Select选择器

item := tree.Sub(page, tree.Name("item"))
values := []string{"metal", "d3d", "vulkan"}
control := components.BeginSelect(canvas, theme, bounds, components.SelectOptions{
    TriggerID: tree.ID(page, "trigger"), Label: "Renderer", Value: value,
    Placeholder: "Select a backend", Open: open, Content: content, Layer: 4,
    Scope: tree.ID(page, "content"), DismissID: tree.ID(page, "dismiss"),
})
control.AddLabel("Native backends")
for index, label := range []string{"Metal", "Direct3D", "Vulkan"} {
    control.AddItem(components.SelectItem{
        ID: item.At(index), Label: label, Value: values[index],
        Selected: value == values[index],
    })
}
control.End()

components.BeginSelect(canvas, theme, invalidBounds, components.SelectOptions{
    TriggerID: tree.ID(page, "trigger"), Label: "Renderer",
    Value: "", Placeholder: "Select a backend", Invalid: true,
})
components.BeginSelect(canvas, theme, disabledBounds, components.SelectOptions{
    TriggerID: tree.ID(page, "disabled"), Label: "Unavailable",
    Placeholder: "Backend unavailable", Disabled: true,
    Size: components.SelectSizeSmall,
})