This is a collection of functions and classes helpful for diagnosing bugs in Qt 4 and Qt 5. It can be included in the application's .pro file by adding: include([path to Qt sources]/tests/manual/diaglib/diaglib.pri) For Qt 4, the environment variable QTDIR may be used: include($$(QTDIR)/tests/manual/diaglib/diaglib.pri) The .pri file adds the define QT_DIAG_LIB, so, diagnostic code can be enlosed within #ifdef to work without it as well. All functions and classes are in the QtDiag namespace. class EventFilter (eventfilter.h): An event filter that logs Qt events to qDebug() depending on configured categories (for example mouse, keyboard, etc). function glInfo() (glinfo.h): Returns a string describing the Open GL configuration (obtained by querying GL_VENDOR and GL_RENDERER). Available only when the QT qmake variable contains opengl. functions dumpNativeWindows(), dumpNativeQtTopLevels(): These functions du,p out the hierarchy of native Windows. Currently implemented for Windows only. function dumpAllWidgets() (qwidgetdump.h): Dumps the hierarchy of QWidgets including information about flags, visibility, geometry, etc. function dumpAllWindows() (qwindowdump.h): Dumps the hierarchy of QWindows including information about flags, visibility, geometry, etc.