com.trolltech.qt.gui
Class QFontMetrics

java.lang.Object
  extended by com.trolltech.qt.internal.QSignalEmitterInternal
      extended by com.trolltech.qt.QSignalEmitter
          extended by com.trolltech.qt.QtJambiObject
              extended by com.trolltech.qt.gui.QFontMetrics
All Implemented Interfaces:
QtJambiInterface, java.lang.Cloneable

public class QFontMetrics
extends QtJambiObject
implements java.lang.Cloneable

The 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 object:

  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. QWidget::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. QPainter::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 width(), leftBearing() and 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.

Example:

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

See also:
QFont, QFontInfo, QFontDatabase, QFontComboBox, and Character Map Example.


Nested Class Summary
 
Nested classes/interfaces inherited from class com.trolltech.qt.QSignalEmitter
QSignalEmitter.AbstractSignal, QSignalEmitter.PrivateSignal0, QSignalEmitter.PrivateSignal1, QSignalEmitter.PrivateSignal2, QSignalEmitter.PrivateSignal3, QSignalEmitter.PrivateSignal4, QSignalEmitter.PrivateSignal5, QSignalEmitter.PrivateSignal6, QSignalEmitter.PrivateSignal7, QSignalEmitter.PrivateSignal8, QSignalEmitter.PrivateSignal9, QSignalEmitter.Signal0, QSignalEmitter.Signal1, QSignalEmitter.Signal2, QSignalEmitter.Signal3, QSignalEmitter.Signal4, QSignalEmitter.Signal5, QSignalEmitter.Signal6, QSignalEmitter.Signal7, QSignalEmitter.Signal8, QSignalEmitter.Signal9
 
Nested classes/interfaces inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
com.trolltech.qt.internal.QSignalEmitterInternal.AbstractSignalInternal
 
Field Summary
 
Fields inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
currentSender
 
Constructor Summary
QFontMetrics(QFont arg__1)
          Constructs a font metrics object for font.
QFontMetrics(QFontMetrics arg__1)
          Constructs a copy of fm.
QFontMetrics(QFont arg__1, QPaintDeviceInterface pd)
          Constructs a font metrics object for font and paintdevice.
 
Method Summary
 int ascent()
          Returns the ascent of the font.
 int averageCharWidth()
          Returns the average width of glyphs in the font.
 QRect boundingRect(char arg__1)
          Returns the rectangle that is covered by ink if character ch were to be drawn at the origin of the coordinate system.
 QRect boundingRect(int x, int y, int width, int height, int flags, java.lang.String text)
          This is an overloaded method provided for convenience.
 QRect boundingRect(int x, int y, int width, int height, int flags, java.lang.String text, int tabStops)
          This is an overloaded method provided for convenience.
 QRect boundingRect(int x, int y, int width, int height, int flags, java.lang.String text, int tabStops, int[] tabArray)
          Returns the bounding rectangle for the given text within the rectangle specified by the x and y coordinates, width, and height.
 QRect boundingRect(QRect rect, int flags, java.lang.String text)
          This is an overloaded function provided for convenience.
 QRect boundingRect(QRect rect, int flags, java.lang.String text, int tabStops)
          This is an overloaded function provided for convenience.
 QRect boundingRect(QRect rect, int flags, java.lang.String text, int tabStops, int[] tabArray)
          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).
 QRect boundingRect(java.lang.String text)
          Returns the bounding rectangle of the characters in the string specified by text.
 int charWidth(java.lang.String str, int pos)
          Returns the width of the character at position pos in the string text.
 QFontMetrics clone()
          This method is reimplemented for internal reasons
 int descent()
          Returns the descent of the font.
 java.lang.String elidedText(java.lang.String text, Qt.TextElideMode mode, int width)
          If the string text is wider than width, returns an elided version of the string (i.
 java.lang.String elidedText(java.lang.String text, Qt.TextElideMode mode, int width, int flags)
          If the string text is wider than width, returns an elided version of the string (i.
 int height()
          Returns the height of the font.
 boolean inFont(char arg__1)
          Returns true if character ch is a valid character in the font; otherwise returns false.
 int leading()
          Returns the leading of the font.
 int leftBearing(char arg__1)
          Returns the left bearing of character ch in the font.
 int lineSpacing()
          Returns the distance from one base line to the next.
 int lineWidth()
          Returns the width of the underline and strikeout lines, adjusted for the point size of the font.
 int maxWidth()
          Returns the width of the widest character in the font.
 int minLeftBearing()
          Returns the minimum left bearing of the font.
 int minRightBearing()
          Returns the minimum right bearing of the font.
 int overlinePos()
          Returns the distance from the base line to where an overline should be drawn.
 int rightBearing(char arg__1)
          Returns the right bearing of character ch in the font.
 QSize size(int flags, java.lang.String text)
          This is an overloaded method provided for convenience.
 QSize size(int flags, java.lang.String text, int tabStops)
          This is an overloaded method provided for convenience.
 QSize size(int flags, java.lang.String text, int tabStops, int[] tabArray)
          Returns the size in pixels of text.
 int strikeOutPos()
          Returns the distance from the base line to where the strikeout line should be drawn.
 QRect tightBoundingRect(java.lang.String text)
          Returns a tight bounding rectangle around the characters in the string specified by text.
 int underlinePos()
          Returns the distance from the base line to where an underscore should be drawn.
 int width(char arg__1)
          This is an overloaded member function, provided for convenience.
 int width(java.lang.String arg__1)
          Returns the width in pixels of the first len characters of text.
 int width(java.lang.String arg__1, int len)
          Returns the width in pixels of the first len characters of text.
 int xHeight()
          Returns the 'x' height of the font.
 
Methods inherited from class com.trolltech.qt.QtJambiObject
dispose, disposed, equals, finalize, reassignNativeResources, tr, tr, tr
 
Methods inherited from class com.trolltech.qt.QSignalEmitter
blockSignals, disconnect, disconnect, signalsBlocked, signalSender, thread
 
Methods inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
__qt_signalInitialization
 
Methods inherited from class java.lang.Object
getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 
Methods inherited from interface com.trolltech.qt.QtJambiInterface
disableGarbageCollection, nativeId, nativePointer, reenableGarbageCollection, setJavaOwnership
 

Constructor Detail

QFontMetrics

public QFontMetrics(QFont arg__1)
Constructs a font metrics object for 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.

Use QFontMetrics(const QFont &, QPaintDevice *) to get the font metrics that are compatible with a certain paint device.


QFontMetrics

public QFontMetrics(QFont arg__1,
                    QPaintDeviceInterface pd)
Constructs a font metrics object for font and paintdevice.

The font metrics will be compatible with the paintdevice passed. If the 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.


QFontMetrics

public QFontMetrics(QFontMetrics arg__1)
Constructs a copy of fm.

Method Detail

ascent

public final int ascent()
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.

See also:
descent().


averageCharWidth

public final int averageCharWidth()
Returns the average width of glyphs in the font.


boundingRect

public final QRect boundingRect(char arg__1)
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.

Warning: The width of the returned rectangle is not the advance width of the character. Use boundingRect(const QString &) or width() instead.

See also:
width().


boundingRect

public final QRect boundingRect(java.lang.String text)
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 layout a set of strings next to each other), use width() instead.

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().

See also:
width(), height(), QPainter::boundingRect(), and tightBoundingRect().


charWidth

public final int charWidth(java.lang.String str,
                           int pos)
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.


descent

public final int descent()
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.

See also:
ascent().


elidedText

public final java.lang.String elidedText(java.lang.String text,
                                         Qt.TextElideMode mode,
                                         int width)
If the string text is wider than width, returns an elided version of the string (i. ., a string with "..." in it). Otherwise, returns the original string.

The 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...").

The width is specified in pixels, not characters.

The flags argument is optional and currently only supports Qt::TextShowMnemonic as value.

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.


elidedText

public final java.lang.String elidedText(java.lang.String text,
                                         Qt.TextElideMode mode,
                                         int width,
                                         int flags)
If the string text is wider than width, returns an elided version of the string (i. ., a string with "..." in it). Otherwise, returns the original string.

The 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...").

The width is specified in pixels, not characters.

The flags argument is optional and currently only supports Qt::TextShowMnemonic as value.

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.


height

public final int height()
Returns the height of the font.

This is always equal to ascent()+descent()+1 (the 1 is for the base line).

See also:
leading(), and lineSpacing().


inFont

public final boolean inFont(char arg__1)
Returns true if character ch is a valid character in the font; otherwise returns false.


leading

public final int leading()
Returns the leading of the font.

This is the natural inter-line spacing.

See also:
height(), and lineSpacing().


leftBearing

public final int leftBearing(char arg__1)
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.

See also:
rightBearing(), minLeftBearing(), and width().


lineSpacing

public final int lineSpacing()
Returns the distance from one base line to the next.

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

See also:
height(), and leading().


lineWidth

public final int lineWidth()
Returns the width of the underline and strikeout lines, adjusted for the point size of the font.

See also:
underlinePos(), overlinePos(), and strikeOutPos().


maxWidth

public final int maxWidth()
Returns the width of the widest character in the font.


minLeftBearing

public final int minLeftBearing()
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.

See also:
minRightBearing(), and leftBearing().


minRightBearing

public final int minRightBearing()
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.

See also:
minLeftBearing(), and rightBearing().


overlinePos

public final int overlinePos()
Returns the distance from the base line to where an overline should be drawn.

See also:
underlinePos(), strikeOutPos(), and lineWidth().


rightBearing

public final int rightBearing(char arg__1)
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.

See width() for a graphical description of this metric.

See also:
leftBearing(), minRightBearing(), and width().


strikeOutPos

public final int strikeOutPos()
Returns the distance from the base line to where the strikeout line should be drawn.

See also:
underlinePos(), overlinePos(), and lineWidth().


tightBoundingRect

public final QRect tightBoundingRect(java.lang.String text)
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() instead.

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

Warning: Calling this method is very slow on Windows.

See also:
width(), height(), and boundingRect().


underlinePos

public final int underlinePos()
Returns the distance from the base line to where an underscore should be drawn.

See also:
overlinePos(), strikeOutPos(), and lineWidth().


width

public final int width(char arg__1)
This is an overloaded member function, provided for convenience.

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() 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.

Warning: 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. Use charWidth() instead if you aren't looking for the width of isolated characters.

See also:
boundingRect(), and charWidth().


width

public final int width(java.lang.String arg__1)
Returns the width in pixels of the first len characters of text. If len is negative (the default), the entire string is used.

Note that this value is not equal to 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.

See also:
boundingRect().


width

public final int width(java.lang.String arg__1,
                       int len)
Returns the width in pixels of the first len characters of text. If len is negative (the default), the entire string is used.

Note that this value is not equal to 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.

See also:
boundingRect().


xHeight

public final int xHeight()
Returns the 'x' height of the font. This is often but not always the same as the height of the character 'x'.


boundingRect

public final QRect boundingRect(int x,
                                int y,
                                int width,
                                int height,
                                int flags,
                                java.lang.String text,
                                int tabStops,
                                int[] tabArray)
Returns the bounding rectangle for the given text within the rectangle specified by the x and y coordinates, width, and height.

If 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).


boundingRect

public final QRect boundingRect(int x,
                                int y,
                                int width,
                                int height,
                                int flags,
                                java.lang.String text,
                                int tabStops)
This is an overloaded method provided for convenience.


boundingRect

public final QRect boundingRect(int x,
                                int y,
                                int width,
                                int height,
                                int flags,
                                java.lang.String text)
This is an overloaded method provided for convenience.


boundingRect

public final QRect boundingRect(QRect rect,
                                int flags,
                                java.lang.String text,
                                int tabStops,
                                int[] tabArray)
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.

The flags argument is the bitwise OR of the following flags:

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.

If 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.

See also:
width(), QPainter::boundingRect(), and Qt::Alignment.


boundingRect

public final QRect boundingRect(QRect rect,
                                int flags,
                                java.lang.String text,
                                int tabStops)
This is an overloaded function provided for convenience.


boundingRect

public final QRect boundingRect(QRect rect,
                                int flags,
                                java.lang.String text)
This is an overloaded function provided for convenience.


size

public final QSize size(int flags,
                        java.lang.String text,
                        int tabStops,
                        int[] tabArray)
Returns the size in pixels of text.

The flags argument is the bitwise OR of the following flags:

If 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.

See also:
boundingRect().


size

public final QSize size(int flags,
                        java.lang.String text,
                        int tabStops)
This is an overloaded method provided for convenience.


size

public final QSize size(int flags,
                        java.lang.String text)
This is an overloaded method provided for convenience.


clone

public QFontMetrics clone()
This method is reimplemented for internal reasons

Overrides:
clone in class java.lang.Object