OpenTTD/OpenTTD
Nov 2023 – Jul 2026
22 Months active
Languages Used
plaintextC++HTMLCMakeTexttextPythonShell
Technical Skills
code maintenanceerror handlingC++Code RefactoringGame DevelopmentTerraforming Logic
Jonathan G Rennison
PROFILE
Jonathan G Rennison
Over 22 months, contributed to OpenTTD/OpenTTD by delivering 18 features and resolving 46 bugs, focusing on stability, maintainability, and gameplay reliability. Work included refining core systems such as train reversal logic, depot handling, and terraforming, as well as enhancing UI elements and debugging tools. Applied C++ and CMake to implement type-safe data structures, optimize algorithms, and modernize build configurations. Addressed edge-case failures in save/load, rendering, and pathfinding, while improving documentation and localization consistency. Emphasized disciplined code refactoring, robust error handling, and traceable commits, resulting in a more maintainable codebase and smoother user experience across multiple gameplay and development workflows.
Overall Statistics
Feature vs Bugs
28%Features
Repository Contributions
80Total
Bugs
46
Commits
80
Features
18
Lines of code
892,152
Activity Months22
Your Network
48 peopleWork History
July 2026
1 Commits
Jul 1, 2026July 2026 monthly summary for OpenTTD/OpenTTD: Focused on stabilizing rail depot rotation path handling by ensuring active path reservations are released before rotation and re-applied afterward to prevent pathfinding conflicts. Delivered a targeted bug fix with clear code changes and verification across the mainline repository.
1 Commits
Jul 1, 2026July 2026 monthly summary for OpenTTD/OpenTTD: Focused on stabilizing rail depot rotation path handling by ensuring active path reservations are released before rotation and re-applied afterward to prevent pathfinding conflicts. Delivered a targeted bug fix with clear code changes and verification across the mainline repository.
July 2026
June 2026
2 Commits
Jun 1, 2026June 2026 – OpenTTD/OpenTTD: Implemented targeted reliability fixes for train reversals around depot boundaries. Addressed edge-cases where vehicles could enter a depot tile during reversals and ensured updates to vehicle status are deferred until all reversals complete. Delivered across two commits, replacing an earlier approach to improve stability of depot-based train operations. Result: smoother train swaps, fewer sporadic reversal failures, and enhanced user experience in core transport gameplay.
June 2026
2 Commits
Jun 1, 2026June 2026 – OpenTTD/OpenTTD: Implemented targeted reliability fixes for train reversals around depot boundaries. Addressed edge-cases where vehicles could enter a depot tile during reversals and ensured updates to vehicle status are deferred until all reversals complete. Delivered across two commits, replacing an earlier approach to improve stability of depot-based train operations. Result: smoother train swaps, fewer sporadic reversal failures, and enhanced user experience in core transport gameplay.
May 2026
7 Commits • 3 Features
May 1, 2026May 2026 performance summary for OpenTTD/OpenTTD. Focused on stability, correctness, and maintainability. Delivered server reliability improvements, robust edge-case handling for editor and command flows, and targeted code cleanups to streamline the codebase. These changes reduce termination-related data loss, prevent common refitting errors, and improve scenario authoring and viewport maintenance.
7 Commits • 3 Features
May 1, 2026May 2026 performance summary for OpenTTD/OpenTTD. Focused on stability, correctness, and maintainability. Delivered server reliability improvements, robust edge-case handling for editor and command flows, and targeted code cleanups to streamline the codebase. These changes reduce termination-related data loss, prevent common refitting errors, and improve scenario authoring and viewport maintenance.
May 2026
April 2026
6 Commits • 1 Features
Apr 1, 2026OpenTTD/OpenTTD — April 2026 monthly summary. Focus this month was delivering targeted gameplay polish, localization consistency, and code quality improvements, with an emphasis on reliability and maintainability that translates into smoother player experiences and long-term project health. Key features delivered - Feature: Improved reverse train mechanics. Refined driving direction and flip logic, ensuring forward-facing movement decisions are applied to the next tile, resulting in more predictable and realistic train behavior during reversals. Commits: 3437a58d5e176ae76056d0ff95e05bb42478fadd; bd1bb3adc8ecb0b42d419a870d2e1270c187169c. Major bugs fixed - Bug: Duplicate language strings in English language file. Fixed duplication of string color codes in english.txt to ensure localization resources are consistent and clear. Commits: 037cd538032b25e480805b089c5ffe6c2735eb48 (Codefix fb795089: Duplicate string colour codes in english.txt (#15449)). - Bug: Correct town placement coordinates when rotating anticlockwise. Corrected coordinate transformation logic for placing towns in JSON when rotation is anticlockwise to ensure accurate town placement on the map. Commit: fd855aa61d4c8ab7a63eaa4ea9fd5a1073db7004. - Bug/Code quality: Spelling fixes and enum refactor. Corrected spelling errors across comments/documentation and refactored EnumClassIndexContainer to EnumIndexArray for better type safety and maintainability. Commits: bbe5dbf2302df6a613d4e2bf65902e8463c394fa; 89174e891a06483f0a92e44e3af06beae80749c4. Overall impact and accomplishments - Improved gameplay reliability: Derivations for reversals now behave more predictably, reducing edge-case anomalies during train operations. - Localization integrity: Removal of duplicate language strings improves translator workload and in-game text consistency across languages. - Map accuracy: Town placement logic now robust under rotation, resulting in fewer manual fixes during scenario creation and mod development. - Maintainability and safety: Code quality refinements and type-safety improvements reduce risk of regressions and simplify future refactors. Technologies/skills demonstrated - C++ and STL usage with std::array and refactors for stronger type safety (EnumIndexArray via typedef). - Refined algorithmic logic for movement direction and rotation handling. - Localization resource management and code cleanup to raise long-term project health. - Focused debugging and commit traceability for reproducible fixes across contributors.
April 2026
6 Commits • 1 Features
Apr 1, 2026OpenTTD/OpenTTD — April 2026 monthly summary. Focus this month was delivering targeted gameplay polish, localization consistency, and code quality improvements, with an emphasis on reliability and maintainability that translates into smoother player experiences and long-term project health. Key features delivered - Feature: Improved reverse train mechanics. Refined driving direction and flip logic, ensuring forward-facing movement decisions are applied to the next tile, resulting in more predictable and realistic train behavior during reversals. Commits: 3437a58d5e176ae76056d0ff95e05bb42478fadd; bd1bb3adc8ecb0b42d419a870d2e1270c187169c. Major bugs fixed - Bug: Duplicate language strings in English language file. Fixed duplication of string color codes in english.txt to ensure localization resources are consistent and clear. Commits: 037cd538032b25e480805b089c5ffe6c2735eb48 (Codefix fb795089: Duplicate string colour codes in english.txt (#15449)). - Bug: Correct town placement coordinates when rotating anticlockwise. Corrected coordinate transformation logic for placing towns in JSON when rotation is anticlockwise to ensure accurate town placement on the map. Commit: fd855aa61d4c8ab7a63eaa4ea9fd5a1073db7004. - Bug/Code quality: Spelling fixes and enum refactor. Corrected spelling errors across comments/documentation and refactored EnumClassIndexContainer to EnumIndexArray for better type safety and maintainability. Commits: bbe5dbf2302df6a613d4e2bf65902e8463c394fa; 89174e891a06483f0a92e44e3af06beae80749c4. Overall impact and accomplishments - Improved gameplay reliability: Derivations for reversals now behave more predictably, reducing edge-case anomalies during train operations. - Localization integrity: Removal of duplicate language strings improves translator workload and in-game text consistency across languages. - Map accuracy: Town placement logic now robust under rotation, resulting in fewer manual fixes during scenario creation and mod development. - Maintainability and safety: Code quality refinements and type-safety improvements reduce risk of regressions and simplify future refactors. Technologies/skills demonstrated - C++ and STL usage with std::array and refactors for stronger type safety (EnumIndexArray via typedef). - Refined algorithmic logic for movement direction and rotation handling. - Localization resource management and code cleanup to raise long-term project health. - Focused debugging and commit traceability for reproducible fixes across contributors.
March 2026
3 Commits • 2 Features
Mar 1, 2026Month 2026-03 — OpenTTD/OpenTTD: Delivered targeted build and UI improvements, plus a critical bug fix. This month focused on reducing maintenance overhead, improving build compatibility with newer compilers, and enhancing operator efficiency in order management. Business value includes faster and more reliable builds, reduced deployment issues, and streamlined workflows for admins and operators.
3 Commits • 2 Features
Mar 1, 2026Month 2026-03 — OpenTTD/OpenTTD: Delivered targeted build and UI improvements, plus a critical bug fix. This month focused on reducing maintenance overhead, improving build compatibility with newer compilers, and enhancing operator efficiency in order management. Business value includes faster and more reliable builds, reduced deployment issues, and streamlined workflows for admins and operators.
March 2026
February 2026
4 Commits
Feb 1, 2026February 2026 (OpenTTD/OpenTTD) focused on reliability, maintainability, and efficiency improvements. No new user-facing features were introduced this month; the work centered on stability fixes, UI accuracy refinements, and codebase optimizations that enhance cross-version compatibility and reduce maintenance burden. These changes mitigate crash scenarios, improve data presentation, and trim binary size, delivering tangible business value through a more stable product with lower risk and faster iteration cycles.
February 2026
4 Commits
Feb 1, 2026February 2026 (OpenTTD/OpenTTD) focused on reliability, maintainability, and efficiency improvements. No new user-facing features were introduced this month; the work centered on stability fixes, UI accuracy refinements, and codebase optimizations that enhance cross-version compatibility and reduce maintenance burden. These changes mitigate crash scenarios, improve data presentation, and trim binary size, delivering tangible business value through a more stable product with lower risk and faster iteration cycles.
January 2026
4 Commits • 1 Features
Jan 1, 2026January 2026: Delivered targeted fixes and navigation/UI improvements for OpenTTD/OpenTTD, focusing on correctness, stability, and user experience. Implemented four changes across town placement, rail system, vehicle navigation, and station UI that reduce gameplay-edge bugs and improve consistency across core subsystems. Key outcomes include corrected tile selection logic for town placement, robust disable_elrails handling for engines with mixed rail types, improved articulated vehicle following behavior for immediate u-turn scenarios, and reliable scrollbar refreshing in the station view when folding/unfolding. These changes enhance gameplay reliability, reduce edge-case failures, and demonstrate solid debugging, cross-module reasoning, and UI/state-management skills.
4 Commits • 1 Features
Jan 1, 2026January 2026: Delivered targeted fixes and navigation/UI improvements for OpenTTD/OpenTTD, focusing on correctness, stability, and user experience. Implemented four changes across town placement, rail system, vehicle navigation, and station UI that reduce gameplay-edge bugs and improve consistency across core subsystems. Key outcomes include corrected tile selection logic for town placement, robust disable_elrails handling for engines with mixed rail types, improved articulated vehicle following behavior for immediate u-turn scenarios, and reliable scrollbar refreshing in the station view when folding/unfolding. These changes enhance gameplay reliability, reduce edge-case failures, and demonstrate solid debugging, cross-module reasoning, and UI/state-management skills.
January 2026
December 2025
5 Commits • 2 Features
Dec 1, 2025December 2025: OpenTTD/OpenTTD—Delivered a mix of feature work, bug fixes, and memory-management improvements. The work improves persistence, usability, stability, and memory handling in the Squirrel scripting environment, with direct business value through better play continuity and smoother UX.
December 2025
5 Commits • 2 Features
Dec 1, 2025December 2025: OpenTTD/OpenTTD—Delivered a mix of feature work, bug fixes, and memory-management improvements. The work improves persistence, usability, stability, and memory handling in the Squirrel scripting environment, with direct business value through better play continuity and smoother UX.
November 2025
5 Commits
Nov 1, 2025November 2025 focused on robustness, reliability, and developer experience in the OpenTTD/OpenTTD repository. Implemented critical fixes across bitset iteration, debug window parsing, CI regression tests, station relocation, and script processing. These changes reduce edge-case failures, improve debugging reliability, and strengthen the stability of the build and runtime behavior.
5 Commits
Nov 1, 2025November 2025 focused on robustness, reliability, and developer experience in the OpenTTD/OpenTTD repository. Implemented critical fixes across bitset iteration, debug window parsing, CI regression tests, station relocation, and script processing. These changes reduce edge-case failures, improve debugging reliability, and strengthen the stability of the build and runtime behavior.
November 2025
October 2025
1 Commits
Oct 1, 2025October 2025: OpenTTD/OpenTTD delivered a bug fix to production history validation, ensuring production history is calculated only for valid cargo types and not for unused slots, thereby preventing erroneous data in industry production statistics. The change enhances data integrity and confidence in metrics used for planning.
October 2025
1 Commits
Oct 1, 2025October 2025: OpenTTD/OpenTTD delivered a bug fix to production history validation, ensuring production history is calculated only for valid cargo types and not for unused slots, thereby preventing erroneous data in industry production statistics. The change enhances data integrity and confidence in metrics used for planning.
September 2025
3 Commits
Sep 1, 2025OpenTTD/OpenTTD — 2025-09: Delivered stability and data integrity improvements through three high-impact fixes in the engine/production flow. Key changes include fixing engine variant cycle detection to prevent self-loops, correcting town rating recalculation after landscape tile changes, and ensuring industry cargo processing works correctly when cargo lists are non-contiguous. These efforts reduce data corruption risk, ensure accurate gameplay metrics, and improve reliability of production and expansion features.
3 Commits
Sep 1, 2025OpenTTD/OpenTTD — 2025-09: Delivered stability and data integrity improvements through three high-impact fixes in the engine/production flow. Key changes include fixing engine variant cycle detection to prevent self-loops, correcting town rating recalculation after landscape tile changes, and ensuring industry cargo processing works correctly when cargo lists are non-contiguous. These efforts reduce data corruption risk, ensure accurate gameplay metrics, and improve reliability of production and expansion features.
September 2025
August 2025
6 Commits
Aug 1, 2025During August 2025 (Month: 2025-08), the OpenTTD/OpenTTD project concentrated on stability, correctness, and UI polish across the core engine, persistence, and UI layers. Delivered targeted bug fixes that improve rendering accuracy, ensure state integrity during company mergers, strengthen save/load robustness, and enhance UI readability. These changes reduce edge-case rendering defects, prevent data corruption, improve persistence reliability, and improve maintainability and developer productivity.
August 2025
6 Commits
Aug 1, 2025During August 2025 (Month: 2025-08), the OpenTTD/OpenTTD project concentrated on stability, correctness, and UI polish across the core engine, persistence, and UI layers. Delivered targeted bug fixes that improve rendering accuracy, ensure state integrity during company mergers, strengthen save/load robustness, and enhance UI readability. These changes reduce edge-case rendering defects, prevent data corruption, improve persistence reliability, and improve maintainability and developer productivity.
July 2025
5 Commits • 1 Features
Jul 1, 2025OpenTTD/OpenTTD — July 2025 monthly summary focused on stability, correctness, and safer core refactors. Delivered targeted bug fixes across UI rendering, graph flow management, and cross-file naming, plus a typed internal refactor to improve future maintainability and safety.
5 Commits • 1 Features
Jul 1, 2025OpenTTD/OpenTTD — July 2025 monthly summary focused on stability, correctness, and safer core refactors. Delivered targeted bug fixes across UI rendering, graph flow management, and cross-file naming, plus a typed internal refactor to improve future maintainability and safety.
July 2025
June 2025
4 Commits • 1 Features
Jun 1, 2025June 2025 OpenTTD/OpenTTD delivered two focused items: a critical UI bug fix for the drag-and-drop NewGRF indicator and a foundational code refactor introducing type-safe indexing. The changes enhance user experience by ensuring the active panel accurately reflects insertion points, and establish safer, more maintainable indexing patterns via TypedIndexContainer, replacing the legacy ReferenceThroughBaseContainer. This work lays groundwork for future indexing features and reduces risk of indexing-related errors.
June 2025
4 Commits • 1 Features
Jun 1, 2025June 2025 OpenTTD/OpenTTD delivered two focused items: a critical UI bug fix for the drag-and-drop NewGRF indicator and a foundational code refactor introducing type-safe indexing. The changes enhance user experience by ensuring the active panel accurately reflects insertion points, and establish safer, more maintainable indexing patterns via TypedIndexContainer, replacing the legacy ReferenceThroughBaseContainer. This work lays groundwork for future indexing features and reduces risk of indexing-related errors.
May 2025
1 Commits
May 1, 2025May 2025 monthly summary for OpenTTD/OpenTTD: Delivered a focused bug fix to improve snowy terrain rendering in the small map vegetation mode. The change ensures snowy MP_CLEAR tiles render correctly by using CLEAR_SNOW when snowy, while continuing to use the existing GetClearGround logic for non-snow cases, aligning small-map visuals with the main rendering path and reducing rendering discrepancies. Commit reference: d107b7c8c0fa01408d8980fa905d8acd3b07c98e (fix for incorrect tile colour in smallmap for snowy MP_CLEAR tiles in vegetation mode).
1 Commits
May 1, 2025May 2025 monthly summary for OpenTTD/OpenTTD: Delivered a focused bug fix to improve snowy terrain rendering in the small map vegetation mode. The change ensures snowy MP_CLEAR tiles render correctly by using CLEAR_SNOW when snowy, while continuing to use the existing GetClearGround logic for non-snow cases, aligning small-map visuals with the main rendering path and reducing rendering discrepancies. Commit reference: d107b7c8c0fa01408d8980fa905d8acd3b07c98e (fix for incorrect tile colour in smallmap for snowy MP_CLEAR tiles in vegetation mode).
May 2025
March 2025
2 Commits • 1 Features
Mar 1, 2025March 2025 monthly summary for OpenTTD/OpenTTD focused on codebase cleanup and rendering API modernization. Key work centered on simplifying the codebase, stabilizing the rendering path, and laying groundwork for future enhancements.
March 2025
2 Commits • 1 Features
Mar 1, 2025March 2025 monthly summary for OpenTTD/OpenTTD focused on codebase cleanup and rendering API modernization. Key work centered on simplifying the codebase, stabilizing the rendering path, and laying groundwork for future enhancements.
February 2025
8 Commits • 1 Features
Feb 1, 2025February 2025 (2025-02) focused on stabilizing core gameplay UX and laying foundations for faster development cycles in OpenTTD/OpenTTD. Delivered three targeted bug fixes that improve data integrity, road-building context, and UI filters, while advancing the codebase with build-system modernization and cleanup. These changes reduce user-facing issues, improve save/load reliability, enhance build performance, and set the stage for safer feature work in upcoming sprints. Key outcomes include: corrected serialization of inaugurated_year_calendar in wallclock saves, proper town index usage in road-building checks, corrected Filtered flag handling in Settings, and a modernization pass for the build system (derived from multiple commits).
8 Commits • 1 Features
Feb 1, 2025February 2025 (2025-02) focused on stabilizing core gameplay UX and laying foundations for faster development cycles in OpenTTD/OpenTTD. Delivered three targeted bug fixes that improve data integrity, road-building context, and UI filters, while advancing the codebase with build-system modernization and cleanup. These changes reduce user-facing issues, improve save/load reliability, enhance build performance, and set the stage for safer feature work in upcoming sprints. Key outcomes include: corrected serialization of inaugurated_year_calendar in wallclock saves, proper town index usage in road-building checks, corrected Filtered flag handling in Settings, and a modernization pass for the build system (derived from multiple commits).
February 2025
January 2025
2 Commits • 1 Features
Jan 1, 2025Month: 2025-01 — OpenTTD/OpenTTD: Delivered a high-impact stability fix and targeted code cleanup focusing on road-edit edge-cases and world-generation state. These changes reduce crashes during road removal operations and simplify world-generation progress tracking, improving gameplay reliability and code maintainability for future development.
January 2025
2 Commits • 1 Features
Jan 1, 2025Month: 2025-01 — OpenTTD/OpenTTD: Delivered a high-impact stability fix and targeted code cleanup focusing on road-edit edge-cases and world-generation state. These changes reduce crashes during road removal operations and simplify world-generation progress tracking, improving gameplay reliability and code maintainability for future development.
December 2024
1 Commits • 1 Features
Dec 1, 2024December 2024 monthly summary for OpenTTD/OpenTTD: Delivered a targeted enhancement to the dump cargo types console command, expanding cargo type visibility and preparation for future classification. The change adds new cargo class definitions to the dump output (oversized, powderized, not pourable, potable, non-potable) and bridges debugging tooling with data-driven cargo classifications. A single commit established this improvement, enabling deeper inspection and faster troubleshooting for cargo type data.
1 Commits • 1 Features
Dec 1, 2024December 2024 monthly summary for OpenTTD/OpenTTD: Delivered a targeted enhancement to the dump cargo types console command, expanding cargo type visibility and preparation for future classification. The change adds new cargo class definitions to the dump output (oversized, powderized, not pourable, potable, non-potable) and bridges debugging tooling with data-driven cargo classifications. A single commit established this improvement, enabling deeper inspection and faster troubleshooting for cargo type data.
December 2024
November 2024
7 Commits • 2 Features
Nov 1, 2024November 2024 OpenTTD/OpenTTD monthly update focusing on stability, correctness, and maintainability. Delivered targeted fixes for data correctness in industry graphs, safe handling of industries with no cargoes, and division-by-zero safeguards in varaction2 parsing. Implemented code maintenance and IO optimizations, and refreshed documentation to improve readability and onboarding for future work.
November 2024
7 Commits • 2 Features
Nov 1, 2024November 2024 OpenTTD/OpenTTD monthly update focusing on stability, correctness, and maintainability. Delivered targeted fixes for data correctness in industry graphs, safe handling of industries with no cargoes, and division-by-zero safeguards in varaction2 parsing. Implemented code maintenance and IO optimizations, and refreshed documentation to improve readability and onboarding for future work.
October 2024
2 Commits
Oct 1, 2024October 2024 (OpenTTD/OpenTTD): Focused on stabilization and code quality improvements. Implemented critical terraforming bug fix for roadway tiles to align with bus behavior, and corrected a coding-standard issue to ensure proper member access. These changes reduce terraforming edge cases, improve reliability, and support maintainability for future development.
2 Commits
Oct 1, 2024October 2024 (OpenTTD/OpenTTD): Focused on stabilization and code quality improvements. Implemented critical terraforming bug fix for roadway tiles to align with bus behavior, and corrected a coding-standard issue to ensure proper member access. These changes reduce terraforming edge cases, improve reliability, and support maintainability for future development.
October 2024
November 2023
1 Commits • 1 Features
Nov 1, 2023Month: 2023-11 — OpenTTD/OpenTTD. Focused on code health and maintainability through targeted cleanup of the sprite cache error handling. Removed obsolete memory error strings to streamline error paths and reduce log noise. The change is tracked under commit e436b3246870b9d8690e1a14b964375799507380. No major bugs fixed this month; primary impact came from maintainability improvements and clearer error handling, positioning the project for faster future iterations. Technologies demonstrated: targeted refactoring, version control discipline, and maintainability-focused coding practices, with emphasis on error handling and memory-related code paths.
November 2023
1 Commits • 1 Features
Nov 1, 2023Month: 2023-11 — OpenTTD/OpenTTD. Focused on code health and maintainability through targeted cleanup of the sprite cache error handling. Removed obsolete memory error strings to streamline error paths and reduce log noise. The change is tracked under commit e436b3246870b9d8690e1a14b964375799507380. No major bugs fixed this month; primary impact came from maintainability improvements and clearer error handling, positioning the project for faster future iterations. Technologies demonstrated: targeted refactoring, version control discipline, and maintainability-focused coding practices, with emphasis on error handling and memory-related code paths.
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Quality Metrics
Correctness95.2%
Maintainability91.8%
Architecture91.2%
Performance92.0%
AI Usage20.8%
Skills & Technologies
Programming Languages
C++CMakeHTMLPythonShellTextYAMLplaintexttext
Technical Skills
API DesignAlgorithm ImplementationAlgorithm OptimizationBug FixBug FixingBuild ConfigurationBuild SystemBuild System ConfigurationC++C++ DevelopmentC++ ProgrammingC++ developmentC++ programmingCMakeCMake scripting
Repositories Contributed To
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