Combined one-pane comparison

Grouped lifecycle evidence records 59 focused Core checks, ten native editor workflows, source/fixture repairs and owned cleanup. This remains a partial port.

History savepoints and gap cleanup — October 16, 2026

Both comparison panes now use one chronological Undo manager, matching CUndo's all-view history. Undo from either focused pane reverses the most recent edit, and restores the matching peer layout/revisions without erasing a newer peer draft. Saved edit identities remain separate for each pane. Repeating the same text on an already Edited row after Save still marks it modified; Undo/Redo and branches in history distinguish that new edit from the saved state. Save and Save As record the current identity without adding metadata to file bytes.

Deleting lines inserted into alignment gaps now removes rows only when both visible panes have Empty/ConflictEmpty records, following CleanEmptyLines. Ordinary blank and Edited empty lines remain real content. Carets and row ranges shift by the removed display records. Undo/Redo restores the pre-cleanup layout. Changes to options/active filters now use the owned Save/reload workflow, clearing old history after acceptance.

The full aligned three-pane result view, complete Windows row/EOL equivalence, IME/multi-caret/wrapped-screen-row behavior and large-file performance remain open. Per-pane format/transformation commands retain their existing paths; this does not certify the entire editor.

Retained in-place editing — October 16, 2026

Native typing, ordinary Cut and Paste now edit the displayed view records rather than recomputing the diff after each input. Touched records become Edited; untouched Removed and neutral whitespace records retain their position and state. Editing a removed combined row includes that row's unselected payload in the working draft without including other untouched removals. Insertions retain Unicode and source endings. Editing across rows joins only the selected text.

Two-pane editing uses the same operation, retaining the opposite pane's payload and inserting Empty alignment records as needed. Missing endings are supplied when a formerly empty/removed record becomes a real line beside other content. The caret uses explicit display coordinates, keeping source offsets separate from synthetic display LF and alignment gaps. New final empty editor records do not add unintended saved bytes.

Undo/Redo snapshots retain both pane layouts, combined rows and annotations. Their restoration does not start another diff helper. Save records edited-row annotations in its clean baseline and retains the current view records; explicit Reload and view/options changes still regenerate comparison data. Operations performed while the initial engine projection is pending retain the existing guarded recomputation path. Whole-document transformations and block-transfer paths still use their existing realignment behavior.

Batch evidence records 55 focused Core checks, grouped native coverage, both product repairs, native readiness repair and owned process cleanup.

This is partial source parity. Exact Windows behavior for every multi-row deletion/padding/ending combination, IME and multi-caret input, mixed whitespace alias selection, wrapped screen-row input and large-file performance remain open. Three-pane source views are intentionally read-only: MainFrm::LoadViews sets only the Bottom/result pane writable in that mode. Writable Base/Mine controls apply to two-pane comparison. The earlier claim that three-pane source editing was missing was incorrect.

Source baseline: 7338078f8ddd924b8cddee35f512f2286072136d, DiffData.cpp::m_YourBaseBoth, MainFrm.cpp::LoadViews/OnViewOnewaydiff, BaseView.cpp::SaveFile and SetMainPage.cpp::OnePane.

The two-file viewer now offers Two-pane view; uncheck it for the combined Base–Mine view. Use one-pane view as default for 2-file diff is exposed in Merge Editor General settings and saved under the source-equivalent OnePane preference. A combined region shows all removed Base lines before all added Mine lines, followed by common lines. Alignment gaps are omitted. Whitespace ignored by the comparison collapses to Mine; filtered non-whitespace payload differences retain removed/added lines. Original bytes/endings and source row IDs stay separate from the synthetic display LF. The whitespace continuation below supersedes the earlier generalization about all ignored whitespace collapsing.

The combined view edits Mine. Untouched removed rows stay display-only. Editing a removed row retains its unselected payload in the result, corresponding to upstream's Edited state, while other removed rows remain excluded. Typing, selection replacement, Find/Replace All, tab/indent operations, Undo/Redo and Save use destination coordinates. Saving retains the chosen Mine encoding/BOM and original line endings and does not write Base. Copy includes selected removed rows. Source-row mappings continue to drive block actions and marks.

The line-diff bar is suppressed in one-pane mode, and the locator uses the combined state's single column. Difference navigation targets the combined removal first. Inline highlights follow the source's adjacent Removed/Added pair rule, font/word options and inline length bound. Source line numbers for removed rows are absent. Format controls and Save As target Mine.

Switching modes prompts Save/Don’t Save/Cancel when drafts are dirty. Successful switches reread the saved files and reset history; Cancel preserves mode/drafts. The preference changes only after the switch is accepted. Single-file and three-pane viewers do not use this combined workflow. Create patch file is disabled while the combined view is active, matching upstream's two-valid-view command gate. Retirement and attached-sheet/busy states fence mode changes.

Remaining: the Mac editor recomputes Subversion alignment after typing; upstream retains its in-place Edited row presentation until reload. Full moved/filtered state aliases, exact full context-menu contents/physical acceptance, source whitespace line number variants, physical switch/Save prompts, clipboard/Find/indent acceptance, light/dark whole-window screenshots, large-file and signed/minimum-OS acceptance remain open. This batch does not certify complete TortoiseMerge parity.

Batch evidence

Four focused Core tests passed; the changed range-validation case passed again after guarding invalid multi-ranges before computing their ends. Unsigned Debug builds passed. The first native run exposed late preference injection; window construction now accepts preferences before it loads. The focused retry exposed a shared render path still using two-pane cells; it now uses the combined projection. The final grouped run passed all thirteen Merge families, including native combined Replace All/Tab and Save/Cancel/Discard mode switches. See the batch record. Test-owned processes/windows/helpers and the verified failed-startup fixture were cleaned up. No installed app, user repository or clipboard was used.

The context audit now identifies the source combined pane as the left view, disables hidden-opposite transfer commands and removes right-only mark actions. Clipboard menu targets capture their pasteboard and support actual combined Copy/Cut/Paste/Undo without affecting a newer menu. See one-pane context parity.

Source whitespace aliases and visibility — October 15, 2026

DiffData::DoTwoWayDiff now supplies the common-row policy in both native modes. Two-pane whitespace/EOL-only common rows use Normal, while payloads made common by case/comment/regex filters use FilteredDiff and stay visible when folding. A separate hide flag preserves the distinction between folding and modified-only Find; neither comparison keys nor displayed line numbers supply edited bytes.

The combined common-row branch follows the pinned CompareWithIgnoreWS rule: Compare whitespaces retains different payloads as RemovedWhitespace/AddedWhitespace; Ignore whitespace changes collapses only a leading-space/tab-only difference and otherwise retains a hidden pair; Ignore all whitespace changes keeps only Mine for common rows, including those made common by another filter. Neutral pairs retain Mine's displayed line number on both rows. They remain searchable by modified-only Find but do not increment Added/Removed counts. Their source color channels keep the neutral defaults independently of the Normal swatches. Hidden legacy per-alias color overrides are not exposed by the native Colors page.

Explicit Save As/export follows BaseView::SaveFile: neutral RemovedWhitespace payloads are retained, while ordinary Removed rows are omitted. Both neutral versions therefore appear in the exported contents, using the selected Mine encoding and captured endings; no display LF is substituted. Native editing uses those retained neutral payloads, with the existing grouped Undo/Redo and working-file freshness checks. No viewing or export action rewrites the inputs.

Displayed duplicate line numbers no longer add a line to the original Mine coordinate space. Selection restoration across mode/filter changes uses the original Mine coordinates; combined editing/export owns its separate serialized payload. This prevents a neutral Base row from shifting a later working-file selection. Existing caret-driven expansion of folded rows is retained.

Grouped evidence records source conditions, actual engine plans, palette/folding/Find and byte mappings, native mode changes and editing/export/Save/Undo. The two-pane and combined editors now search active-pane source states on the visible folding projection. Neutral RemovedWhitespace and AddedWhitespace are separate navigable blocks; Normal and FilteredDiff are skipped. Forward Added/Removed accepts Empty padding, while backward Empty accepts Added/Removed, using the entry state throughout as upstream LinesInOneChange does. Navigation selects the whole block in both panes, retains the backward entry caret, and stops at boundaries. Toolbar, context commands and Control-Up/Down use the same search and availability gates. Navigation evidence records the source, focused Core results, initial fixture failure and final grouped native pass. This selection is also the existing transfer/Copy block selection. Three-pane navigation now shares the search with explicit engine peer mappings. Independent boundary highlights and insertion carets now preserve block-only Copy/Cut/Paste semantics; neutral-row Copy uses exact combined display coordinates. Wrapped screen-row grouping still requires a further port. Combined inline navigation is disabled in source because the opposite pane is hidden. Undo/Redo now follows source all-pane selection clearing and target caret restoration; the earlier block-restoring result history was corrected. The October 16 continuation adds in-place Edited row retention; all whitespace aliases/legacy overrides, physical/VoiceOver/large-file and signed App Store acceptance also remain open. This does not certify the complete Merge/editor family.

Initial first-difference selection now searches the combined source-state list, so a neutral Base alias before the first engine changed region is selected first. The selected display block remains distinct from the insertion caret.

The final-record continuation adds the source two-pane NoEnding EOF post-pass while keeping those original empty terminal records out of combined view. Edited empty user records remain part of combined editing.

The common-record family now retains the source's Base EOL on unsplit common combined records while keeping Mine's payload and encoding. Two-pane originals and unedited drafts remain independent. Split neutral aliases still retain each side's own ending; earlier blanket statements about all common records preserving Mine endings are superseded by this scope.

Reload and pane-switch choices now share the owned per-pane Save transaction, including Save left/right/both and direct document-owned history invalidation. See the reload continuation.