QFontMetrics class provides font metrics information. 更多...
| 头： | #include <QFontMetrics> |
| qmake: | QT += gui |
注意： 此类的所有函数 可重入 .
| QFontMetrics (const QFont & font ) | |
| QFontMetrics (const QFont & font , QPaintDevice * paintdevice ) | |
| QFontMetrics (const QFontMetrics & fm ) | |
| ~QFontMetrics () | |
| int | ascent () const |
| int | averageCharWidth () const |
| QRect | boundingRect (QChar ch ) const |
| QRect | boundingRect (const QString & text ) const |
| QRect | boundingRect (const QRect & rect , int flags , const QString & text , int tabStops = 0, int * tabArray = Q_NULLPTR) const |
| QRect | boundingRect (int x , int y , int width , int height , int flags , const QString & text , int tabStops = 0, int * tabArray = Q_NULLPTR) const |
| int | capHeight () const |
| int | descent () const |
| QString | elidedText (const QString & text , Qt::TextElideMode mode , int width , int flags = 0) const |
| int | height () const |
| bool | inFont (QChar ch ) const |
| bool | inFontUcs4 (uint ucs4 ) const |
| int | leading () const |
| int | leftBearing (QChar ch ) const |
| int | lineSpacing () const |
| int | lineWidth () const |
| int | maxWidth () const |
| int | minLeftBearing () const |
| int | minRightBearing () const |
| int | overlinePos () const |
| int | rightBearing (QChar ch ) const |
| QSize | size (int flags , const QString & text , int tabStops = 0, int * tabArray = Q_NULLPTR) const |
| int | strikeOutPos () const |
| void | swap (QFontMetrics & other ) |
| QRect | tightBoundingRect (const QString & text ) const |
| int | underlinePos () const |
| int | width (const QString & text , int len = -1) const |
| int | width (QChar ch ) const |
| int | xHeight () const |
| bool | operator!= (const QFontMetrics & other ) const |
| QFontMetrics & | operator= (const QFontMetrics & fm ) |
| QFontMetrics & | operator= (QFontMetrics && other ) |
| bool | operator== (const QFontMetrics & other ) const |
QFontMetrics class provides font metrics information.
QFontMetrics functions calculate the size of characters and strings for a given font. There are three ways you can create a QFontMetrics 对象：
(Note: If you use a printer font the values returned may be inaccurate. Printer fonts are not always accessible so the nearest screen font is used if a printer font is supplied.)
Once created, the object provides functions to access the individual metrics of the font, its characters, and for strings rendered in the font.
有几个字体操作函数： ascent (), descent (), height (), leading () 和 lineSpacing () 返回字体的基本大小特性。 underlinePos (), overlinePos (), strikeOutPos () 和 lineWidth () 函数，返回下划线、上划线或删除线字符的行属性。这些函数都很快。
There are also some functions that operate on the set of glyphs in the font: minLeftBearing (), minRightBearing () 和 maxWidth (). These are by necessity slow, and we recommend avoiding them if possible.
对于各字符，可以获取其 width (), leftBearing () 和 rightBearing () and find out whether it is in the font using inFont (). You can also treat the character as a string, and use the string functions on it.
字符串函数包括 width (), to return the width of a string in pixels (or points, for a printer), boundingRect (), to return a rectangle large enough to contain the rendered string, and size (), to return the size of that rectangle.
范例：
QFont font("times", 24); QFontMetrics fm(font); int pixelsWide = fm.width("What's the width of this text?"); int pixelsHigh = fm.height();
另请参阅 QFont , QFontInfo , QFontDatabase ，和 字符映射范例 .
构造字体规格对象为 font .
The font metrics will be compatible with the paintdevice used to create font .
The font metrics object holds the information for the font that is passed in the constructor at the time it is created, and is not updated if the font's attributes are changed later.
使用 QFontMetrics (const QFont &, QPaintDevice *) to get the font metrics that are compatible with a certain paint device.
构造字体规格对象为 font and paintdevice .
字体规格将兼容传递 paintdevice。若 paintdevice is 0, the metrics will be screen-compatible, ie. the metrics you get if you use the font for drawing text on a widgets or pixmaps , not on a QPicture or QPrinter .
The font metrics object holds the information for the font that is passed in the constructor at the time it is created, and is not updated if the font's attributes are changed later.
构造副本为 fm .
销毁字体规格对象并释放所有分配资源。
返回字体的上升。
The ascent of a font is the distance from the baseline to the highest position characters extend to. In practice, some font designers break this rule, e.g. when they put more than one accent on top of a character, or to accommodate an unusual character in an exotic language, so it is possible (though rare) that this value will be too small.
另请参阅 descent ().
返回字体字形的平均宽度。
该函数在 Qt 4.2 引入。
Returns the rectangle that is covered by ink if character ch were to be drawn at the origin of the coordinate system.
Note that the bounding rectangle may extend to the left of (0, 0) (e.g., for italicized fonts), and that the text output may cover all pixels in the bounding rectangle. For a space character the rectangle will usually be empty.
Note that the rectangle usually extends both above and below the base line.
警告： The width of the returned rectangle is not the advance width of the character. Use boundingRect(const QString &) or width () 代替。
另请参阅 width ().
Returns the bounding rectangle of the characters in the string specified by text . The bounding rectangle always covers at least the set of pixels the text would cover if drawn at (0, 0).
Note that the bounding rectangle may extend to the left of (0, 0), e.g. for italicized fonts, and that the width of the returned rectangle might be different than what the width () method returns.
If you want to know the advance width of the string (to lay out a set of strings next to each other), use width () 代替。
换行符被处理成正常字符， not 作为换行。
The height of the bounding rectangle is at least as large as the value returned by height ().
另请参阅 width (), height (), QPainter::boundingRect ()，和 tightBoundingRect ().
这是重载函数。
Returns the bounding rectangle of the characters in the string specified by text , which is the set of pixels the text would cover if drawn at (0, 0). The drawing, and hence the bounding rectangle, is constrained to the rectangle rect .
flags 自变量是下列标志的按位 OR：
Qt::AlignHCenter | Qt::AlignVCenter
)
Qt::Horizontal alignment defaults to Qt::AlignLeft and vertical alignment defaults to Qt::AlignTop .
If several of the horizontal or several of the vertical alignment flags are set, the resulting alignment is undefined.
若 Qt::TextExpandTabs is set in flags , then: if tabArray is non-null, it specifies a 0-terminated sequence of pixel-positions for tabs; otherwise if tabStops is non-zero, it is used as the tab spacing (in pixels).
Note that the bounding rectangle may extend to the left of (0, 0), e.g. for italicized fonts, and that the text output may cover all pixels in the bounding rectangle.
Newline characters are processed as linebreaks.
Despite the different actual character heights, the heights of the bounding rectangles of "Yes" and "yes" are the same.
The bounding rectangle returned by this function is somewhat larger than that calculated by the simpler boundingRect () function. This function uses the maximum left and right font bearings as is necessary for multi-line text to align correctly. Also, fontHeight() and lineSpacing () are used to calculate the height, rather than individual character heights.
另请参阅 width (), QPainter::boundingRect ()，和 Qt::Alignment .
这是重载函数。
Returns the bounding rectangle for the given text within the rectangle specified by the x and y coordinates, width ，和 height .
若 Qt::TextExpandTabs is set in flags and tabArray is non-null, it specifies a 0-terminated sequence of pixel-positions for tabs; otherwise, if tabStops is non-zero, it is used as the tab spacing (in pixels).
返回字体的大写高度。
The cap height of a font is the height of a capital letter above the baseline. It specifically is the height of capital letters that are flat - such as H or I - as opposed to round letters such as O, or pointed letters like A, both of which may display overshoot.
该函数在 Qt 5.8 引入。
另请参阅 ascent ().
返回字体的下降。
The descent is the distance from the base line to the lowest point characters extend to. In practice, some font designers break this rule, e.g. to accommodate an unusual character in an exotic language, so it is possible (though rare) that this value will be too small.
另请参阅 ascent ().
若字符串 text 宽于 width , returns an elided version of the string (i.e., a string with "..." in it). Otherwise, returns the original string.
mode parameter specifies whether the text is elided on the left (e.g., "...tech"), in the middle (e.g., "Tr...ch"), or on the right (e.g., "Trol...").
width 以像素为单位指定，而不是字符。
flags 自变量是可选的，且目前只支持 Qt::TextShowMnemonic 作为值。
The elide mark follows the
layoutdirection
. For example, it will be on the right side of the text for right-to-left layouts if the
mode
is
Qt::ElideLeft
, and on the left side of the text if the
mode
is
Qt::ElideRight
.
该函数在 Qt 4.2 引入。
返回字体的高度。
另请参阅 leading () 和 lineSpacing ().
返回
true
若字符
ch
是字体中的有效字符；否则返回
false
.
返回
true
若字符
ucs4
encoded in UCS-4/UTF-32 is a valid character in the font; otherwise returns
false
.
返回字体的前导。
这是自然行间间距。
另请参阅 height () 和 lineSpacing ().
Returns the left bearing of character ch in the font.
The left bearing is the right-ward distance of the left-most pixel of the character from the logical origin of the character. This value is negative if the pixels of the character extend to the left of the logical origin.
See width( QChar ) for a graphical description of this metric.
另请参阅 rightBearing (), minLeftBearing ()，和 width ().
返回从一基线到下一基线的距离。
返回下划线和删除线的宽度，调节字体的点大小。
另请参阅 underlinePos (), overlinePos ()，和 strikeOutPos ().
返回字体中最宽字符的宽度。
返回字体的最小左倾角。
这是最小 leftBearing (字符) 对于字体中的所有字符。
注意：此函数会非常慢，若字体很大。
另请参阅 minRightBearing () 和 leftBearing ().
返回字体的最小右倾角。
这是最小 rightBearing (字符) 对于字体中的所有字符。
注意：此函数会非常慢，若字体很大。
另请参阅 minLeftBearing () 和 rightBearing ().
返回基线到应绘制上划线的距离。
另请参阅 underlinePos (), strikeOutPos ()，和 lineWidth ().
Returns the right bearing of character ch in the font.
The right bearing is the left-ward distance of the right-most pixel of the character from the logical origin of a subsequent character. This value is negative if the pixels of the character extend to the right of the width () of the character.
见 width () 了解此指标的图形描述。
另请参阅 leftBearing (), minRightBearing ()，和 width ().
返回像素大小为 text .
flags 自变量是下列标志的按位 OR：
若 Qt::TextExpandTabs is set in flags , then: if tabArray is non-null, it specifies a 0-terminated sequence of pixel-positions for tabs; otherwise if tabStops is non-zero, it is used as the tab spacing (in pixels).
Newline characters are processed as linebreaks.
Despite the different actual character heights, the heights of the bounding rectangles of "Yes" and "yes" are the same.
另请参阅 boundingRect ().
返回基线到应绘制删除线的距离。
另请参阅 underlinePos (), overlinePos ()，和 lineWidth ().
交换此字体规格实例同 other 。此函数非常快，且从不失败。
该函数在 Qt 5.0 引入。
Returns a tight bounding rectangle around the characters in the string specified by text . The bounding rectangle always covers at least the set of pixels the text would cover if drawn at (0, 0).
Note that the bounding rectangle may extend to the left of (0, 0), e.g. for italicized fonts, and that the width of the returned rectangle might be different than what the width () method returns.
If you want to know the advance width of the string (to lay out a set of strings next to each other), use width () 代替。
换行符被处理成正常字符， not 作为换行。
警告： 在 Windows 调用此方法很慢。
该函数在 Qt 4.3 引入。
另请参阅 width (), height ()，和 boundingRect ().
返回基线到应绘制下划线的距离。
另请参阅 overlinePos (), strikeOutPos ()，和 lineWidth ().
Returns the width in pixels of the first len 字符的 text 。若 len 为负 (默认)，使用整个字符串。
Note that this value is not 等于 boundingRect ().width(); boundingRect () returns a rectangle describing the pixels this string will cover whereas width() returns the distance to where the next string should be drawn.
另请参阅 boundingRect ().
这是重载函数。
Returns the logical width of character ch in pixels. This is a distance appropriate for drawing a subsequent character after ch .
Some of the metrics are described in the image to the right. The central dark rectangles cover the logical width () of each character. The outer pale rectangles cover the leftBearing () 和 rightBearing () of each character. Notice that the bearings of "f" in this particular font are both negative, while the bearings of "o" are both positive.
警告： This function will produce incorrect results for Arabic characters or non-spacing marks in the middle of a string, as the glyph shaping and positioning of marks that happens when processing strings cannot be taken into account. When implementing an interactive text control, use QTextLayout 代替。
另请参阅 boundingRect ().
Returns the 'x' height of the font. This is often but not always the same as the height of the character 'x'.
返回
true
if
other
不等于此对象；否则返回
false
.
Two font metrics are considered equal if they were constructed from the same QFont and the paint devices they were constructed for are considered compatible.
另请参阅 operator== ().
赋值字体规格 fm .
移动赋值 other 到此 QFontMetrics 实例。
该函数在 Qt 5.2 引入。
返回
true
if
other
等于此对象；否则返回
false
.
Two font metrics are considered equal if they were constructed from the same QFont and the paint devices they were constructed for are considered compatible.
另请参阅 operator!= ().