GL: print a message about GPU validation in verbose log output.

src/Magnum/GL/Context.cpp

@@ -474,8 +474,10 @@ Context::Context(NoCreateT, Utility::Arguments& args, Int argc, const char** arg
         .setFromEnvironment("log")
         .parse(argc, argv);
 
-    /* Decide whether to display initialization log */
+    /* Decide how to display initialization log */
-    if(!(args.value("log") == "quiet" || args.value("log") == "QUIET"))
+    if(args.value("log") == "verbose" || args.value("log") == "VERBOSE")
+        _internalFlags |= InternalFlag::DisplayVerboseInitializationLog;
+    else if(!(args.value("log") == "quiet" || args.value("log") == "QUIET"))
         _internalFlags |= InternalFlag::DisplayInitializationLog;
 
     /* Decide whether to enable GPU validation */
@@ -755,6 +757,8 @@ bool Context::tryCreate() {
 
             if((detectedDriver() & DetectedDriver::Amd) && !(flags() & Flag::Debug)) {
                 Warning{} << "GL::Context: GPU validation on AMD drivers requires debug context to work properly";
+            } else if(_internalFlags >= InternalFlag::DisplayVerboseInitializationLog) {
+                Debug{} << "GL::Context: enabling GPU validation";
             }
 
         } else Warning{} << "GL::Context: GPU validation requested, but GL_KHR_debug not supported";

src/Magnum/GL/Context.h

@@ -733,7 +733,8 @@ class MAGNUM_GL_EXPORT Context {
 
         enum class InternalFlag: UnsignedByte {
             DisplayInitializationLog = 1 << 0,
-            GpuValidation = 1 << 1
+            DisplayVerboseInitializationLog = DisplayInitializationLog|(1 << 1),
+            GpuValidation = 1 << 2
         };
         typedef Containers::EnumSet<InternalFlag> InternalFlags;
         CORRADE_ENUMSET_FRIEND_OPERATORS(InternalFlags)