#include <opennurbs_font.h>

Public Member Functions
	ON_FontMetrics ()=default

	ON_FontMetrics (const ON_FontMetrics &)=default

	~ON_FontMetrics ()=default

int	Ascent () const

bool	AscentDescentAndUPMAreValid () const

int	AscentOfCapital () const

int	AscentOfI () const

int	AscentOfx () const

int	Descent () const

void	Dump (class ON_TextLog &text_log) const

double	GlyphScale (double text_height) const

bool	HeightsAreValid () const

bool	IsSet () const

bool	IsSetAndValid () const

bool	IsUnset () const

int	LineSpace () const

ON_FontMetrics &	operator= (const ON_FontMetrics &)=default

void	SetAscentOfCapital (double ascent_of_capital)

void	SetAscentOfCapital (int ascent_of_capital)

void	SetAscentOfI (int ascent_of_capital)

void	SetAscentOfx (double ascent_of_x)

void	SetAscentOfx (int ascent_of_x)

void	SetHeights (double ascent, double descent, double UPM, double line_space)

void	SetHeights (int ascent, int descent, int UPM, int line_space)

void	SetStrikeout (double strikeout_position, double strikeout_thickness)

void	SetStrikeout (int strikeout_position, int strikeout_thickness)

void	SetUnderscore (double underscore_position, double underscore_thickness)

void	SetUnderscore (int underscore_position, int underscore_thickness)

int	StrikeoutPosition () const

int	StrikeoutThickness () const

int	UnderscorePosition () const

int	UnderscoreThickness () const

int	UPM () const

Static Public Member Functions
static const ON_FontMetrics	Normalize (const ON_FontMetrics &font_metrics)

static const ON_FontMetrics	Scale (const ON_FontMetrics &font_metrics, double scale)

Static Public Attributes
static const double	DefaultLineFeedRatio
	1.6 More...

static const ON__UINT32	HeightOfCapitalCodePoint
	'I' More...

static const ON_FontMetrics	LastResortMetrics

static const ON_FontMetrics	LastResortNormalizedMetrics

static const ON_FontMetrics	Unset
	All properties are zero. More...

Constructor & Destructor Documentation

◆ ON_FontMetrics() [1/2]

ON_FontMetrics::ON_FontMetrics ( )

default

◆ ~ON_FontMetrics()

ON_FontMetrics::~ON_FontMetrics ( )

default

◆ ON_FontMetrics() [2/2]

ON_FontMetrics::ON_FontMetrics ( const ON_FontMetrics & )

default

Member Function Documentation

◆ Ascent()

int ON_FontMetrics::Ascent ( ) const

Returns: Signed distance from the baseline to highest point on a glyph outline.

Remarks: If every glyph outline in the font has (0,0) on the baseline, then Ascent() is the maximum glyph bounding box Y.

Ascent typically includes internal leading, the space used for diacritcial marks above capital latin letters. For this reason, Ascent is typically greater than AscentOfCapital.

Windows: = DWRITE_FONT_METRICS.ascent

◆ AscentDescentAndUPMAreValid()

bool ON_FontMetrics::AscentDescentAndUPMAreValid ( ) const

Returns: True if all of the following are true. UPM() > 0 At least one of Ascent() or Descent() is not zero. Ascent() > Descent() None of UPM(), Ascent(), or Descent() is ON_UNSET_INT_INDEX or -ON_UNSET_INT_INDEX.

◆ AscentOfCapital()

int ON_FontMetrics::AscentOfCapital ( ) const

Returns: The font's typographic capital height.

Remarks: The primary uses of AscentOfCapital() are: 1) Calculate a scale factor to produce text with a user specified "text height". 2) To calculate insertion location for ON::TextVerticalAlignment::Middle and ON::TextVerticalAlignment::Top.

From 2005-2018 opennurbs used the ascent of a capital I. Beginning in 2018 this value is taken from the system font metrics so that fonts designed to render Asian language text, symbols, and emojis will display as expected and lines of text containing mulitiple fonts will render more clearly.

The value (user specified text height)/AscentOfCapital() is used as the scale factor to render glyphs when user interface has provided a "text height" value.

If the capial height property of a font is not available, the ascent of I or H can be used instead. (There are commonly used fonts where using other glyphs gives undesirable results.)OfI.

Windows: = DWRITE_FONT_METRICS.capHeight Apple: = CTFontGetAscent(...)

◆ AscentOfI()

int ON_FontMetrics::AscentOfI ( ) const

Returns: AscentOfCapital()

◆ AscentOfx()

int ON_FontMetrics::AscentOfx ( ) const

Returns: The font's typographic x-height.

Remarks: The x-height is used to help select a substitute font to use for missing glyphs.

◆ Descent()

int ON_FontMetrics::Descent ( ) const

Returns: Signed distance from the English baseline to lowest point on a glyph outline.

Remarks: This value is typically negative because glyphs for letters like 'g' and 'j' typically have a portion of their outline below the baseline. However, some fonts have positive descent. If every glyph outline in the font has (0,0) on the baseline, then Descent() is the minimum glyph bounding box Y.

Windows: = -DWRITE_FONT_METRICS.descent

◆ Dump()

void ON_FontMetrics::Dump ( class ON_TextLog & text_log ) const

◆ GlyphScale()

double ON_FontMetrics::GlyphScale ( double text_height ) const

Description: Parameters: height_of_capital - [in] The desired height of typical capital latin letter glyphs. For fonts like Arial, Helvetica, and Times Roman the heights of the H and I glyphs = font's height of capital. Returns: text_height / AscentOfCapital().

◆ HeightsAreValid()

bool ON_FontMetrics::HeightsAreValid ( ) const

Returns: True if all of the following are true. AscentDescentAndUPMAreValid() is true LineSpace() >= Ascent() - Descent() AscentOfCapital() <= Ascent() AscentOfx() <= Ascent()

◆ IsSet()

bool ON_FontMetrics::IsSet ( ) const

Returns true if at least one metric is not zero.

◆ IsSetAndValid()

bool ON_FontMetrics::IsSetAndValid ( ) const

Returns: True if all of the following are true. HeightsAreValid() is true. AscentOfCapital() > 0

◆ IsUnset()

bool ON_FontMetrics::IsUnset ( ) const

Returns true if all metrics are zero

◆ LineSpace()

int ON_FontMetrics::LineSpace ( ) const

Returns: The positive distance to move the base line when moving to a new line of text.

Remarks: For almost every font used to render English text, LineSpace() > (Ascent() - Descent()).

This metric is sometimes called "height", but that term is often confused with (Ascent() - Descent()).

For fonts designed to render horizontal lines of text, LineSpace() is a vertical distance. For fonts designed to render vertical lines of text, LineSpace() is a horizontal distance. Depending on the context, the direction to move can be up, down, left or right.

Windows: = DWRITE_FONT_METRICS.ascent

DWRITE_FONT_METRICS.descent
DWRITE_FONT_METRICS.lineGap;

◆ Normalize()

static const ON_FontMetrics ON_FontMetrics::Normalize ( const ON_FontMetrics & font_metrics )

static

◆ operator=()

ON_FontMetrics& ON_FontMetrics::operator= ( const ON_FontMetrics & )

default

◆ Scale()

static const ON_FontMetrics ON_FontMetrics::Scale	(	const ON_FontMetrics &	font_metrics,
		double	scale
	)

static

◆ SetAscentOfCapital() [1/2]

void ON_FontMetrics::SetAscentOfCapital ( double ascent_of_capital )

◆ SetAscentOfCapital() [2/2]

void ON_FontMetrics::SetAscentOfCapital ( int ascent_of_capital )

◆ SetAscentOfI()

void ON_FontMetrics::SetAscentOfI ( int ascent_of_capital )

◆ SetAscentOfx() [1/2]

void ON_FontMetrics::SetAscentOfx ( double ascent_of_x )

◆ SetAscentOfx() [2/2]

void ON_FontMetrics::SetAscentOfx ( int ascent_of_x )

◆ SetHeights() [1/2]

void ON_FontMetrics::SetHeights	(	double	ascent,
		double	descent,
		double	UPM,
		double	line_space
	)

◆ SetHeights() [2/2]

void ON_FontMetrics::SetHeights	(	int	ascent,
		int	descent,
		int	UPM,
		int	line_space
	)

◆ SetStrikeout() [1/2]

void ON_FontMetrics::SetStrikeout	(	double	strikeout_position,
		double	strikeout_thickness
	)

◆ SetStrikeout() [2/2]

void ON_FontMetrics::SetStrikeout	(	int	strikeout_position,
		int	strikeout_thickness
	)

◆ SetUnderscore() [1/2]

void ON_FontMetrics::SetUnderscore	(	double	underscore_position,
		double	underscore_thickness
	)

◆ SetUnderscore() [2/2]

void ON_FontMetrics::SetUnderscore	(	int	underscore_position,
		int	underscore_thickness
	)

◆ StrikeoutPosition()

int ON_FontMetrics::StrikeoutPosition ( ) const

Returns: Signed distance from baseline to center of strikeout. A positive value indicates the strikeout is above the baseline (common). Remarks: The signed distance from the baseline to the bottom of the strikeout is StrikeoutPosition() - StrikeoutThickness()/2.

◆ StrikeoutThickness()

int ON_FontMetrics::StrikeoutThickness ( ) const

Returns: Thickness of strikeout. Remarks: The signed distance from the baseline to the bottom of the strikeout is StrikeoutPosition() - StrikeoutThickness()/2.

◆ UnderscorePosition()

int ON_FontMetrics::UnderscorePosition ( ) const

Returns: Signed distance from baseline to center of underscore. A negative value indicates the underscore is below the baseline (common). Remarks: The signed distance from the baseline to the bottom of the underscore is UnderscorePosition() - UnderscoreThickness()/2.

◆ UnderscoreThickness()

int ON_FontMetrics::UnderscoreThickness ( ) const

Returns: Thickness of underscore Remarks: The signed distance from the baseline to the bottom of the underscore is UnderscorePosition() - UnderscoreThickness()/2.

◆ UPM()

int ON_FontMetrics::UPM ( ) const

Returns: The "units per EM". This is the height and width of the square grid where the font glyphs are designed.
Remarks: The width of the 'M' glyph in a font can be different from UPM. The height of the 'M' glyph in a font is typically less than UPM. In TrueType fonts, UPM is often a power of two and generally 1024 or 2048. In OpenType fonts, UPM is often 1000. In PostScript fonts, UPM is often 1000.

Windows: = DWRITE_FONT_METRICS.designUnitsPerEm

Member Data Documentation

◆ DefaultLineFeedRatio

const double ON_FontMetrics::DefaultLineFeedRatio

static

1.6

ON_FontMetric::DefaultLineFeedRatio*ON_FontMetrics().AscentOfCapital() can be used to cook up a line space value when using the ON_FontMetrics.LineSpace() value defined by the font is not desired.

◆ HeightOfCapitalCodePoint

const ON__UINT32 ON_FontMetrics::HeightOfCapitalCodePoint

static

'I'

UNICODE code point of the glyph used to determine HeightOfCapital() when no reaonable value is available from the font definition. Currently this is the 'I' glyph. Opennurbs has used 'I' since 2005. It is possible 'H' would work as well. All other glyphs, in particular 'M' and 'W', do not work.

◆ LastResortMetrics

const ON_FontMetrics ON_FontMetrics::LastResortMetrics

static

Used when it is impossible to find font metrics (missing font for example) and something valid is required for a computation. Currently LastResortMetrics.UPM() is 2048 and this value is chosen because it is the largest common UPM found in real fonts encountered in March 2018.

◆ LastResortNormalizedMetrics

const ON_FontMetrics ON_FontMetrics::LastResortNormalizedMetrics

static

Used when it is impossible to find normalized font metrics (missing font for example) and something valid is required for a computation.

◆ Unset

const ON_FontMetrics ON_FontMetrics::Unset

static

All properties are zero.

Public Member Functions

Static Public Member Functions

Static Public Attributes

Constructor & Destructor Documentation

◆ ON_FontMetrics() [1/2]

◆ ~ON_FontMetrics()

◆ ON_FontMetrics() [2/2]

Member Function Documentation

◆ Ascent()

◆ AscentDescentAndUPMAreValid()

◆ AscentOfCapital()

◆ AscentOfI()

◆ AscentOfx()

◆ Descent()

◆ Dump()

◆ GlyphScale()

◆ HeightsAreValid()

◆ IsSet()

◆ IsSetAndValid()

◆ IsUnset()

◆ LineSpace()

◆ Normalize()

◆ operator=()

◆ Scale()

◆ SetAscentOfCapital() [1/2]

◆ SetAscentOfCapital() [2/2]

◆ SetAscentOfI()

◆ SetAscentOfx() [1/2]

◆ SetAscentOfx() [2/2]

◆ SetHeights() [1/2]

◆ SetHeights() [2/2]

◆ SetStrikeout() [1/2]

◆ SetStrikeout() [2/2]

◆ SetUnderscore() [1/2]

◆ SetUnderscore() [2/2]

◆ StrikeoutPosition()

◆ StrikeoutThickness()

◆ UnderscorePosition()

◆ UnderscoreThickness()

◆ UPM()

Member Data Documentation

◆ DefaultLineFeedRatio

◆ HeightOfCapitalCodePoint

◆ LastResortMetrics

◆ LastResortNormalizedMetrics

◆ Unset