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Elias Naur
3d37491342
The unit.Value is a struct and thus more inconvenient to use than its
underlying float32 type. In addition, most uses don't need a general
value, but rather a specific unit given by the context. This change
replaces unit.Value with two float32 units, Dp and Sp. It also changes
variables and parameters of unit.Value to a specific unit type matching
the context. That is, unit.Dp everywhere except for text sizes which are
in Sp.
Switching to typed float32s has multiple advantages
- They can be constants:
const touchSlop = unit.Dp(16)
- Casting untyped constants is no longer necessary:
insets := layout.UniformInset(16)
- Calculation with values is natural:
func (s ScrollbarStyle) Width() unit.Dp {
return s.Indicator.MinorWidth + s.Track.MinorPadding + s.Track.MinorPadding
}
The main API change is that calls to gtx.Px must be replaced with either
gtx.Dp or gtx.Sp depending on the unit.
Idea by Christophe Meessen.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
62 lines
1.4 KiB
Go
62 lines
1.4 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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s := c.PxPerDp
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if s == 0. {
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s = 1.
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}
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return int(math.Round(float64(s) * 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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s := c.PxPerSp
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if s == 0. {
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s = 1.
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}
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return int(math.Round(float64(s) * float64(v)))
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}
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