ProjectEngine v1.2.0 — Unified Gantt engine, retained rendering and large-project improvements

[TMailletFR]

ProjectEngine v1.2.0

ProjectEngine v1.2.0 is a major architecture, performance and reliability release focused on the Gantt engine.

This version consolidates dozens of internal R&D iterations into a smaller set of meaningful product improvements:

• a unified Gantt update pipeline;
• better behavior on large schedules;
• retained and differential rendering;
• a single SVG dependency layer;
• more faithful restoration of the saved workbook state;
• fixes for Critical Path and Constraints controls;
• a substantially stronger validation and non-regression framework.

The release was developed and validated using both the standard ProjectEngine workbook and a large-scale test schedule containing approximately 1,200 tasks.

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Highlights

Unified Gantt update pipeline

The main Gantt workflows now converge through a common update and rendering pipeline, including:

• Update Gantt;
• Full Update;
• TEST;
• SCENARIO;
• RESET;
• LOCK;
• Critical Path and Longest Path modes;
• scale changes;
• Drag operations.

This reduces divergence between historical rendering paths and gives the main Gantt actions a more consistent set of rules for projection, dependencies, validation and finalization.

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Retained rendering

ProjectEngine no longer assumes that an unchanged Gantt must be fully destroyed and recreated.

The renderer can now inspect the existing Excel objects, adopt those that remain valid, compare them with the expected state and decide whether each object should be:

• added;
• modified;
• deleted;
• or retained unchanged.

In final unchanged-render validation:

• the standard workbook retained 88 existing objects with no additions or deletions;
• the 1,200-task workbook retained 1,741 existing objects with no additions or deletions.

This reduces unnecessary object reconstruction while preserving native Excel interaction.

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Improved large-project behavior

The performance campaign focused on exposing scaling costs that were not visible on smaller schedules.

The work includes:

• grouped WBS/CALC synchronization instead of repeated cell-by-cell transfers;
• indexed in-memory execution structures;
• shared compiled topology for scheduling and analytics;
• differential and local rendering paths;
• reduced repeated parent/child and dependency resolution;
• targeted dependency rerouting when the schedule structure allows it.

A Core FULL benchmark on the 1,200-task test schedule measured a 12.2% improvement in its specific protocol.

A separate worksheet-level optimization measured 14.5% on its targeted scope.

These figures come from different benchmarks and should not be combined into a single overall performance percentage.

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Single SVG dependency layer

Dependency links are now consolidated into a single generated SVG layer instead of thousands of individual Excel line segments.

The dependency renderer includes:

• route and endpoint calculation;
• persistent caching;
• geometry signatures;
• affected-link detection;
• targeted rerouting;
• SVG serialization and replacement;
• validation that only one dependency layer exists.

This substantially reduces the number of native Excel objects required to display complex dependency networks.

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Saved Gantt state restored more faithfully

For the controls covered by the final validation campaign, the workbook now reopens in the state in which it was saved.

The tested lifecycle included:

1. changing the Gantt mode;
2. saving the workbook;
3. fully closing Excel;
4. reopening the workbook;
5. inspecting the state before any user action;
6. testing both the first cold interaction and subsequent warm interactions.

The workbook no longer performs a complete Gantt render solely to reconstruct these interface states at startup.

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Fixed

Critical Path and Longest Path styles

The first Critical Path or Longest Path mode change after opening a workbook could previously leave the Gantt in an incomplete visual state.

ProjectEngine can now hydrate the required rendering records locally before applying the requested style.

On the 1,200-task validation workbook:

• first cold transition: approximately 5.5–6.0 seconds;
• subsequent warm transitions: approximately 0.42–0.57 seconds.

These transitions do not run the planning core, trigger a complete Gantt rebuild or reroute the full dependency network.

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Single / Multiple Critical Path button

The business state could previously change while the physical Gantt button remained in its previous position.

The button now reflects the selected Single or Multiple Critical Path mode immediately and remains consistent after save, close and reopen.

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Constraints toggle

The Constraints control now performs the expected visible action.

Constraints OFF:

• removes the constraint markers;
• removes the associated cell borders;
• updates the physical button state.

Constraints ON:

• restores the overlay from the existing projection;
• restores the markers and borders;
• avoids a planning recalculation;
• avoids a complete Gantt rebuild.

Final validation confirmed the sequence:

• 18 constraints → 0 → 18;
• no duplicate constraint objects;
• persistence after reopening the workbook.

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Empty SCENARIO activation

SCENARIO mode can now be activated even when no existing yellow scenario values are present.

The scenario dataset is initialized correctly and the mode remains usable.

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Drag pre-commit behavior

The nominal Drag path no longer restores the previous physical geometry immediately before committing the requested change.

Rollback behavior remains available when a Drag transaction fails.

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Reliability and validation

This release also introduces or strengthens internal safeguards covering:

• standard and 1,200-task schedules;
• cold and warm execution;
• full, partial, local and style-only updates;
• Day, Week and Month scales;
• Critical Path and Longest Path modes;
• TEST, SCENARIO, RESET and LOCK workflows;
• save, full close and reopen lifecycles;
• duplicate and stale Excel objects;
• SVG dependency-layer integrity;
• retained-render counters;
• source-module and workbook alignment;
• forensic and end-to-end validation.

These checks are intended to make rendering, persistence and incremental-update regressions easier to detect before release.

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Known limitations

• A destructive native Excel Gantt rebuild remains expensive on very large schedules.
• Excel and Office can still introduce significant execution-time variance between otherwise identical runs.
• The first Critical Path or Longest Path change after opening a large workbook may require several seconds to hydrate the retained rendering state.
• Some Drag scenarios still require broader real-world validation.
• The saved-state lifecycle when starting from a non-Gantt worksheet has not yet been fully validated.
• Task bars remain native Excel objects; the experimental SVG task-bar renderer is not part of this release.

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Upgrade notes

ProjectEngine remains:

• fully Excel-native;
• local and offline;
• open source;
• available in English and French;
• free of installers, servers and user accounts.

As always, keep a backup of active project workbooks before replacing an existing ProjectEngine version.

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Links

• Documentation and source code:
  https://github.com/TMailletFR/ProjectEngine

• Project website:
  https://tmailletfr.github.io/ProjectEngine/

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This discussion was created from the release ProjectEngine v1.2.0 — Unified Gantt engine, retained rendering and large-project improvements.