Macro zng_wgt::node::command_property
source · macro_rules! command_property { ($( $(#[$on_cmd_attrs:meta])* $vis:vis fn $command:ident { cmd: $cmd_init:expr $(, enabled: $enabled_var:expr)? $(, widget_impl: $Wgt:ty)? $(,)? } )+) => { ... }; }
Expand description
Declare one or more command event properties.
Each declaration expands to two properties on_$command
and on_pre_$command
.
The preview properties call on_pre_command
, the main event properties call on_command
.
§Examples
command_property! {
/// Paste command property docs.
pub fn paste {
cmd: PASTE_CMD.scoped(WIDGET.id()),
// enabled: LocalVar(true), // default enabled
}
}
§Command
The cmd:
expression evaluates on init to generate the command, this allows for the
creation of widget scoped commands. The new command property event handler will receive events
for the command and scope that target the widget where the property is set.
If the command is scoped on the root widget and the command property is set on the same root widget a second handle is taken for the window scope too, so callers can target the window using the window ID or the root widget ID.
§Enabled
The enabled:
expression evaluates on init to generate a boolean variable that defines
if the command handle is enabled. Command event handlers track both their existence and
the enabled flag, see Command::subscribe
for details.
If not provided the command is always enabled.
§Async
Async event handlers are supported by properties generated by this macro, but only the code before the first .await
executes
in the event track, subsequent code runs in widget updates.
§Implement For
You can implement the new properties for a widget or mix-in using the widget_impl:
directive:
/// Clipboard handler.
#[widget_mixin]
pub struct ClipboardMix<P>(P);
command_property! {
/// Paste command property docs.
pub fn paste {
cmd: PASTE_CMD.scoped(WIDGET.id()),
widget_impl: ClipboardMix<P>,
}
}