Module overlay_trigger 

OverlayTrigger — the shared “this widget opens that overlay” wrapper.

Used by Dialog, Snackbar, Wizard and PopoverWidget whenever a caller replaces the default Button trigger with a widget of their own.

One control, on whichever node takes focus

To a screen reader a trigger is one control, and the node focus lands on is that control: it carries the role, the name, the popup state, and it answers Enter, Space and the AT Click. Which node that is depends on what was wrapped, and is decided once, as it mounts:

• A widget that takes no focus (a panel, a glyph, a label): the trigger’s own node is the button. It is the Tab stop and it carries everything above.
• A control of its own (a Button, an IconButton, anything that is or holds a focus stop, even one disabled as it mounts): that control is the button. Its role and its own text stand, the opening routes and the popup state are added to it, and the trigger’s node is structure, which the tree walk leaves out. The name given to the trigger is not used there: the control’s own text is what a sighted user reads on it, and a second button around the first would be one control heard as two.

Pointer, touch and pen

The trigger has no geometry and no press visual of its own: it forwards the caller’s child, whose target and appearance are the child’s. The opener is an on_tap, attached beside the handlers already there (the external bucket), so it happens on the release for every pointer kind and never replaces what the child does itself. It goes on two nodes:

• the wrapped widget, so a tap anywhere on it opens, its margins and its non-interactive parts included;
• the wrapped control, when that is a node inside the widget rather than the widget itself. A control that handles taps of its own takes a tap before any ancestor sees it, so an opener left on the wrapper alone would answer Enter, Space and a reader’s Click and never a click.

A tap is delivered to the innermost node that recognizes it, and nowhere else, so a click on the control opens once, beside the control’s own response to it.

Opening on another button

The trigger opens on the buttons the wrapped widget accepts taps from, ButtonMask::PRIMARY unless it says otherwise. To open on a right click, give the wrapped widget .accept_tap_buttons(ButtonMask::SECONDARY); the inner control gets the same mask for the opener, so a left click on it stays the control’s own. A second click with the same button on an open trigger closes it.

PopoverWidget::new(OverlayTrigger::around(
    tag_chip.accept_tap_buttons(ButtonMask::SECONDARY),
))
.content(tag_menu)

Structs

OverlayTrigger

Wraps an arbitrary widget so it can drive a popover.