donner::Length< T > Struct Template Reference

Parses a CSS <length-percentage> type as defined by https://www.w3.org/TR/css-values-3/#typedef-length-percentage. More...

#include "donner/base/Length.h"

Public Types
enum class	Extent {   X ,   Y ,   Mixed }
	Selects which extent of the viewbox to use for percentage and viewbox-relative length conversions, see toPixels(). More...
using	Unit = LengthUnit
	The unit identifier for the length.

Public Member Functions
	Length ()=default
	Default constructor, initializes to unitless 0.
	Length (T value, Unit unit=Unit::None)
	Construct a length from a value and unit.
bool	operator== (const Length &other) const
	Equality operator, using near-equals comparison for the value.
std::partial_ordering	operator<=> (const Length &other) const
	Spaceship operator, first ordered by the unit if they are not the same, then by the value (with a near-equals comparison).
bool	isAbsoluteSize () const
	Returns true if the length is an absolute dimension (not a percentage or relative unit).
T	toPixels (const Box< T > &viewbox, const FontMetrics &fontMetrics, Extent extent=Extent::Mixed) const
	Convert the length to pixels, following the ratios at https://www.w3.org/TR/css-values/#absolute-lengths and https://www.w3.org/TR/css-values/#relative-lengths.

Public Attributes
T	value = T(0)
	The numeric value of the length.
Unit	unit = Unit::None
	The unit identifier of the length.

Friends
std::ostream &	operator<< (std::ostream &os, const Length< T > &length)
	ostream-output operator for Length.

Detailed Description

template<typename T>
struct donner::Length< T >

Parses a CSS <length-percentage> type as defined by https://www.w3.org/TR/css-values-3/#typedef-length-percentage.

A length is composed of a number followed by a unit identifier.

Unit identifiers are split into two categories, absolute and relative:

• Absolute: https://www.w3.org/TR/css-values-3/#absolute-lengths
  • cm, mm, Q, in, pc, pt, and px
• Relative: https://www.w3.org/TR/css-values-3/#relative-lengths
  • em, ex, ch, rem, vw, vh, vmin, vmax

The unit may be omitted for '0', which is unitless.

For a percentage, the number is followed by the '%' character.

Examples:

• 0
• 10px
• 50%

Template Parameters

T	Value storage type, typically double.

Member Enumeration Documentation

Extent

template<typename T >

enum class donner::Length::Extent

strong

Selects which extent of the viewbox to use for percentage and viewbox-relative length conversions, see toPixels().

Enumerator
X	Use X component of viewbox for percentage calculations.
Y	Use Y component of viewbox for percentage calculations.
Mixed	Use diagonal extent of viewbox.

Constructor & Destructor Documentation

Length()

template<typename T >

donner::Length< T >::Length ( T value, Unit unit = Unit::None )

inlineexplicit

Construct a length from a value and unit.

Parameters

value	The numeric value of the length.
unit	The unit identifier of the length.

Member Function Documentation

toPixels()

template<typename T >

T donner::Length< T >::toPixels ( const Box< T > & viewbox, const FontMetrics & fontMetrics, Extent extent = Extent::Mixed ) const

inline

Convert the length to pixels, following the ratios at https://www.w3.org/TR/css-values/#absolute-lengths and https://www.w3.org/TR/css-values/#relative-lengths.

Parameters

viewbox	Viewbox of the element for computing viewbox-relative conversions.
fontMetrics	Font size information for font-relative sizes.
extent	Which extent of the viewbox to use for percentage and viewbox-relative length.

Returns

Length in pixels.

Friends And Related Symbol Documentation

operator<<

template<typename T >

std::ostream & operator<< ( std::ostream & os, const Length< T > & length )

friend

ostream-output operator for Length.

Parameters

os	The ostream to write to.
length	Length class to output.

Returns

The ostream that was written to, for chaining.

---

The documentation for this struct was generated from the following file:

• donner/base/Length.h