QFontMetrics ¶

概要 ¶

详细描述 ¶

QFontMetrics functions calculate the size of characters and strings for a given font. There are three ways you can create a QFontMetrics 对象：

1. Calling the QFontMetrics constructor with a QFont creates a font metrics object for a screen-compatible font, i.e. the font cannot be a printer font. If the font is changed later, the font metrics object is not updated.

   (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.)

2. fontMetrics() returns the font metrics for a widget’s font. This is equivalent to QFontMetrics (widget-> font() ). If the widget’s font is changed later, the font metrics object is not updated.

3. fontMetrics() returns the font metrics for a painter’s current font. If the painter’s font is changed later, the font metrics object is not updated.

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() and lineSpacing() return the basic size properties of the font. The underlinePos() , overlinePos() , strikeOutPos() and 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() and maxWidth() . These are by necessity slow, and we recommend avoiding them if possible.

For each character, you can get its horizontalAdvance() , 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 horizontalAdvance() , 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：

font = QFont("times", 24)
fm = QFontMetrics(font)
pixelsWide = fm.width("What's the width of this text?")
pixelsHigh = fm.height()
											

另请参阅

QFont QFontInfo QFontDatabase 字符映射范例

class QFontMetrics ( arg__1 ) ¶

QFontMetrics(font, pd)

QFontMetrics(arg__1)

参数

• pd – QPaintDevice

• font – QFont

• arg__1 – QFont

PySide2.QtGui.QFontMetrics. ascent ( ) ¶

返回类型

int

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()

PySide2.QtGui.QFontMetrics. averageCharWidth ( ) ¶

返回类型

int

Returns the average width of glyphs in the font.

PySide2.QtGui.QFontMetrics. boundingRect ( r , flags , text [ , tabstops=0 [ , tabarray=None ] ] ) ¶

参数

• r – QRect

• flags – int

• text – unicode

• tabstops – int

• tabarray – int

返回类型

QRect

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 argument is the bitwise OR of the following flags:

• AlignLeft aligns to the left border, except for Arabic and Hebrew where it aligns to the right.

• AlignRight aligns to the right border, except for Arabic and Hebrew where it aligns to the left.

• AlignJustify produces justified text.

• AlignHCenter aligns horizontally centered.

• AlignTop aligns to the top border.

• AlignBottom aligns to the bottom border.

• AlignVCenter aligns vertically centered

• AlignCenter (== Qt::AlignHCenter | Qt::AlignVCenter )

• TextSingleLine ignores newline characters in the text.

• TextExpandTabs expands tabs (see below)

• TextShowMnemonic interprets “&x” as x ; i.e., underlined.

• TextWordWrap breaks the text to fit the rectangle.

Horizontal alignment defaults to AlignLeft and vertical alignment defaults to AlignTop .

If several of the horizontal or several of the vertical alignment flags are set, the resulting alignment is undefined.

若 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

horizontalAdvance() boundingRect() Alignment

PySide2.QtGui.QFontMetrics. boundingRect ( text ) ¶

参数

text – unicode

返回类型

QRect

PySide2.QtGui.QFontMetrics. boundingRect ( x , y , w , h , flags , text [ , tabstops=0 [ , tabarray=None ] ] ) ¶

参数

• x – int

• y – int

• w – int

• h – int

• flags – int

• text – unicode

• tabstops – int

• tabarray – int

返回类型

QRect

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 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).

PySide2.QtGui.QFontMetrics. boundingRectChar ( arg__1 ) ¶

参数

arg__1 – QChar

返回类型

QRect

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 (const QString &) or horizontalAdvance() 代替。

另请参阅

horizontalAdvance()

PySide2.QtGui.QFontMetrics. capHeight ( ) ¶

返回类型

int

Returns the cap height of the font.

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.

另请参阅

ascent()

PySide2.QtGui.QFontMetrics. charWidth ( str , pos ) ¶

参数

• str – unicode

• pos – int

返回类型

int

注意

此函数被弃用。

Returns the width of the character at position pos in the string text .

The whole string is needed, as the glyph drawn may change depending on the context (the letter before and after the current one) for some languages (e.g. Arabic).

This function also takes non spacing marks and ligatures into account.

PySide2.QtGui.QFontMetrics. descent ( ) ¶

返回类型

int

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()

PySide2.QtGui.QFontMetrics. elidedText ( text , mode , width [ , flags=0 ] ) ¶

参数

• text – unicode

• mode – TextElideMode

• width – int

• flags – int

返回类型

unicode

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 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 .

PySide2.QtGui.QFontMetrics. fontDpi ( ) ¶

返回类型

qreal

返回字体 DPI (每英寸点数)。

PySide2.QtGui.QFontMetrics. height ( ) ¶

返回类型

int

返回字体的高度。

这始终等于 ascent() + descent() .

另请参阅

leading() lineSpacing()

PySide2.QtGui.QFontMetrics. horizontalAdvance ( arg__1 ) ¶

参数

arg__1 – QChar

返回类型

int

这是重载函数。

Returns the horizontal advance 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. The central dark rectangles cover the logical horizontalAdvance() of each character. The outer pale rectangles cover the leftBearing() and 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()

PySide2.QtGui.QFontMetrics. horizontalAdvance ( arg__1 [ , len=-1 ] ) ¶

参数

• arg__1 – unicode

• len – int

返回类型

int

Returns the horizontal advance in pixels of the first len characters of text 。若 len is negative (the default), the entire string is used.

This is the distance appropriate for drawing a subsequent character after text .

另请参阅

boundingRect()

PySide2.QtGui.QFontMetrics. inFont ( arg__1 ) ¶

参数

arg__1 – QChar

返回类型

bool

返回 true if character ch is a valid character in the font; otherwise returns false .

PySide2.QtGui.QFontMetrics. inFontUcs4 ( ucs4 ) ¶

参数

ucs4 – uint

返回类型

bool

返回 true if the character ucs4 encoded in UCS-4/UTF-32 is a valid character in the font; otherwise returns false .

PySide2.QtGui.QFontMetrics. leading ( ) ¶

返回类型

int

Returns the leading of the font.

This is the natural inter-line spacing.

另请参阅

height() lineSpacing()

PySide2.QtGui.QFontMetrics. leftBearing ( arg__1 ) ¶

参数

arg__1 – QChar

返回类型

int

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.

见 horizontalAdvance() for a graphical description of this metric.

另请参阅

rightBearing() minLeftBearing() horizontalAdvance()

PySide2.QtGui.QFontMetrics. lineSpacing ( ) ¶

返回类型

int

Returns the distance from one base line to the next.

This value is always equal to leading() + height() .

另请参阅

height() leading()

PySide2.QtGui.QFontMetrics. lineWidth ( ) ¶

返回类型

int

Returns the width of the underline and strikeout lines, adjusted for the point size of the font.

另请参阅

underlinePos() overlinePos() strikeOutPos()

PySide2.QtGui.QFontMetrics. maxWidth ( ) ¶

返回类型

int

Returns the width of the widest character in the font.

PySide2.QtGui.QFontMetrics. minLeftBearing ( ) ¶

返回类型

int

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() leftBearing()

PySide2.QtGui.QFontMetrics. minRightBearing ( ) ¶

返回类型

int

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() rightBearing()

PySide2.QtGui.QFontMetrics. __ne__ ( other ) ¶

参数

other – QFontMetrics

返回类型

bool

返回 true if other is not equal to this object; otherwise returns 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==()

PySide2.QtGui.QFontMetrics. __eq__ ( other ) ¶

参数

other – QFontMetrics

返回类型

bool

返回 true if other is equal to this object; otherwise returns 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!=()

PySide2.QtGui.QFontMetrics. overlinePos ( ) ¶

返回类型

int

Returns the distance from the base line to where an overline should be drawn.

另请参阅

underlinePos() strikeOutPos() lineWidth()

PySide2.QtGui.QFontMetrics. rightBearing ( arg__1 ) ¶

参数

arg__1 – QChar

返回类型

int

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 horizontalAdvance() of the character.

见 horizontalAdvance() for a graphical description of this metric.

另请参阅

leftBearing() minRightBearing() horizontalAdvance()

PySide2.QtGui.QFontMetrics. size ( flags , str [ , tabstops=0 [ , tabarray=None ] ] ) ¶

参数

• flags – int

• str – unicode

• tabstops – int

• tabarray – int

返回类型

QSize

Returns the size in pixels of text .

flags argument is the bitwise OR of the following flags:

• TextSingleLine ignores newline characters.

• TextExpandTabs expands tabs (see below)

• TextShowMnemonic interprets “&x” as x ; i.e., underlined.

• TextWordWrap breaks the text to fit the rectangle.

若 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()

PySide2.QtGui.QFontMetrics. strikeOutPos ( ) ¶

返回类型

int

Returns the distance from the base line to where the strikeout line should be drawn.

另请参阅

underlinePos() overlinePos() lineWidth()

PySide2.QtGui.QFontMetrics. swap ( other ) ¶

参数

other – QFontMetrics

Swaps this font metrics instance with other 。此函数非常快，且从不失败。

PySide2.QtGui.QFontMetrics. tightBoundingRect ( text ) ¶

参数

text – unicode

返回类型

QRect

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 horizontalAdvance() 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 horizontalAdvance() 代替。

Newline characters are processed as normal characters, not as linebreaks.

警告

Calling this method is very slow on Windows.

另请参阅

horizontalAdvance() height() boundingRect()

PySide2.QtGui.QFontMetrics. underlinePos ( ) ¶

返回类型

int

Returns the distance from the base line to where an underscore should be drawn.

另请参阅

overlinePos() strikeOutPos() lineWidth()

PySide2.QtGui.QFontMetrics. width ( arg__1 [ , len=-1 ] ) ¶

参数

• arg__1 – unicode

• len – int

返回类型

int

注意

此函数被弃用。

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() .; boundingRect() returns a rectangle describing the pixels this string will cover whereas returns the distance to where the next string should be drawn.

in Qt 5.11. Use horizontalAdvance() 代替。

另请参阅

boundingRect() horizontalAdvance()

PySide2.QtGui.QFontMetrics. width ( arg__1 , len , flags ) ¶

参数

• arg__1 – unicode

• len – int

• flags – int

返回类型

int

注意

此函数被弃用。

PySide2.QtGui.QFontMetrics. widthChar ( arg__1 ) ¶

参数

arg__1 – QChar

返回类型

int

注意

此函数被弃用。

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 of each character. The outer pale rectangles cover the leftBearing() and 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.

in Qt 5.11. Use horizontalAdvance() 代替。

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() horizontalAdvance()

PySide2.QtGui.QFontMetrics. xHeight ( ) ¶

返回类型

int

Returns the ‘x’ height of the font. This is often but not always the same as the height of the character ‘x’.