders/MeshVisualizerGL.cpp

@@ -29,6 +29,7 @@
 
 #include <Corrade/Containers/EnumSet.hpp>
 #include <Corrade/Containers/Iterable.h>
+#include <Corrade/Containers/Optional.h>
 #include <Corrade/Containers/StringView.h>
 #include <Corrade/Utility/Resource.h>
 

src/Magnum/Shaders/Test/LineGLTest.cpp

@@ -26,6 +26,7 @@
 
 #include <Corrade/Containers/GrowableArray.h>
 #include <Corrade/Containers/Iterable.h>
+#include <Corrade/Containers/Optional.h>
 #include <Corrade/Containers/StridedArrayView.h>
 #include <Corrade/Containers/String.h>
 #include <Corrade/Containers/StringIterable.h>

src/Magnum/Shaders/Test/MeshVisualizerGLTest.cpp

@@ -27,6 +27,7 @@
 
 #include <numeric> /* std::iota() */
 #include <Corrade/Containers/ArrayViewStl.h>
+#include <Corrade/Containers/Optional.h>
 #include <Corrade/Containers/Pair.h>
 #include <Corrade/Containers/StridedArrayView.h>
 #include <Corrade/Containers/String.h>

src/Magnum/Shaders/Test/VertexColorGLTest.cpp

@@ -25,6 +25,7 @@
     DEALINGS IN THE SOFTWARE.
 */
 
+#include <Corrade/Containers/Optional.h>
 #include <Corrade/Containers/Pair.h>
 #include <Corrade/Containers/StridedArrayView.h>
 #include <Corrade/Containers/String.h>

src/Magnum/Text/Test/DistanceFieldGlyphCacheGLTest.cpp

@@ -24,6 +24,7 @@
     DEALINGS IN THE SOFTWARE.
 */
 
+#include <Corrade/Containers/Optional.h>
 #include <Corrade/Containers/StridedArrayView.h>
 #include <Corrade/Containers/String.h>
 #include <Corrade/PluginManager/AbstractManager.h>

src/Magnum/TextureTools/Test/DistanceFieldGLBenchmark.cpp

@@ -24,6 +24,7 @@
     DEALINGS IN THE SOFTWARE.
 */
 
+#include <Corrade/Containers/Optional.h>
 #include <Corrade/Containers/String.h>
 #include <Corrade/PluginManager/AbstractManager.h>
 #include <Corrade/Utility/Path.h>

src/Magnum/TextureTools/Test/DistanceFieldGLTest.cpp

@@ -24,6 +24,7 @@
     DEALINGS IN THE SOFTWARE.
 */
 
+#include <Corrade/Containers/Optional.h>
 #include <Corrade/Containers/StridedArrayView.h>
 #include <Corrade/Containers/String.h>
 #include <Corrade/PluginManager/AbstractManager.h>

src/MagnumPlugins/MagnumFont/Test/MagnumFontGLTest.cpp

@@ -24,6 +24,7 @@
     DEALINGS IN THE SOFTWARE.
 */
 
+#include <Corrade/Containers/Optional.h>
 #include <Corrade/Containers/StridedArrayView.h>
 #include <Corrade/Containers/String.h>
 #include <Corrade/Containers/Triple.h>