Simpledisplay - empty handler doesn't work

[helikopterodaktyl]

What determines what is usable as a handler and what isn't? I am getting inconsistent behavior

import arsd.simpledisplay;
import std.stdio;

void main()
{
    SimpleWindow window = new SimpleWindow(Size(1024, 768), "Test");

    void foo()
    {
    }

    // works
    window.eventLoop(1,
        () { foo(); }
    );

    // doesn't work
    window.eventLoop(1,
        () { writeln("test"); }
    );

    // doesn't work
    window.eventLoop(1,
        () {}
    );

}

[adamdruppe]

They need to be delegates instead of function pointers. That's why the error message in that case suggests trying the delegate keyword - it specifies to the compiler that you need that specifically (though it is true the library could convert them internally too...).

The difference between them is a delegate accesses some local data and a function pointer doesn't. So { foo(); } works because foo is the local data it accesses. writeln doesn't because it is global, not local. And empty {} needs no extra data at all. So the compiler types them as function pointer.

If you use the delegate keyword though, the compiler just passes it a null pointer to local data, which since it doesn't use anyway, all works nicely.

Since you can just add the keyword on the outside when needed, I think that's good enough but it is tempting to make the library just go ahead and convert when necessary too, it wouldn't be that hard to add.