path: root/src/corelib/io/qloggingcategory.cpp

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#include "qloggingcategory.h"
#include "qloggingcategory_p.h"
#include "qloggingregistry_p.h"

QT_BEGIN_NAMESPACE

const char qtDefaultCategoryName[] = "default";

Q_GLOBAL_STATIC_WITH_ARGS(QLoggingCategory, qtDefaultCategory,
                          (qtDefaultCategoryName))

/*!
    \class QLoggingCategory
    \inmodule QtCore
    \since 5.2

    \brief A category, or 'area' in the logging infrastructure.

    QLoggingCategory represents a certain logging category - identified
    by a string - at runtime. Whether a category should be actually logged or
    not can be checked with the \l isEnabled() methods.

    \section1 Creating category objects

    Qt provides the \l Q_LOGGING_CATEGORY(), Q_DECLARE_LOGGING_CATEGORY() macros
    to conveniently create static QLoggingCategory objects on the heap:

    \snippet qloggingcategory/main.cpp 1

    \section1 Checking category configuration

    QLoggingCategory provides two isEnabled methods, a template one and a
    non-template one, for checking whether the current category is enabled.
    The template version checks for the most common case that no special rules
    are applied in inline code, and should be preferred:

    \snippet qloggingcategory/main.cpp 2

    Note that qCDebug() prevents arguments from being evaluated
    if the string won't print, so calling isEnabled explicitly is not needed:
    \l isEnabled().

    \snippet qloggingcategory/main.cpp 3

    \section1 Default configuration

    In the default configuration \l isEnabled() will return true for all
    \l QtMsgType types except QtDebugMsg: QtDebugMsg is only active by default
    for the \c "default" category.

    \section1 Changing configuration

    The default configuration can be changed by calling \l setEnabled(). However,
    this only affects the current category object, not e.g. another object for the
    same category name. Use either \l setFilterRules() or \l installFilter() to
    configure categories globally.
*/

/*!
    Constructs a QLoggingCategory object with the provided \a category name.
    The object becomes the local identifier for the category.

    If \a category is \c{0}, the category name is changed to \c{"default"}.
*/
QLoggingCategory::QLoggingCategory(const char *category)
    : name(0),
      enabledDebug(false),
      enabledWarning(true),
      enabledCritical(true)
{
    bool isDefaultCategory
            = (category == 0) || (strcmp(category, qtDefaultCategoryName) == 0);

    if (isDefaultCategory) {
        // normalize default category names, so that we can just do
        // pointer comparison in QLoggingRegistry::updateCategory
        name = qtDefaultCategoryName;
        enabledDebug = true;
    } else {
        name = category;
    }

    if (QLoggingRegistry *reg = QLoggingRegistry::instance())
        reg->registerCategory(this);}

/*!
    Destructs a QLoggingCategory object
*/
QLoggingCategory::~QLoggingCategory()
{
    if (QLoggingRegistry *reg = QLoggingRegistry::instance())
        reg->unregisterCategory(this);
}

/*!
   \fn const char *QLoggingCategory::categoryName() const

    Returns the name of the category.
*/

/*!
    \fn bool QLoggingCategory::isEnabled() const

    Returns true if a message of the template \c QtMsgType argument should be
    shown. Returns false otherwise.

    \note The qCDebug, qCWarning, qCCritical macros already do this check before
    executing any code. However, calling this method may be useful to avoid
    expensive generation of data that is only used for debug output.
*/

/*!
    Returns true if a message of type \a msgtype for the category should be
    shown. Returns false otherwise.

    \note The templated, inline version of this method, \l isEnabled(), is
    optimized for the common case that no configuration is set, and should
    generally be preferred.
*/
bool QLoggingCategory::isEnabled(QtMsgType msgtype) const
{
    switch (msgtype) {
    case QtDebugMsg: return enabledDebug;
    case QtWarningMsg: return enabledWarning;
    case QtCriticalMsg: return enabledCritical;
    case QtFatalMsg: return true;
    default: break;
    }
    return false;
}

/*!
    Changes the type \a type for the category to \a enable.

    Changes only affect the current QLoggingCategory object, and won't
    change e.g. the settings of another objects for the same category name.

    \note QtFatalMsg cannot be changed. It will always return true.
*/
void QLoggingCategory::setEnabled(QtMsgType type, bool enable)
{
    switch (type) {
    case QtDebugMsg: enabledDebug = enable; break;
    case QtWarningMsg: enabledWarning = enable; break;
    case QtCriticalMsg: enabledCritical = enable; break;
    case QtFatalMsg:
    default: break;
    }
}

/*!
    \fn QLoggingCategory &QLoggingCategory::operator()()

    Returns the object itself. This allows both a QLoggingCategory variable, and
    a factory method returning a QLoggingCategory, to be used in qCDebug(),
    qCWarning(), qCCritial() macros.
 */

/*!
    Returns the category "default" that is used e.g. by qDebug(), qWarning(),
    qCritical(), qFatal().
 */
QLoggingCategory &QLoggingCategory::defaultCategory()
{
    return *qtDefaultCategory();
}

/*!
    \typedef QLoggingCategory::CategoryFilter

    This is a typedef for a pointer to a function with the following
    signature:

    \snippet qloggingcategory/main.cpp 20

    A function with this signature can be installed with \l installFilter().
*/

/*!
    Installs a function \a filter that is used to determine which categories
    and message types should be enabled. Returns a pointer to the previous
    installed filter.

    Every QLoggingCategory object created is passed to the filter, and the
    filter is free to change the respective category configuration with
    \l setEnabled().

    An alternative way of configuring the default filter is via
    \l setFilterRules().
 */
QLoggingCategory::CategoryFilter
QLoggingCategory::installFilter(QLoggingCategory::CategoryFilter filter)
{
    return QLoggingRegistry::instance()->installFilter(filter);
}


/*!
    Configures which categories and message types should be enabled through a
    a set of \a rules.

    Each line in \a rules must have the format

    \code
    <category>[.<type>] = true|false
    \endcode

    where \c <category> is the name of the category, potentially with \c{*} as a
    wildcard symbol at the start and/or the end. The optional \c <type> must
    be either \c debug, \c warning, or \c critical.

    The rules might be ignored if a custom category filter is installed with
    \l installFilter().
*/
void QLoggingCategory::setFilterRules(const QString &rules)
{
    QLoggingRegistry::instance()->rulesParser.setRules(rules);
}

/*!
    \macro qCDebug(category)
    \relates QLoggingCategory
    \since 5.2

    Returns an output stream for debug messages in the logging category
    \a category.

    The macro expands to code that first checks whether
    \l QLoggingCategory::isEnabled() evaluates for debug output to \c{true}.
    If so, the stream arguments are processed and sent to the message handler.

    Example:

    \snippet qloggingcategory/main.cpp 10

    \note Arguments are not processed if debug output for the category is not
    enabled, so do not rely on any side effects.

    \sa qDebug()
*/

/*!
    \macro qCWarning(category)
    \relates QLoggingCategory
    \since 5.2

    Returns an output stream for warning messages in the logging category
    \a category.

    The macro expands to code that first checks whether
    \l QLoggingCategory::isEnabled() evaluates for warning output to \c{true}.
    If so, the stream arguments are processed and sent to the message handler.

    Example:

    \snippet qloggingcategory/main.cpp 11

    \note Arguments are not processed if warning output for the category is not
    enabled, so do not rely on any side effects.

    \sa qWarning()
*/

/*!
    \macro qCCritical(category)
    \relates QLoggingCategory
    \since 5.2

    Returns an output stream for critical messages in the logging category
    \a category.

    The macro expands to code that first checks whether
    \l QLoggingCategory::isEnabled() evaluates for critical output to \c{true}.
    If so, the stream arguments are processed and sent to the message handler.

    Example:

    \snippet qloggingcategory/main.cpp 12

    \note Arguments are not processed if critical output for the category is not
    enabled, so do not reply on any side effects.

    \sa qCritical()
*/

/*!
    \macro Q_DECLARE_LOGGING_CATEGORY(name)
    \relates QLoggingCategory
    \since 5.2

    Declares a logging category \a name. The macro can be used to declare
    a common logging category shared in different parts of the program.

    This macro must be used outside of a class or method.
*/

/*!
    \macro Q_LOGGING_CATEGORY(name, string)
    \relates QLoggingCategory
    \since 5.2

    Defines a logging category \a name, and makes it configurable under the
    \a string identifier.

    Only one translation unit in a library or executable can define a category
    with a specific name.

    This macro must be used outside of a class or method.
*/

QT_END_NAMESPACE