View Template Comparer (VTC) — Developer Guide

VTC is a testing tool for side-by-side view-template comparison with staged local edits and a single Process execution path.

Current Architecture

Command + window

VtcCommand is the Revit command entrypoint.
VtcCommandHandler builds document-scoped services and constructs VtcWindowViewModel.
VtcWindow is the shell view; Process/Preview UX is driven from VM + XAML templates.

Source: src/Tools/Testing/VTC/Features/VtcCommand.cs:14 Source: src/Tools/Testing/VTC/Features/VtcCommandHandler.cs:48 Source: src/Tools/Testing/VTC/UI/Views/VtcWindow.xaml:1

Core services

IVtcComparisonService compares/extracts and now provides BatchApply(...).
IVtcSerializationService now only supports CreateTemplateFromModel + ApplyModel.
IVtcTemplateStorageService remains the cache Save/Load surface.

Source: src/Tools/Testing/VTC/Contracts/IVtcComparisonService.cs:24 Source: src/Tools/Testing/VTC/Contracts/IVtcSerializationService.cs:6 Source: src/Tools/Testing/VTC/Services/VtcTemplateStorageService.cs:203

REV2 Data Contracts

Added contracts used by Process + Preview:

VtcOutputMode
VtcPendingOverride (uses EditedSide)
VtcProcessResult
VtcPreviewItem
UI-local preview hierarchy node: VtcPreviewTreeNode

Source: src/Tools/Testing/VTC/Contracts/VtcEnums.cs:206 Source: src/Tools/Testing/VTC/Contracts/VtcDataModels.cs:224 Source: src/Tools/Testing/VTC/Contracts/VtcDataModels.cs:233 Source: src/Tools/Testing/VTC/Contracts/VtcDataModels.cs:238 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcWindowViewModel.cs:2142

Process Flow (REV2)

Dialog body + validity gating

VtcProcessDialogBodyViewModel implements IAlertBody and raises ValidityChanged when OutputMode or NewTemplateName changes, enabling DisableWhenInvalid button gating.

Radio bindings use VtcEnumToBoolConverter. Read-only Process counters in VtcBodyTemplates.xaml are explicitly bound Mode=OneWay to avoid WPF attempting TwoWay updates on read-only VM properties.

Source: src/Tools/Testing/VTC/UI/ViewModels/VtcProcessDialogBodyViewModel.cs:13 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcProcessDialogBodyViewModel.cs:70 Source: src/Tools/Testing/VTC/UI/Resources/VtcBodyTemplates.xaml:354 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcWindowViewModel.cs:601

VM execution semantics

Process() builds preview and opens Process dialog.
ExecuteProcess(...) handles overwrite-left, overwrite-right, and create-merged.
Pending overrides are applied only when selected side matches pending edited side.
Process command gating now requires HasSelections || HasProcessablePendingOverrides (prevents no-op Process when staged edits exist but are ineligible).
Create-merged model merge removes base-side keyed list items when the user selected the opposite side and that keyed item is missing there (preserves LeftMissing/RightMissing selection intent).
During ApplySnapshot, missing-side selections for category/workset/link now clear/reset base-side override state instead of no-op preserving base values.
Success clears pending/local edits and rebuilds comparison.
Process conflicts preserve failed pending overrides by restoring them after rebuild for retry.

Source: src/Tools/Testing/VTC/UI/ViewModels/VtcWindowViewModel.cs:563 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcWindowViewModel.cs:1511 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcWindowViewModel.cs:1620 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcWindowViewModel.cs:1940 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcWindowViewModel.cs:1766 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcWindowViewModel.cs:1898 Source: src/Tools/Testing/VTC/Revit/Services/VtcComparisonService.cs:376 Source: src/Tools/Testing/VTC/Revit/Services/VtcComparisonService.cs:1395 Source: src/Tools/Testing/VTC/Revit/Services/VtcComparisonService.cs:1694

Batch apply behavior

VtcComparisonService.BatchApply(...) runs all selected changes + eligible pending overrides in one parent transaction. Each individual selection/pending-override apply runs in its own SubTransaction; expected per-setting failures are captured as conflicts and rolled back so failed keys do not leave partial writes. Unexpected exceptions still propagate.

Source: src/Tools/Testing/VTC/Revit/Services/VtcComparisonService.cs:98 Source: src/Tools/Testing/VTC/Revit/Services/VtcComparisonService.cs:120 Source: src/Tools/Testing/VTC/Revit/Services/VtcComparisonService.cs:163 Source: src/Tools/Testing/VTC/Revit/Services/VtcComparisonService.cs:187

Local Override Model

VtcDiffTreeNode owns local override state on canonical nodes (OriginalNode ?? this) so filtered proxy nodes remain consistent.

Local writes: SetLocalOverrideData(...)
Local reads: GetCategoryDataForSide(...)
Inline displays: LeftCategoryData / RightCategoryData
Side-specific local-state flags: HasLocalOverrideLeft / HasLocalOverrideRight
Per-side and all-side clear APIs

Source: src/Tools/Testing/VTC/UI/ViewModels/VtcDiffTreeNode.cs:213 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcDiffTreeNode.cs:253 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcDiffTreeNode.cs:261 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcDiffTreeNode.cs:278 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcDiffTreeNode.cs:247

Pending Override Lifecycle Rules

Implemented behavior:

Pending overrides tracked by key in VM.
Any rebuild/pairing swap clears pending/local edits with explicit notice.
Selection-side flip for a key invalidates pending/local state for that key, but SelectedSide=None no longer purges staged edits.
Failed pending overrides from Process conflicts are restored after rebuild and remain retry-eligible even if their diff row no longer exists.
Preview rows/tree are backed by indexed key lookup (_nodeByKeyIndex) rebuilt with tree rebuilds.
Preview pending count uses Process eligibility (GetEligiblePendingOverrides) so Preview reflects what Process will attempt.

Source: src/Tools/Testing/VTC/UI/ViewModels/VtcWindowViewModel.cs:46 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcWindowViewModel.cs:541 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcWindowViewModel.cs:1546 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcWindowViewModel.cs:1766 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcWindowViewModel.cs:1898 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcWindowViewModel.cs:398

UI Composition (REV2)

Inspector + Preview + Library tabs
Inspector now exposes explicit per-row side actions (Use Left, Use Right, Clear) and per-side override edit actions (Edit Left, Edit Right).
Tree rows expose per-side inline edit buttons so edit intent is separate from selection intent.
Library save menu now includes Left/Right/Merged save targets (SaveMergedTemplateCommand persists a merged model built from selections + eligible pending overrides)
BottomPanel footer with Close and Process

Source: src/Tools/Testing/VTC/UI/Views/VtcWindow.xaml:1123 Source: src/Tools/Testing/VTC/UI/Views/VtcWindow.xaml:317 Source: src/Tools/Testing/VTC/UI/Views/VtcWindow.xaml:1297 Source: src/Tools/Testing/VTC/UI/Views/VtcWindow.xaml:1244 Source: src/Tools/Testing/VTC/UI/Views/VtcWindow.xaml:1267 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcWindowViewModel.cs:1365 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcWindowViewModel.cs:1687 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcWindowViewModel.cs:2089 Source: src/Tools/Testing/VTC/UI/Views/VtcWindow.xaml:1330

Preview uses a dedicated hierarchy (PreviewTreeRoots) rendered in a TreeView. Preview selection uses OnPreviewTreeItemSelected to call shared navigation logic (NavigateToPreviewSetting) that will:

clear search/filter state,
select target node,
expand only the target ancestor path and BringIntoView the realized TreeViewItem.

Source: src/Tools/Testing/VTC/UI/Views/VtcWindow.xaml:1241 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcWindowViewModel.cs:458 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcWindowViewModel.cs:1943 Source: src/Tools/Testing/VTC/UI/Views/VtcWindow.xaml.cs:139 Source: src/Tools/Testing/VTC/UI/Views/VtcWindow.xaml.cs:153

Selection visual contract

Gold border/checkmark/glow represent selection.
Manual staged overrides now use an explicit Edited badge with side-colored dots in TreeView, Inspector, and Preview.
Hover emphasis preserves existing diff tint and uses typography emphasis (no dark hover fill on diff cells).
Storyboard uses (UIElement.Effect).(DropShadowEffect.Opacity).
Effect instance uses x:Shared="False" resource (VtcSelectionGlowEffect) to keep animations valid per cell.
Conflict visuals override selection visuals.

Source: src/Tools/Testing/VTC/UI/Resources/VtcDiffStyles.xaml:12 Source: src/Tools/Testing/VTC/UI/Resources/VtcDiffStyles.xaml:51 Source: src/Tools/Testing/VTC/UI/Views/VtcWindow.xaml:276 Source: src/Tools/Testing/VTC/UI/Views/VtcWindow.xaml:687 Source: src/Tools/Testing/VTC/UI/Resources/VtcDiffStyles.xaml:475 Source: src/Tools/Testing/VTC/UI/Resources/VtcDiffStyles.xaml:507

Design-time preview contract

VtcWindow XAML declares a design-time instance of VtcWindowDesignTimeViewModel.
Non-design runtime construction stays constructor-injected, while sandbox fallback still uses the design-time VM.
The design-time VM now mirrors the live window binding surface used by the REV2 shell (tree/filter/inspector/library/link commands) and seeds representative REV2 tab/tree data.

Source: src/Tools/Testing/VTC/UI/Views/VtcWindow.xaml:14 Source: src/Tools/Testing/VTC/UI/Views/VtcWindow.xaml.cs:31 Source: src/Tools/Testing/VTC/DesignTime/VtcWindowDesignTimeViewModel.cs:27 Source: src/Tools/Testing/VTC/DesignTime/VtcWindowDesignTimeViewModel.cs:83 Source: src/Tools/Testing/VTC/DesignTime/VtcWindowDesignTimeViewModel.cs:160

Removed/Retired Paths

The REV2 implementation removes legacy VTC transfer/apply surfaces:

IVtcDumpService / VtcDumpService
serialization Export / Import
VM Export/Import/Dump/Merge-to-new/apply-to-left-right command paths
legacy floating apply bar and transfer/create-merged library sections

Source: src/Tools/Testing/VTC/Contracts/IVtcSerializationService.cs:6 Source: src/Tools/Testing/VTC/Revit/Services/VtcSerializationService.cs:30 Source: src/Tools/Testing/VTC/UI/ViewModels/VtcWindowViewModel.cs:563 Source: src/Tools/Testing/VTC/UI/Views/VtcWindow.xaml:1244

Tests

VtcWindowViewModelTests now validates local staging, idempotent same-side selection, side-specific override editing, clear-selection pending-retention semantics, Process gating for ineligible pending edits, Process overwrite/create-merged flows, conflict marker mapping, failed-pending-override retention after Process conflicts, and merged-save model generation for missing-side and pending-override scenarios.

Source: src/Tools/Testing/VTC/Tests/VtcWindowViewModelTests.cs:38 Source: src/Tools/Testing/VTC/Tests/VtcWindowViewModelTests.cs:79 Source: src/Tools/Testing/VTC/Tests/VtcWindowViewModelTests.cs:92 Source: src/Tools/Testing/VTC/Tests/VtcWindowViewModelTests.cs:127 Source: src/Tools/Testing/VTC/Tests/VtcWindowViewModelTests.cs:262 Source: src/Tools/Testing/VTC/Tests/VtcWindowViewModelTests.cs:347

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