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janet/ffitest/gtk.janet

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# FFI is best used with a wrapper like the one below
# An even more sophisticated macro wrapper could add
# better doc strings, better parameter checking, etc.
(defn defnative-context
"Load a dynamic library and set it as the context for following declarations"
[location]
(setdyn :raw-native (raw-native location)))
(defmacro defnative
"Declare a native binding"
[name ret-type & body]
(def signature-args (last body))
(def defn-args (seq [_ :in signature-args] (gensym)))
(def raw-symbol (string/replace-all "-" "_" name))
(def $sig (symbol name "-signature-"))
(def $pointer (symbol name "-raw-pointer-"))
~(upscope
(def ,$pointer :private (as-macro ,assert (,native-lookup (,dyn :raw-native) ,raw-symbol)))
(def ,$sig :private (,native-signature :default ,ret-type ,;signature-args))
(defn ,name [,;defn-args]
(,native-call ,$pointer ,$sig ,;defn-args))))
(defnative-context "/usr/lib/libgtk-3.so")
(defnative gtk-application-new :ptr [:ptr :uint])
(defnative g-signal-connect-data :ulong [:ptr :ptr :ptr :ptr :ptr :int])
(defnative g-application-run :int [:ptr :int :ptr])
(defnative gtk-application-window-new :ptr [:ptr])
(defnative gtk-button-new-with-label :ptr [:ptr])
(defnative gtk-container-add :void [:ptr :ptr])
(defnative gtk-widget-show-all :void [:ptr])
(defnative gtk-button-set-label :void [:ptr :ptr])
# GTK follows a strict convention for callbacks. This lets us use
# a single "standard" callback whose behavior is specified by userdata.
# This lets use callbacks without code generation, so no issues with iOS, SELinux, etc.
# Limitation is that we cannot generate arbitrary closures to pass into apis.
# However, any stubs we need we would simply need to compile ourselves, so
# Janet includes a common stub out of the box.
(def cb (native-trampoline :default))
(defn on-active
[app]
(def window (gtk-application-window-new app))
(def btn (gtk-button-new-with-label "Click Me!"))
(g-signal-connect-data btn "clicked" cb
(fn [btn] (gtk-button-set-label btn "Hello World"))
nil 1)
(gtk-container-add window btn)
(gtk-widget-show-all window))
(defn main
[&]
(def app (gtk-application-new "org.janet-lang.example.HelloApp" 0))
(g-signal-connect-data app "activate" cb on-active nil 1)
(g-application-run app 0 nil))