glyph-tile-display

name	glyph_tile_display
description	Guide to the GnollHack glyph-to-tile rendering pipeline. Covers glyph numbering, the multi-layer display system, the LayerInfo struct, tile sheet atlases, the Glyph2Tile mapping, double-buffered MapData, and how SkiaSharp renders tiles on the C# side.

Glyph and Tile Display

Critical Rules

• Do NOT assume one glyph = one tile. A single tile on screen is composed of multiple layers (Background, Floor, Feature, Monster, Object, etc.).
• Always update via newsym(). Do not try to draw directly to the screen from C game logic. Call newsym(x, y) to notify the display engine.
• Double-buffering: The map state is double-buffered to prevent tearing during UI updates.

Layers (LayerInfo)

Each cell has 11 layers rendered back-to-front:

1. Background (Solid color or wallpaper)
2. Floor (Dungeon floor, water, lava)
3. Feature (Walls, doors, stairs)
4. Object (Items on the floor)
5. Monster (Creatures, player)
6. Monster_Effect (Status icons on monsters)
7. Effect (Spells, explosions)
8. Cloud (Gas, fog)
9. Lighting (Shadows, visibility masks)
10. Cursor (Player targeting cursor)
11. UI (Hover text, selection highlights)

C-Side Mapping (src/drawing.c)

• glyph2tile[MAX_GLYPH]: Maps a glyph ID to a tile ID within a tileset.
• LayerInfo: Struct sent across the P/Invoke bridge containing the tile IDs for all 11 layers of a specific coordinate.

C# Side Rendering (win/win32/xpl/GnollHackX/GnollHackX/Views/MapCanvas.cs)

• SkiaSharp: Uses SKCanvas.DrawImage() to render tile atlases.
• TileSet: Represents a PNG sprite sheet containing tiles of a specific size (e.g., 64x96).
• MapData: A grid of LayerInfo objects used by the MapCanvas to draw the visible screen.