E2 - Development Guide

This guide summarizes the architecture and implementation standards used across the editor codebase.

Editor Status (October 2025)

Editor	State	Notes
Overworld	Stable	Full feature set; continue regression testing after palette fixes.
Message	Stable	Re-test rendering after recent palette work.
Emulator	Stable	UI and core subsystems aligned with production builds.
Palette	Stable	Serves as the source of truth for palette helpers.
Assembly	Stable	No outstanding refactors.
Dungeon	Experimental	Requires thorough manual coverage before release.
Graphics	Experimental	Large rendering changes in flight; validate texture pipeline.
Sprite	Experimental	UI patterns still migrating to the new card system.

Screen Editor Notes

• Title screen: Vanilla ROM tilemap parsing remains broken. Implement a DMA parser and confirm the welcome screen renders before enabling painting.
• Overworld map: Mode 7 tiling, palette switching, and custom map import/export are in place. The next milestone is faster tile painting.
• Dungeon map: Rendering is wired up; tile painting and ROM write-back are still pending.

1. Core Architectural Patterns

These patterns, established during the Overworld Editor refactoring, should be applied to all new and existing editor components.

Pattern 1: Modular Systems

Principle: Decompose large, monolithic editor classes into smaller, single-responsibility modules.

• Rendering: All drawing logic should be extracted into dedicated *Renderer classes (e.g., OverworldEntityRenderer). The main editor class should delegate drawing calls, not implement them.
• UI Panels: Complex UI panels should be managed by their own classes (e.g., MapPropertiesSystem), which then communicate with the parent editor via callbacks.
• Interaction: Canvas interaction logic (mouse handling, editing modes) should be separated from the main editor class to simplify state management.

Benefit: Smaller, focused modules are easier to test, debug, and maintain. The main editor class becomes a coordinator, which is a much cleaner architecture.

Pattern 2: Callback-Based Communication

Principle: Use std::function callbacks for child-to-parent communication to avoid circular dependencies.

• Implementation: A parent editor provides its child components with callbacks (typically via a SetCallbacks method) during initialization. The child component invokes these callbacks to notify the parent of events or to request actions (like a refresh).
• Example: MapPropertiesSystem receives a RefreshCallback from OverworldEditor. When a property is changed in the UI, it calls the function, allowing the OverworldEditor to execute the refresh logic without the MapPropertiesSystem needing to know anything about the editor itself.

Pattern 3: Centralized Progressive Loading via <tt>gfx::Arena</tt>

Principle: All expensive asset loading operations must be performed asynchronously to prevent UI freezes. The gfx::Arena singleton provides a centralized, priority-based system for this.

• How it Works:
  1. Queue: Instead of loading a texture directly, queue it with the arena: gfx::Arena::Get().QueueDeferredTexture(bitmap, priority);
  2. Prioritize: Assign a numerical priority. Lower numbers are higher priority. Use a high priority for assets the user is currently viewing and a low priority for assets that can be loaded in the background.
  3. Process: In the main Update() loop of an editor, process a small batch of textures each frame: auto batch = gfx::Arena::Get().GetNextDeferredTextureBatch(4, 2); (e.g., 4 high-priority, 2 low-priority).
• Benefit: This provides a globally consistent, non-blocking loading mechanism that is available to all editors and ensures the UI remains responsive.

2. UI & Theming System

To ensure a consistent and polished look and feel, all new UI components must adhere to the established theme and helper function system.

2.1. The Theme System (<tt>AgentUITheme</tt>)

• Principle: Never use hardcoded colors (ImVec4)**. All UI colors must be derived from the central theme.
• Implementation: The AgentUITheme system (src/app/editor/agent/agent_ui_theme.h) provides a struct of semantic color names (e.g., panel_bg_color, status_success, provider_ollama). These colors are automatically derived from the application's current ThemeManager.

• **Usage: Fetch the theme at the beginning of a draw call and use the semantic colors:

  cpp const auto& theme = AgentUI::GetTheme(); ImGui::PushStyleColor(ImGuiCol_ChildBg, theme.panel_bg_color);

2.2. Reusable UI Helper Functions

• Principle: Encapsulate common UI patterns into helper functions to reduce boilerplate and ensure consistency.
• Available Helpers (in AgentUI and gui namespaces):
  • Panels: AgentUI::PushPanelStyle() / PopPanelStyle()
  • Headers: AgentUI::RenderSectionHeader(icon, label, color)
  • Indicators: AgentUI::RenderStatusIndicator() (status dot), AgentUI::StatusBadge() (colored text badge).
  • Buttons: AgentUI::StyledButton(), AgentUI::IconButton().
  • Layout: AgentUI::VerticalSpacing(), AgentUI::HorizontalSpacing().
• Benefit: Creates a consistent visual language and makes the UI code far more readable and maintainable.

2.3. Toolbar Implementation (<tt>CompactToolbar</tt>)

• Stretching: To prevent ImGui from stretching the last item in a toolbar, do not use ImGui::BeginGroup(). Instead, manage layout with ImGui::SameLine() and end the toolbar with ImGui::NewLine().
• Separators: Use ImGui::SeparatorEx(ImGuiSeparatorFlags_Vertical) for vertical separators that do not affect item layout.
• Property Inputs: Use the toolbar.AddProperty() method for consistent spacing and sizing of input fields within the toolbar.

3. Key System Implementations & Gotchas

3.1. Graphics Refresh Logic

• Immediate vs. Deferred: When a visual property changes, the texture must be updated on the GPU immediately. Use Renderer::Get().RenderBitmap() for an immediate, blocking update. UpdateBitmap() is deferred and should not be used for changes the user expects to see instantly.
• Call Order is Critical: When a property affecting graphics is changed, the correct sequence of operations is crucial:
  1. Update the property in the data model.
  2. Call the relevant Load*() method (e.g., map.LoadAreaGraphics()) to load the new data from the ROM into memory.
  3. Force a redraw/re-render of the bitmap.

3.2. Multi-Area Map Configuration

• Use the Helper: When changing a map's area size (e.g., from Small to Large), you must use the zelda3::Overworld::ConfigureMultiAreaMap() method. Do not set the area_size property directly.
• Why: This method correctly handles the complex logic of assigning parent IDs to all sibling maps and updating the necessary ROM data for persistence. Failure to use it will result in inconsistent state and refresh bugs.

3.3. Version-Specific Feature Gating

• Principle: The UI must adapt to the features supported by the loaded ROM. Do not show UI for features that are not available.
• Implementation: Check the ROM's asm_version byte before rendering a UI component. If the feature is not supported, display a helpful message (e.g., "This feature requires ZSCustomOverworld v3+") instead of the UI.

3.4. Entity Visibility for Visual Testing

• Standard: All overworld entity markers (entrances, exits, items, sprites) should be rendered with a high-contrast color and an alpha of 0.85f to ensure they are clearly visible against any background.
  • Entrances: Bright yellow-gold
  • Exits: Cyan-white
  • Items: Bright red
  • Sprites: Bright magenta

4. Clang Tooling Configuration

The repository ships curated .clangd and .clang-tidy files that mirror our Google-style C++23 guidelines while accommodating ROM hacking patterns.

• .clangd consumes build/compile_commands.json, enumerates src/, incl/, third_party/, generated directories, and sets feature flags such as YAZE_WITH_GRPC, YAZE_WITH_JSON, and Z3ED_AI so IntelliSense matches the active preset.
• .clang-tidy enables the clang-analyzer, performance, bugprone, readability, modernize, google, and abseil suites, but relaxes common ROM hacking pain points (magic numbers, explicit integer sizing, C arrays, carefully scoped narrowing conversions).
• The gfx::SnesColor utilities intentionally return ImVec4 values in 0‑255 space; rely on the helper converters instead of manual scaling to avoid precision loss.
• Regenerate the compilation database whenever you reconfigure: cmake --preset mac-dbg (or the platform equivalent) and ensure the file lives at build/compile_commands.json.
• Spot-check tooling with clang-tidy path/to/file.cc -p build --quiet or a batch run via presets before sending larger patches.

5. Debugging and Testing

5.1. Quick Debugging with Startup Flags

To accelerate your debugging workflow, use command-line flags to jump directly to specific editors and open relevant UI cards:

# Quick dungeon room testing
./yaze --rom_file=zelda3.sfc --editor=Dungeon --cards="Room 0"
 
# Compare multiple rooms
./yaze --rom_file=zelda3.sfc --editor=Dungeon --cards="Room 0,Room 1,Room 105"
 
# Full dungeon workspace
./yaze --rom_file=zelda3.sfc --editor=Dungeon \
  --cards="Rooms List,Room Matrix,Object Editor,Palette Editor"
 
# Enable debug logging
./yaze --debug --log_file=debug.log --rom_file=zelda3.sfc --editor=Dungeon

Available Editors: Assembly, Dungeon, Graphics, Music, Overworld, Palette, Screen, Sprite, Message, Hex, Agent, Settings

Dungeon Editor Cards: Rooms List, Room Matrix, Entrances List, Room Graphics, Object Editor, Palette Editor, Room N (where N is room ID 0-319)

See debugging-startup-flags.md for complete documentation.

5.2. Testing Strategies

For a comprehensive overview of debugging tools and testing strategies, including how to use the logging framework, command-line test runners, and the GUI automation harness for AI agents, please refer to the Debugging and Testing Guide.

5. Command-Line Flag Standardization

Decision: All binaries in the yaze project (yaze, z3ed, yaze_test, etc.) will standardize on the Abseil Flags library for command-line argument parsing.

Rationale

• Consistency: Provides a single, consistent flag system and user experience across all tools.
• Industry Standard: Abseil is a battle-tested and well-documented library used extensively by Google.
• Features: It provides robust features out-of-the-box, including automatic --help generation, type safety, validation, and --flagfile support.
• Reduced Maintenance: Eliminates the need to maintain multiple custom flag parsers, reducing the project's technical debt.
• Existing Dependency: Abseil is already included as a dependency via gRPC, so this adds no new third-party code.

Migration Plan

The project will migrate away from the legacy yaze::util::Flag system and manual parsing in phases. All new flags should be implemented using ABSL_FLAG.

• Phase 1 (Complete): z3ed and yaze_emu_test already use Abseil flags.
• Phase 2 (In Progress): The main yaze application will be migrated from the custom util::Flag system to Abseil flags.
• Phase 3 (Future): The yaze_test runner's manual argument parsing will be replaced with Abseil flags.
• Phase 4 (Cleanup): The legacy util::flag source files will be removed from the project.

Developers should refer to the Abseil Flags Guide for documentation on defining, declaring, and accessing flags.

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When working with bitmaps and textures, understand that two memory locations must stay synchronized:

1. **data_ vector**: C++ std::vector<uint8_t> holding pixel data
2. **surface_->pixels**: SDL surface's raw pixel buffer (used for texture creation)

Critical Rules:

• Use set_data() for bulk data replacement (syncs both vector and surface)
• Use WriteToPixel() for single-pixel modifications
• Never assign directly to mutable_data() for replacements (only updates vector, not surface)
• Always call ProcessTextureQueue() every frame to process pending texture operations

Example:

// WRONG - only updates vector
bitmap.mutable_data() = new_data;
 
// CORRECT - updates both vector and SDL surface
bitmap.set_data(new_data);

3.6. Graphics Sheet Management

Graphics sheets (223 total) are managed centrally by gfx::Arena. When modifying a sheet:

1. Modify the sheet: auto& sheet = Arena::Get().mutable_gfx_sheet(index);
2. Notify Arena: Arena::Get().NotifySheetModified(index);
3. Changes automatically propagate to all editors

Default palettes are applied during ROM loading based on sheet index:

• Sheets 0-112: Dungeon main palettes
• Sheets 113-127: Sprite palettes
• Sheets 128-222: HUD/menu palettes

Naming Conventions

• Load: Reading data from ROM into memory
• Render: Processing graphics data into bitmaps/textures (CPU pixel operations)
• Draw: Displaying textures/shapes on canvas via ImGui (GPU rendering)
• Update: UI state changes, property updates, input handling