Add QGIS_PROTECT_QOBJECT_THREAD_ACCESS macro

Either shows a warning when a qobject function is accessed
from a thread which the object doesn't have affinity with,
OR causes a fatal error if the AGGRESSIVE_SAFE_MODE cmake flag
is set.

We should ensure this macro is present for all qobject methods
which may potentially be called from threads

CMakeLists.txt

@@ -692,6 +692,8 @@ else()
   set(QGISDEBUG FALSE)
 endif()
 
+set (AGGRESSIVE_SAFE_MODE FALSE CACHE BOOL "Forces a aggressive safe mode where issues like unsafe thread access will resort in fatal exceptions")
+
 if(MSVC)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /utf-8 /std:c++17")
   set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} /utf-8 /std:c++17")

cmake_templates/qgsconfig.h.in

@@ -90,6 +90,8 @@
 
 #cmakedefine QGISDEBUG
 
+#cmakedefine AGGRESSIVE_SAFE_MODE
+
 #cmakedefine HAVE_QUICK
 
 #cmakedefine HAVE_QT5SERIALPORT

src/core/qgsthreadingutils.h

@@ -19,6 +19,7 @@
 #define SIP_NO_FILE
 
 #include "qgis_core.h"
+#include "qgsconfig.h"
 
 #include "qgsfeedback.h"
 
@@ -26,6 +27,15 @@
 #include <QSemaphore>
 #include <memory>
 
+#ifdef AGGRESSIVE_SAFE_MODE
+#define QGIS_PROTECT_QOBJECT_THREAD_ACCESS if ( QThread::currentThread() != thread() ) {qFatal( "%s", QStringLiteral("%2 (%1:%3) is run from a different thread than the object %4 lives in [0x%5 vs 0x%6]" ).arg( QString( __FILE__ ), QString( __FUNCTION__ ), QString::number( __LINE__  ), objectName() ).arg( reinterpret_cast< qint64 >( QThread::currentThread() ), 0, 16 ).arg( reinterpret_cast< qint64 >( thread() ), 0, 16 ).toLocal8Bit().constData() ); }
+#elif defined(QGISDEBUG)
+#define QGIS_PROTECT_QOBJECT_THREAD_ACCESS if ( QThread::currentThread() != thread() ) {qWarning() << QStringLiteral("%2 (%1:%3) is run from a different thread than the object %4 lives in [0x%5 vs 0x%6]" ).arg( QString( __FILE__ ), QString( __FUNCTION__ ), QString::number( __LINE__  ), objectName() ).arg( reinterpret_cast< qint64 >( QThread::currentThread() ), 0, 16 ).arg( reinterpret_cast< qint64 >( thread() ), 0, 16 ).toLocal8Bit().constData(); }
+#else
+#define QGIS_PROTECT_QOBJECT_THREAD_ACCESS do {} while(false);
+#endif
+
+
 /**
  * \ingroup core
  * \brief Provides threading utilities for QGIS.