cacao/appkit/src/view/traits.rs

//! Various traits used for Views.

use crate::dragdrop::{DragInfo, DragOperation};
use crate::view::ViewHandle;

pub trait ViewController {
    /// Where possible, we try to respect the lazy-ish-loading of macOS/iOS systems. This hook
    /// notifies you when the `View` has actually loaded into memory, and you're free to do things
    /// with it.
    ///
    /// Note that you can trigger the view to load earlier, if need be... and in many cases it's
    /// fine. This is a platform-specific detail you may want to read up on. :)
    fn did_load(&mut self, _view: ViewHandle) {}

    /// Invoked when the dragged image enters destination bounds or frame; returns dragging operation to perform.
    fn dragging_entered(&self, _info: DragInfo) -> DragOperation { DragOperation::None }
    
    /// Invoked when the image is released, allowing the receiver to agree to or refuse drag operation.
    fn prepare_for_drag_operation(&self, _info: DragInfo) -> bool { false }

    /// Invoked after the released image has been removed from the screen, signaling the receiver to import the pasteboard data.
    fn perform_drag_operation(&self, _info: DragInfo) -> bool { false }

    /// Invoked when the dragging operation is complete, signaling the receiver to perform any necessary clean-up.
    fn conclude_drag_operation(&self, _info: DragInfo) {}

    /// Invoked when the dragged image exits the destination’s bounds rectangle (in the case of a view) or its frame 
    /// rectangle (in the case of a window object).
    fn dragging_exited(&self, _info: DragInfo) {}
}