QFontMetrics 类提供字体规格信息。 更多...
QFontMetrics 类提供字体规格信息。
QFontMetrics functions calculate the size of characters and strings for a given font. There are three ways you can create a QFontMetrics object:
(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.
There are several functions that operate on the font: ascent (), descent (), height (), leading () 和 lineSpacing () return the basic size properties of the font. The underlinePos (), overlinePos (), strikeOutPos () 和 lineWidth () functions, return the properties of the line that underlines, overlines or strikes out the characters. These functions are all fast.
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.
For each character, you can get its 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.
The string functions include 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();
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 .
The font metrics will be compatible with the paintdevice passed. 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 .
Returns the ascent of the font.
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 ().
Returns the average width of glyphs in the font.
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 指定通过 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 layout a set of strings next to each other), use width () 代替。
Newline characters are processed as normal characters, not as linebreaks.
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 ().
tabArray argument may also be None.
tabArray argument may also be None.
Returns the descent of the font.
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 argument is optional and currently only supports Qt.TextShowMnemonic 作为值。
The elide mark will follow the layout direction ; it will be on the right side of the text for right-to-left layouts, and on the left side for right-to-left layouts. Note that this behavior is independent of the text language.
该函数在 Qt 4.2 引入。
返回字体的高度。
这始终等于 ascent ()+ descent ()+1 (the 1 is for the base line).
另请参阅 leading () 和 lineSpacing ().
Returns true if character ch is a valid character in the font; otherwise returns false.
Returns true if the given character encoded in UCS-4/UTF-32 is a valid character in the font; otherwise returns false.
该函数在 Qt 4.8 引入。
Returns the leading of the font.
This is the natural inter-line spacing.
另请参阅 height () and 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 ().
Returns the distance from one base line to the next.
This value is always equal to leading ()+ height ().
另请参阅 height () and leading ().
Returns the width of the underline and strikeout lines, adjusted for the point size of the font.
另请参阅 underlinePos (), overlinePos ()，和 strikeOutPos ().
Returns the width of the widest character in the font.
Returns the minimum left bearing of the font.
This is the smallest leftBearing(char) of all characters in the font.
Note that this function can be very slow if the font is large.
另请参阅 minRightBearing () 和 leftBearing ().
Returns the minimum right bearing of the font.
This is the smallest rightBearing(char) of all characters in the font.
Note that this function can be very slow if the font is large.
另请参阅 minLeftBearing () 和 rightBearing ().
Returns the distance from the base line to where an overline should be drawn.
另请参阅 underlinePos (), strikeOutPos ()，和 lineWidth ().
Returns the right bearing of character ch 在 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 () for a graphical description of this metric.
另请参阅 leftBearing (), minRightBearing ()，和 width ().
tabArray argument may also be None.
Returns the size in pixels of text .
flags argument is the bitwise OR of the following flags:
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 ().
Returns the distance from the base line to where the strikeout line should be drawn.
另请参阅 underlinePos (), overlinePos ()，和 lineWidth ().
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 layout a set of strings next to each other), use width () 代替。
Newline characters are processed as normal characters, not as linebreaks.
警告： Calling this method is very slow on Windows.
该函数在 Qt 4.3 引入。
另请参阅 width (), height ()，和 boundingRect ().
Returns the distance from the base line to where an underscore should be drawn.
另请参阅 overlinePos (), strikeOutPos ()，和 lineWidth ().
Returns the width in pixels of the first len characters of text 。若 len is negative (the default), the entire string is used.
Note that this value is not 等于 boundingRect ().width(); boundingRect () 返回 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 ().
Returns the 'x' height of the font. This is often but not always the same as the height of the character 'x'.
