It is a bit hard to explain unfortunately. The problem are the GTK callbacks and signals. In C we can connect to a signal name given as a string providing a callback proc and a pointer to arbitrary data. In higher level languages we try to archive type safety, so we have to ensure that our provided data match our proc signature.
My nim-gi module ([https://github.com/StefanSalewski/nim-gi2](https://github.com/StefanSalewski/nim-gi2)) can generate already some nice bindings (at least for Linux AMD64 and GTK 3.22), and with some help of Mr J. Mansour I created a first working test with a connect macro which looks like this: # TODO: this macro will be moved to library module! macro connect(widget: Widget; signal: string; p: typed; arg: typed): typed = inc(ProcID) let wt = getType(widget) # widget type let at = getType(arg) # argument type let signalName = ($signal).replace("-", "_") # maybe we should just use plain proc names let procNameCdecl = newIdentNode("connect_for_signal_cdecl_" & signalName & $ProcID) let procName = newIdentNode("connect_for_signal_" & signalName & $ProcID) let scName = newIdentNode("sc" & signalName) result = quote do: proc `procNameCdecl`(button: ptr Object00 , data: pointer) {.cdecl.} = var h: pointer = g_object_get_qdata(button, Quark) `p`(cast[`wt`](h), cast[`at`](data)) proc `procName`(self: `wt`; p: proc (self: `wt`, arg: `at`); a: `at`) = `scName`(self, `procNameCdecl`, cast[pointer](a)) `procName`(`widget`, `p`, `arg`) and is called like connect(button1, "clicked", clickd, "Hello") (Full code at [https://github.com/StefanSalewski/nim-gi2](https://github.com/StefanSalewski/nim-gi2)) I am not sure if the macro has good shape, but it seems to work. Indeed it should not really work -- the passed in string "Hello" is collected by the GC at some time... So what we need is a way to make that arbitrary typed data parameter persistent. For ref to objects a GC_ref would do. All other data which are not refs should need a copy which is then passed to the callback. So question is: How can I check if the parameter is a ref on which I can call GR_ref. And if not a ref, how can I do best a persistent copy, maybe a deep copy? In best case it should be even possible to free that data later again, because GTK allows disconnecting of callbacks. But that is rarely used, and the data is generally small, so not much Ram is wasted.
