func canvasDraw(c jquery.JQuery) {
if c.Attr("width") == "" && c.Attr("height") == "" {
// Determine height from aspect ratio and parent's width.
aspect := 1.5 // 3 by 2 aspect ratio
attr := c.Attr("aspect")
if attr != "" {
_, err := fmt.Sscanf(attr, "%f", &aspect)
if err != nil {
panic(err)
}
}
parent := c.Parent()
w := parent.Width()
c.SetAttr("width", w)
c.SetAttr("height", float64(w)/aspect)
}
d, _ := getDrawerListener(c)
if d != nil {
go d.Draw(canvasContext(c))
}
}
