com.trolltech.qt.gui
Class QFontMetricsF

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.QFontMetricsF
All Implemented Interfaces:
QtJambiInterface, java.lang.Cloneable

public class QFontMetricsF
extends QtJambiObject
implements java.lang.Cloneable

The QFontMetricsF class provides font metrics information. QFontMetricsF functions calculate the size of characters and strings for a given font. You can construct a QFontMetricsF object with an existing QFont to obtain metrics for that font. If the 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);
    QFontMetricsF fm = new QFontMetricsF(font);
    double pixelsWide = fm.width("What's the width of this text?");
    double pixelsHigh = fm.height();

See also:
QFont, QFontInfo, and QFontDatabase.


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
QFontMetricsF(QFont arg__1)
          Constructs a font metrics object for font.
QFontMetricsF(QFontMetrics arg__1)
          Constructs a font metrics object with floating point precision from the given fontMetrics object.
QFontMetricsF(QFontMetricsF arg__1)
          Constructs a copy of fm.
QFontMetricsF(QFont arg__1, QPaintDeviceInterface pd)
          Constructs a font metrics object for font and paintdevice.
 
Method Summary
 double ascent()
          Returns the ascent of the font.
 double averageCharWidth()
          Returns the average width of glyphs in the font.
 QRectF boundingRect(char arg__1)
          Returns the bounding rectangle of the character ch relative to the left-most point on the base line.
 QRectF boundingRect(QRectF rect, int flags, java.lang.String text)
          This is an overloaded function provided for convenience.
 QRectF boundingRect(QRectF rect, int flags, java.lang.String text, int tabStops)
          Returns the bounding rectangle of the characters in the given text.
 QRectF boundingRect(QRectF rect, int flags, java.lang.String text, int tabStops, int[] tabArray)
          Returns the bounding rectangle of the characters in the given text.
 QRectF boundingRect(java.lang.String string)
          Returns the bounding rectangle of the characters in the string specified by text.
 QFontMetricsF clone()
          This method is reimplemented for internal reasons
 double descent()
          Returns the descent of the font.
 java.lang.String elidedText(java.lang.String text, Qt.TextElideMode mode, double 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, double width, int flags)
          If the string text is wider than width, returns an elided version of the string (i.
 double 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.
 double leading()
          Returns the leading of the font.
 double leftBearing(char arg__1)
          Returns the left bearing of character ch in the font.
 double lineSpacing()
          Returns the distance from one base line to the next.
 double lineWidth()
          Returns the width of the underline and strikeout lines, adjusted for the point size of the font.
 double maxWidth()
          Returns the width of the widest character in the font.
 double minLeftBearing()
          Returns the minimum left bearing of the font.
 double minRightBearing()
          Returns the minimum right bearing of the font.
 double overlinePos()
          Returns the distance from the base line to where an overline should be drawn.
 double rightBearing(char arg__1)
          Returns the right bearing of character ch in the font.
 QSizeF size(int flags, java.lang.String text)
          This is an overloaded function provided for convenience.
 QSizeF size(int flags, java.lang.String text, int tabStops)
          This is an overloaded function provided for convenience.
 QSizeF size(int flags, java.lang.String text, int tabStops, int[] tabArray)
          Returns the size in pixels of the characters in the given text.
 double strikeOutPos()
          Returns the distance from the base line to where the strikeout line should be drawn.
 QRectF tightBoundingRect(java.lang.String text)
          Returns a tight bounding rectangle around the characters in the string specified by text.
 double underlinePos()
          Returns the distance from the base line to where an underscore should be drawn.
 double width(char arg__1)
          This is an overloaded member function, provided for convenience.
 double width(java.lang.String string)
          Returns the width in pixels of the characters in the given text.
 double 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

QFontMetricsF

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


QFontMetricsF

public QFontMetricsF(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.


QFontMetricsF

public QFontMetricsF(QFontMetrics arg__1)
Constructs a font metrics object with floating point precision from the given fontMetrics object.


QFontMetricsF

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

Method Detail

ascent

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


boundingRect

public final QRectF boundingRect(char arg__1)
Returns the bounding rectangle of the character ch relative to the left-most point on the base line.

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.

Note that the rectangle usually extends both above and below the base line.

See also:
width().


boundingRect

public final QRectF boundingRect(java.lang.String string)
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 height().

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


descent

public final double descent()
Returns the descent of the font.

The descent is the distance from the base line to the lowest point characters extend to. (Note that this is different from X, which adds 1 pixel.) 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,
                                         double 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.


elidedText

public final java.lang.String elidedText(java.lang.String text,
                                         Qt.TextElideMode mode,
                                         double 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.


height

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

This is the natural inter-line spacing.

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


leftBearing

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


minLeftBearing

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

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


rightBearing

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

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


width

public final double 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().


width

public final double width(java.lang.String string)
Returns the width in pixels of the characters in the given text.

Note that this value is not equal to the width returned by boundingRect().width() because 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 double 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 QRectF boundingRect(QRectF rect,
                                 int flags,
                                 java.lang.String text,
                                 int tabStops,
                                 int[] tabArray)
Returns the bounding rectangle of the characters in the given text. This is the set of pixels the text would cover if drawn when constrained to the bounding rectangle specified by 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.

These flags are defined in Qt::AlignmentFlag .

If Qt::TextExpandTabs is set in flags, the following behavior is used to interpret tab characters in the text:

Note that the bounding rectangle may extend to the left of (0, 0), e.g. for italicized fonts.

Newline characters are processed as line breaks.

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 QRectF boundingRect(QRectF rect,
                                 int flags,
                                 java.lang.String text,
                                 int tabStops)
Returns the bounding rectangle of the characters in the given text. This is the set of pixels the text would cover if drawn when constrained to the bounding rectangle specified by rect.

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

  • Qt::AlignLeft aligns to the left border, except for Arabic and Hebrew where it aligns to the right.
  • Qt::AlignRight aligns to the right border, except for Arabic and Hebrew where it aligns to the left.
  • Qt::AlignJustify produces justified text.
  • Qt::AlignHCenter aligns horizontally centered.
  • Qt::AlignTop aligns to the top border.
  • Qt::AlignBottom aligns to the bottom border.
  • Qt::AlignVCenter aligns vertically centered
  • Qt::AlignCenter (== Qt::AlignHCenter | Qt::AlignVCenter)
  • Qt::TextSingleLine ignores newline characters in the text.
  • Qt::TextExpandTabs expands tabs (see below)
  • Qt::TextShowMnemonic interprets "&x" as x, i.e. underlined.
  • Qt::TextWordBreak breaks the text to fit the rectangle.
  • 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.

    These flags are defined in Qt::AlignmentFlag.

    If Qt::TextExpandTabs is set in flags, the following behavior is used to interpret tab characters in the text:

  • If tabArray is non-null, it specifies a 0-terminated sequence of pixel-positions for tabs in the text.
  • 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.

    Newline characters are processed as line breaks.

    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 minLeftBearing() maximum left and minRightBearing() 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.


    boundingRect

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


    size

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

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

    These flags are defined in Qt::TextFlags.

    If Qt::TextExpandTabs is set in flags, the following behavior is used to interpret tab characters in the text:

    Newline characters are processed as line breaks.

    Note: 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 QSizeF size(int flags,
                             java.lang.String text,
                             int tabStops)
    This is an overloaded function provided for convenience.


    size

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


    clone

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

    Overrides:
    clone in class java.lang.Object