REQ: gtk.Builder: support for attribute "object" in glib.CallbackContext

[pebbe]

I tried to convert a simple C example into Go with go-gtk.

Here is the original: Werkzeugleiste.

Here is my Go version: 16werkzeug.go

It has to do with how this fragment is used by the builder:

<signal name="activate" handler="fettschreiben" object="textview" />

The C version uses the simple gtk_builder_connect_signals, without a custom connect function, to set up the signals, and all works fine. The handler receives a pointer to the GtkWidget "textview"

In the Go version, I have to use a custom connect function to get to the "textview" widget from within the handler. Is it possible to include access to such an object from the default context, with something like glib.CallbackContext.GetObject() ?

[mattn]

gtk.WidgetFromObject(ctx.Target().(*glib.GObject))

This is way to get gtk.Widget from event callback context.

[pebbe]

That gives me the widget that made the callback, not the widget the signal is linked to through the "object" attribute.

[mattn]

Do you want API to gtk_builder_get_object ?

[pebbe]

Suppose you got this in your builder interface:

<object class="GtkButton" id="my-button">
  <signal name="clicked" handler="myHandler" swapped="no"/>
</object>

In Go, you can do something like this:

func myHandler(ctx interface{}) {
    widget := gtk.WidgetFromObject(ctx.(*glib.CallbackContext).Target().(*glib.GObject))
    /* ... */
}

---

But when you have something like this:

<object class="GtkAction" id="fettschrift">
  <signal name="activate" handler="myHandler" object="textview" />
</object>

<object class="GtkTextView" id="textview" />

... and you try the same thing in Go, you get an error:

GLib-GObject-WARNING **: invalid cast from 'GtkAction' to 'GtkWidget'

How, in this case, do I get to the widget "textview"?

In C, the handler simply gets a pointer to "textview" directly. See this example: Werkzeugleiste

[mattn]

The first arguments of ConnectSignalsFull is BuilderConnectFunc.

type BuilderConnectFunc func(builder *Builder, obj *glib.GObject, sig, handler string, conn *glib.GObject, flags glib.ConnectFlags, user_data interface{})

Second argument conn should be the object attribute, as I can see the doc of GtkBuilder.