//! The curve viewer state: the `curve` node's control points as draggable
 //! handles, entered from the node's context menu ("Edit Handles").
 //!
 //! This is now one [`HandleSource`] on the framework in
 //! [`crate::viewer_state`], which owns everything that used to live here:
 //! projection, hit-testing, the drag model, per-gesture undo, snapping, the
 //! HUD, and write-back through the SetParam resync sequence. What is left is
 //! the part that is actually about curves — an open-ended list of world
 //! positions in the "Points" parameter, which the pointer may extend and trim.
 //!
 //! The behaviour that survives the move, because it is the framework's now:
 //!
 //! - **left press on a handle** grabs it; dragging moves the point on the
 //!   camera-facing plane at its own depth, so orbiting between edits never
 //!   makes a drag jump;
 //! - **left press on empty space** appends a point there, at the depth of the
 //!   last one, and immediately drags it;
 //! - **right press on a handle** deletes it; Delete/Backspace deletes the
 //!   selected one;
 //! - **undo / redo** step one gesture at a time — a whole drag is one step,
 //!   an add-and-drag is one step, a delete is one step;
 //! - **Escape** exits.
 
 use crate::app::FsNode;
 use crate::geometry::{format_curve_points, node_param_str, parse_curve_points};
 use crate::viewer_state::HandleSource;
 use glam::Vec3;
 
 /// Re-exported for the call sites that predate the framework. The projection
 /// helpers are the framework's; this module is only the curve's handles.
 pub use crate::viewer_state::{
     find_node_by_id, find_node_by_id_mut, project_point, unproject_point, HANDLE_HIT_RADIUS,
 };
 
 pub struct CurveHandles;
 
 impl HandleSource for CurveHandles {
     fn name(&self) -> &'static str {
         "Curve Points"
     }
 
     fn accepts(&self, node_type: &str) -> bool {
         node_type.eq_ignore_ascii_case("curve")
     }
 
     fn read(&self, node: &FsNode) -> Vec<Vec3> {
         parse_curve_points(&node_param_str(node, "Points", ""))
     }
 
     fn write(&self, node: &mut FsNode, handles: &[Vec3]) {
         let formatted = format_curve_points(handles);
         if let Some(p) = node.params.iter_mut().find(|p| p.name == "Points") {
             p.default = formatted;
         }
     }
 
     fn extensible(&self) -> bool {
         true
     }
 
     fn hints(&self) -> &'static str {
         "drag to move, click to add, right-click or Del to remove"
     }
 }