%% one line of a draw in the WIDE, NARROW or ALPHA_ANTIALIASED mode on an M1 (Metal has only aliased lines).
flowchart TD
    A["Line-list or strip draw,<br/>mode WIDE, NARROW<br/>or ALPHA"] --> B["Vertex shader<br/>captures its outputs"]
    B --> C["Object function:<br/>one thread per line"]
    C --> D["Clip to w ≥ 10⁻⁶ and to the<br/>viewport + 8 px, in clip space;<br/>map to pixels with the<br/>first vertex's viewport"]
    D --> E{"mode"}
    E -- "WIDE" --> F["Rectangle<br/>1.4 px wide"]
    E -- "NARROW, or ALPHA<br/>without a float4 o0" --> G["Rectangle<br/>1.0 px wide"]
    E -- "ALPHA" --> H["2 px wide + ½ px caps<br/>(+ √2/2 with MSAA),<br/>corners carry across,<br/>along and length"]
    F --> I["Two clockwise triangles,<br/>offsets scaled by w"]
    G --> I
    H --> I
    I --> J["Metal rasterizes<br/>(no depth bias)"]
    J --> K{"ALPHA?"}
    K -- no --> L["Pixel shader"]
    K -- yes --> M["Pixel shader, then<br/>o0.a × box-filtered coverage;<br/>discard where it is 0"]