Trait Cascade 

pub trait Cascade {
    // Provided methods
    fn keystroke(
        &mut self,
        _field: &FieldRef,
        change: Keystroke,
    ) -> KeystrokeOutcome { ... }
    fn keystroke_commit(&mut self, _field: &FieldRef, _value: &str) -> bool { ... }
    fn validate(&mut self, _field: &FieldRef, _value: &str) -> bool { ... }
    fn calculate(&mut self, _writes: &mut FieldWrites, _trigger: &FieldRef) { ... }
    fn format(&mut self, _field: &FieldRef, _value: &str) -> Option<String> { ... }
    fn pointer(
        &mut self,
        _field: &FieldRef,
        _trigger: PointerTrigger,
        _held: Modifiers,
    ) { ... }
    fn take_focus_request(&mut self) -> Option<u32> { ... }
    fn drain_border_style_writes(&mut self) -> Vec<(u32, BorderStyle)> { ... }
}

The script hooks a commit passes through.

One implementation ships here — NoScripts — and its behaviour is the method defaults below. See the module documentation for why those are the specification rather than a placeholder.

Provided Methods

fn keystroke( &mut self, _field: &FieldRef, change: Keystroke, ) -> KeystrokeOutcome

The keystroke hook, with no commit imminent: may rewrite or reject what is being typed.

fn keystroke_commit(&mut self, _field: &FieldRef, _value: &str) -> bool

The keystroke hook with a commit imminent: may reject the commit.

fn validate(&mut self, _field: &FieldRef, _value: &str) -> bool

The validation hook: may reject the commit.

fn calculate(&mut self, _writes: &mut FieldWrites, _trigger: &FieldRef)

The calculation hook: may rewrite other fields’ values.

fn format(&mut self, _field: &FieldRef, _value: &str) -> Option<String>

The format hook: may return a display string that does not change the stored value.

None means “display the raw value”, which is exactly what a build without scripts does — and exactly why such a build shows 1234 where a formatting script would show a currency amount.

fn pointer( &mut self, _field: &FieldRef, _trigger: PointerTrigger, _held: Modifiers, )

A pointer or focus event reached a field.

This hook changes nothing and cannot refuse anything, which is why it returns () where the four above return an answer: the six /AA entries it covers can talk to the host and read the form, and event.value is not even live for them. A viewer runs them for their side effects and carries on regardless.

It is one method over six triggers rather than six methods because nothing downstream branches on which one fired — the branch is inside the implementation, on the event object it populates.

fn take_focus_request(&mut self) -> Option<u32>

The field a script asked the keyboard for, drained.

A position in the document-wide field list — the space FieldRef::index counts in — or None when nothing asked.

Recorded while a script runs and spent afterwards. Moving the keyboard from inside a running script would re-enter the routing the script is already inside, so the request is written down here and the caller routes it through the same path a click takes: the outgoing field’s /AA /Bl, then the incoming field’s /AA /Fo.

The default is None — NoScripts’s answer and every non-scripting cascade’s, because with no engine nothing can ask.

fn drain_border_style_writes(&mut self) -> Vec<(u32, BorderStyle)>

Field.borderStyle writes a script made, drained.

Each entry is a /Fields position and the style the setter accepted. Spent after the script returns so the appearance regenerates through the ordinary path rather than from inside a native function.

Dyn Compatibility

This trait is dyn compatible.

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

Implementors

impl Cascade for NoScripts

impl Cascade for ScriptCascade

Available on crate feature javascript only.