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gfx: no image blit, no additive blend, no polygon/gradient, no font API — the 15-primitive surface caps every consumer at a 1982 look (Tidepool forcing-function)

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
35/100
Issue type
Feature
Clarity
Clearly specified
Activity status
Active
Tech stack
c
Domain
computer-graphics, testing-qa

Research direction

Start in src/ext_gfx.c, focusing on the existing SDL loader, framebuffer texture path, and current gfx primitives. Review src/draw.eigs and the lib/ui consumers, then inspect how headless draw-list entries and gfx_read pixel tests are structured under xvfb. Done means the requested image, blend, geometry, alpha, and font capabilities are implemented with dependency-free loading and coverage for each builtin.

Written by the indexing model from the issue text.

Description

area:gfx enhancement found-by:consumer

Forcing-function report from Tidepool (maintainer's call, 2026-09-20: the gfx fleet "looks like it was from the early 80s — necessary to have started there, for the language, but not modern"). Measured against src/ext_gfx.c on main a22f8dd, the runtime's drawing surface is 15 builtins: gfx_open close title clear present poll delay ticks clip read fb point line rect rrect circle text text_width text_height. What a modern-looking 2D game needs and cannot get from that set:

Already there (so the ask is smaller than it looks): a global SDL_BLENDMODE_BLEND (line 486); gfx_rect/gfx_circle take an optional alpha (538–612); textures exist internally (SDL_CreateTexture/UpdateTexture/RenderCopy are loaded for gfx_fb); SDL2_ttf is probed for gfx_text; inflate/deflate builtins exist (make zlib).

Missing:

  1. No image path. Nothing loads a raster or blits one. Every consumer draws with circles and lines; a background plate, a sprite, a particle texture, a generated concept art (Tidepool docs/concept-2026-09-20.png, made in one minute) cannot reach the screen. Ask: gfx_image_load of path → handle (PNG decode in C on top of the existing inflate — no SDL2_image dependency, which is not on the dev box anyway; RGBA with real alpha), gfx_image_draw of [img, x, y, w, h, alpha, angle_deg], gfx_image_size, and a framebuffer-backed gfx_image_from_fb so procedural art can be cached once and blitted many times.
  2. No additive blend. Glow is BLENDMODE_ADD; a bioluminescent look is impossible with alpha-blend only. Ask: gfx_blend of mode ("blend" | "add" | "none"), state held per subsequent draw.
  3. gfx_line/gfx_point have no alpha (rect/circle do). Ask: same optional trailing alpha on all four.
  4. No filled polygon / gradient / soft circle. A cell body is a smooth blob, a water background is a gradient, a glow is a radial falloff. Ask: gfx_polygon of [[x,y]…, r, g, b, a] (SDL_RenderGeometry, already in SDL2 ≥ 2.0.18) and gfx_circle_soft of [cx, cy, radius, r, g, b, a, feather] — or just gfx_polygon plus item 1 and let lib/ build the rest.
  5. Text is a bitmap font unless a system TTF happens to be found, with no size/weight API beyond scale. Ask: gfx_font of [path, size] → handle, gfx_text accepting a font handle.

Consumer evidence: Tidepool's renderer uses exactly gfx_circle/line/rect/rrect/point/text/clear/present (src/draw.eigs), DMG uses gfx_fb, DeslanStudio uses lib/ui on the same primitives. All three are capped by the same five gaps. The identity of the Tidepool look (translucent, glowing, dark pool) survives — it needs items 1, 2 and 4 to render the way the concept frame shows it.

Keep it dependency-free (EigenScript has none): PNG via inflate, geometry via SDL_RenderGeometry through the existing dlsym loader, nothing new to link. Each builtin lands with a headless draw-list entry (the renderer is headless-inspectable and consumers' tests assert on it) and a gfx_read pixel test under xvfb.

Dominant language
C
Stars
3
Forks
7
Avg merge
3h 56m
Merged PRs (30d)
102

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