Documentation
¶
Overview ¶
Package unit defines units of length such as inches or pixels.
Functions like Inches and Pixels return a Value in the corresponding unit. For example:
v := unit.Inches(4.5)
represents four and a half inches.
Converting between pixels (px), physical units (dp, pt, in, mm) and font-face-relative measures (em, ex, ch) depends on the context, such as the screen's DPI resolution and the active font face. That context is represented by the Converter type.
Conversions may be lossy. Converting 4.5 inches to pixels and back may result in something slightly different than 4.5. Similarly, converting 4 inches and 0.5 inches to pixels and then adding the results won't necessarily equal the conversion of 4.5 inches to pixels.
Note that what CSS (Cascading Style Sheets) calls "px" differs from what this package calls "px". For legacy reasons, the CSS semantics are that 1 inch should roughly equal 96csspx regardless of the actual DPI resolution, as per https://developer.mozilla.org/en/docs/Web/CSS/length. This package's semantics are that 1px means exactly one physical pixel, always. This package represents 1csspx as 1.666666667dp, since there are 160 density independent pixels per inch, the same definition as Android.
Index ¶
Constants ¶
const ( DensityIndependentPixelsPerInch = 160 MillimetresPerInch = 25.4 PointsPerInch = 72 )
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Converter ¶
type Converter interface {
// Convert converts v to the given unit.
Convert(v Value, to Unit) Value
// Pixels converts v to a 26.6 fixed-point number of physical pixels.
Pixels(v Value) fixed.Int26_6
}
Converter converts values from one unit to another. Conversions may be lossy.
type Unit ¶
type Unit uint8
Unit is a unit of length, such as inches or pixels.
const ( // Px is a physical pixel, regardless of the DPI resolution. Px Unit = iota // Dp is 1 density independent pixel: 1/160th of an inch. Dp // Pt is 1 point: 1/72th of an inch. Pt // Mm is 1 millimetre: 1/25.4th of an inch. Mm // In is 1 inch. // // If the context does not specify a DPI resolution, the recommended // fallback value for conversion is 72 pixels per inch. In // Em is the height of the active font face, disregarding extra leading // such as from double-spaced lines of text. // // If the context does not specify an active font face, the recommended // fallback value for conversion is 12pt. Em // Ex is the x-height of the active font face. // // If the context does not specify an x-height, the recommended fallback // value for conversion is 0.5em. Ex // Ch is the character width of the numeral zero glyph '0' of the active // font face. // // If the context does not specify a '0' glyph, the recommended fallback // value for conversion is 0.5em. Ch )
type Value ¶
Value is a number and a unit.
func Millimetres ¶
Millimetres returns the given number of Mm as a Value.
Source Files