Detailed Description
The QChar class provides a lightweight Unicode character.
Unicode characters are (so far) 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 "short int". (In a few years it may be necessary to make
QChar 32-bit when more than 65536 Unicode code points have been
defined and come into use.)
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
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 U+0000),
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), isLetterOrNumber(),
and isDigit() (decimal digits). All of these are wrappers around
category() which return the Unicode-defined category of each
character.
QChar further 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 mirrored(), 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. Qt tries, but not very hard: operator==() and friends
will do comparison based purely on the numeric Unicode value (code
point) of the characters, and upper() and lower() will do case
changes when the character has a well-defined upper/lower-case
equivalent. There is no provision for locale-dependent case
folding rules or comparison; these functions are meant to be fast
so they can be used unambiguously in data structures. (See
QString::localeAwareCompare() though.)
The conversion functions include unicode() (to a scalar), latin1()
(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.
More information can be found in the document About Unicode.
See also QString, QCharRef, and Text Related Classes.
Member Type Documentation
QChar::Category
This enum maps the Unicode character categories.
The following characters are normative in Unicode:
- QChar::Mark_NonSpacing - Unicode class name Mn
- QChar::Mark_SpacingCombining - Unicode class name Mc
- QChar::Mark_Enclosing - Unicode class name Me
- QChar::Number_DecimalDigit - Unicode class name Nd
- QChar::Number_Letter - Unicode class name Nl
- QChar::Number_Other - Unicode class name No
- QChar::Separator_Space - Unicode class name Zs
- QChar::Separator_Line - Unicode class name Zl
- QChar::Separator_Paragraph - Unicode class name Zp
- QChar::Other_Control - Unicode class name Cc
- QChar::Other_Format - Unicode class name Cf
- QChar::Other_Surrogate - Unicode class name Cs
- QChar::Other_PrivateUse - Unicode class name Co
- QChar::Other_NotAssigned - Unicode class name Cn
The following categories are informative in Unicode:
- QChar::Letter_Uppercase - Unicode class name Lu
- QChar::Letter_Lowercase - Unicode class name Ll
- QChar::Letter_Titlecase - Unicode class name Lt
- QChar::Letter_Modifier - Unicode class name Lm
- QChar::Letter_Other - Unicode class name Lo
- QChar::Punctuation_Connector - Unicode class name Pc
- QChar::Punctuation_Dash - Unicode class name Pd
- QChar::Punctuation_Open - Unicode class name Ps
- QChar::Punctuation_Close - Unicode class name Pe
- QChar::Punctuation_InitialQuote - Unicode class name Pi
- QChar::Punctuation_FinalQuote - Unicode class name Pf
- QChar::Punctuation_Other - Unicode class name Po
- QChar::Symbol_Math - Unicode class name Sm
- QChar::Symbol_Currency - Unicode class name Sc
- QChar::Symbol_Modifier - Unicode class name Sk
- QChar::Symbol_Other - Unicode class name So
There are two categories that are specific to Qt:
- QChar::NoCategory - used when Qt is dazed and confused and cannot
make sense of anything.
- QChar::Punctuation_Dask - old typo alias for Punctuation_Dash
QChar::CombiningClass
This enum type defines names for some of the Unicode combining
classes. See the Unicode
Standard for a description of the values.
QChar::Decomposition
This enum type defines the Unicode decomposition attributes. See
the Unicode Standard for a
description of the values.
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.
QChar::Joining
This enum type defines the Unicode joining attributes. See the Unicode Standard for a
description of the values.
Member Function Documentation
QChar::QChar ()
Constructs a null QChar (one that isNull()).
QChar::QChar ( char c )
Constructs a QChar corresponding to ASCII/Latin-1 character c.
QChar::QChar ( uchar c )
Constructs a QChar corresponding to ASCII/Latin-1 character c.
QChar::QChar ( uchar c, uchar r )
Constructs a QChar for Unicode cell c in row r.
QChar::QChar ( const QChar & c )
Constructs a copy of c. This is a deep copy, if such a
lightweight object can be said to have deep copies.
QChar::QChar ( ushort rc )
Constructs a QChar for the character with Unicode code point rc.
QChar::QChar ( short rc )
Constructs a QChar for the character with Unicode code point rc.
QChar::QChar ( uint rc )
Constructs a QChar for the character with Unicode code point rc.
QChar::QChar ( int rc )
Constructs a QChar for the character with Unicode code point rc.
Category QChar::category () const
Returns the character category.
See also Category.
uchar QChar::cell () const
Returns the cell (least significant byte) of the Unicode
character.
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.
const QString & QChar::decomposition () const
Warning: This function is not reentrant.
Decomposes a character into its parts. Returns QString::null 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.
See also Direction.
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::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
(ASCII NUL); otherwise returns FALSE.
bool QChar::isNumber () const
Returns TRUE if the character is a number (of any sort - Number_*
categories); 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.
Joining QChar::joining () const
Warning: This function is not supported (it may change to use
Unicode character classes).
Returns information about the joining properties of the character
(needed for example, for Arabic).
char QChar::latin1 () const
Returns the Latin-1 value of this character, or 0 if it
cannot be represented in Latin-1.
QChar QChar::lower () const
Returns the lowercase equivalent if the character is uppercase;
otherwise returns the character itself.
bool QChar::mirrored () const
Returns TRUE if the character is a mirrored character (one that
should be reversed if the text direction is reversed); otherwise
returns FALSE.
QChar QChar::mirroredChar () const
Returns the mirrored character if this character is a mirrored
character, otherwise returns the character itself.
bool QChar::networkOrdered () [static]
This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.
Returns TRUE if this character is in network byte order (MSB
first); otherwise returns FALSE. This is platform dependent.
QChar::operator char () const
Returns the Latin-1 character equivalent to the QChar, or 0. This
is mainly useful for non-internationalized software.
See also unicode().
uchar QChar::row () const
Returns the row (most significant byte) of the Unicode character.
ushort QChar::unicode () const
Returns the numeric Unicode value equal to the QChar. Normally,
you should use QChar objects as they are equivalent, but for some
low-level tasks (e.g. indexing into an array of Unicode
information), this function is useful.
ushort & QChar::unicode ()
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns a reference to the numeric Unicode value equal to the
QChar.
QChar QChar::upper () const
Returns the uppercase equivalent if the character is lowercase;
otherwise returns the character itself.
Related Functions
int operator!= ( QChar c1, QChar c2 )
Returns TRUE if c1 and c2 are not the same Unicode
character; otherwise returns FALSE.
int operator!= ( char ch, QChar c )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns TRUE if c is not the ASCII/Latin-1 character ch;
otherwise returns FALSE.
int operator!= ( QChar c, char ch )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns TRUE if c is not the ASCII/Latin-1 character ch;
otherwise returns FALSE.
int operator< ( QChar c1, QChar c2 )
Returns TRUE if the numeric Unicode value of c1 is less than
that of c2; otherwise returns FALSE.
int operator< ( QChar c, char ch )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns TRUE if the numeric Unicode value of c is less than that
of the ASCII/Latin-1 character ch; otherwise returns FALSE.
int operator< ( char ch, QChar c )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns TRUE if the numeric Unicode value of the ASCII/Latin-1
character ch is less than that of c; otherwise returns
FALSE.
int operator<= ( QChar c1, QChar c2 )
Returns TRUE if the numeric Unicode value of c1 is less than
that of c2, or they are the same Unicode character; otherwise
returns FALSE.
int operator<= ( QChar c, char ch )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns TRUE if the numeric Unicode value of c is less than or
equal to that of the ASCII/Latin-1 character ch; otherwise
returns FALSE.
int operator<= ( char ch, QChar c )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns TRUE if the numeric Unicode value of the ASCII/Latin-1
character ch is less than or equal to that of c; otherwise
returns FALSE.
bool operator== ( QChar c1, QChar c2 )
Returns TRUE if c1 and c2 are the same Unicode character;
otherwise returns FALSE.
bool operator== ( char ch, QChar c )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns TRUE if c is the ASCII/Latin-1 character ch;
otherwise returns FALSE.
bool operator== ( QChar c, char ch )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns TRUE if c is the ASCII/Latin-1 character ch;
otherwise returns FALSE.
int operator> ( QChar c1, QChar c2 )
Returns TRUE if the numeric Unicode value of c1 is greater than
that of c2; otherwise returns FALSE.
int operator> ( QChar c, char ch )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns TRUE if the numeric Unicode value of c is greater than
that of the ASCII/Latin-1 character ch; otherwise returns FALSE.
int operator> ( char ch, QChar c )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns TRUE if the numeric Unicode value of the ASCII/Latin-1
character ch is greater than that of c; otherwise returns
FALSE.
int operator>= ( QChar c1, QChar c2 )
Returns TRUE if the numeric Unicode value of c1 is greater than
that of c2, or they are the same Unicode character; otherwise
returns FALSE.
int operator>= ( QChar c, char ch )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns TRUE if the numeric Unicode value of c is greater than
or equal to that of the ASCII/Latin-1 character ch; otherwise
returns FALSE.
int operator>= ( char ch, QChar c )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns TRUE if the numeric Unicode value of the ASCII/Latin-1
character ch is greater than or equal to that of c;
otherwise returns FALSE.
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