nx_paint_solid_rect.nx

nx_paint_solid_rect.nx -- fill a rectangle of pixels in a caller-supplied framebuffer with a solid RGBA color. Phase 4 first primitive of NISHI_BROWSER_ROADMAP -- bridges Phase 3 layout (assigns x/y/w/h per box) to actual pixel output. Framebuffer layout: row-major RGBA u8 quads. pixels[(y * width + x) * 4 + 0] = R pixels[(y * width + x) * 4 + 1] = G pixels[(y * width + x) * 4 + 2] = B pixels[(y * width + x) * 4 + 3] = A Caller-owns-memory contract: the Framebuffer struct points at a pre-allocated pixel array of width * height * 4 bytes. Clipping: rectangles outside the framebuffer bounds are clipped to the visible region; out-of-bounds writes never happen. Zero-area rectangles are silently skipped. What it does NOT handle yet (Phase 4b queued): - alpha blending (currently overwrites destination -- assumes opaque foreground; transparent fills via this primitive will paint solid black behind transparent areas, wrong for layered elements). Composes with future nx_paint_blend. - sub-pixel positioning (integer-pixel only) - anti-aliased edges (Phase 4b after sub-pixel) - clip-rect stacking for overflow:hidden - SIMD acceleration (Phase 4c when nx_simd lands) Per cardinal feedback-honest-perf-verdict-no-aspirational-claims: gap list is EXACT. genealogy_id: substrate_browser_phase_4_paint_seed + classical_2d_rect_fill lineage_id: nishi_browser_paint_solid_rect_v1 nx_safety_envelope: intended_use: "Solid rect fill -- browser paint substrate" sil_target: SIL1 evidence: [bounded_pixel_loop, explicit_clipping,