Rendered Edit Session

Split view and rendered-only mode share one RenderedEditSession and the same source_epoch invalidation path per tab.

PRD: Rendered Edit Session (RS-6, split view parity)

Problem

Split view previously used a separate egui editor id (split_preview_rendered) while rendered-only mode used main_editor_rendered. That created two session instances per tab in egui temp memory — switching modes or editing across panes could leave stale block buffers or lose active edit state.

Unified editor id

Both panes now call rendered_editor_id(tab.id) from src/markdown/rendered_session.rs:

pub fn rendered_editor_id(tab_id: usize) -> Id {
    Id::new("main_editor_rendered").with(tab_id)
}

Wired in src/app/central_panel.rs for:

• ViewMode::Rendered — full rendered editor
• ViewMode::Split — right preview pane (left pane is raw EditorWidget)

Same id ⇒ same RenderedEditSession, viewport-culling cache, and widget-id scope when toggling R/S/V or switching between rendered and split.

Shared source_epoch

Both panes read Tab::source_epoch() via MarkdownEditor::source_epoch(...).

Edit source	Epoch bump?	Undo path
Raw pane (split left)	Yes — EditorWidget → Tab::record_external_edit_from_snapshot()	Operation diff via FerriteEditor snapshot
Rendered block commit	No — Tab::record_edit_from_snapshot()	One logical undo step per block commit — see undo granularity
Undo / redo	Yes — Tab::undo() / redo()	Clears session buffers via epoch

On epoch mismatch, load_for_epoch calls RenderedEditSession::invalidate_buffers() (trace log includes stored vs current epoch and editor id). Raw edits while a rendered block is active are authoritative: buffers clear; the user reloads from source on next block activation.

Rendered → raw consistency

Rendered commits write directly to Tab::content. The raw pane reads the same string on the next frame — no extra sync step. Do not bump source_epoch on rendered commits (stable TextEdit widget ids within a session).

Related modules

File	Role
src/markdown/rendered_session.rs	rendered_editor_id, load_for_epoch, save_for_epoch
src/app/central_panel.rs	Passes rendered_editor_id(tab.id) + source_epoch to both rendered paths
src/editor/widget.rs	Raw split pane; bumps epoch on content change
src/state.rs	source_epoch, record_external_edit_from_snapshot, undo/redo epoch bumps
src/markdown/editor.rs	show_rendered_editor — session load/save inside push_id(editor_id) + push_id(source_epoch)

Tests

cargo test rendered_session:: (when test suite compiles):

• rendered_editor_id_unifies_single_and_split_view
• session_persists_across_rendered_view_mode_switch
• rs6_raw_edit_epoch_bump_invalidates_session_buffers
• load_for_epoch_invalidates_when_epoch_changes

Manual verification (RS-6)

1. Open a markdown doc; switch to Split (R → S or view toggle).
2. Click a heading in the rendered pane; type several characters (do not blur yet).
3. Click the raw pane; append a line of text.
4. Confirm the rendered pane shows the new raw content on the next frame.
5. Click the heading again — it should reflect source (prior in-buffer edit discarded unless committed before raw edit).
6. Toggle Rendered ↔ Split — active session state (if any committed block) should feel consistent; no duplicate focus traps.