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QChar Class Reference
[QtCore module]

The QChar class provides a 16-bit Unicode character. More...

#include <QChar>

Note: All the functions in this class are reentrant.

Public Types

  • enum Category { Mark_NonSpacing, Mark_SpacingCombining, Mark_Enclosing, Number_DecimalDigit, ..., NoCategory }
  • enum Decomposition { NoDecomposition, Canonical, Circle, Compat, ..., Wide }
  • enum Direction { DirAL, DirAN, DirB, DirBN, ..., DirWS }
  • enum Joining { Center, Dual, OtherJoining, Right }
  • enum SpecialCharacter { Null, Nbsp, ReplacementCharacter, ObjectReplacementCharacter, ..., LineSeparator }
  • enum UnicodeVersion { Unicode_1_1, Unicode_2_0, Unicode_2_1_2, Unicode_3_0, ..., Unicode_Unassigned }

Public Functions

Static Public Members

Related Non-Members


Detailed Description

The QChar class provides a 16-bit Unicode character.

In Qt, Unicode characters are 16-bit entities without any markup or structure. This class represents such an entity. It is lightweight, so it can be used everywhere. Most compilers treat it like a unsigned short.

QChar provides a full complement of testing/classification functions, converting to and from other formats, converting from composed to decomposed Unicode, and trying to compare and case-convert if you ask it to.

The classification functions include functions like those in the standard C++ header <cctype> (formerly <ctype.h>), but operating on the full range of Unicode characters. They all return true if the character is a certain type of character; otherwise they return false. These classification functions are isNull() (returns true if the character is '\0'), isPrint() (true if the character is any sort of printable character, including whitespace), isPunct() (any sort of punctation), isMark() (Unicode Mark), isLetter() (a letter), isNumber() (any sort of numeric character, not just 0-9), isLetterOrNumber(), and isDigit() (decimal digits). All of these are wrappers around category() which return the Unicode-defined category of each character.

QChar also provides direction(), which indicates the "natural" writing direction of this character. The joining() function indicates how the character joins with its neighbors (needed mostly for Arabic) and finally hasMirrored(), which indicates whether the character needs to be mirrored when it is printed in its "unnatural" writing direction.

Composed Unicode characters (like å) can be converted to decomposed Unicode ("a" followed by "ring above") by using decomposition().

In Unicode, comparison is not necessarily possible and case conversion is very difficult at best. Unicode, covering the "entire" world, also includes most of the world's case and sorting problems. operator==() and friends will do comparison based purely on the numeric Unicode value (code point) of the characters, and toUpper() and toLower() will do case changes when the character has a well-defined uppercase/lowercase equivalent. For locale-dependent comparisons, use QString::localeAwareCompare().

The conversion functions include unicode() (to a scalar), toLatin1() (to scalar, but converts all non-Latin-1 characters to 0), row() (gives the Unicode row), cell() (gives the Unicode cell), digitValue() (gives the integer value of any of the numerous digit characters), and a host of constructors.

QChar provides constructors and cast operators that make it easy to convert to and from traditional 8-bit chars. If you defined QT_NO_CAST_FROM_ASCII and QT_NO_CAST_TO_ASCII, as explained in the QString documentation, you will need to explicitly call fromAscii() or fromLatin1(), or use QLatin1Char, to construct a QChar from an 8-bit char, and you will need to call toAscii() or toLatin1() to get the 8-bit value back.

See also QString, Unicode, and QLatin1Char.


Member Type Documentation

enum QChar::Category

This enum maps the Unicode character categories.

The following characters are normative in Unicode:

ConstantValueDescription
QChar::Mark_NonSpacing1Unicode class name Mn
QChar::Mark_SpacingCombining2Unicode class name Mc
QChar::Mark_Enclosing3Unicode class name Me
QChar::Number_DecimalDigit4Unicode class name Nd
QChar::Number_Letter5Unicode class name Nl
QChar::Number_Other6Unicode class name No
QChar::Separator_Space7Unicode class name Zs
QChar::Separator_Line8Unicode class name Zl
QChar::Separator_Paragraph9Unicode class name Zp
QChar::Other_Control10Unicode class name Cc
QChar::Other_Format11Unicode class name Cf
QChar::Other_Surrogate12Unicode class name Cs
QChar::Other_PrivateUse13Unicode class name Co
QChar::Other_NotAssigned14Unicode class name Cn

The following categories are informative in Unicode:

ConstantValueDescription
QChar::Letter_Uppercase15Unicode class name Lu
QChar::Letter_Lowercase16Unicode class name Ll
QChar::Letter_Titlecase17Unicode class name Lt
QChar::Letter_Modifier18Unicode class name Lm
QChar::Letter_Other19Unicode class name Lo
QChar::Punctuation_Connector20Unicode class name Pc
QChar::Punctuation_Dash21Unicode class name Pd
QChar::Punctuation_Open22Unicode class name Ps
QChar::Punctuation_Close23Unicode class name Pe
QChar::Punctuation_InitialQuote24Unicode class name Pi
QChar::Punctuation_FinalQuote25Unicode class name Pf
QChar::Punctuation_Other26Unicode class name Po
QChar::Symbol_Math27Unicode class name Sm
QChar::Symbol_Currency28Unicode class name Sc
QChar::Symbol_Modifier29Unicode class name Sk
QChar::Symbol_Other30Unicode class name So
QChar::NoCategory0Qt cannot find an appropriate category for the character.

See also category().

enum QChar::Decomposition

This enum type defines the Unicode decomposition attributes. See the Unicode Standard for a description of the values.

ConstantValue
QChar::NoDecomposition0
QChar::Canonical1
QChar::Circle8
QChar::Compat16
QChar::Final6
QChar::Font2
QChar::Fraction17
QChar::Initial4
QChar::Isolated7
QChar::Medial5
QChar::Narrow13
QChar::NoBreak3
QChar::Small14
QChar::Square15
QChar::Sub10
QChar::Super9
QChar::Vertical11
QChar::Wide12

See also decomposition().

enum QChar::Direction

This enum type defines the Unicode direction attributes. See the Unicode Standard for a description of the values.

In order to conform to C/C++ naming conventions "Dir" is prepended to the codes used in the Unicode Standard.

ConstantValue
QChar::DirAL13
QChar::DirAN5
QChar::DirB7
QChar::DirBN18
QChar::DirCS6
QChar::DirEN2
QChar::DirES3
QChar::DirET4
QChar::DirL0
QChar::DirLRE11
QChar::DirLRO12
QChar::DirNSM17
QChar::DirON10
QChar::DirPDF16
QChar::DirR1
QChar::DirRLE14
QChar::DirRLO15
QChar::DirS8
QChar::DirWS9

See also direction().

enum QChar::Joining

This enum type defines the Unicode joining attributes. See the Unicode Standard for a description of the values.

ConstantValue
QChar::Center3
QChar::Dual1
QChar::OtherJoining0
QChar::Right2

See also joining().

enum QChar::SpecialCharacter

ConstantValueDescription
QChar::Null0x0000A QChar with this value isNull().
QChar::Nbsp0x00a0Non-breaking space.
QChar::ReplacementCharacter0xfffd 
QChar::ObjectReplacementCharacter0xfffc 
QChar::ByteOrderMark0xfeff 
QChar::ByteOrderSwapped0xfffe 
QChar::ParagraphSeparator0x2029 
QChar::LineSeparator0x2028 

enum QChar::UnicodeVersion

Specifies which version of the Unicode standard introduced a certain character.

ConstantValueDescription
QChar::Unicode_1_11Version 1.1.
QChar::Unicode_2_02Version 2.0.
QChar::Unicode_2_1_23Version 2.1.2.
QChar::Unicode_3_04Version 3.0.
QChar::Unicode_3_15Version 3.1.
QChar::Unicode_3_26Version 3.2.
QChar::Unicode_4_07Version 4.0.
QChar::Unicode_Unassigned0The value is not assigned to any character in version 4.0 of Unicode.

See also unicodeVersion().


Member Function Documentation

QChar::QChar ()

Constructs a null QChar ('\0').

See also isNull().

QChar::QChar ( char ch )

Constructs a QChar corresponding to ASCII/Latin-1 character ch.

QChar::QChar ( uchar ch )

Constructs a QChar corresponding to ASCII/Latin-1 character ch.

QChar::QChar ( QLatin1Char ch )

Constructs a QChar corresponding to ASCII/Latin-1 character ch.

QChar::QChar ( uchar cell, uchar row )

Constructs a QChar for Unicode cell cell in row row.

See also cell() and row().

QChar::QChar ( ushort code )

Constructs a QChar for the character with Unicode code point code.

QChar::QChar ( short code )

Constructs a QChar for the character with Unicode code point code.

QChar::QChar ( uint code )

Constructs a QChar for the character with Unicode code point code.

QChar::QChar ( int code )

Constructs a QChar for the character with Unicode code point code.

QChar::QChar ( SpecialCharacter ch )

Constructs a QChar for the predefined character value ch.

Category QChar::category () const

Returns the character's category.

uchar QChar::cell () const

Returns the cell (least significant byte) of the Unicode character.

See also row().

unsigned char QChar::combiningClass () const

Returns the combining class for the character as defined in the Unicode standard. This is mainly useful as a positioning hint for marks attached to a base character.

The Qt text rendering engine uses this information to correctly position non-spacing marks around a base character.

QString QChar::decomposition () const

Decomposes a character into its parts. Returns an empty string if no decomposition exists.

Decomposition QChar::decompositionTag () const

Returns the tag defining the composition of the character. Returns QChar::Single if no decomposition exists.

int QChar::digitValue () const

Returns the numeric value of the digit, or -1 if the character is not a digit.

Direction QChar::direction () const

Returns the character's direction.

QChar QChar::fromAscii ( char c )   [static]

Converts the ASCII character c to its equivalent QChar. This is mainly useful for non-internationalized software.

An alternative is to use QLatin1Char.

See also fromLatin1(), unicode(), and QTextCodec::codecForCStrings().

QChar QChar::fromLatin1 ( char c )   [static]

Converts the Latin-1 character c to its equivalent QChar. This is mainly useful for non-internationalized software.

See also fromAscii(), unicode(), and QTextCodec::codecForCStrings().

bool QChar::hasMirrored () const

Returns true if the character should be reversed if the text direction is reversed; otherwise returns false.

See also mirroredChar().

bool QChar::isDigit () const

Returns true if the character is a decimal digit (Number_DecimalDigit); otherwise returns false.

bool QChar::isLetter () const

Returns true if the character is a letter (Letter_* categories); otherwise returns false.

bool QChar::isLetterOrNumber () const

Returns true if the character is a letter or number (Letter_* or Number_* categories); otherwise returns false.

bool QChar::isLower () const

Returns true if the character is a lowercase letter, i.e. category() is Letter_Lowercase.

See also isUpper(), toLower(), and toUpper().

bool QChar::isMark () const

Returns true if the character is a mark (Mark_* categories); otherwise returns false.

bool QChar::isNull () const

Returns true if the character is the Unicode character 0x0000 ('\0'); otherwise returns false.

bool QChar::isNumber () const

Returns true if the character is a number (Number_* categories, not just 0-9); otherwise returns false.

See also isDigit().

bool QChar::isPrint () const

Returns true if the character is a printable character; otherwise returns false. This is any character not of category Cc or Cn.

Note that this gives no indication of whether the character is available in a particular font.

bool QChar::isPunct () const

Returns true if the character is a punctuation mark (Punctuation_* categories); otherwise returns false.

bool QChar::isSpace () const

Returns true if the character is a separator character (Separator_* categories); otherwise returns false.

bool QChar::isSymbol () const

Returns true if the character is a symbol (Symbol_* categories); otherwise returns false.

bool QChar::isUpper () const

Returns true if the character is an uppercase letter, i.e. category() is Letter_Uppercase.

See also isLower(), toUpper(), and toLower().

Joining QChar::joining () const

This function is under development and is subject to change.

Returns information about the joining properties of the character (needed for certain languages such as Arabic).

QChar QChar::mirroredChar () const

Returns the mirrored character if this character is a mirrored character; otherwise returns the character itself.

See also hasMirrored().

uchar QChar::row () const

Returns the row (most significant byte) of the Unicode character.

See also cell().

const char QChar::toAscii () const

Returns the character value of the QChar obtained using the current codec used to read C strings, or 0 if the character is not representable using this codec. The default codec handles Latin-1 encoded text, but this can be changed to assist developers writing source code using other encodings.

The main purpose of this function is to preserve ASCII characters used in C strings. This is mainly useful for developers of non-internationalized software.

See also toLatin1(), unicode(), and QTextCodec::codecForCStrings().

const char QChar::toLatin1 () const

Returns the Latin-1 character equivalent to the QChar, or 0. This is mainly useful for non-internationalized software.

See also toAscii(), unicode(), and QTextCodec::codecForCStrings().

QChar QChar::toLower () const

Returns the lowercase equivalent if the character is uppercase; otherwise returns the character itself.

QChar QChar::toUpper () const

Returns the uppercase equivalent if the character is lowercase; otherwise returns the character itself.

ushort & QChar::unicode ()

Returns a reference to the numberic Unicode value of the QChar.

const ushort QChar::unicode () const

This is an overloaded member function, provided for convenience.

UnicodeVersion QChar::unicodeVersion () const

Returns the Unicode version that introduced this character.


Related Non-Members

bool operator!= ( QChar c1, QChar c2 )

This is an overloaded member function, provided for convenience.

Returns true if c1 and c2 are not the same Unicode character; otherwise returns false.

bool operator< ( QChar c1, QChar c2 )

Returns true if the numeric Unicode value of c1 is less than that of c2; otherwise returns false.

QDataStream & operator<< ( QDataStream & out, const QChar & chr )

This is an overloaded member function, provided for convenience.

Writes the char chr to the stream out.

See also Format of the QDataStream operators.

bool operator<= ( QChar c1, QChar c2 )

Returns true if the numeric Unicode value of c1 is less than or equal to that of c2; otherwise returns false.

bool operator== ( QChar c1, QChar c2 )

This is an overloaded member function, provided for convenience.

Returns true if c1 and c2 are the same Unicode character; otherwise returns false.

bool operator> ( QChar c1, QChar c2 )

Returns true if the numeric Unicode value of c1 is greater than that of c2; otherwise returns false.

bool operator>= ( QChar c1, QChar c2 )

Returns true if the numeric Unicode value of c1 is greater than or equal to that of c2; otherwise returns false.

QDataStream & operator>> ( QDataStream & in, QChar & chr )

This is an overloaded member function, provided for convenience.

Reads a char from the stream in into char chr.

See also Format of the QDataStream operators.

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