QFontMetricsF Class

See also QFont, QFontInfo, QFontDatabase

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.

Constructs a font metrics object for font and paintdevice.

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

This function was introduced in Qt 5.13.

Constructs a font metrics object with floating point precision from the given fontMetrics object.

Constructs a copy of fm.

Destroys the font metrics object and frees all allocated resources.

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 a certain character, so it is possible (though rare) that this value will be too small.

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Returns the average width of glyphs in the font.

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 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() 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().

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Returns the bounding rectangle of the characters in the string specified by text laid out using option. 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() 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().

This function was introduced in Qt 6.3.

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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.

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This is an overloaded function.

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. If rect is a reference to a nullptr object, e.g. when passing a default constructed QRectF, the bounding rectangle will not constrain itself to the size.

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::TextWordWrap 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 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.

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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.

This function was introduced in Qt 5.8.

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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 a certain character, so it is possible (though rare) that this value will be too small.

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If the string text is wider than width, returns an elided version of the string (i.e., a string with "..." in it). Otherwise, returns the original string.

The mode parameter specifies whether the text is elided on the left (for example, "...tech"), in the middle (for example, "Tr...ch"), or on the right (for example, "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 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.

Returns the font DPI.

This function was introduced in Qt 5.14.

Returns the height of the font.

This is always equal to ascent()+descent().

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

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

This function was introduced in Qt 5.11.

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This is an overloaded function.

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 to the right. 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.

This function was introduced in Qt 5.11.

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Returns the horizontal advance in pixels of text laid out using option.

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

This function was introduced in Qt 6.3.

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

Returns true if the character given by ch, encoded in UCS-4/UTF-32, is a valid character in the font; otherwise returns false.

Returns the leading of the font.

This is the natural inter-line spacing.

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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 horizontalAdvance() for a graphical description of this metric.

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Returns the distance from one base line to the next.

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

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

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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.

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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.

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

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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.

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

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Returns the size in pixels of the characters in the given text.

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

• Qt::TextSingleLine ignores newline characters.

• Qt::TextExpandTabs expands tabs (see below)

• Qt::TextShowMnemonic interprets "&x" as x; i.e., underlined.

• Qt::TextWordWrap breaks the text to fit the rectangle.

These flags are defined in the Qt::TextFlag enum.

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).

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.

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

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Swaps this font metrics instance with other. This function is very fast and never fails.

This function was introduced in Qt 5.0.

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() instead.

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

See Also▲

Returns a tight bounding rectangle around the characters in the string specified by text laid out using option. 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() instead.

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

This function was introduced in Qt 6.3.

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

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

This is an overloaded function.

Returns true if the font metrics are not equal to the other font metrics; otherwise returns false.

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Assigns the font metrics fm to this font metrics object.

Assigns other to this object.

Move-assigns other to this QFontMetricsF instance.

Returns true if the font metrics are equal to the other font metrics; 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 to be compatible.