vsync not determined by sdl correctly?

[jobf]

I'm testing with lime 8.1.1

When I enable vsync in the project.xml it seems to be ignored for hashlink or linux native builds, e.g.

<window width="800" height="600" vsync="true"/>

My display refresh rate is 59.93 hz so with vsync true I'd expect to see deltaTime in the update function fluctuate around 15 or 16 ms on average, however it's more like 32 or 33 ms.

The way I am testing this is as follows, in a class which extends lime.app.Application

override function update(deltaTime: Int): Void
{
    trace(deltaTime);
}

I understand that for web builds, the update rate is determined by window.requestAnimationFrame() which is already using vsync rate, and can confirm that if I build for web I do see deltaTime traces fluctuate around 15 or 16 ms on average. So perhaps this only relates to the SDL backend?