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The <QtGlobal> header file provides basic declarations and is included by all other Qt headers. More...
The <QtGlobal> header file provides basic declarations and is included by all other Qt headers.
The declarations include types, functions and macros.
The type definitions are partly convenience definitions for basic types (some of which guarantee certain bit-sizes on all platforms supported by Qt), partly types related to Qt message handling. The functions are related to generating messages, Qt version handling and comparing and adjusting object values. And finally, some of the declared macros enable programmers to add compiler or platform specific code to their applications, while others are convenience macros for larger operations.
The header file declares several type definitions that guarantee a specified bit-size on all platforms supported by Qt for various basic types, for example qint8 which is a signed char guaranteed to be 8-bit on all platforms supported by Qt. The header file also declares the qlonglong type definition for long long int (__int64 on Windows).
Several convenience type definitions are declared: qreal for double, uchar for unsigned char, uint for unsigned int, ulong for unsigned long and ushort for unsigned short.
Finally, the QtMsgType definition identifies the various messages that can be generated and sent to a Qt message handler; QtMsgHandler is a type definition for a pointer to a function with the signature void myMsgHandler(QtMsgType, const char *).
The <QtGlobal> header file contains several functions comparing and adjusting an object's value. These functions take a template type as argument: You can retrieve the absolute value of an object using the qAbs() function, and you can bound a given object's value by given minimum and maximum values using the qBound() function. You can retrieve the minimum and maximum of two given objects using qMin() and qMax() respectively. All these functions return a corresponding template type; the template types can be replaced by any other type. For example:
int myValue = 10;
int minValue = 2;
int maxValue = 6;
int boundedValue = qBound(minValue, myValue, maxValue);
// boundedValue == 6
<QtGlobal> also contains functions that generate messages from the given string argument: qCritical(), qDebug(), qFatal() and qWarning(). These functions call the message handler with the given message. For example:
if (!driver()->isOpen() || driver()->isOpenError()) {
qWarning("QSqlQuery::exec: database not open");
return false;
}
The remaining functions are qRound() and qRound64(), which both accept a qreal value as their argument returning the value rounded up to the nearest integer and 64-bit integer respectively, the qInstallMsgHandler() function which installs the given QtMsgHandler, and the qVersion() function which returns the version number of Qt at run-time as a string.
The <QtGlobal> header file provides a range of macros (Q_CC_*) that are defined if the application is compiled using the specified platforms. For example, the Q_CC_SUN macro is defined if the application is compiled using Forte Developer, or Sun Studio C++. The header file also declares a range of macros (Q_OS_*) that are defined for the specified platforms. For example, Q_OS_X11 which is defined for the X Window System.
The purpose of these macros is to enable programmers to add compiler or platform specific code to their application.
The remaining macros are convenience macros for larger operations: The QT_TRANSLATE_NOOP() and QT_TR_NOOP() macros provide the possibility of marking text for dynamic translation, i.e. translation without changing the stored source text. The Q_ASSERT() and Q_ASSERT_X() enables warning messages of various level of refinement. The Q_FOREACH() and foreach() macros implement Qt's foreach loop.
The Q_INT64_C() and Q_UINT64_C() macros wrap signed and unsigned 64-bit integer literals in a platform-independent way. The Q_CHECK_PTR() macro prints a warning containing the source code's file name and line number, saying that the program ran out of memory, if the pointer is 0. The qPrintable() macro represent an easy way of printing text.
Finally, the QT_POINTER_SIZE macro expands to the size of a pointer in bytes, and the QT_VERSION and QT_VERSION_STR macros expand to a numeric value or a string, respectively, specifying Qt's version number, i.e the version the application is compiled against.
See also <QtAlgorithms> and QSysInfo.
This is a typedef for a pointer to a function with the following signature:
void myMsgHandler(QtMsgType, const char *);
See also QtMsgType and qInstallMsgHandler().
This enum describes the messages that can be sent to a message handler (QtMsgHandler). You can use the enum to identify and associate the various message types with the appropiate actions.
| Constant | Value | Description |
|---|---|---|
| QtDebugMsg | 0 | A message generated by the qDebug() function. |
| QtWarningMsg | 1 | A message generated by the qWarning() function. |
| QtCriticalMsg | 2 | A message generated by the qCritical() function. |
| QtFatalMsg | 3 | A message generated by the qFatal() function. |
| QtSystemMsg | QtCriticalMsg |
See also QtMsgHandler and qInstallMsgHandler().
Typedef for signed char. This type is guaranteed to be 8-bit on all platforms supported by Qt.
Typedef for signed short. This type is guaranteed to be 16-bit on all platforms supported by Qt.
Typedef for signed int. This type is guaranteed to be 32-bit on all platforms supported by Qt.
Typedef for long long int (__int64 on Windows). This type is guaranteed to be 64-bit on all platforms supported by Qt.
Literals of this type can be created using the Q_INT64_C() macro:
qint64 value = Q_INT64_C(932838457459459);
See also Q_INT64_C(), quint64, and qlonglong.
Typedef for long long int (__int64 on Windows). This is the same as qint64.
See also qulonglong and qint64.
Typedef for double.
Typedef for unsigned char. This type is guaranteed to be 8-bit on all platforms supported by Qt.
Typedef for unsigned short. This type is guaranteed to be 16-bit on all platforms supported by Qt.
Typedef for unsigned int. This type is guaranteed to be 32-bit on all platforms supported by Qt.
Typedef for unsigned long long int (unsigned __int64 on Windows). This type is guaranteed to be 64-bit on all platforms supported by Qt.
Literals of this type can be created using the Q_UINT64_C() macro:
quint64 value = Q_UINT64_C(932838457459459);
See also Q_UINT64_C(), qint64, and qulonglong.
Typedef for unsigned long long int (unsigned __int64 on Windows). This is the same as quint64.
See also quint64 and qlonglong.
Convenience typedef for unsigned char.
Convenience typedef for unsigned int.
Convenience typedef for unsigned long.
Convenience typedef for unsigned short.
Returns the absolute value of value. For example:
int absoluteValue;
int myValue = -4;
absoluteValue = qAbs(myValue);
// absoluteValue == 4
Returns value bounded by min and max. This is equivalent to qMax(min, qMin(value, max)). For example:
int myValue = 10;
int minValue = 2;
int maxValue = 6;
int boundedValue = qBound(minValue, myValue, maxValue);
// boundedValue == 6
Calls the message handler with the critical message msg. If no message handler has been installed, the message is printed to stderr. Under Windows, the message is sent to the debugger.
This function takes a format string and a list of arguments, similar to the C printf() function.
Example:
void load(const QString &fileName)
{
QFile file(fileName);
if (!file.exists())
qCritical("File '%s' does not exist!", qPrintable(fileName));
}
Warning: The internal buffer is limited to 8192 bytes, including the '\0'-terminator.
Warning: Passing (const char *)0 as argument to qCritical might lead to crashes on certain platforms due to the platforms printf implementation.
See also qDebug(), qWarning(), qFatal(), qInstallMsgHandler(), and Debugging Techniques.
Calls the message handler with the debug message msg. If no message handler has been installed, the message is printed to stderr. Under Windows, the message is sent to the debugger. This function does nothing if QT_NO_DEBUG_OUTPUT was defined during compilation.
If you pass the function a format string and a list of arguments, it works in similar way to the C printf() function.
Example:
qDebug("Items in list: %d", myList.size());
If you include <QtDebug>, a more convenient syntax is also available:
qDebug() << "Brush:" << myQBrush << "Other value:" << i;
This syntax automatically puts a single space between each item, and outputs a newline at the end. It supports many C++ and Qt types.
Warning: The internal buffer is limited to 8192 bytes, including the '\0'-terminator.
Warning: Passing (const char *)0 as argument to qDebug might lead to crashes on certain platforms due to the platform's printf() implementation.
See also qWarning(), qCritical(), qFatal(), qInstallMsgHandler(), and Debugging Techniques.
Calls the message handler with the fatal message msg. If no message handler has been installed, the message is printed to stderr. Under Windows, the message is sent to the debugger.
For a release library this function will exit the application with return value 1. For the debug version this function will abort on Unix systems to create a core dump, and report a _CRT_ERROR on Windows allowing to connect a debugger to the application.
This function takes a format string and a list of arguments, similar to the C printf() function.
Example:
int divide(int a, int b)
{
if (b == 0) // program error
qFatal("divide: cannot divide by zero");
return a / b;
}
Warning: The internal buffer is limited to 8192 bytes, including the '\0'-terminator.
Warning: Passing (const char *)0 as argument to qFatal might lead to crashes on certain platforms due to the platforms printf implementation.
See also qDebug(), qCritical(), qWarning(), qInstallMsgHandler(), and Debugging Techniques.
Installs a Qt message handler whis has been defined previously. Returns a pointer to the message handler.
The message handler is a function that prints out debug messages, warnings, critical and fatal error messages. The Qt library (debug version) contains hundreds of warning messages that are printed when internal errors (usually invalid function arguments) occur. If you implement your own message handler, you get total control of these messages.
The default message handler prints the message to the standard output under X11 or to the debugger under Windows. If it is a fatal message, the application aborts immediately.
Only one message handler can be defined, since this is usually done on an application-wide basis to control debug output.
To restore the message handler, call qInstallMsgHandler(0).
Example:
#include <qapplication.h>
#include <stdio.h>
#include <stdlib.h>
void myMessageOutput(QtMsgType type, const char *msg)
{
switch (type) {
case QtDebugMsg:
fprintf(stderr, "Debug: %s\n", msg);
break;
case QtWarningMsg:
fprintf(stderr, "Warning: %s\n", msg);
break;
case QtCriticalMsg:
fprintf(stderr, "Critical: %s\n", msg);
break;
case QtFatalMsg:
fprintf(stderr, "Fatal: %s\n", msg);
abort();
}
}
int main(int argc, char **argv)
{
qInstallMsgHandler(myMessageOutput);
QApplication app(argc, argv);
...
return app.exec();
}
See also qDebug(), qWarning(), qCritical(), qFatal(), QtMsgType, and Debugging Techniques.
Use QSysInfo::MacintoshVersion instead.
See also QSysInfo.
Returns the maximum of value1 and value2. For example:
int myValue = 6;
int yourValue = 4;
int maxValue = qMax(myValue, yourValue);
// maxValue == myValue
Returns the minimum of value1 and value2. For example:
int myValue = 6;
int yourValue = 4;
int minValue = qMin(myValue, yourValue);
// minValue == yourValue
Rounds value to the nearest 64-bit integer. For example:
qreal valueA = 42949672960.3;
qreal valueB = 42949672960.7;
int roundedValueA = qRound(valueA);
\\ roundedValueA = 42949672960
int roundedValueB = qRound(valueB);
\\ roundedValueB = 42949672961
Rounds value to the nearest integer. For example:
qreal valueA = 2.3;
qreal valueB = 2.7;
int roundedValueA = qRound(valueA);
\\ roundedValueA = 2
int roundedValueB = qRound(valueB);
\\ roundedValueB = 3
Returns the version number of Qt at run-time as a string (for example, "4.1.2"). This may be a different version than the version the application was compiled against.
See also QT_VERSION_STR.
Calls the message handler with the warning message msg. If no message handler has been installed, the message is printed to stderr. Under Windows, the message is sent to the debugger. This function does nothing if QT_NO_WARNING_OUTPUT was defined during compilation; it exits if the environment variable QT_FATAL_WARNINGS is defined.
This function takes a format string and a list of arguments, similar to the C printf() function.
Example:
void f(int c)
{
if (c > 200)
qWarning("f: bad argument, c == %d", c);
}
Warning: The internal buffer is limited to 8192 bytes, including the '\0'-terminator.
Warning: Passing (const char *)0 as argument to qWarning might lead to crashes on certain platforms due to the platforms printf implementation.
See also qDebug(), qCritical(), qFatal(), qInstallMsgHandler(), and Debugging Techniques.
Expands to the size of a pointer in bytes (4 or 8). This is equivalent to sizeof(void *) but can be used in a preprocessor directive.
Marks the string literal sourceText for dynamic translation in the given context, i.e the stored sourceText will not be altered. The context is typically a class. For example:
static const char *greeting_strings[] = {
QT_TRANSLATE_NOOP("FriendlyConversation", "Hello"),
QT_TRANSLATE_NOOP("FriendlyConversation", "Goodbye")
};
QString FriendlyConversation::greeting(int type)
{
return tr(greeting_strings[type]);
}
QString global_greeting(int type)
{
return qApp->translate("FriendlyConversation",
greeting_strings[type]);
}
The macro expands to sourceText.
See also QT_TR_NOOP() and Internationalization with Qt.
Marks the string literal sourceText for dynamic translation in the current context (class), i.e the stored sourceText will not be altered. For example:
QString FriendlyConversation::greeting(int type)
{
static const char *greeting_strings[] = {
QT_TR_NOOP("Hello"),
QT_TR_NOOP("Goodbye")
};
return tr(greeting_strings[type]);
}
The macro expands to sourceText.
See also QT_TRANSLATE_NOOP() and Internationalization with Qt.
This macro expands a numeric value of the form 0xMMNNPP (MM = major, NN = minor, PP = patch) that specifies Qt's version number. For example, if you compile your application against Qt 4.1.2, the QT_VERSION macro will expand to 0x040102.
You can use QT_VERSION to use the latest Qt features where available. For example:
#if QT_VERSION >= 0x040100
QIcon icon = style()->standardIcon(QStyle::SP_TrashIcon);
#else
QPixmap pixmap = style()->standardPixmap(QStyle::SP_TrashIcon);
QIcon icon(pixmap);
#endif
See also QT_VERSION_STR and qVersion().
This macro expands to a string that specifies Qt's version number (for example, "4.1.2"). This is the version against which the application is compiled.
See also qVersion() and QT_VERSION.
Prints a warning message containing the source code file name and line number if test is false.
Q_ASSERT() is useful for testing pre- and post-conditions during development. It does nothing if QT_NO_DEBUG was defined during compilation.
Example:
// File: div.cpp
#include <QtGlobal>
int divide(int a, int b)
{
Q_ASSERT(b != 0);
return a / b;
}
If b is zero, the Q_ASSERT statement will output the following message using the qFatal() function:
ASSERT: "b == 0" in file div.cpp, line 7
See also Q_ASSERT_X(), qFatal(), and Debugging Techniques.
Prints the message what together with the location where, the source file name and line number if test is false.
Q_ASSERT_X is useful for testing pre- and post-conditions during development. It does nothing if QT_NO_DEBUG was defined during compilation.
Example:
// File: div.cpp
#include <QtGlobal>
int divide(int a, int b)
{
Q_ASSERT_X(b != 0, "divide", "division by zero");
return a / b;
}
If b is zero, the Q_ASSERT_X statement will output the following message using the qFatal() function:
ASSERT failure in divide: "division by zero", file div.cpp, line 7
See also Q_ASSERT(), qFatal(), and Debugging Techniques.
Defined if the application is compiled using Borland/Turbo C++.
Defined if the application is compiled using Reliant C++.
Defined if the application is compiled using Comeau C++.
Defined if the application is compiled using DEC C++.
Defined if the application is compiled using Edison Design Group C++.
Defined if the application is compiled using Green Hills Optimizing C++ Compilers.
Defined if the application is compiled using GNU C++.
Defined if the application is compiled using MetaWare High C/C++.
Defined if the application is compiled using HP aC++.
Defined if the application is compiled using Intel C++ for Linux, Intel C++ for Windows.
Defined if the application is compiled using KAI C++.
Defined if the application is compiled using MIPSpro C++.
Defined if the application is compiled using Microsoft Visual C/C++, Intel C++ for Windows.
Defined if the application is compiled using Metrowerks CodeWarrior.
Defined if the application is compiled using CenterLine C++.
Defined if the application is compiled using Portland Group C++.
Defined if the application is compiled using Forte Developer, or Sun Studio C++.
Defined if the application is compiled using Digital Mars C/C++ (used to be Symantec C++).
Defined if the application is compiled using SCO OUDK and UDK.
Defined if the application is compiled using Watcom C++.
If pointer is 0, prints a warning message containing the source code's file name and line number, saying that the program ran out of memory.
Q_CHECK_PTR does nothing if QT_NO_DEBUG was defined during compilation.
Example:
int *a;
Q_CHECK_PTR(a = new int[80]); // WRONG!
a = new (nothrow) int[80]; // Right
Q_CHECK_PTR(a);
See also qWarning() and Debugging Techniques.
You can use this macro to specify information about a custom type Type. With accurate type information, Qt's generic containers can choose appropriate storage methods and algorithms.
Flags can be one of the following:
Example of a "primitive" type:
struct Point2D
{
int x;
int y;
};
Q_DECLARE_TYPEINFO(Point2D, Q_PRIMITIVE_TYPE);
Example of a movable type:
class Point2D
{
public:
Point2D() { data = new int[2]; }
Point2D(const Point2D &other) { ... }
~Point2D() { delete[] data; }
Point2D &operator=(const Point2D &other) { ... }
int x() const { return data[0]; }
int y() const { return data[1]; }
private:
int *data;
};
Q_DECLARE_TYPEINFO(Point2D, Q_MOVABLE_TYPE);
Same as foreach(variable, container).
This macro is available even when no_keywords is specified using the .pro file's CONFIG variable.
See also foreach().
Same as forever.
This macro is available even when no_keywords is specified using the .pro file's CONFIG variable.
See also foreach().
Wraps the signed 64-bit integer literal in a platform-independent way. For example:
qint64 value = Q_INT64_C(932838457459459);
See also qint64 and Q_UINT64_C().
Defined on AIX.
Defined on Any BSD 4.4 system.
Defined on BSD/OS.
Defined on Cygwin.
Defined on Darwin OS (synonym for Q_OS_MAC).
Defined on DG/UX.
Defined on DYNIX/ptx.
Defined on FreeBSD.
Defined on HP-UX.
Defined on GNU Hurd.
Defined on SGI Irix.
Defined on Linux.
Defined on LynxOS.
Defined on MS-DOS and Windows.
Defined on NetBSD.
Defined on OS/2.
Defined on OpenBSD.
Defined on XFree86 on OS/2 (not PM).
Defined on HP Tru64 UNIX.
Defined on QNX RTP 6.1.
Defined on QNX.
Defined on Reliant UNIX.
Defined on SCO OpenServer 5.
Defined on Sun Solaris.
Defined on DEC Ultrix.
Defined on Any UNIX BSD/SYSV system.
Defined on UnixWare 7, Open UNIX 8.
Defined on Win32 (Windows 98/ME and Windows NT/2000/XP).
Wraps the unsigned 64-bit integer literal in a platform-independent way. For example:
quint64 value = Q_UINT64_C(932838457459459);
See also quint64 and Q_INT64_C().
Indicates to the compiler that the parameter with the specified name is not used in the body of a function. This can be used to suppress compiler warnings while allowing functions to be defined with meaningful parameter names in their signatures.
Defined on X11.
See also Q_WS_MAC, Q_WS_WIN, and Q_WS_QWS.
Defined on Mac OS X.
See also Q_WS_WIN, Q_WS_X11, and Q_WS_QWS.
Defined on Qtopia Core.
See also Q_WS_MAC, Q_WS_WIN, and Q_WS_X11.
Defined on Windows.
See also Q_WS_MAC, Q_WS_X11, and Q_WS_QWS.
This macro is used to implement Qt's foreach loop. The variable parameter is a variable name or variable definition; the container parameter is a Qt container whose value type corresponds to the type of the variable. See The foreach Keyword for details.
If you're worried about namespace pollution, you can disable this macro by adding the following line to your .pro file:
CONFIG += no_keywords
See also Q_FOREACH().
This macro is provided for convenience for writing infinite loops.
Example:
forever {
...
}
It is equivalent to for (;;).
If you're worried about namespace pollution, you can disable this macro by adding the following line to your .pro file:
CONFIG += no_keywords
See also Q_FOREVER.
Returns str as a const char *. This is equivalent to str.toLocal8bit().constData().
Example:
qWarning("%s: %s", qPrintable(key), qPrintable(value));
See also qDebug(), qWarning(), qCritical(), and qFatal().
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