Menu

Menu puts a button on the page and hangs a list of actions behind it, and returns the index of the item clicked. 0-indexed, nil if no item is clicked.

It is a button that carries several presses rather than one, so a row of related actions — rename, duplicate, delete — takes a single button's worth of space.

API

func Menu(c *tgframe.Container, label string, items []string, conf ...*MenuConf) *int

• c is the container to add the menu to.
• label is the text on the button that opens it.
• items are the actions in the dropdown, in the order they are shown.
• conf is an optional configuration, at most one.

// MenuConf is the configuration for the Menu component.
type MenuConf struct {
	tgframe.Base // ID

	// Color defines the color of the button that opens the menu.
	Color tcutil.Color

	// Disabled is true if the button that opens the menu is disabled.
	Disabled bool
}

Example

	items := []string{"Rename", "Duplicate", "Delete"}
	picked := tgcomp.Menu(p.Main, "Actions", items)

	action := "none"
	if picked != nil {
		action = items[*picked]
	}

	tgcomp.Text(p.Main, "Action: "+action,
		&tgcomp.TextConf{ID: "menu_result"})

The click lasts one run

A menu reports a pick the way Button reports a press: the index is there for exactly the run that handles the click, and nil again on the next one. Act on it where you get it, or keep it yourself:

if picked := tgcomp.Menu(p.Main, "Actions", items); picked != nil {
	applyAction(items[*picked])
}

There is no "currently selected item" to read back later. A menu is a list of things to do; a list of things to be is Select or Radio, which keep what was chosen.

Identity

Each item claims a click id of its own, the menu's id with the item's index behind it — menu_component_Actions_0 for the first item of a menu labelled Actions. Two menus with the same label therefore collide, and the run reports duplicated component id; give one of them a Conf.ID, and its items follow:

tgcomp.Menu(p.Main, "Actions", items)
tgcomp.Menu(p.Main, "Actions", items, &tgcomp.MenuConf{ID: "row_actions"})

Because the ids carry the index, a click naming an index the menu no longer has — items dropped between the draw and the press — is not a pick, and the run reads it as nil rather than as the last item.

Rendering

Whether the dropdown is open lives on the client, which the server never sees and never sets. The items are written every run, open or not.

Clicking an item closes the dropdown, as does clicking outside it or pressing Escape. Escape goes to whichever overlay was opened last, so a menu opened inside a dialog closes on the first press and leaves the dialog for the second.

Disabled is on the button, not the items: a disabled menu cannot be opened at all.

Inside a form

Picking an item sends the form it is written in, the way pressing a Button does. A menu item is an action to take now, so it does not sit in the form's queue waiting for something else to send it: the run that reports the pick is the one that reads the values queued before it.