setPrimitiveType method

@override void setPrimitiveType(PrimitiveType type)

How the following draws assemble their vertices.

Strips and points are capabilities, since 1.0.0-rc.1: PrimitiveType.triangleStrip and PrimitiveType.lineStrip need DeviceFeature.primitiveStrips, PrimitiveType.point needs DeviceFeature.pointPrimitives, and triangle and line lists need nothing. A backend calls PrimitiveTypeFeatures.checkFeatures here, so a topology it lacks is refused by name from this call, before a draw. Every backend in this repository that draws lists both.

Primitive restart is always on for strips, on every backend that lists primitiveStrips: an all-ones index (IndexTypeFeatures.restartIndex) in an indexed strip ends it, and the next index starts a new one — WebGPU's rule, and WebGL2's fixed-index restart. A list has no restart.

What the contract also promises is that a backend never assembles one primitive as another, because three points drawn as a triangle is a picture nobody asked for and no error anywhere.

Held by the conformance check every primitive type is assembled as itself or refused, which draws all five and compares how much each one painted, and draws a strip through a restart.

Implementation

@override
void setPrimitiveType(PrimitiveType type) {
  primitiveType = type;
  commands.add(RecordedPrimitiveType(type));
}