79 lines
1.9 KiB
Go
79 lines
1.9 KiB
Go
// SPDX-License-Identifier: Unlicense OR MIT
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/*
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Package unit implements device independent units.
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Device independent pixel, or dp, is the unit for sizes independent of
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the underlying display device.
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Scaled pixels, or sp, is the unit for text sizes. An sp is like dp with
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text scaling applied.
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Finally, pixels, or px, is the unit for display dependent pixels. Their
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size vary between platforms and displays.
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To maintain a constant visual size across platforms and displays, always
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use dps or sps to define user interfaces. Only use pixels for derived
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values.
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*/
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package unit
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import (
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"math"
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)
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// Metric converts Values to device-dependent pixels, px. The zero
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// value represents a 1-to-1 scale from dp, sp to pixels.
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type Metric struct {
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// PxPerDp is the device-dependent pixels per dp.
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PxPerDp float32
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// PxPerSp is the device-dependent pixels per sp.
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PxPerSp float32
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}
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type (
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// Dp represents device independent pixels. 1 dp will
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// have the same apparent size across platforms and
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// display resolutions.
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Dp float32
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// Sp is like UnitDp but for font sizes.
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Sp float32
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)
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// Dp converts v to pixels, rounded to the nearest integer value.
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func (c Metric) Dp(v Dp) int {
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return int(math.Round(float64(nonZero(c.PxPerDp)) * float64(v)))
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}
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// Sp converts v to pixels, rounded to the nearest integer value.
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func (c Metric) Sp(v Sp) int {
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return int(math.Round(float64(nonZero(c.PxPerSp)) * float64(v)))
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}
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// DpToSp converts v dp to sp.
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func (c Metric) DpToSp(v Dp) Sp {
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return Sp(float32(v) * nonZero(c.PxPerDp) / nonZero(c.PxPerSp))
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}
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// SpToDp converts v sp to dp.
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func (c Metric) SpToDp(v Sp) Dp {
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return Dp(float32(v) * nonZero(c.PxPerSp) / nonZero(c.PxPerDp))
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}
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// PxToSp converts v px to sp.
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func (c Metric) PxToSp(v int) Sp {
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return Sp(float32(v) / nonZero(c.PxPerSp))
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}
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// PxToDp converts v px to dp.
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func (c Metric) PxToDp(v int) Dp {
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return Dp(float32(v) / nonZero(c.PxPerDp))
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}
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func nonZero(v float32) float32 {
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if v == 0. {
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return 1
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}
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return v
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}
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