Add VGA Text Buffer Writer Implementation

[ViktorPopp]

Summary

This pull request introduces a low-level system for writing text to the VGA text buffer, enabling formatted text output in environments like an operating system kernel. The implementation includes a global writer instance, custom data structures, and macros for convenient printing.

Features

• Global Writer: A thread-safe, lazily initialized Writer instance for managing text output.
• Color Management: Support for VGA's 16 standard colors, with customizable foreground and background combinations.
• Screen Characters and Buffer: Structures to represent individual characters and the VGA text buffer, ensuring proper memory handling.
• Writer Functionality:
  • Writing individual ASCII bytes or strings to the screen.
  • Automatic line wrapping and scrolling.
  • Clearing rows for clean output management.
• Formatting Integration: Compatibility with Rust's formatting macros (write!, writeln!).
• Macros: Custom print! and println! macros for seamless text output.

Why This Is Needed

This feature is critical for enabling low-level text output without relying on external libraries or higher-level abstractions. It provides a foundational mechanism for debugging, logging, and user interaction in a bare-metal environment.

Testing

• Verified output to the VGA text buffer in a simulated environment.
• Tested handling of long strings, line wrapping, and scrolling behavior.
• Ensured proper functionality of custom macros and formatting integration.

Future Improvements

• Extend support for additional VGA modes or higher resolutions.
• Add support for non-ASCII character sets if needed.
• Explore optimizations for rendering efficiency.

Impact

This addition lays the groundwork for further development of text-based user interfaces and debugging tools in the kernel. It provides a reliable and efficient mechanism for interacting with the VGA hardware.