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UndoRedoCommand

agg_gui::undo

Trait UndoRedoCommand 

Source 
pub trait UndoRedoCommand: 'static {
    // Required methods
    fn name(&self) -> &str;
    fn do_it(&mut self);
    fn undo_it(&mut self);
    fn as_any_mut(&mut self) -> &mut dyn Any;
}
Expand description

A named, reversible operation.

Implement this trait to participate in the shared undo/redo stack. The do_it / undo_it methods are called by UndoBuffer on redo and undo respectively.

as_any_mut is the escape hatch for in-stroke coalescing — see UndoBuffer::try_coalesce_last. Implementations downcast the top-of-stack command back to their concrete type and merge a fresh same-stroke action into the existing one (replacing its after snapshot) instead of pushing a new command. Required so multi-event strokes — slider drag, node drag, typing into a number field — land as a single undo step.

Every implementor must provide as_any_mut — typically the one-liner { self }. Commands that don’t want coalescing leave the method alone; their try_coalesce_last predicate just returns false and add_and_do runs the usual path.

Required Methods§

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fn name(&self) -> &str

Short human-readable description, e.g. "insert text".

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fn do_it(&mut self)

Re-apply the operation (called on Redo).

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fn undo_it(&mut self)

Reverse the operation (called on Undo).

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fn as_any_mut(&mut self) -> &mut dyn Any

Downcast hook for in-stroke coalescing. Implementors forward self; the predicate passed to UndoBuffer::try_coalesce_last runs cmd.as_any_mut().downcast_mut::<ConcreteType>() to inspect the top of the stack.

Dyn Compatibility§

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors§