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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>
56 lines
1.3 KiB
Go
56 lines
1.3 KiB
Go
// SPDX-License-Identifier: Unlicense OR MIT
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package widget
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import (
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"image"
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"gioui.org/f32"
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"gioui.org/layout"
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"gioui.org/op"
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"gioui.org/op/clip"
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"gioui.org/op/paint"
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"gioui.org/unit"
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)
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// Image is a widget that displays an image.
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type Image struct {
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// Src is the image to display.
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Src paint.ImageOp
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// Fit specifies how to scale the image to the constraints.
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// By default it does not do any scaling.
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Fit Fit
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// Position specifies where to position the image within
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// the constraints.
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Position layout.Direction
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// Scale is the ratio of image pixels to
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// dps. If Scale is zero Image falls back to
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// a scale that match a standard 72 DPI.
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Scale float32
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}
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const defaultScale = float32(160.0 / 72.0)
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func (im Image) Layout(gtx layout.Context) layout.Dimensions {
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scale := im.Scale
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if scale == 0 {
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scale = defaultScale
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}
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size := im.Src.Size()
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wf, hf := float32(size.X), float32(size.Y)
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w, h := gtx.Dp(unit.Dp(wf*scale)), gtx.Dp(unit.Dp(hf*scale))
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dims, trans := im.Fit.scale(gtx.Constraints, im.Position, layout.Dimensions{Size: image.Pt(w, h)})
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defer clip.Rect{Max: dims.Size}.Push(gtx.Ops).Pop()
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pixelScale := scale * gtx.Metric.PxPerDp
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trans = trans.Mul(f32.Affine2D{}.Scale(f32.Point{}, f32.Pt(pixelScale, pixelScale)))
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defer op.Affine(trans).Push(gtx.Ops).Pop()
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im.Src.Add(gtx.Ops)
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paint.PaintOp{}.Add(gtx.Ops)
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return dims
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}
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