code: func NewGLTriangles(shader *glhf.Shader, t pixel.Triangles) *GLTriangles {
  	var gt *GLTriangles
  	mainthread.Call(func() {
  		gt = &GLTriangles{
  			vs:     glhf.MakeVertexSlice(shader, 0, t.Len()),
  			shader: shader,
  		}
  	})
  	gt.SetLen(t.Len())
  	gt.Update(t)
  	return gt
  }
docs: // NewGLTriangles returns GLTriangles initialized with the data from the supplied Triangles.
  //
  // Only draw the Triangles using the provided Shader.