Enum Event 

pub enum Event {
    Insert {
        position: usize,
        text: String,
        cursor_id: CursorId,
    },
    Delete {
        range: Range<usize>,
        deleted_text: String,
        cursor_id: CursorId,
    },
    MoveCursor {
        cursor_id: CursorId,
        old_position: usize,
        new_position: usize,
        old_anchor: Option<usize>,
        new_anchor: Option<usize>,
        old_sticky_column: usize,
        new_sticky_column: usize,
    },
    AddCursor {
        cursor_id: CursorId,
        position: usize,
        anchor: Option<usize>,
    },
    RemoveCursor {
        cursor_id: CursorId,
        position: usize,
        anchor: Option<usize>,
    },
    Scroll {
        line_offset: isize,
    },
    SetViewport {
        top_line: usize,
    },
    Recenter,
    SetAnchor {
        cursor_id: CursorId,
        position: usize,
    },
    ClearAnchor {
        cursor_id: CursorId,
    },
    ChangeMode {
        mode: String,
    },
    AddOverlay {
        namespace: Option<OverlayNamespace>,
        range: Range<usize>,
        face: OverlayFace,
        priority: i32,
        message: Option<String>,
        extend_to_line_end: bool,
        url: Option<String>,
    },
    RemoveOverlay {
        handle: OverlayHandle,
    },
    RemoveOverlaysInRange {
        range: Range<usize>,
    },
    ClearNamespace {
        namespace: OverlayNamespace,
    },
    ClearOverlays,
    ShowPopup {
        popup: PopupData,
    },
    HidePopup,
    ClearPopups,
    PopupSelectNext,
    PopupSelectPrev,
    PopupPageDown,
    PopupPageUp,
    AddMarginAnnotation {
        line: usize,
        position: MarginPositionData,
        content: MarginContentData,
        annotation_id: Option<String>,
    },
    RemoveMarginAnnotation {
        annotation_id: String,
    },
    RemoveMarginAnnotationsAtLine {
        line: usize,
        position: MarginPositionData,
    },
    ClearMarginPosition {
        position: MarginPositionData,
    },
    ClearMargins,
    SetLineNumbers {
        enabled: bool,
    },
    SplitPane {
        direction: SplitDirection,
        new_buffer_id: BufferId,
        ratio: f32,
    },
    CloseSplit {
        split_id: SplitId,
    },
    SetActiveSplit {
        split_id: SplitId,
    },
    AdjustSplitRatio {
        split_id: SplitId,
        delta: f32,
    },
    NextSplit,
    PrevSplit,
    Batch {
        events: Vec<Event>,
        description: String,
    },
    BulkEdit {
        old_snapshot: Option<Arc<BufferSnapshot>>,
        new_snapshot: Option<Arc<BufferSnapshot>>,
        old_cursors: Vec<(CursorId, usize, Option<usize>)>,
        new_cursors: Vec<(CursorId, usize, Option<usize>)>,
        description: String,
        edits: Vec<(usize, usize, usize)>,
        displaced_markers: Vec<(u64, usize)>,
    },
}

Core event types representing all possible state changes

Variants

Insert

Insert text at a position

Fields

position: usize

text: String

cursor_id: CursorId

Delete

Delete a range of text

Fields

range: Range<usize>

deleted_text: String

cursor_id: CursorId

MoveCursor

Move a cursor to a new position

Fields

cursor_id: CursorId

old_position: usize

new_position: usize

old_anchor: Option<usize>

new_anchor: Option<usize>

old_sticky_column: usize

new_sticky_column: usize

AddCursor

Add a new cursor

Fields

cursor_id: CursorId

position: usize

anchor: Option<usize>

RemoveCursor

Remove a cursor (stores cursor state for undo)

Fields

cursor_id: CursorId

position: usize

anchor: Option<usize>

Scroll

Scroll the viewport

Fields

line_offset: isize

SetViewport

Set viewport to specific position

Fields

top_line: usize

Recenter

Center the viewport on the cursor

SetAnchor

Set the anchor (selection start) for a cursor

Fields

cursor_id: CursorId

position: usize

ClearAnchor

Clear the anchor and reset deselect_on_move for a cursor Used to cancel Emacs mark mode

Fields

cursor_id: CursorId

ChangeMode

Change mode (if implementing modal editing)

Fields

mode: String

AddOverlay

Add an overlay (for decorations like underlines, highlights)

Fields

namespace: Option<OverlayNamespace>

range: Range<usize>

face: OverlayFace

priority: i32

message: Option<String>

extend_to_line_end: bool

Whether to extend the overlay’s background to the end of the visual line

url: Option<String>

Optional URL for OSC 8 terminal hyperlinks

RemoveOverlay

Remove overlay by handle

Fields

handle: OverlayHandle

RemoveOverlaysInRange

Remove all overlays in a range

Fields

range: Range<usize>

ClearNamespace

Clear all overlays in a namespace

Fields

namespace: OverlayNamespace

ClearOverlays

Clear all overlays

ShowPopup

Show a popup

Fields

popup: PopupData

HidePopup

Hide the topmost popup

ClearPopups

Clear all popups

PopupSelectNext

Navigate popup selection (for list popups)

PopupSelectPrev

PopupPageDown

PopupPageUp

AddMarginAnnotation

Margin events Add a margin annotation

Fields

line: usize

position: MarginPositionData

content: MarginContentData

annotation_id: Option<String>

RemoveMarginAnnotation

Remove margin annotation by ID

Fields

annotation_id: String

RemoveMarginAnnotationsAtLine

Remove all margin annotations at a specific line

Fields

line: usize

position: MarginPositionData

ClearMarginPosition

Clear all margin annotations in a position

Fields

position: MarginPositionData

ClearMargins

Clear all margin annotations

SetLineNumbers

Enable/disable line numbers

Fields

enabled: bool

SplitPane

Split view events Split the active pane

Fields

direction: SplitDirection

new_buffer_id: BufferId

ratio: f32

CloseSplit

Close a split pane

Fields

split_id: SplitId

SetActiveSplit

Set the active split pane

Fields

split_id: SplitId

AdjustSplitRatio

Adjust the split ratio

Fields

split_id: SplitId

delta: f32

NextSplit

Navigate to next split

PrevSplit

Navigate to previous split

Batch

Batch of events that should be undone/redone atomically Used for multi-cursor operations where all cursors perform the same action

Fields

events: Vec<Event>

description: String

BulkEdit

Efficient bulk edit that stores tree snapshots for O(1) undo/redo Used for multi-cursor operations, toggle comment, indent/dedent, etc. This avoids O(n²) complexity by applying all edits in a single tree pass.

Key insight: PieceTree uses Arc (persistent data structure), so storing trees for undo/redo is O(1) (Arc clone), not O(n) (content copy).

Fields

old_snapshot: Option<Arc<BufferSnapshot>>

Buffer state before the edit (for undo)

new_snapshot: Option<Arc<BufferSnapshot>>

Buffer state after the edit (for redo)

old_cursors: Vec<(CursorId, usize, Option<usize>)>

Cursor states before the edit

new_cursors: Vec<(CursorId, usize, Option<usize>)>

Cursor states after the edit

description: String

Human-readable description

edits: Vec<(usize, usize, usize)>

Edit operations as (position, delete_len, insert_len), sorted descending by position. Used to replay marker adjustments on undo/redo:

• On redo: replayed as-is (same adjustments as the forward path)
• On undo: inverse() swaps del_len/ins_len (reverse adjustments)

displaced_markers: Vec<(u64, usize)>

Marker positions displaced by deletions: (marker_id_raw, original_byte_position). On undo, after marker adjustments, these markers are restored to their original positions. This fixes the limitation where markers inside a deleted range collapse and can’t be precisely restored by undo.

Implementations

impl Event

pub fn inverse(&self) -> Option<Self>

Returns the inverse event for undo functionality Uses UNDO_SENTINEL cursor_id to avoid moving the cursor during undo

pub fn modifies_buffer(&self) -> bool

Returns true if this event modifies the buffer content

pub fn is_write_action(&self) -> bool

Returns true if this event is a write action (modifies state in a way that should be undoable) Returns false for readonly actions like cursor movement, scrolling, viewport changes, etc.

Write actions include:

• Buffer modifications (Insert, Delete)
• Cursor structure changes (AddCursor, RemoveCursor)
• Batches containing write actions

Readonly actions include:

• Cursor movement (MoveCursor)
• Scrolling and viewport changes (Scroll, SetViewport)
• UI events (overlays, popups, margins, mode changes, etc.)

pub fn cursor_id(&self) -> Option<CursorId>

Returns the cursor ID associated with this event, if any

Trait Implementations

impl Clone for Event

fn clone(&self) -> Event

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Event

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for Event

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl EventHooks for Event

fn before_hook(&self, buffer_id: BufferId) -> Option<HookArgs>

Get the “before” hook args for this event (if any)

fn after_hook(&self, buffer_id: BufferId) -> Option<HookArgs>

Get the “after” hook args for this event (if any)

impl Serialize for Event

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.