feat(tracker): implement more proper menus, with Undo&Redo

Closes #24

tracker/menu.go

@@ -0,0 +1,151 @@
+package tracker
+
+import (
+	"image"
+	"image/color"
+
+	"gioui.org/io/pointer"
+	"gioui.org/layout"
+	"gioui.org/op"
+	"gioui.org/op/clip"
+	"gioui.org/op/paint"
+	"gioui.org/unit"
+	"gioui.org/widget"
+	"gioui.org/widget/material"
+)
+
+type Menu struct {
+	Visible   bool
+	clickable widget.Clickable
+	tags      []bool
+	clicks    []int
+	hover     int
+}
+
+type MenuStyle struct {
+	Menu          *Menu
+	Title         string
+	IconColor     color.NRGBA
+	TextColor     color.NRGBA
+	ShortCutColor color.NRGBA
+	FontSize      unit.Value
+	IconSize      unit.Value
+	HoverColor    color.NRGBA
+}
+
+type MenuItem struct {
+	IconBytes    []byte
+	Text         string
+	ShortcutText string
+	Disabled     bool
+}
+
+func (m *Menu) Clicked() (int, bool) {
+	if len(m.clicks) == 0 {
+		return 0, false
+	}
+	first := m.clicks[0]
+	for i := 1; i < len(m.clicks); i++ {
+		m.clicks[i-1] = m.clicks[i]
+	}
+	m.clicks = m.clicks[:len(m.clicks)-1]
+	return first, true
+}
+
+func (m *MenuStyle) Layout(gtx C, items ...MenuItem) D {
+	contents := func(gtx C) D {
+		flexChildren := make([]layout.FlexChild, len(items))
+		for i, item := range items {
+			// make sure we have a tag for every item
+			for len(m.Menu.tags) <= i {
+				m.Menu.tags = append(m.Menu.tags, false)
+			}
+			// handle pointer events for this item
+			for _, ev := range gtx.Events(&m.Menu.tags[i]) {
+				e, ok := ev.(pointer.Event)
+				if !ok {
+					continue
+				}
+				switch e.Type {
+				case pointer.Press:
+					m.Menu.clicks = append(m.Menu.clicks, i)
+					m.Menu.Visible = false
+				case pointer.Enter:
+					m.Menu.hover = i + 1
+				case pointer.Leave:
+					if m.Menu.hover == i+1 {
+						m.Menu.hover = 0
+					}
+				}
+			}
+			// layout contents for this item
+			i2 := i // avoid loop variable getting updated in closure
+			item2 := item
+			flexChildren[i] = layout.Rigid(func(gtx C) D {
+				defer op.Save(gtx.Ops).Load()
+				var macro op.MacroOp
+				if i2 == m.Menu.hover-1 && !item2.Disabled {
+					macro = op.Record(gtx.Ops)
+				}
+				icon := widgetForIcon(item2.IconBytes)
+				if !item2.Disabled {
+					icon.Color = m.IconColor
+				} else {
+					icon.Color = mediumEmphasisTextColor
+				}
+				iconInset := layout.Inset{Left: unit.Dp(12), Right: unit.Dp(6)}
+				textLabel := LabelStyle{Text: item2.Text, FontSize: m.FontSize, Color: m.TextColor}
+				if item2.Disabled {
+					textLabel.Color = mediumEmphasisTextColor
+				}
+				shortcutLabel := LabelStyle{Text: item2.ShortcutText, FontSize: m.FontSize, Color: m.ShortCutColor}
+				shortcutInset := layout.Inset{Left: unit.Dp(12), Right: unit.Dp(12), Bottom: unit.Dp(2), Top: unit.Dp(2)}
+				dims := layout.Flex{Axis: layout.Horizontal, Alignment: layout.Middle}.Layout(gtx,
+					layout.Rigid(func(gtx C) D {
+						return iconInset.Layout(gtx, func(gtx C) D {
+							return icon.Layout(gtx, m.IconSize)
+						})
+					}),
+					layout.Rigid(textLabel.Layout),
+					layout.Flexed(1, func(gtx C) D { return D{Size: image.Pt(gtx.Constraints.Max.X, 1)} }),
+					layout.Rigid(func(gtx C) D {
+						return shortcutInset.Layout(gtx, shortcutLabel.Layout)
+					}),
+				)
+				if i2 == m.Menu.hover-1 && !item2.Disabled {
+					recording := macro.Stop()
+					paint.FillShape(gtx.Ops, m.HoverColor, clip.Rect{
+						Max: image.Pt(dims.Size.X, dims.Size.Y),
+					}.Op())
+					recording.Add(gtx.Ops)
+				}
+				if !item2.Disabled {
+					rect := image.Rect(0, 0, dims.Size.X, dims.Size.Y)
+					pointer.Rect(rect).Add(gtx.Ops)
+					pointer.InputOp{Tag: &m.Menu.tags[i2],
+						Types: pointer.Press | pointer.Enter | pointer.Leave,
+					}.Add(gtx.Ops)
+				}
+				return dims
+			})
+		}
+		return layout.Flex{Axis: layout.Vertical}.Layout(gtx, flexChildren...)
+	}
+	popup := Popup(&m.Menu.Visible)
+	popup.NE = unit.Dp(0)
+	popup.ShadowN = unit.Dp(0)
+	popup.NW = unit.Dp(0)
+	return popup.Layout(gtx, contents)
+}
+
+func PopupMenu(th *material.Theme, menu *Menu) MenuStyle {
+	return MenuStyle{
+		Menu:          menu,
+		IconColor:     white,
+		TextColor:     white,
+		ShortCutColor: mediumEmphasisTextColor,
+		FontSize:      unit.Dp(16),
+		IconSize:      unit.Dp(16),
+		HoverColor:    menuHoverColor,
+	}
+}