Strategic Plan: Graphics, Performance and Full Functionality

Summary

This step establishes a strategic plan to get the emulator fully functional with visible graphics, stable performance (~60 FPS), functional controls and compatibility with GB and GBC ROMs. Task 1 (diagnosis of the current state) and Task 2 (activation of manual loading of default tiles) are completed as part of Phase 1 of the plan.

An automated diagnostic script is created that checks available ROMs, system components, and emulator status. Modified `viboy.py` to activate manual loading of tiles by default, allowing progress with visible graphics while investigating why games do not load tiles automatically.

Hardware Concept

The Game Boy uses VRAM (Video RAM) to store tiles (8x8 pixel graphic patterns) and tilemaps (maps that indicate which tiles to display in which position). Normally, games load their tiles into VRAM during initialization, but on our emulator currently the VRAM remains empty after loading a ROM.

To move development forward while this issue is investigated, we use a temporary function `load_test_tiles()` that manually loads test tiles into VRAM. This function loads 4 test tiles with different patterns (white, checkerboard, horizontal lines, vertical lines) and configures a basic tilemap to display them on the screen.

Fountain:Pan Docs - "Tile Data" (0x8000-0x97FF) and "Tile Map" (0x9800-0x9BFF)

Implementation

General Strategic Plan

The plan is divided into 3 main phases:

1. Phase 1: Diagnostics and Graphics Activation(Steps 0311-0312)
   • Check current status (graphics, FPS, controls)
   • Activate manual loading of tiles to have something visible
   • Verify that rendering works
2. Phase 2: Optimization and Stability(Steps 0313-0314)
   • Ensure stable FPS ~60 FPS
   • Check GB/GBC compatibility
   • Optimize rendering if necessary
3. Phase 3: Controls and Gameplay(Steps 0315-0316)
   • Verify that the controls work
   • Test with multiple ROMs (GB and GBC)
   • Iterate until full functionality is achieved

Tasks Implemented in this Step

Task 1: Diagnostic Script

The script `tools/diagnostico_estado_actual_step_0311.ps1` is created that automatically verifies:

• Available ROMs (GB and GBC) in the `roms/` directory
• System components (Python, compiled Cython/C++ modules)
• Emulator status and manual tile loading functionality

The script generates a report in Markdown (`DIAGNOSTIC_STATUS_ACTUAL_STEP_0311.md`) with all the information collected.

Task 2: Activation of Manual Default Tiles Loading

Modify `src/viboy.py` to change the default value of `load_test_tiles` from `False` to `True`:

def load_cartridge(self, rom_path: str | Path, load_test_tiles: bool = True) -> None:

This means that test tiles will now be loaded automatically when loading a ROM, without the need for the `--load-test-tiles` flag. This change is temporary and is clearly documented in the code.

Modified Components

• tools/diagnosis_current_state_step_0311.ps1: PowerShell script for automated diagnosis
• src/viboy.py: Changed `load_test_tiles=False` to `load_test_tiles=True` by default
• DIAGNOSIS_CURRENT_STATUS_STEP_0311.md: Report generated by the diagnostic script

Design Decisions

• Manual loading of tiles by default:Temporarily activated to allow progress with visible graphics. This does not interfere with the investigation of the actual automatic tile loading problem.
• Simplified diagnostic script:We opt for a simple script that avoids escaping complexities in PowerShell with embedded Python code. ROM loading verification is documented as manual.
• Iterative plan:The plan is divided into clear phases that allow for incremental progress and continuous verification.

Affected Files

• tools/diagnosis_current_state_step_0311.ps1- Automated diagnostic script (new)
• src/viboy.py- Changed: `load_test_tiles=True` by default (line 189)
• DIAGNOSIS_CURRENT_STATUS_STEP_0311.md- Diagnostic report (generated)

Tests and Verification

Diagnostic Script:

• ✅ Successfully executed: `powershell -ExecutionPolicy Bypass -File tools/diagnostico_estado_actual_step_0311.ps1`
• ✅ Report generated: `DIAGNOSTIC_ESTADO_ACTUAL_STEP_0311.md`
• ✅ 2 GB ROMs (pkmn.gb, tetris.gb) and 2 GBC ROMs (mario.gbc, tetris_dx.gbc) detected
• ✅ Python 3.13.5 available
• ⚠️ Cython/C++ modules not found (may need to be recompiled)

Tiles Activation:

• ✅ Correctly modified code in `src/viboy.py`
• ✅ Updated documentation in docstrings
• ⏳ Visual verification pending (requires running emulator with ROM)

Sources consulted

• Bread Docs:Tile Data and Tile Map
• Strategic Plan Step 0311: Complete plan document with objectives and phases

Educational Integrity

Next Steps

Continue with the following tasks of the Strategic Plan:

• [ ] Task 3:Verify rendering with visually loaded tiles
• [ ] Task 4:Measure and optimize performance (stable FPS ~60)
• [ ] Task 5:Check GB/GBC compatibility with multiple ROMs
• [ ] Task 6:Verify that the controls work correctly
• [ ] Task 7:Iterative testing with multiple ROMs and documentation
• [ ] Task 8:Generate complete final documentation

Immediate Priority:Task 3 (visual verification of tiled rendering) to confirm that manual loading activation is working correctly.