Split app UI layout packages

internal/appui/layout/header/dropdown.go

@@ -0,0 +1,88 @@
+package header
+
+import (
+	"image"
+
+	"gioui.org/layout"
+	"gioui.org/op"
+	"gioui.org/unit"
+)
+
+func AnchoredMenuX(triggerWidth, menuWidth int) int {
+	return triggerWidth - menuWidth
+}
+
+func AnchoredMenuOriginX(containerWidth, rowOriginX, triggerRightX, menuWidth int) int {
+	x := rowOriginX + triggerRightX - menuWidth
+	if x < 0 {
+		return 0
+	}
+	if x+menuWidth > containerWidth {
+		return max(0, containerWidth-menuWidth)
+	}
+	return x
+}
+
+type DropdownAnchor struct {
+	TriggerRightX  int
+	TriggerBottomY int
+}
+
+func (a DropdownAnchor) Point() image.Point {
+	return image.Pt(a.TriggerRightX, a.TriggerBottomY)
+}
+
+type DropdownSurface struct {
+	ContainerWidth int
+	LeftInset      int
+	TopInset       int
+}
+
+func (s DropdownSurface) MenuConstraints(gtx layout.Context) layout.Context {
+	menuGTX := gtx
+	menuGTX.Constraints.Min = image.Point{}
+	menuGTX.Constraints.Max.X = max(0, s.ContainerWidth)
+	return menuGTX
+}
+
+func (s DropdownSurface) Origin(anchor DropdownAnchor, menuWidth int) image.Point {
+	x := s.LeftInset + AnchoredMenuOriginX(s.ContainerWidth, 0, anchor.TriggerRightX, menuWidth)
+	y := s.TopInset + anchor.TriggerBottomY
+	return image.Pt(x, y)
+}
+
+func (s DropdownSurface) Draw(gtx layout.Context, anchor DropdownAnchor, menu layout.Widget) layout.Dimensions {
+	menuGTX := s.MenuConstraints(gtx)
+	menuOps := op.Record(gtx.Ops)
+	menuDims := layout.Inset{Top: unit.Dp(6)}.Layout(menuGTX, menu)
+	menuCall := menuOps.Stop()
+	menuOrigin := s.Origin(anchor, menuDims.Size.X)
+	stack := op.Offset(menuOrigin).Push(gtx.Ops)
+	menuCall.Add(gtx.Ops)
+	stack.Pop()
+	return layout.Dimensions{Size: gtx.Constraints.Max}
+}
+
+type ActionMetrics struct {
+	RowOriginX int
+	Spacing    int
+	RowDims    layout.Dimensions
+	SyncDims   layout.Dimensions
+	LockDims   layout.Dimensions
+	MainDims   layout.Dimensions
+}
+
+func (m ActionMetrics) SyncAnchor() DropdownAnchor {
+	return DropdownAnchor{
+		TriggerRightX:  m.RowOriginX + m.SyncDims.Size.X,
+		TriggerBottomY: m.RowDims.Size.Y,
+	}
+}
+
+func (m ActionMetrics) MainAnchor() DropdownAnchor {
+	triggerRightX := m.SyncDims.Size.X + m.Spacing + m.LockDims.Size.X + m.Spacing + m.MainDims.Size.X
+	return DropdownAnchor{
+		TriggerRightX:  m.RowOriginX + triggerRightX,
+		TriggerBottomY: m.RowDims.Size.Y,
+	}
+}