sporel-lib-core.render/README.md

lib-core.render

Colored-quad tile-grid renderer + tag-driven entity-render. Reads lib-core.maps's tilemap (v0.1: draw_map), and lib-core.composition's tag-index (v0.2: draw_entities).

Version: 0.3.0 Lib-ID: lib-core.render Requires: lib-core.maps v>=0.5.7, lib-core.composition v>=0.4.0 Tags: render, tiles, draw, colored-quads, entities

Topology

graph LR
  this["lib-core.render"]
  lib_core_maps["lib-core.maps"]
  this --> lib_core_maps
  lib_core_composition["lib-core.composition"]
  this --> lib_core_composition
  engine["engine.*"]
  this --> engine

API

render.draw_map(map_id)

Syntax: render.draw_map(map_id: string | nil) -> integer

Example:

function render(ctx)
    engine.render.clear_color(engine.render.rgb(20, 20, 30))
    local n = render.draw_map()  -- uses current-map
end

Description: Iterates the tiles of the specified map (or current-map when nil), drawing one colored rect per tile at (tx * tile_size, ty * tile_size). Tile color is read from the tilemap's tile.color = {r, g, b}; if missing or malformed, falls back to magenta as a visible "missing-color" debug-marker. Must be called from inside a render hook. Returns the number of tiles drawn (for smoke verification + debug).

render.draw_entities(filter)

Syntax: render.draw_entities({tag: string}) -> integer

Example:

function render_fn(ctx)
    camera.begin()
    render.draw_map()
    render.draw_entities{ tag = "renderable" }
    camera.finish()
end

Description: Iterates entities tagged with filter.tag (via composition.list_by_tag) and renders each according to its sprite-properties. position.x/position.y is treated as the visual CENTER of the entity in all render-paths. Returns the number of entities drawn.

Three sprite-property paths are tried per entity, in order:

1. sprite_atlas (string, atlas-texture-path) + sprite_uv.{x,y,w,h} (numbers) — renders the sub-rectangle of the atlas via engine.render.draw_sprite_transform. Optional sprite_scale (number, default 1.0) scales the rendered quad uniformly around its visual center; useful when a sprite-atlas's native pixel size doesn't match the project tile-scale. Atlas textures are loaded once and cached internally on first use; no eviction.
2. sprite_color (uint32 0xRRGGBBAA) + sprite_w + sprite_h (numbers) — renders a colored rect via engine.render.draw_rect.
3. None of the above — magenta 16×16 fallback rect (debug-marker).

Filter shape {tag = "..."} is the only supported form in v0.2.0; template-id-based or property-predicate filters are deferred (loud-error for malformed filters; see Phase-A Spec A-Q3).

Conventions

• Colored-quads only in v0.1.0. Texture-rendering, multi-layer composition, post-processing, parallax, shaders, hot-reload all DEPRECATED-MVP.
• World-space coords; pair with lib-core.camera to support panning + zoom.
• Magenta fallback [255, 0, 255] is intentional: high-visibility debug-marker for malformed color-data.
• Y-down-positive per ADR-0031.

Consumer pattern

local maps   = require("lib-core.maps")
local render = require("lib-core.render")
local camera = require("lib-core.camera")

function render_fn(ctx)
    engine.render.clear_color(engine.render.rgb(20, 20, 30))
    camera.begin()
    render.draw_map()
    camera.finish()
end

CHANGELOG

v0.3.0 (2026-06-20)

• Added optional sprite_scale (number) on path (1). Defaults to 1.0 when absent — v0.2.0 consumers unchanged. Lets templates whose native sprite resolution doesn't match the project tile-scale rescale at render time without re-baking the atlas.
• Composition dep tightened to v0.3.0 (matches current sibling-tree state; no API impact, just resolution-correctness).

v0.2.0 (Phase A.2 — 2026-06-09)

• Added draw_entities(filter) tag-driven entity-render. Two sprite- property paths (sprite_atlas+sprite_uv / sprite_color+sprite_w+ sprite_h) plus magenta-fallback. position.x/.y is visual-center.
• Atlas-texture cache (no eviction in v0.2.0).
• New dep: lib-core.composition v0.1.0.

v0.1.0 (P.0)

• Initial release: draw_map colored-quad iterator.

References

• Spec v0.1.0 (P.0): meta/docs/superpowers/specs/2026-05-09-p0-lib-render-design.md
• Spec v0.2.0 (Phase A): meta/docs/superpowers/specs/2026-06-09-phase-A-inactive-entities-composition-actor-reentry-design.md
• Architecture: meta/docs/architecture/render-pipeline.md
• ADR-0001 (engine knows verbs, libs bring nouns)
• ADR-0031 (pixel-convention: Y-down-positive)
• ADR-0038 (API-Doc-Convention)