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Diffstat (limited to 'doc/src/development/debug.qdoc')
| -rw-r--r-- | doc/src/development/debug.qdoc | 40 |
1 files changed, 28 insertions, 12 deletions
diff --git a/doc/src/development/debug.qdoc b/doc/src/development/debug.qdoc index 32d09b541..ad26997a3 100644 --- a/doc/src/development/debug.qdoc +++ b/doc/src/development/debug.qdoc @@ -123,18 +123,29 @@ \section1 Warning and Debugging Messages - Qt includes global macros for writing out warning and debug - text. You can use them for the following purposes: + Qt includes global C++ macros for writing out warning and debug text. + The plain macros use a default \l {QLoggingCategory}{logging category}; + the categorized logging macros allow you to specify the category. + You can use them for the following purposes: - \list - \li qDebug() is used for writing custom debug output. - \li qInfo() is used for informational messages. - \li qWarning() is used to report warnings and recoverable errors in - your application. - \li qCritical() is used for writing critical error messages and - reporting system errors. - \li qFatal() is used for writing fatal error messages shortly before exiting. - \endlist + \table + \header \li Plain macro \li Categorized macro \li Purpose + \row \li qDebug() + \li qCDebug() + \li Used for writing custom debug output + \row \li qInfo() + \li qCInfo() + \li Used for informational messages + \row \li qWarning() + \li qCWarning() + \li Used to report warnings and recoverable errors in your application or library + \row \li qCritical() + \li qCCritical() + \li Used for writing critical error messages and reporting system errors + \row \li qFatal() + \li - + \li Used for writing messages about fatal errors shortly before exiting + \endtable If you include the <QtDebug> header file, the \c qDebug() macro can also be used as an output stream. For example: @@ -150,7 +161,7 @@ by setting the \c QT_MESSAGE_PATTERN environment variable. For example: \code - QT_MESSAGE_PATTERN="[%{type}] %{appname} (%{file}:%{line}) - %{message}" + QT_MESSAGE_PATTERN="[%{time process} %{type}] %{appname} %{category} %{function} - %{message}" \endcode The format is documented in qSetMessagePattern(). You can also install your @@ -169,6 +180,8 @@ looks or acts strangely. More useful if you use \l{QObject::setObjectName()}{object names} than not, but often useful even without names. + In QML, \l {QtQuick::Item::}{dumpItemTree()} serves the same purpose. + \section1 Providing Support for the qDebug() Stream Operator You can implement the stream operator used by qDebug() to provide @@ -224,6 +237,9 @@ therefore recommend that you use a debug version of Qt when developing Qt-based software. + Logging and \l {LoggingCategory}{categorized logging} are also + possible in \l {Debugging QML Applications}{QML}. + \section1 Common Bugs There is one bug that is so common that it deserves mention here: |