QChar Class

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

• List of all members, including inherited members

Note: All functions in this class are reentrant.

Public Types

Public Functions

Static Public Members

Related Non-Members

Macros

Detailed Description

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 an 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, not just for the ASCII range. 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. Some of these also calculate the derived properties (for example isSpace() returns true if the character is of category Separator_* or an exceptional code point from Other_Control category).

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

Composed Unicode characters (like ring) 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 fromLatin1(), or use QLatin1Char, to construct a QChar from an 8-bit char, and you will need to call toLatin1() to get the 8-bit value back.

Starting with Qt 6.0, most QChar constructors are explicit. This is done to avoid dangerous mistakes when accidentally mixing integral types and strings. You can opt-out (and make these constructors implicit) by defining the macro QT_IMPLICIT_QCHAR_CONSTRUCTION.

For more information see "About the Unicode Character Database".

See also Unicode, QString, and QLatin1Char.

Member Type Documentation

enum QChar::Category

This enum maps the Unicode character categories.

The following characters are normative in Unicode:

The following categories are informative in Unicode:

See also category().

enum QChar::Decomposition

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

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.

See also direction().

enum QChar::JoiningType

since 5.3

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

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

See also joiningType().

[since 5.1] enum QChar::Script

This enum type defines the Unicode script property values.

For details about the Unicode script property values see Unicode Standard Annex #24.

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

This enum was introduced or modified in Qt 5.1.

See also script().

enum QChar::SpecialCharacter

enum QChar::UnicodeVersion

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

See also unicodeVersion() and currentUnicodeVersion().

Member Function Documentation

QChar::QChar(uchar ch)

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

See also QT_NO_CAST_FROM_ASCII and QT_RESTRICTED_CAST_FROM_ASCII.

QChar::QChar(char ch)

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

See also QT_NO_CAST_FROM_ASCII.

[since 5.10] QChar::QChar(wchar_t ch)

Constructs a QChar corresponding to the wide character ch.

This function was introduced in Qt 5.10.

[since 5.10] QChar::QChar(char16_t ch)

Constructs a QChar corresponding to the UTF-16 character ch.

This function was introduced in Qt 5.10.

QChar::QChar(QLatin1Char ch)

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

QChar::QChar(QChar::SpecialCharacter ch)

Constructs a QChar for the predefined character value ch.

QChar::QChar(int 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(short code)

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

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()

Constructs a null QChar ('\0').

See also isNull().

QChar::Category QChar::category() const

Returns the character's category.

[static] QChar::Category QChar::category(char32_t ucs4)

This is an overloaded function.

Returns the category of the UCS-4-encoded character specified by ucs4.

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.

[static] unsigned char QChar::combiningClass(char32_t ucs4)

This is an overloaded function.

Returns the combining class for the UCS-4-encoded character specified by ucs4, as defined in the Unicode standard.

[static] QChar::UnicodeVersion QChar::currentUnicodeVersion()

Returns the most recent supported Unicode version.

QString QChar::decomposition() const

Decomposes a character into it's constituent parts. Returns an empty string if no decomposition exists.

[static] QString QChar::decomposition(char32_t ucs4)

This is an overloaded function.

Decomposes the UCS-4-encoded character specified by ucs4 into it's constituent parts. Returns an empty string if no decomposition exists.

QChar::Decomposition QChar::decompositionTag() const

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

[static] QChar::Decomposition QChar::decompositionTag(char32_t ucs4)

This is an overloaded function.

Returns the tag defining the composition of the UCS-4-encoded character specified by ucs4. Returns QChar::NoDecomposition if no decomposition exists.

int QChar::digitValue() const

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

[static] int QChar::digitValue(char32_t ucs4)

This is an overloaded function.

Returns the numeric value of the digit specified by the UCS-4-encoded character, ucs4, or -1 if the character is not a digit.

QChar::Direction QChar::direction() const

Returns the character's direction.

[static] QChar::Direction QChar::direction(char32_t ucs4)

This is an overloaded function.

Returns the direction of the UCS-4-encoded character specified by ucs4.

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

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

An alternative is to use QLatin1Char.

See also toLatin1() and unicode().

[static, since 6.0] QChar QChar::fromUcs2(char16_t c)

Constructs a QChar from UTF-16 character c.

This function was introduced in Qt 6.0.

See also fromUcs4().

[static, since 6.0] R QChar::fromUcs4(char32_t c)

Returns an anonymous struct that

• contains a char16_t chars[2] array,
• can be implicitly converted to a QStringView, and
• iterated over with a C++11 ranged for loop.

If c requires surrogates, chars[0] contains the high surrogate and chars[1] the low surrogate, and the QStringView has size 2. Otherwise, chars[0] contains c and chars[1] is null, and the QStringView has size 1.

This allows easy use of the result:

QString s;
s += QChar::fromUcs4(ch);

for (char16_t c16 : QChar::fromUcs4(ch))
    use(c16);

This function was introduced in Qt 6.0.

See also fromUcs2() and requiresSurrogates().

bool QChar::hasMirrored() const

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

A bit faster equivalent of (ch.mirroredChar() != ch).

See also mirroredChar().

[static, since 5.0] bool QChar::hasMirrored(char32_t ucs4)

This is an overloaded function.

Returns true if the UCS-4-encoded character specified by ucs4 should be reversed if the text direction is reversed; otherwise returns false.

A bit faster equivalent of (QChar::mirroredChar(ucs4) != ucs4).

This function was introduced in Qt 5.0.

See also mirroredChar().

[static] char16_t QChar::highSurrogate(char32_t ucs4)

Returns the high surrogate part of a UCS-4-encoded code point. The returned result is undefined if ucs4 is smaller than 0x10000.

bool QChar::isDigit() const

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

See also isNumber().

[static, since 5.0] bool QChar::isDigit(char32_t ucs4)

This is an overloaded function.

Returns true if the UCS-4-encoded character specified by ucs4 is a decimal digit (Number_DecimalDigit); otherwise returns false.

This function was introduced in Qt 5.0.

See also isNumber().

bool QChar::isHighSurrogate() const

Returns true if the QChar is the high part of a UTF16 surrogate (for example if its code point is in range [0xd800..0xdbff]); false otherwise.

[static] bool QChar::isHighSurrogate(char32_t ucs4)

This is an overloaded function.

Returns true if the UCS-4-encoded character specified by ucs4 is the high part of a UTF16 surrogate (for example if its code point is in range [0xd800..0xdbff]); false otherwise.

bool QChar::isLetter() const

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

[static, since 5.0] bool QChar::isLetter(char32_t ucs4)

This is an overloaded function.

Returns true if the UCS-4-encoded character specified by ucs4 is a letter (Letter_* categories); otherwise returns false.

This function was introduced in Qt 5.0.

bool QChar::isLetterOrNumber() const

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

[static, since 5.0] bool QChar::isLetterOrNumber(char32_t ucs4)

This is an overloaded function.

Returns true if the UCS-4-encoded character specified by ucs4 is a letter or number (Letter_* or Number_* categories); otherwise returns false.

This function was introduced in Qt 5.0.

bool QChar::isLowSurrogate() const

Returns true if the QChar is the low part of a UTF16 surrogate (for example if its code point is in range [0xdc00..0xdfff]); false otherwise.

[static] bool QChar::isLowSurrogate(char32_t ucs4)

This is an overloaded function.

Returns true if the UCS-4-encoded character specified by ucs4 is the low part of a UTF16 surrogate (for example if its code point is in range [0xdc00..0xdfff]); false otherwise.

bool QChar::isLower() const

Returns true if the character is a lowercase letter, for example category() is Letter_Lowercase.

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

[static, since 5.0] bool QChar::isLower(char32_t ucs4)

This is an overloaded function.

Returns true if the UCS-4-encoded character specified by ucs4 is a lowercase letter, for example category() is Letter_Lowercase.

This function was introduced in Qt 5.0.

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

bool QChar::isMark() const

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

See QChar::Category for more information regarding marks.

[static, since 5.0] bool QChar::isMark(char32_t ucs4)

This is an overloaded function.

Returns true if the UCS-4-encoded character specified by ucs4 is a mark (Mark_* categories); otherwise returns false.

This function was introduced in Qt 5.0.

[since 5.0] bool QChar::isNonCharacter() const

Returns true if the QChar is a non-character; false otherwise.

Unicode has a certain number of code points that are classified as "non-characters:" that is, they can be used for internal purposes in applications but cannot be used for text interchange. Those are the last two entries each Unicode Plane ([0xfffe..0xffff], [0x1fffe..0x1ffff], etc.) as well as the entries in range [0xfdd0..0xfdef].

This function was introduced in Qt 5.0.

[static, since 5.0] bool QChar::isNonCharacter(char32_t ucs4)

This is an overloaded function.

Returns true if the UCS-4-encoded character specified by ucs4 is a non-character; false otherwise.

Unicode has a certain number of code points that are classified as "non-characters:" that is, they can be used for internal purposes in applications but cannot be used for text interchange. Those are the last two entries each Unicode Plane ([0xfffe..0xffff], [0x1fffe..0x1ffff], etc.) as well as the entries in range [0xfdd0..0xfdef].

This function was introduced in Qt 5.0.

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().

[static, since 5.0] bool QChar::isNumber(char32_t ucs4)

This is an overloaded function.

Returns true if the UCS-4-encoded character specified by ucs4 is a number (Number_* categories, not just 0-9); otherwise returns false.

This function was introduced in Qt 5.0.

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 Other_*.

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

[static, since 5.0] bool QChar::isPrint(char32_t ucs4)

This is an overloaded function.

Returns true if the UCS-4-encoded character specified by ucs4 is a printable character; otherwise returns false. This is any character not of category Other_*.

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

This function was introduced in Qt 5.0.

bool QChar::isPunct() const

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

[static, since 5.0] bool QChar::isPunct(char32_t ucs4)

This is an overloaded function.

Returns true if the UCS-4-encoded character specified by ucs4 is a punctuation mark (Punctuation_* categories); otherwise returns false.

This function was introduced in Qt 5.0.

bool QChar::isSpace() const

Returns true if the character is a separator character (Separator_* categories or certain code points from Other_Control category); otherwise returns false.

[static, since 5.0] bool QChar::isSpace(char32_t ucs4)

This is an overloaded function.

Returns true if the UCS-4-encoded character specified by ucs4 is a separator character (Separator_* categories or certain code points from Other_Control category); otherwise returns false.

This function was introduced in Qt 5.0.

[since 5.0] bool QChar::isSurrogate() const

Returns true if the QChar contains a code point that is in either the high or the low part of the UTF-16 surrogate range (for example if its code point is in range [0xd800..0xdfff]); false otherwise.

This function was introduced in Qt 5.0.

[static, since 5.0] bool QChar::isSurrogate(char32_t ucs4)

This is an overloaded function.

Returns true if the UCS-4-encoded character specified by ucs4 contains a code point that is in either the high or the low part of the UTF-16 surrogate range (for example if its code point is in range [0xd800..0xdfff]); false otherwise.

This function was introduced in Qt 5.0.

bool QChar::isSymbol() const

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

[static, since 5.0] bool QChar::isSymbol(char32_t ucs4)

This is an overloaded function.

Returns true if the UCS-4-encoded character specified by ucs4 is a symbol (Symbol_* categories); otherwise returns false.

This function was introduced in Qt 5.0.

bool QChar::isTitleCase() const

Returns true if the character is a titlecase letter, for example category() is Letter_Titlecase.

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

[static, since 5.0] bool QChar::isTitleCase(char32_t ucs4)

This is an overloaded function.

Returns true if the UCS-4-encoded character specified by ucs4 is a titlecase letter, for example category() is Letter_Titlecase.

This function was introduced in Qt 5.0.

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

bool QChar::isUpper() const

Returns true if the character is an uppercase letter, for example category() is Letter_Uppercase.

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

[static, since 5.0] bool QChar::isUpper(char32_t ucs4)

This is an overloaded function.

Returns true if the UCS-4-encoded character specified by ucs4 is an uppercase letter, for example category() is Letter_Uppercase.

This function was introduced in Qt 5.0.

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

[since 5.3] QChar::JoiningType QChar::joiningType() const

Returns information about the joining type attributes of the character (needed for certain languages such as Arabic or Syriac).

This function was introduced in Qt 5.3.

[static, since 5.3] QChar::JoiningType QChar::joiningType(char32_t ucs4)

This is an overloaded function.

Returns information about the joining type attributes of the UCS-4-encoded character specified by ucs4 (needed for certain languages such as Arabic or Syriac).

This function was introduced in Qt 5.3.

[static] char16_t QChar::lowSurrogate(char32_t ucs4)

Returns the low surrogate part of a UCS-4-encoded code point. The returned result is undefined if ucs4 is smaller than 0x10000.

QChar QChar::mirroredChar() const

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

See also hasMirrored().

[static] char32_t QChar::mirroredChar(char32_t ucs4)

This is an overloaded function.

Returns the mirrored character if the UCS-4-encoded character specified by ucs4 is a mirrored character; otherwise returns the character itself.

See also hasMirrored().

[static] bool QChar::requiresSurrogates(char32_t ucs4)

Returns true if the UCS-4-encoded character specified by ucs4 can be split into the high and low parts of a UTF16 surrogate (for example if its code point is greater than or equals to 0x10000); false otherwise.

uchar QChar::row() const

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

See also cell().

[since 5.1] QChar::Script QChar::script() const

Returns the Unicode script property value for this character.

This function was introduced in Qt 5.1.

[static, since 5.1] QChar::Script QChar::script(char32_t ucs4)

This is an overloaded function.

Returns the Unicode script property value for the character specified in its UCS-4-encoded form as ucs4.

This function was introduced in Qt 5.1.

[static] char32_t QChar::surrogateToUcs4(char16_t high, char16_t low)

Converts a UTF16 surrogate pair with the given high and low values to it's UCS-4-encoded code point.

[static] char32_t QChar::surrogateToUcs4(QChar high, QChar low)

This is an overloaded function.

Converts a UTF16 surrogate pair (high, low) to it's UCS-4-encoded code point.

QChar QChar::toCaseFolded() const

Returns the case folded equivalent of the character. For most Unicode characters this is the same as toLower().

[static] char32_t QChar::toCaseFolded(char32_t ucs4)

This is an overloaded function.

Returns the case folded equivalent of the UCS-4-encoded character specified by ucs4. For most Unicode characters this is the same as toLower().

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 unicode().

QChar QChar::toLower() const

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

[static] char32_t QChar::toLower(char32_t ucs4)

This is an overloaded function.

Returns the lowercase equivalent of the UCS-4-encoded character specified by ucs4 if the character is uppercase or titlecase; otherwise returns the character itself.

QChar QChar::toTitleCase() const

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

[static] char32_t QChar::toTitleCase(char32_t ucs4)

This is an overloaded function.

Returns the title case equivalent of the UCS-4-encoded character specified by ucs4 if the character is lowercase or uppercase; otherwise returns the character itself.

QChar QChar::toUpper() const

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

[static] char32_t QChar::toUpper(char32_t ucs4)

This is an overloaded function.

Returns the uppercase equivalent of the UCS-4-encoded character specified by ucs4 if the character is lowercase or titlecase; otherwise returns the character itself.

char16_t QChar::unicode() const

Returns the numeric Unicode value of the QChar.

char16_t &QChar::unicode()

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

QChar::UnicodeVersion QChar::unicodeVersion() const

Returns the Unicode version that introduced this character.

[static] QChar::UnicodeVersion QChar::unicodeVersion(char32_t ucs4)

This is an overloaded function.

Returns the Unicode version that introduced the character specified in its UCS-4-encoded form as ucs4.

QString str = getString();
if (str == 123) {
    // Oops, meant str == "123". By default does not compile,
    // *unless* this macro is defined, in which case, it's interpreted
    // as `if (str == QChar(123))`, that is, `if (str == '{')`.
    // Likely, not what we meant.
}

QChar c1 =  'x'; // OK, unless QT_NO_CAST_FROM_ASCII is defined
QChar c2 = u'x'; // always OK, recommended
QChar c3 = QLatin1Char('x'); // always OK, recommended

// from int to 1 UTF-16 code unit: must guarantee that the input is <= 0xFFFF
QChar c4 = 120;        // compile error, unless QT_IMPLICIT_QCHAR_CONSTRUCTION is defined
QChar c5(120);         // OK (direct initialization)
auto  c6 = QChar(120); // ditto

// from int/char32_t to 1/2 UTF-16 code units:
// 𝄞 'MUSICAL SYMBOL G CLEF' (U+1D11E)
auto c7 = QChar(0x1D11E);           // compiles, but undefined behavior at runtime
auto c8 = QChar::fromUcs4(0x1D11E);       // always OK
auto c9 = QChar::fromUcs4(U'\U0001D11E'); // always OK
// => use c8/c9 as QStringView objects