Fix and improve PostMessage

examples/postmessage/postmessage.go

@@ -5,12 +5,13 @@ import (
 	"encoding/json"
 	"fmt"
 	"image"
+	_ "image/gif"
 	_ "image/jpeg"
 	_ "image/png"
 	"io/ioutil"
 	"log"
+	"math/rand"
 	"net/http"
-	"runtime/cgo"
 
 	"github.com/gen2brain/iup-go/iup"
 )
@@ -42,10 +43,8 @@ func main() {
 	iup.MainLoop()
 }
 
-func messageCb(ih iup.Ihandle, s string, i int, f float64, p *cgo.Handle) int {
-	b := p.Value().([]byte)
-	defer p.Delete()
-
+func messageCb(ih iup.Ihandle, s string, i int, p any) int {
+	b := p.([]byte)
 	img, _, err := image.Decode(bytes.NewReader(b))
 	if err != nil {
 		log.Fatalln(err)
@@ -68,32 +67,44 @@ func messageCb(ih iup.Ihandle, s string, i int, f float64, p *cgo.Handle) int {
 func buttonCb(ih iup.Ihandle) int {
 	ih.SetAttribute("ACTIVE", "NO")
 
+	type xkcd struct {
+		Id    int64  `json:"num,omitempty"`
+		Title string `json:"title,omitempty"`
+		Alt   string `json:"alt,omitempty"`
+		Img   string `json:"img,omitempty"`
+	}
+
 	go func() {
-		res, err := http.Get("https://random-xkcd-img.herokuapp.com/")
+		random := rand.Intn(2800-1) + 1
+
+		res, err := http.Get(fmt.Sprintf("https://xkcd.com/%d/info.0.json", random))
 		if err != nil {
 			log.Println(err)
+			return
 		}
 		defer res.Body.Close()
 
-		var ret map[string]string
+		var ret xkcd
 		err = json.NewDecoder(res.Body).Decode(&ret)
 		if err != nil {
 			log.Println(err)
+			return
 		}
 
-		img, err := http.Get(ret["url"])
+		img, err := http.Get(ret.Img)
 		if err != nil {
 			log.Println(err)
+			return
 		}
 		defer img.Body.Close()
 
 		b, err := ioutil.ReadAll(img.Body)
 		if err != nil {
 			log.Println(err)
+			return
 		}
 
-		h := cgo.NewHandle(b)
-		iup.PostMessage(iup.GetHandle("label"), ret["title"], len(b), 1.0, h)
+		iup.PostMessage(iup.GetHandle("label"), ret.Alt, 0, b)
 	}()
 
 	return iup.DEFAULT

iup/bind_callbacks.go

@@ -1,8 +1,10 @@
 package iup
 
 import (
+	"fmt"
 	"runtime/cgo"
 	"sync"
+	"sync/atomic"
 	"unsafe"
 )
 
@@ -399,6 +401,7 @@ import "C"
 
 var (
 	callbacks sync.Map
+	messages  atomic.Int64
 )
 
 //--------------------
@@ -1279,7 +1282,7 @@ func setSpinFunc(ih Ihandle, f SpinFunc) {
 //--------------------
 
 // PostMessageFunc for POSTMESSAGE_CB callback.
-type PostMessageFunc func(Ihandle, string, int, float64, *cgo.Handle) int
+type PostMessageFunc func(Ihandle, string, int, any) int
 
 //export goIupPostMessageCB
 func goIupPostMessageCB(ih unsafe.Pointer, s unsafe.Pointer, i C.int, d C.double, p unsafe.Pointer) C.int {
@@ -1292,10 +1295,12 @@ func goIupPostMessageCB(ih unsafe.Pointer, s unsafe.Pointer, i C.int, d C.double
 	ch := h.(cgo.Handle)
 	f := ch.Value().(PostMessageFunc)
 
-	goS := C.GoString((*C.char)(s))
-	goP := (*cgo.Handle)(p)
+	m, ok := callbacks.LoadAndDelete(fmt.Sprintf("POSTMESSAGE_MSG_%s_%d", uuid, int(d)))
+	if !ok {
+		panic("cannot load and delete message " + fmt.Sprintf("POSTMESSAGE_MSG_%s_%d", uuid, int(d)))
+	}
 
-	return C.int(f((Ihandle)(ih), goS, int(i), float64(d), goP))
+	return C.int(f((Ihandle)(ih), C.GoString((*C.char)(s)), int(i), m))
 }
 
 // setPostMessageFunc for POSTMESSAGE_CB.

iup/bind_events.go

@@ -1,6 +1,7 @@
 package iup
 
 import (
+	"fmt"
 	"runtime/cgo"
 	"unsafe"
 )
@@ -65,7 +66,10 @@ func PostMessage(ih Ihandle, s string, i int, d float64, p cgo.Handle) {
 	cS := C.CString(s)
 	defer C.free(unsafe.Pointer(cS))
 
-	C.IupPostMessage(ih.ptr(), cS, C.int(i), C.double(d), unsafe.Pointer(&p))
+	count := messages.Add(1)
+	callbacks.Store(fmt.Sprintf("POSTMESSAGE_MSG_%s_%d", ih.GetAttribute("UUID"), count), p)
+
+	C.IupPostMessage(ih.ptr(), cS, C.int(i), C.double(count), nil)
 }
 
 // Flush processes all pending messages in the message queue.

iup/bind_handle.go

@@ -10,6 +10,10 @@ import (
 #include <stdlib.h>
 #include "iup.h"
 
+static uintptr_t ih(Ihandle* i) {
+        return (uintptr_t)(i);
+}
+
 static Ihandle* pih(uintptr_t p) {
 	return (Ihandle*)(p);
 }
@@ -24,7 +28,7 @@ import "C"
 type Ihandle uintptr
 
 func mkih(p *C.Ihandle) Ihandle {
-	return Ihandle(unsafe.Pointer(p))
+	return Ihandle(C.ih(p))
 }
 
 func cih(ih Ihandle) *C.char {