introducing keep alives, where necessary

app.go

@@ -235,7 +235,7 @@ func (a *app) AddImageProvider(id string, ip *ImageProvider) error {
 
 	var ret C.int
 	a.RunMain(func() {
-		ret = C.gml_app_add_imageprovider(a.app, idC, ip.ip, apiErr.err)
+		ret = C.gml_app_add_imageprovider(a.app, idC, ip.ptr, apiErr.err)
 	})
 	if ret != 0 {
 		return apiErr.Err("failed to add image provider")

image.go

@@ -40,7 +40,7 @@ import (
 
 type Image struct {
 	freed bool
-	img   C.gml_image
+	ptr   C.gml_image
 }
 
 func NewImage() (img *Image) {
@@ -56,7 +56,7 @@ func newImage(imgC C.gml_image, free bool) (img *Image) {
 
 	img = &Image{
 		freed: !free,
-		img:   imgC,
+		ptr:   imgC,
 	}
 
 	// Always free the C++ value if defined so.
@@ -72,7 +72,7 @@ func freeImage(img *Image) {
 		return
 	}
 	img.freed = true
-	C.gml_image_free(img.img)
+	C.gml_image_free(img.ptr)
 }
 
 func (img *Image) Free() {
@@ -81,7 +81,7 @@ func (img *Image) Free() {
 
 // Reset the image to an empty image.
 func (img *Image) Reset() {
-	C.gml_image_reset(img.img)
+	C.gml_image_reset(img.ptr)
 
 	// Prevent the GC from freeing. Go issue 13347
 	runtime.KeepAlive(img)
@@ -89,7 +89,7 @@ func (img *Image) Reset() {
 
 // SetTo performs a shallow copy.
 func (img *Image) SetTo(other *Image) {
-	C.gml_image_set_to(img.img, other.img)
+	C.gml_image_set_to(img.ptr, other.ptr)
 
 	// Prevent the GC from freeing. Go issue 13347
 	runtime.KeepAlive(img)
@@ -116,7 +116,7 @@ func (img *Image) LoadFromGoImage(gimg image.Image) error {
 	defer errorPool.Put(apiErr)
 
 	ret := C.gml_image_load_from_rgba(
-		img.img,
+		img.ptr,
 		(*C.char)(unsafe.Pointer(&imgRGBA.Pix[0])),
 		C.int(len(imgRGBA.Pix)),
 		C.int(b.Dx()),
@@ -146,7 +146,7 @@ func (img *Image) LoadFromFile(filename string) error {
 	apiErr := errorPool.Get()
 	defer errorPool.Put(apiErr)
 
-	ret := C.gml_image_load_from_file(img.img, filenameC, apiErr.err)
+	ret := C.gml_image_load_from_file(img.ptr, filenameC, apiErr.err)
 	if ret != 0 {
 		return apiErr.Err("failed to load from file")
 	}
@@ -165,7 +165,7 @@ func (img *Image) LoadFromData(data []byte) error {
 	apiErr := errorPool.Get()
 	defer errorPool.Put(apiErr)
 
-	ret := C.gml_image_load_from_data(img.img, (*C.char)(unsafe.Pointer(&data[0])), C.int(len(data)), apiErr.err)
+	ret := C.gml_image_load_from_data(img.ptr, (*C.char)(unsafe.Pointer(&data[0])), C.int(len(data)), apiErr.err)
 	if ret != 0 {
 		return apiErr.Err("failed to load from data")
 	}

imageprovider.go

@@ -65,8 +65,8 @@ type ImageProviderCallback func(id string, img *Image) error
 
 type ImageProvider struct {
 	freed bool
-	ip    C.gml_image_provider
-	ptr   unsafe.Pointer
+	ptr   C.gml_image_provider
+	goPtr unsafe.Pointer
 
 	callback ImageProviderCallback
 }
@@ -79,15 +79,15 @@ func NewImageProvider(
 	ip := &ImageProvider{
 		callback: callback,
 	}
-	ip.ptr = pointer.Save(ip)
-	ip.ip = C.gml_image_provider_new(ip.ptr, C.int(aspectRatioMode), C.int(transformMode))
+	ip.goPtr = pointer.Save(ip)
+	ip.ptr = C.gml_image_provider_new(ip.goPtr, C.int(aspectRatioMode), C.int(transformMode))
 
 	// Always free the C++ value.
 	runtime.SetFinalizer(ip, freeImageProvider)
 
 	// Check if something failed.
 	// This should never happen. Otherwise this signalizes a fatal error.
-	if ip.ip == nil {
+	if ip.ptr == nil {
 		panic(fmt.Errorf("failed to create gml imageprovider: C pointer is nil"))
 	}
 
@@ -99,8 +99,8 @@ func freeImageProvider(ip *ImageProvider) {
 		return
 	}
 	ip.freed = true
-	C.gml_image_provider_free(ip.ip)
-	pointer.Unref(ip.ptr)
+	C.gml_image_provider_free(ip.ptr)
+	pointer.Unref(ip.goPtr)
 }
 
 func (ip *ImageProvider) Free() {
@@ -139,7 +139,6 @@ func gml_image_provider_request_go_slot(
 
 		// Emit the finished signal on the image response.
 		// Must always be triggered!
-		// TODO: should run on main?
 		C.gml_image_response_emit_finished(imgResp, errStrC)
 	}()
 }

variant.go

@@ -111,6 +111,9 @@ func ToVariant(i interface{}) *Variant {
 		}
 	}
 
+	// Prevent the GC from freeing. Go issue 13347
+	runtime.KeepAlive(i)
+
 	return newVariant(ptr)
 }