forked from joejulian/gio
Elias Naur
e2d0b3cfca
With an inverted baseline, the zero value results in the widget baseline aligned to its bottom. Signed-off-by: Elias Naur <mail@eliasnaur.com>
101 lines
2.1 KiB
Go
101 lines
2.1 KiB
Go
// SPDX-License-Identifier: Unlicense OR MIT
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package layout
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import (
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"image"
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"gioui.org/op"
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)
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// Stack lays out child elements on top of each other,
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// according to an alignment direction.
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type Stack struct {
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// Alignment is the direction to align children
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// smaller than the available space.
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Alignment Direction
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maxSZ image.Point
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}
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// StackChild is the layout result of a call to End.
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type StackChild struct {
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macro op.MacroOp
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dims Dimensions
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}
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// Rigid lays out a widget with the same constraints that were
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// passed to Init.
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func (s *Stack) Rigid(gtx *Context, w Widget) StackChild {
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cs := gtx.Constraints
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cs.Width.Min = 0
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cs.Height.Min = 0
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var m op.MacroOp
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m.Record(gtx.Ops)
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dims := gtx.Layout(cs, w)
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m.Stop()
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s.expand(dims)
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return StackChild{m, dims}
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}
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// Expand lays out a widget.
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func (s *Stack) Expand(gtx *Context, w Widget) StackChild {
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var m op.MacroOp
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m.Record(gtx.Ops)
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cs := Constraints{
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Width: Constraint{Min: s.maxSZ.X, Max: gtx.Constraints.Width.Max},
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Height: Constraint{Min: s.maxSZ.Y, Max: gtx.Constraints.Height.Max},
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}
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dims := gtx.Layout(cs, w)
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m.Stop()
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s.expand(dims)
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return StackChild{m, dims}
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}
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func (s *Stack) expand(dims Dimensions) {
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if w := dims.Size.X; w > s.maxSZ.X {
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s.maxSZ.X = w
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}
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if h := dims.Size.Y; h > s.maxSZ.Y {
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s.maxSZ.Y = h
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}
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}
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// Layout a list of children. The order of the children determines their laid
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// out order.
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func (s *Stack) Layout(gtx *Context, children ...StackChild) {
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maxSZ := gtx.Constraints.Constrain(s.maxSZ)
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s.maxSZ = image.Point{}
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var baseline int
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for _, ch := range children {
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sz := ch.dims.Size
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var p image.Point
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switch s.Alignment {
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case N, S, Center:
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p.X = (maxSZ.X - sz.X) / 2
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case NE, SE, E:
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p.X = maxSZ.X - sz.X
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}
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switch s.Alignment {
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case W, Center, E:
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p.Y = (maxSZ.Y - sz.Y) / 2
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case SW, S, SE:
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p.Y = maxSZ.Y - sz.Y
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}
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var stack op.StackOp
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stack.Push(gtx.Ops)
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op.TransformOp{}.Offset(toPointF(p)).Add(gtx.Ops)
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ch.macro.Add(gtx.Ops)
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stack.Pop()
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if baseline == 0 {
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if b := ch.dims.Baseline; b != 0 {
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baseline = b + maxSZ.Y - sz.Y - p.Y
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}
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}
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}
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gtx.Dimensions = Dimensions{
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Size: maxSZ,
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Baseline: baseline,
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}
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}
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