Struct GenerationCounter 

pub struct GenerationCounter { /* private fields */ }

A monotonically increasing counter for tracking data changes.

Store in ExtensionCaches alongside your data. Call bump() when data changes (in handle_command or prepare). In your canvas::Program implementation, compare the generation against a saved value in your Program::State to decide whether to clear and redraw the cache.

Example

struct MyState {
    generation: u64,
    cache: canvas::Cache,
}

impl canvas::Program<Message> for MyProgram {
    type State = MyState;

    fn draw(&self, state: &MyState, ...) -> Vec<Geometry> {
        if state.generation != self.current_generation {
            state.cache.clear();
            // update state.generation after draw
        }
        vec![state.cache.draw(renderer, bounds.size(), |frame| { ... })]
    }
}

Implementations

impl GenerationCounter

pub fn new() -> Self

Create a new counter starting at zero.

pub fn get(&self) -> u64

Return the current generation value.

pub fn bump(&mut self)

Increment the generation. Wraps on overflow (u64 – effectively never).

Trait Implementations

impl Clone for GenerationCounter

fn clone(&self) -> GenerationCounter

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for GenerationCounter

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for GenerationCounter

fn default() -> Self

Returns the “default value” for a type.