Gantt Charts: Part 1 with Aleksander Wojtasz

Mike Wolfe -

Imagine being able to drag-and-drop schedule items directly on a Gantt chart interface—all built entirely within Microsoft Access without any third-party controls.

In this Access Europe user group presentation, Aleksander Wojtasz demonstrates how to create an interactive Gantt chart scheduling system using pure Access and Windows GDI (Graphics Device Interface) API calls. The solution enables real-time drag-and-drop functionality, dynamic resizing, and interactive visual feedback, all while maintaining performance through efficient memory management and drawing techniques.

This presentation offers Access developers a powerful new approach to building sophisticated scheduling interfaces that rival commercial alternatives, complete with downloadable example databases and detailed technical explanations.

Core Technologies

GDI Library Basics

  • Windows Graphics Device Interface (GDI32.DLL)
  • Present since early Windows versions
  • Handles low-level drawing operations
  • No additional components required

Key Components

  • Device Context (drawing canvas)
  • Device Independent Bitmap (memory bitmap)
  • Memory arrays for coordinate tracking
  • Event handlers for mouse interaction

Implementation Overview

Drawing Operations

  • Lines with customizable styles and colors
  • Rectangles with optional rounded corners
  • Text with font control
  • Image handling and stretching
  • Background grid patterns

Mouse Interaction

  • Real-time drag and drop
  • Edge detection for resizing
  • Coordinate translation
  • Event handling for mouse up/down/move

Data Management

  • In-memory arrays for performance
  • Updates only on completed actions
  • Layout tracking for hit detection
  • Efficient redrawing techniques

Technical Architecture

Canvas Class Module

  • Handles all drawing operations
  • Manages GDI resources
  • Coordinates mouse interaction
  • Maintains layout information

Supporting Components

  • Job tracking tables
  • Resource management
  • Status handling
  • Context menu integration

Performance Considerations

Memory Management

  • Efficient array usage
  • Coordinate caching
  • Minimal database updates
  • Smart redraw logic

Security Settings

  • Requires macro security consideration
  • Options for trusted locations
  • Certificate signing possibilities
  • Performance impact awareness

Practical Applications

Sample Implementation

  • Car repair workshop scheduling
  • Technician assignment
  • Job status tracking
  • Interactive timeline management

Real-World Usage

  • Home renovation scheduling
  • Resource allocation
  • Project timeline visualization
  • Status tracking

Conclusion

Aleksander's presentation demonstrates a sophisticated yet maintainable approach to creating interactive Gantt charts in Access without external dependencies. The solution combines Windows API calls with efficient memory management to deliver smooth performance while maintaining full database integration. The enthusiastic response from attendees and requests for follow-up presentations underscore the value of this innovative approach.

Recording

The full recording is available on YouTube:

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  • Interact directly with presenters during Q&A sessions
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  • Share your own experiences and challenges
  • Get immediate answers to your specific questions
  • Participate in group discussions

With multiple user groups across different time zones (and languages!), you're sure to find a meeting time that works for your schedule.

Acknowledgements

  • Base cover image generated by FLUX-schnell
  • Initial draft generated by Claude-3.5-Sonnet