diff --git a/rtgui/batchqueue.cc b/rtgui/batchqueue.cc
index 1d52c96e6..de9864226 100644
--- a/rtgui/batchqueue.cc
+++ b/rtgui/batchqueue.cc
@@ -50,12 +50,10 @@ struct NLParams {
     Glib::ustring queueErrorMessage;
 };
 
-int bqnotifylistenerUI (void* data)
+bool bqnotifylistenerUI(NLParams* params)
 {
-    NLParams* params = static_cast<NLParams*>(data);
     params->listener->queueSizeChanged (params->qsize, params->queueEmptied, params->queueError, params->queueErrorMessage);
-    delete params;
-    return 0;
+    return false;
 }
 
 }
@@ -438,16 +436,12 @@ void BatchQueue::cancelItems (const std::vector<ThumbBrowserEntryBase*>& items)
             if (entry->thumbnail)
                 entry->thumbnail->imageRemovedFromQueue ();
 
-            const auto func = [](gpointer data) -> gboolean {
-                const BatchQueueEntry* const bqe = static_cast<BatchQueueEntry*>(data);
-
+            const auto func = [](BatchQueueEntry* bqe) -> bool {
                 ::g_remove(bqe->savedParamsFile.c_str());
-                delete bqe;
-
-                return FALSE;
+                return false;
             };
 
-            idle_register.add(func, entry);
+            idle_register.add<BatchQueueEntry>(func, entry, true);
         }
 
         for (const auto entry : fd)
@@ -608,12 +602,14 @@ void BatchQueue::setProgress(double p)
     }
 
     // No need to acquire the GUI, setProgressUI will do it
-    const auto func = [](gpointer data) -> gboolean {
-        static_cast<BatchQueue*>(data)->redraw();
-        return FALSE;
-    };
+    const auto func =
+        [](BatchQueue* bq) -> bool
+        {
+            bq->redraw();
+            return false;
+        };
 
-    idle_register.add(func, this);
+    idle_register.add<BatchQueue>(func, this, false);
 }
 
 void BatchQueue::setProgressStr(const Glib::ustring& str)
@@ -643,7 +639,7 @@ void BatchQueue::error(const Glib::ustring& descr)
         params->queueEmptied = false;
         params->queueError = true;
         params->queueErrorMessage = descr;
-        idle_register.add(bqnotifylistenerUI, params);
+        idle_register.add<NLParams>(bqnotifylistenerUI, params, true);
     }
 }
 
@@ -985,7 +981,7 @@ void BatchQueue::notifyListener (bool queueEmptied)
         }
         params->queueEmptied = queueEmptied;
         params->queueError = false;
-        idle_register.add(bqnotifylistenerUI, params);
+        idle_register.add<NLParams>(bqnotifylistenerUI, params, true);
     }
 }
 
diff --git a/rtgui/batchqueuepanel.cc b/rtgui/batchqueuepanel.cc
index bc03c2386..d718de677 100644
--- a/rtgui/batchqueuepanel.cc
+++ b/rtgui/batchqueuepanel.cc
@@ -170,13 +170,14 @@ BatchQueuePanel::BatchQueuePanel (FileCatalog* aFileCatalog) : parent(nullptr)
     show_all ();
 
     if (batchQueue->loadBatchQueue()) {
-        const auto func = [](gpointer data) -> gboolean {
-            static_cast<BatchQueue*>(data)->resizeLoadedQueue();
+        const auto func =
+            [](BatchQueue* bq) -> bool
+            {
+                bq->resizeLoadedQueue();
+                return false;
+            };
 
-            return FALSE;
-        };
-
-        idle_register.add(func, batchQueue, G_PRIORITY_LOW);
+        idle_register.add<BatchQueue>(func, batchQueue, false, G_PRIORITY_LOW);
     }
 }
 
diff --git a/rtgui/bayerprocess.cc b/rtgui/bayerprocess.cc
index 2a65a158e..ad9db9c2c 100644
--- a/rtgui/bayerprocess.cc
+++ b/rtgui/bayerprocess.cc
@@ -723,49 +723,51 @@ void BayerProcess::FrameCountChanged(int n, int frameNum)
         int n;
         int frameNum;
     };
-    const auto func = [](gpointer data) -> gboolean {
-        Data *d = static_cast<Data *>(data);
-        BayerProcess *me = d->me;
-        me->imageNumber->block (true);
-        int n = d->n;
-        int frameNum = d->frameNum;
 
-        me->imageNumber->remove_all();
-        me->imageNumber->append("1");
-        for(int i = 2; i <= std::min(n, 4); ++i) {
-            std::ostringstream entry;
-            entry << i;
-            me->imageNumber->append(entry.str());
-        }
-        me->imageNumber->set_active(std::min(frameNum, n - 1));
-        if(n == 1) {
-            me->imageNumberBox->hide();
-        } else {
-            me->imageNumberBox->show();
-        }
-        me->imageNumber->block (false);
-        delete d;
-        return FALSE;
-    };
+    const auto func =
+        [](Data* d) -> bool
+        {
+            BayerProcess *me = d->me;
+            me->imageNumber->block (true);
+            int n = d->n;
+            int frameNum = d->frameNum;
 
-    idle_register.add(func, new Data { this, n, frameNum });
+            me->imageNumber->remove_all();
+            me->imageNumber->append("1");
+            for(int i = 2; i <= std::min(n, 4); ++i) {
+                std::ostringstream entry;
+                entry << i;
+                me->imageNumber->append(entry.str());
+            }
+            me->imageNumber->set_active(std::min(frameNum, n - 1));
+            if(n == 1) {
+                me->imageNumberBox->hide();
+            } else {
+                me->imageNumberBox->show();
+            }
+            me->imageNumber->block (false);
+            return false;
+        };
+
+    idle_register.add<Data>(func, new Data{this, n, frameNum}, true);
 }
 
 void BayerProcess::autoContrastChanged (double autoContrast)
 {
     struct Data {
-        BayerProcess *me;
+        BayerProcess* self;
         double autoContrast;
     };
-    const auto func = [](gpointer data) -> gboolean {
-        Data *d = static_cast<Data *>(data);
-        BayerProcess *me = d->me;
-        me->disableListener();
-        me->dualDemosaicContrast->setValue(d->autoContrast);
-        me->enableListener();
-        delete d;
-        return FALSE;
-    };
 
-    idle_register.add(func, new Data { this, autoContrast });
+    const auto func =
+        [](Data* data) -> bool
+        {
+            BayerProcess* const self = data->self;
+            self->disableListener();
+            self->dualDemosaicContrast->setValue(data->autoContrast);
+            self->enableListener();
+            return false;
+        };
+
+    idle_register.add<Data>(func, new Data{this, autoContrast}, true);
 }
diff --git a/rtgui/blackwhite.cc b/rtgui/blackwhite.cc
index 47ab24f5e..359207115 100644
--- a/rtgui/blackwhite.cc
+++ b/rtgui/blackwhite.cc
@@ -375,12 +375,14 @@ void BlackWhite::BWChanged  (double redbw, double greenbw, double bluebw)
     nextgreenbw = greenbw;
     nextbluebw = bluebw;
 
-    const auto func = [](gpointer data) -> gboolean {
-        static_cast<BlackWhite*>(data)->BWComputed_();
-        return FALSE;
-    };
+    const auto func =
+        [](BlackWhite* self) -> bool
+        {
+            self->BWComputed_();
+            return false;
+        };
 
-    idle_register.add(func, this);
+    idle_register.add<BlackWhite>(func, this, false);
 }
 
 bool BlackWhite::BWComputed_ ()
diff --git a/rtgui/colorappearance.cc b/rtgui/colorappearance.cc
index 14e630f3c..489b793da 100644
--- a/rtgui/colorappearance.cc
+++ b/rtgui/colorappearance.cc
@@ -1452,63 +1452,63 @@ void ColorAppearance::setDefaults (const ProcParams* defParams, const ParamsEdit
 void ColorAppearance::autoCamChanged (double ccam, double ccamout)
 {
     struct Data {
-        ColorAppearance *me;
+        ColorAppearance* me;
         double ccam;
         double ccamout;
     };
 
-    const auto func = [](gpointer data) -> gboolean {
-        Data *d = static_cast<Data *>(data);
-        ColorAppearance *me = d->me;
-        me->disableListener();
-        me->degree->setValue(d->ccam);
-        me->degreeout->setValue(d->ccamout);
-        me->enableListener();
-        delete d;
-        return FALSE;
-    };
+    const auto func =
+        [](Data* data) -> bool
+        {
+            ColorAppearance* const self = data->me;
+            self->disableListener();
+            self->degree->setValue(data->ccam);
+            self->degreeout->setValue(data->ccamout);
+            self->enableListener();
+            return false;
+        };
 
-    idle_register.add(func, new Data { this, ccam, ccamout });
+    idle_register.add<Data>(func, new Data{this, ccam, ccamout}, true);
 }
 
 void ColorAppearance::adapCamChanged (double cadap)
 {
     struct Data {
-        ColorAppearance *me;
+        ColorAppearance* self;
         double cadap;
     };
 
-    const auto func = [](gpointer data) -> gboolean {
-        Data *d = static_cast<Data *>(data);
-        ColorAppearance *me = d->me;
-        me->disableListener();
-        me->adapscen->setValue(d->cadap);
-        me->enableListener();
-        delete d;
-        return FALSE;
-    };
+    const auto func =
+        [](Data* data) -> bool
+        {
+            ColorAppearance* const self = data->self;
+            self->disableListener();
+            self->adapscen->setValue(data->cadap);
+            self->enableListener();
+            return false;
+        };
 
-    idle_register.add(func, new Data { this, cadap });
+    idle_register.add<Data>(func, new Data{this, cadap}, true);
 }
 
 void ColorAppearance::ybCamChanged (int ybsc)
 {
     struct Data {
-        ColorAppearance *me;
+        ColorAppearance* self;
         int ybsc;
     };
 
-    const auto func = [](gpointer data) -> gboolean {
-        Data *d = static_cast<Data *>(data);
-        ColorAppearance *me = d->me;
-        me->disableListener();
-        me->ybscen->setValue(d->ybsc);
-        me->enableListener();
-        delete d;
-        return FALSE;
-    };
+    const auto func =
+        [](Data* data) -> bool
+        {
+            ColorAppearance* self = data->self;
+            self->disableListener();
+            self->ybscen->setValue(data->ybsc);
+            self->enableListener();
+            return false;
+        };
 
-    idle_register.add(func, new Data { this, ybsc });
+    idle_register.add<Data>(func, new Data{this, ybsc}, true);
 }
 
 void ColorAppearance::colorForValue (double valX, double valY, enum ColorCaller::ElemType elemType, int callerId, ColorCaller *caller)
diff --git a/rtgui/colortoning.cc b/rtgui/colortoning.cc
index 2f32d9b0b..f1e11a945 100644
--- a/rtgui/colortoning.cc
+++ b/rtgui/colortoning.cc
@@ -689,24 +689,24 @@ void ColorToning::setAdjusterBehavior (bool splitAdd, bool satThresholdAdd, bool
 
 void ColorToning::autoColorTonChanged(int satthres, int satprot)
 {
-        struct Data {
-            ColorToning *me;
-            int satthres;
-            int satprot;
+    struct Data {
+        ColorToning *self;
+        int satthres;
+        int satprot;
+    };
+
+    const auto func =
+        [](Data* data) -> bool
+        {
+            ColorToning* const self = data->self;
+            self->disableListener();
+            self->satProtectionThreshold->setValue(data->satthres);
+            self->saturatedOpacity->setValue(data->satprot);
+            self->enableListener();
+            return false;
         };
 
-        const auto func = [](gpointer data) -> gboolean {
-            Data *d = static_cast<Data *>(data);
-            ColorToning *me = d->me;
-            me->disableListener();
-            me->satProtectionThreshold->setValue(d->satthres);
-            me->saturatedOpacity->setValue(d->satprot);
-            me->enableListener ();
-            delete d;
-            return FALSE;
-        };
-
-        idle_register.add(func, new Data { this, satthres, satprot });
+    idle_register.add<Data>(func, new Data{this, satthres, satprot}, true);
 }
 
 void ColorToning::adjusterChanged (ThresholdAdjuster* a, double newBottom, double newTop)
diff --git a/rtgui/crop.cc b/rtgui/crop.cc
index d5b246107..edf76b6b1 100644
--- a/rtgui/crop.cc
+++ b/rtgui/crop.cc
@@ -38,18 +38,16 @@ public:
         : crop(_crop), notify(_notify) {}
 };
 
-int refreshSpinsUI (void* data)
+bool refreshSpinsUI(RefreshSpinHelper* rsh)
 {
-    RefreshSpinHelper* rsh = static_cast<RefreshSpinHelper*>(data);
-    rsh->crop->refreshSpins (rsh->notify);
-    delete rsh;
-    return 0;
+    rsh->crop->refreshSpins(rsh->notify);
+    return false;
 }
 
-int notifyListenerUI (void* data)
+bool notifyListenerUI(Crop* self)
 {
-    static_cast<Crop*>(data)->notifyListener();
-    return 0;
+    self->notifyListener();
+    return false;
 }
 
 }
@@ -515,16 +513,14 @@ void Crop::enabledChanged ()
 
 void Crop::hFlipCrop ()
 {
-
     nx = maxw - nx - nw;
-    idle_register.add(refreshSpinsUI, new RefreshSpinHelper(this, false));
+    idle_register.add<RefreshSpinHelper>(refreshSpinsUI, new RefreshSpinHelper(this, false), true);
 }
 
 void Crop::vFlipCrop ()
 {
-
     ny = maxh - ny - nh;
-    idle_register.add(refreshSpinsUI, new RefreshSpinHelper(this, false));
+    idle_register.add<RefreshSpinHelper>(refreshSpinsUI, new RefreshSpinHelper(this, false), true);
 }
 
 void Crop::rotateCrop (int deg, bool hflip, bool vflip)
@@ -564,7 +560,7 @@ void Crop::rotateCrop (int deg, bool hflip, bool vflip)
     }
 
     lastRotationDeg = deg;
-    idle_register.add(refreshSpinsUI, new RefreshSpinHelper(this, false));
+    idle_register.add<RefreshSpinHelper>(refreshSpinsUI, new RefreshSpinHelper(this, false), true);
 }
 
 void Crop::positionChanged ()
@@ -578,7 +574,7 @@ void Crop::positionChanged ()
     int W = nw;
     int H = nh;
     cropMoved (X, Y, W, H);
-    idle_register.add(notifyListenerUI, this);
+    idle_register.add<Crop>(notifyListenerUI, this, false);
 }
 
 void Crop::widthChanged ()
@@ -591,7 +587,7 @@ void Crop::widthChanged ()
     int W = (int)w->get_value ();
     int H = nh;
     cropWidth2Resized (X, Y, W, H);
-    idle_register.add(notifyListenerUI, this);
+    idle_register.add<Crop>(notifyListenerUI, this, false);
 }
 
 void Crop::heightChanged ()
@@ -604,7 +600,7 @@ void Crop::heightChanged ()
     int W = nw;
     int H = (int)h->get_value ();
     cropHeight2Resized (X, Y, W, H);
-    idle_register.add(notifyListenerUI, this);
+    idle_register.add<Crop>(notifyListenerUI, this, false);
 }
 
 // Fixed ratio toggle button
@@ -656,7 +652,7 @@ void Crop::adjustCropToRatio()
     }
 
     // This will save the options
-    idle_register.add(refreshSpinsUI, new RefreshSpinHelper(this, true));
+    idle_register.add<RefreshSpinHelper>(refreshSpinsUI, new RefreshSpinHelper(this, true), true);
 }
 
 void Crop::refreshSize ()
@@ -742,14 +738,14 @@ void Crop::sizeChanged(int x, int y, int ow, int oh)
         y
     };
 
-    const auto func = [](gpointer data) -> gboolean {
-        Params* const params = static_cast<Params*>(data);
-        params->crop->setDimensions(params->x, params->y);
-        delete params;
-        return FALSE;
-    };
+    const auto func =
+        [](Params* params) -> bool
+        {
+            params->crop->setDimensions(params->x, params->y);
+            return false;
+        };
 
-    idle_register.add(func, params);
+    idle_register.add<Params>(func, params, true);
 }
 
 bool Crop::refreshSpins (bool notify)
@@ -813,7 +809,7 @@ void Crop::cropMoved (int &X, int &Y, int &W, int &H)
     nw = W;
     nh = H;
 
-    idle_register.add(refreshSpinsUI, new RefreshSpinHelper(this, false));
+    idle_register.add<RefreshSpinHelper>(refreshSpinsUI, new RefreshSpinHelper(this, false), true);
 //  Glib::signal_idle().connect (sigc::mem_fun(*this, &Crop::refreshSpins));
 }
 
@@ -857,7 +853,7 @@ void Crop::cropWidth1Resized (int &X, int &Y, int &W, int &H, float custom_ratio
     nw = W;
     nh = H;
 
-    idle_register.add(refreshSpinsUI, new RefreshSpinHelper(this, false));
+    idle_register.add<RefreshSpinHelper>(refreshSpinsUI, new RefreshSpinHelper(this, false), true);
 }
 
 void Crop::cropWidth2Resized (int &X, int &Y, int &W, int &H, float custom_ratio)
@@ -897,7 +893,7 @@ void Crop::cropWidth2Resized (int &X, int &Y, int &W, int &H, float custom_ratio
     nw = W;
     nh = H;
 
-    idle_register.add(refreshSpinsUI, new RefreshSpinHelper(this, false));
+    idle_register.add<RefreshSpinHelper>(refreshSpinsUI, new RefreshSpinHelper(this, false), true);
 }
 
 void Crop::cropHeight1Resized (int &X, int &Y, int &W, int &H, float custom_ratio)
@@ -940,7 +936,7 @@ void Crop::cropHeight1Resized (int &X, int &Y, int &W, int &H, float custom_rati
     nw = W;
     nh = H;
 
-    idle_register.add(refreshSpinsUI, new RefreshSpinHelper(this, false));
+    idle_register.add<RefreshSpinHelper>(refreshSpinsUI, new RefreshSpinHelper(this, false), true);
 }
 
 void Crop::cropHeight2Resized (int &X, int &Y, int &W, int &H, float custom_ratio)
@@ -980,7 +976,7 @@ void Crop::cropHeight2Resized (int &X, int &Y, int &W, int &H, float custom_rati
     nw = W;
     nh = H;
 
-    idle_register.add(refreshSpinsUI, new RefreshSpinHelper(this, false));
+    idle_register.add<RefreshSpinHelper>(refreshSpinsUI, new RefreshSpinHelper(this, false), true);
 }
 
 void Crop::cropTopLeftResized (int &X, int &Y, int &W, int &H, float custom_ratio)
@@ -1022,7 +1018,7 @@ void Crop::cropTopLeftResized (int &X, int &Y, int &W, int &H, float custom_rati
     nw = W;
     nh = H;
 
-    idle_register.add(refreshSpinsUI, new RefreshSpinHelper(this, false));
+    idle_register.add<RefreshSpinHelper>(refreshSpinsUI, new RefreshSpinHelper(this, false), true);
 }
 
 void Crop::cropTopRightResized (int &X, int &Y, int &W, int &H, float custom_ratio)
@@ -1062,7 +1058,7 @@ void Crop::cropTopRightResized (int &X, int &Y, int &W, int &H, float custom_rat
     nw = W;
     nh = H;
 
-    idle_register.add(refreshSpinsUI, new RefreshSpinHelper(this, false));
+    idle_register.add<RefreshSpinHelper>(refreshSpinsUI, new RefreshSpinHelper(this, false), true);
 }
 
 void Crop::cropBottomLeftResized (int &X, int &Y, int &W, int &H, float custom_ratio)
@@ -1102,7 +1098,7 @@ void Crop::cropBottomLeftResized (int &X, int &Y, int &W, int &H, float custom_r
     nw = W;
     nh = H;
 
-    idle_register.add(refreshSpinsUI, new RefreshSpinHelper(this, false));
+    idle_register.add<RefreshSpinHelper>(refreshSpinsUI, new RefreshSpinHelper(this, false), true);
 }
 
 void Crop::cropBottomRightResized (int &X, int &Y, int &W, int &H, float custom_ratio)
@@ -1139,7 +1135,7 @@ void Crop::cropBottomRightResized (int &X, int &Y, int &W, int &H, float custom_
     nw = W;
     nh = H;
 
-    idle_register.add(refreshSpinsUI, new RefreshSpinHelper(this, false));
+    idle_register.add<RefreshSpinHelper>(refreshSpinsUI, new RefreshSpinHelper(this, false), true);
 }
 
 void Crop::cropInit (int &x, int &y, int &w, int &h)
@@ -1253,12 +1249,12 @@ void Crop::cropResized (int &x, int &y, int& x2, int& y2)
     nw = W;
     nh = H;
 
-    idle_register.add(refreshSpinsUI, new RefreshSpinHelper(this, false));
+    idle_register.add<RefreshSpinHelper>(refreshSpinsUI, new RefreshSpinHelper(this, false), true);
 }
 
 void Crop::cropManipReady ()
 {
-    idle_register.add(notifyListenerUI, this);
+    idle_register.add<Crop>(notifyListenerUI, this, false);
 }
 
 double Crop::getRatio () const
diff --git a/rtgui/crophandler.cc b/rtgui/crophandler.cc
index c00cccf6c..579d9af5b 100644
--- a/rtgui/crophandler.cc
+++ b/rtgui/crophandler.cc
@@ -338,9 +338,9 @@ void CropHandler::setDetailedCrop(
         bool expected = false;
 
         if (redraw_needed.compare_exchange_strong(expected, true)) {
-            const auto func = [](gpointer data) -> gboolean {
-                CropHandler* const self = static_cast<CropHandler*>(data);
-
+            const auto func =
+                [](CropHandler* self) -> bool
+                {
                 self->cimg.lock ();
 
                 if (self->redraw_needed.exchange(false)) {
@@ -350,7 +350,7 @@ void CropHandler::setDetailedCrop(
                         self->cropimg.clear();
                         self->cropimgtrue.clear();
                         self->cimg.unlock ();
-                        return FALSE;
+                        return false;
                     }
 
                     if (!self->cropimg.empty()) {
@@ -398,10 +398,10 @@ void CropHandler::setDetailedCrop(
                     self->cimg.unlock();
                 }
 
-                return FALSE;
+                return false;
             };
 
-            idle_register.add(func, this/*, G_PRIORITY_HIGH_IDLE*/);
+            idle_register.add<CropHandler>(func, this, false);
         }
     }
 
diff --git a/rtgui/dirpyrdenoise.cc b/rtgui/dirpyrdenoise.cc
index 81d7cff9a..72360b1de 100644
--- a/rtgui/dirpyrdenoise.cc
+++ b/rtgui/dirpyrdenoise.cc
@@ -284,32 +284,32 @@ DirPyrDenoise::~DirPyrDenoise ()
 void DirPyrDenoise::chromaChanged (double autchroma, double autred, double autblue)
 {
     struct Data {
-        DirPyrDenoise *me;
+        DirPyrDenoise* self;
         double autchroma;
         double autred;
         double autblue;
     };
 
-    const auto func = [](gpointer data) -> gboolean {
-        Data *d = static_cast<Data *>(data);
-        DirPyrDenoise *me = d->me;
-        me->disableListener();
-        me->chroma->setValue(d->autchroma);
-        me->redchro->setValue(d->autred);
-        me->bluechro->setValue(d->autblue);
-        me->enableListener();
-        delete d;
-        return FALSE;
-    };
+    const auto func =
+        [](Data* data) -> bool
+        {
+            DirPyrDenoise* const self = data->self;
+            self->disableListener();
+            self->chroma->setValue(data->autchroma);
+            self->redchro->setValue(data->autred);
+            self->bluechro->setValue(data->autblue);
+            self->enableListener();
+            return false;
+        };
 
-    idle_register.add(func, new Data { this, autchroma, autred, autblue });
+    idle_register.add<Data>(func, new Data{this, autchroma, autred, autblue}, true);
 }
 
 void DirPyrDenoise::noiseTilePrev (int tileX, int tileY, int prevX, int prevY, int sizeT, int sizeP)
 {
     if (!batchMode) {
         struct Data {
-            DirPyrDenoise *me;
+            DirPyrDenoise* self;
             int tileX;
             int tileY;
             int prevX;
@@ -318,26 +318,26 @@ void DirPyrDenoise::noiseTilePrev (int tileX, int tileY, int prevX, int prevY, i
             int sizeP;
         };
 
-        const auto func = [](gpointer data) -> gboolean {
-            Data *d = static_cast<Data *>(data);
-            DirPyrDenoise *me = d->me;
-            me->TileLabels->set_text(
-                Glib::ustring::compose(M("TP_DIRPYRDENOISE_CHROMINANCE_PREVIEW_TILEINFO"),
-                                       Glib::ustring::format(std::fixed, std::setprecision(0), d->sizeT),
-                                       Glib::ustring::format(std::fixed, std::setprecision(0), d->tileX),
-                                       Glib::ustring::format(std::fixed, std::setprecision(0), d->tileY))
-            );
-            me->PrevLabels->set_text(
-                Glib::ustring::compose(M("TP_DIRPYRDENOISE_CHROMINANCE_PREVIEW_INFO"),
-                                       Glib::ustring::format(std::fixed, std::setprecision(0), d->sizeP),
-                                       Glib::ustring::format(std::fixed, std::setprecision(0), d->prevX),
-                                       Glib::ustring::format(std::fixed, std::setprecision(0), d->prevY))
-            );
-            delete d;
-            return FALSE;
-        };
+        const auto func =
+            [](Data* data) -> bool
+            {
+                DirPyrDenoise* self = data->self;
+                self->TileLabels->set_text(
+                    Glib::ustring::compose(M("TP_DIRPYRDENOISE_CHROMINANCE_PREVIEW_TILEINFO"),
+                                           Glib::ustring::format(std::fixed, std::setprecision(0), data->sizeT),
+                                           Glib::ustring::format(std::fixed, std::setprecision(0), data->tileX),
+                                           Glib::ustring::format(std::fixed, std::setprecision(0), data->tileY))
+                );
+                self->PrevLabels->set_text(
+                    Glib::ustring::compose(M("TP_DIRPYRDENOISE_CHROMINANCE_PREVIEW_INFO"),
+                                           Glib::ustring::format(std::fixed, std::setprecision(0), data->sizeP),
+                                           Glib::ustring::format(std::fixed, std::setprecision(0), data->prevX),
+                                           Glib::ustring::format(std::fixed, std::setprecision(0), data->prevY))
+                );
+                return false;
+            };
 
-        idle_register.add(func, new Data { this, tileX, tileY, prevX, prevY, sizeT, sizeP });
+        idle_register.add<Data>(func, new Data{this, tileX, tileY, prevX, prevY, sizeT, sizeP}, true);
     }
 }
 
@@ -345,20 +345,20 @@ void DirPyrDenoise::noiseChanged (double nresid, double highresid)
 {
     if (!batchMode) {
         struct Data {
-            DirPyrDenoise *me;
+            DirPyrDenoise* self;
             double nresid;
             double highresid;
         };
 
-        const auto func = [](gpointer data) -> gboolean {
-            Data *d = static_cast<Data *>(data);
-            DirPyrDenoise *me = d->me;
-            me->updateNoiseLabel(d->nresid, d->highresid);
-            delete d;
-            return FALSE;
-        };
+        const auto func =
+            [](Data* data) -> bool
+            {
+                DirPyrDenoise* const self = data->self;
+                self->updateNoiseLabel(data->nresid, data->highresid);
+                return false;
+            };
 
-        idle_register.add(func, new Data { this, nresid, highresid });
+        idle_register.add<Data>(func, new Data{this, nresid, highresid}, true);
     }
 }
 
diff --git a/rtgui/editorpanel.cc b/rtgui/editorpanel.cc
index 1f46d60e7..d86612c9f 100644
--- a/rtgui/editorpanel.cc
+++ b/rtgui/editorpanel.cc
@@ -45,10 +45,8 @@ struct spparams {
     Glib::RefPtr<Gtk::CssProvider> cssProvider;
 };
 
-int setprogressStrUI ( void *p )
+bool setprogressStrUI(spparams* s)
 {
-    spparams *s = static_cast<spparams*> (p);
-
     if ( ! s->str.empty() ) {
         s->pProgress->set_text ( M (s->str) );
     }
@@ -67,8 +65,7 @@ int setprogressStrUI ( void *p )
         }
     }
 
-    delete s;
-    return FALSE;
+    return false;
 }
 
 
@@ -498,7 +495,7 @@ EditorPanel::EditorPanel (FilePanel* filePanel)
 
     // build left side panel
     leftbox = new Gtk::Paned (Gtk::ORIENTATION_VERTICAL);
-    
+
     // make a subbox to allow resizing of the histogram (if it's on the left)
     leftsubbox = new Gtk::Box (Gtk::ORIENTATION_VERTICAL);
     leftsubbox->set_size_request (230, 250);
@@ -520,7 +517,7 @@ EditorPanel::EditorPanel (FilePanel* filePanel)
     leftsubbox->pack_start (*history);
 
     leftsubbox->show_all ();
-    
+
     leftbox->pack2 (*leftsubbox, true, true);
     leftbox->show_all ();
 
@@ -638,14 +635,14 @@ EditorPanel::EditorPanel (FilePanel* filePanel)
 
     // build right side panel
     vboxright = new Gtk::Paned (Gtk::ORIENTATION_VERTICAL);
-    
+
     vsubboxright = new Gtk::Box (Gtk::ORIENTATION_VERTICAL, 0);
     vsubboxright->set_size_request (300, 250);
 
     vsubboxright->pack_start (*ppframe, Gtk::PACK_SHRINK, 2);
     // main notebook
     vsubboxright->pack_start (*tpc->toolPanelNotebook);
-    
+
     vboxright->pack2 (*vsubboxright, true, true);
 
     // Save buttons
@@ -862,7 +859,7 @@ EditorPanel::EditorPanel (FilePanel* filePanel)
     if (tbTopPanel_1) {
         tbTopPanel_1->signal_toggled().connect ( sigc::mem_fun (*this, &EditorPanel::tbTopPanel_1_toggled) );
     }
-    
+
 }
 
 EditorPanel::~EditorPanel ()
@@ -1192,7 +1189,7 @@ void EditorPanel::setProgress(double p)
     spparams *s = new spparams;
     s->val = p;
     s->pProgress = progressLabel;
-    idle_register.add(setprogressStrUI, s);
+    idle_register.add<spparams>(setprogressStrUI, s, true);
 }
 
 void EditorPanel::setProgressStr(const Glib::ustring& str)
@@ -1201,7 +1198,7 @@ void EditorPanel::setProgressStr(const Glib::ustring& str)
     s->str = str;
     s->val = -1;
     s->pProgress = progressLabel;
-    idle_register.add(setprogressStrUI, s);
+    idle_register.add<spparams>(setprogressStrUI, s, true);
 }
 
 void EditorPanel::setProgressState(bool inProcessing)
@@ -1217,30 +1214,27 @@ void EditorPanel::setProgressState(bool inProcessing)
     p->inProcessing = inProcessing;
     p->epih = epih;
 
-    const auto func = [] (gpointer data) -> gboolean {
-        spsparams* const p = static_cast<spsparams*> (data);
-
-        if (p->epih->destroyed)
+    const auto func =
+        [](spsparams* p) -> bool
         {
-            if (p->epih->pending == 1) {
-                delete p->epih;
-            } else {
-                p->epih->pending--;
+            if (p->epih->destroyed)
+            {
+                if (p->epih->pending == 1) {
+                    delete p->epih;
+                } else {
+                    p->epih->pending--;
+                }
+
+                return false;
             }
 
-            delete p;
+            p->epih->epanel->refreshProcessingState (p->inProcessing);
+            p->epih->pending--;
 
-            return 0;
-        }
+            return false;
+        };
 
-        p->epih->epanel->refreshProcessingState (p->inProcessing);
-        p->epih->pending--;
-        delete p;
-
-        return FALSE;
-    };
-
-    idle_register.add (func, p);
+    idle_register.add<spsparams>(func, p, true);
 }
 
 void EditorPanel::error(const Glib::ustring& descr)
@@ -1261,30 +1255,27 @@ void EditorPanel::error(const Glib::ustring& title, const Glib::ustring& descr)
     p->title = title;
     p->epih = epih;
 
-    const auto func = [] (gpointer data) -> gboolean {
-        errparams* const p = static_cast<errparams*> (data);
-
-        if (p->epih->destroyed)
+    const auto func =
+        [](errparams* p) -> bool
         {
-            if (p->epih->pending == 1) {
-                delete p->epih;
-            } else {
-                p->epih->pending--;
+            if (p->epih->destroyed)
+            {
+                if (p->epih->pending == 1) {
+                    delete p->epih;
+                } else {
+                    p->epih->pending--;
+                }
+
+                return false;
             }
 
-            delete p;
+            p->epih->epanel->displayError (p->title, p->descr);
+            p->epih->pending--;
 
-            return 0;
-        }
+            return false;
+        };
 
-        p->epih->epanel->displayError (p->title, p->descr);
-        p->epih->pending--;
-        delete p;
-
-        return FALSE;
-    };
-
-    idle_register.add (func, p);
+    idle_register.add<errparams>(func, p, true);
 }
 
 void EditorPanel::displayError(const Glib::ustring& title, const Glib::ustring& descr)
@@ -2376,7 +2367,7 @@ void EditorPanel::updateHistogramPosition (int oldPosition, int newPosition)
                 leftbox->pack1(*histogramPanel, false, false);
                 histogramPanel->unreference();
             }
-            
+
             leftbox->set_position(options.histogramHeight);
             histogramPanel->reorder (Gtk::POS_LEFT);
             break;
@@ -2396,14 +2387,14 @@ void EditorPanel::updateHistogramPosition (int oldPosition, int newPosition)
                 vboxright->pack1 (*histogramPanel, false, false);
                 histogramPanel->unreference();
             }
-            
-            vboxright->set_position(options.histogramHeight); 
+
+            vboxright->set_position(options.histogramHeight);
             histogramPanel->reorder (Gtk::POS_RIGHT);
             break;
     }
 
     iareapanel->imageArea->setPointerMotionHListener (histogramPanel);
-    
+
 }
 
 
diff --git a/rtgui/filebrowser.cc b/rtgui/filebrowser.cc
index f83e39146..f2ce2cb79 100644
--- a/rtgui/filebrowser.cc
+++ b/rtgui/filebrowser.cc
@@ -568,31 +568,30 @@ void FileBrowser::doubleClicked (ThumbBrowserEntryBase* entry)
 void FileBrowser::addEntry (FileBrowserEntry* entry)
 {
     struct addparams {
-        FileBrowser *browser;
-        FileBrowserEntry *entry;
+        FileBrowser* self;
+        FileBrowserEntry* entry;
         unsigned int session_id;
     };
 
     addparams* const ap = new addparams;
     entry->setParent (this);
-    ap->browser = this;
+    ap->self = this;
     ap->entry = entry;
     ap->session_id = session_id();
 
-    const auto func = [](gpointer data) -> gboolean {
-        addparams* const ap = static_cast<addparams*>(data);
-        if (ap->session_id != ap->browser->session_id()) {
-            delete ap->entry;
-            delete ap;
-        } else {
-            ap->browser->addEntry_(ap->entry);
-            delete ap;
-        }
+    const auto func =
+        [](addparams* ap) -> bool
+        {
+            if (ap->session_id != ap->self->session_id()) {
+                delete ap->entry;
+            } else {
+                ap->self->addEntry_(ap->entry);
+            }
 
-        return FALSE;
-    };
+            return false;
+        };
 
-    idle_register.add(func, ap);
+    idle_register.add<addparams>(func, ap, true);
 }
 
 void FileBrowser::addEntry_ (FileBrowserEntry* entry)
@@ -1935,13 +1934,14 @@ void FileBrowser::_thumbRearrangementNeeded ()
 
 void FileBrowser::thumbRearrangementNeeded ()
 {
-    const auto func = [](gpointer data) -> gboolean {
-        static_cast<FileBrowser*>(data)->_thumbRearrangementNeeded();
+    const auto func =
+        [](FileBrowser* self) -> bool
+        {
+            self->_thumbRearrangementNeeded();
+            return false;
+        };
 
-        return FALSE;
-    };
-
-    idle_register.add(func, this);
+    idle_register.add<FileBrowser>(func, this, false);
 }
 
 void FileBrowser::selectionChanged ()
diff --git a/rtgui/filebrowserentry.cc b/rtgui/filebrowserentry.cc
index c91f95912..5d47a54ea 100644
--- a/rtgui/filebrowserentry.cc
+++ b/rtgui/filebrowserentry.cc
@@ -233,31 +233,29 @@ void FileBrowserEntry::updateImage(rtengine::IImage8* img, double scale, const r
 
     const gint priority = G_PRIORITY_LOW;
 
-    const auto func = [](gpointer data) -> gboolean {
-        tiupdate* const params = static_cast<tiupdate*>(data);
-        FileBrowserEntryIdleHelper* const feih = params->feih;
+    const auto func =
+        [](tiupdate* params) -> bool
+        {
+            FileBrowserEntryIdleHelper* const feih = params->feih;
 
-        if (feih->destroyed) {
-            if (feih->pending == 1) {
-                delete feih;
-            } else {
-                feih->pending--;
+            if (feih->destroyed) {
+                if (feih->pending == 1) {
+                    delete feih;
+                } else {
+                    feih->pending--;
+                }
+
+                params->img->free ();
+                return false;
             }
 
-            params->img->free ();
-            delete params;
-            return 0;
-        }
+            feih->fbentry->_updateImage (params->img, params->scale, params->cropParams);
+            feih->pending--;
 
-        feih->fbentry->_updateImage (params->img, params->scale, params->cropParams);
-        feih->pending--;
+            return false;
+        };
 
-        delete params;
-
-        return FALSE;
-    };
-
-    idle_register.add(func, param, priority);
+    idle_register.add<tiupdate>(func, param, true, priority);
 }
 
 void FileBrowserEntry::_updateImage(rtengine::IImage8* img, double s, const rtengine::procparams::CropParams& cropParams)
diff --git a/rtgui/filecatalog.cc b/rtgui/filecatalog.cc
index 55e293718..e9d1720b9 100644
--- a/rtgui/filecatalog.cc
+++ b/rtgui/filecatalog.cc
@@ -873,13 +873,14 @@ void FileCatalog::previewsFinished (int dir_id)
         currentEFS = dirEFS;
     }
 
-    const auto func = [](gpointer data) -> gboolean {
-        static_cast<FileCatalog*>(data)->previewsFinishedUI();
+    const auto func =
+        [](FileCatalog* self) -> bool
+        {
+            self->previewsFinishedUI();
+            return false;
+        };
 
-        return FALSE;
-    };
-
-    idle_register.add(func, this);
+    idle_register.add<FileCatalog>(func, this, false);
 }
 
 void FileCatalog::setEnabled (bool e)
@@ -941,24 +942,22 @@ struct FCOIParams {
     std::vector<Thumbnail*> tmb;
 };
 
-int openRequestedUI (void* p)
+bool openRequestedUI(FCOIParams* params)
 {
-    FCOIParams* params = static_cast<FCOIParams*>(p);
     params->catalog->_openImage (params->tmb);
-    delete params;
-
-    return 0;
+    return false;
 }
 
 void FileCatalog::filterApplied()
 {
-    const auto func = [](gpointer data) -> gboolean {
-        static_cast<FileCatalog*>(data)->_refreshProgressBar();
+    const auto func =
+        [](FileCatalog* self) -> bool
+        {
+            self->_refreshProgressBar();
+            return false;
+        };
 
-        return FALSE;
-    };
-
-    idle_register.add(func, this);
+    idle_register.add<FileCatalog>(func, this, false);
 }
 
 void FileCatalog::openRequested(const std::vector<Thumbnail*>& tmb)
@@ -971,7 +970,7 @@ void FileCatalog::openRequested(const std::vector<Thumbnail*>& tmb)
         tmb[i]->increaseRef ();
     }
 
-    idle_register.add(openRequestedUI, params);
+    idle_register.add<FCOIParams>(openRequestedUI, params, true);
 }
 
 void FileCatalog::deleteRequested(const std::vector<FileBrowserEntry*>& tbe, bool inclBatchProcessed)
@@ -1229,7 +1228,7 @@ void FileCatalog::developRequested(const std::vector<FileBrowserEntry*>& tbe, bo
                     params.resize.width = options.fastexport_resize_width;
                     params.resize.height = options.fastexport_resize_height;
                 }
-                
+
                 params.resize.enabled = options.fastexport_resize_enabled;
                 params.resize.scale = options.fastexport_resize_scale;
                 params.resize.appliesTo = options.fastexport_resize_appliesTo;
@@ -1903,7 +1902,7 @@ void FileCatalog::addAndOpenFile (const Glib::ustring& fname)
         params->catalog = this;
         params->tmb.push_back (tmb);
         tmb->increaseRef ();
-        idle_register.add(openRequestedUI, params);
+        idle_register.add<FCOIParams>(openRequestedUI, params, true);
 
     } catch(Gio::Error&) {}
 }
diff --git a/rtgui/filepanel.cc b/rtgui/filepanel.cc
index f75983ac0..c842dad66 100644
--- a/rtgui/filepanel.cc
+++ b/rtgui/filepanel.cc
@@ -139,12 +139,14 @@ FilePanel::FilePanel () : parent(nullptr), error(0)
 
     fileCatalog->setFileSelectionListener (this);
 
-    const auto func = [](gpointer data) -> gboolean {
-        static_cast<FilePanel*>(data)->init();
-        return FALSE;
-    };
+    const auto func =
+        [](FilePanel* self) -> bool
+        {
+            self->init();
+            return false;
+        };
 
-    idle_register.add(func, this);
+    idle_register.add<FilePanel>(func, this, false);
 
     show_all ();
 }
diff --git a/rtgui/flatfield.cc b/rtgui/flatfield.cc
index 057ce731c..ae94255a7 100644
--- a/rtgui/flatfield.cc
+++ b/rtgui/flatfield.cc
@@ -412,18 +412,19 @@ void FlatField::setShortcutPath(const Glib::ustring& path)
 void FlatField::flatFieldAutoClipValueChanged(int n)
 {
     struct Data {
-        FlatField *me;
+        FlatField* self;
         int n;
     };
-    const auto func = [](gpointer data) -> gboolean {
-        Data *d = static_cast<Data *>(data);
-        FlatField *me = d->me;
-        me->disableListener();
-        me->flatFieldClipControl->setValue (d->n);
-        me->enableListener();
-        delete d;
-        return FALSE;
-    };
 
-    idle_register.add(func, new Data { this, n });
-}
\ No newline at end of file
+    const auto func =
+        [](Data* data) -> bool
+        {
+            FlatField* const self = data->self;
+            self->disableListener();
+            self->flatFieldClipControl->setValue (data->n);
+            self->enableListener();
+            return false;
+        };
+
+    idle_register.add<Data>(func, new Data{this, n}, true);
+}
diff --git a/rtgui/guiutils.cc b/rtgui/guiutils.cc
index f8129b0fb..257927b0c 100644
--- a/rtgui/guiutils.cc
+++ b/rtgui/guiutils.cc
@@ -43,39 +43,14 @@ IdleRegister::~IdleRegister()
     destroy();
 }
 
-void IdleRegister::add(GSourceFunc function, gpointer data, gint priority)
-{
-    const auto dispatch = [](gpointer data) -> gboolean {
-        DataWrapper* const data_wrapper = static_cast<DataWrapper*>(data);
-
-        if (!data_wrapper->function(data_wrapper->data)) {
-            data_wrapper->self->mutex.lock();
-            data_wrapper->self->ids.erase(data_wrapper);
-            data_wrapper->self->mutex.unlock();
-
-            delete data_wrapper;
-            return FALSE;
-        }
-
-        return TRUE;
-    };
-
-    DataWrapper* const data_wrapper = new DataWrapper{
-        this,
-        function,
-        data
-    };
-
-    mutex.lock();
-    ids[data_wrapper] = gdk_threads_add_idle_full(priority, dispatch, data_wrapper, nullptr);
-    mutex.unlock();
-}
-
 void IdleRegister::destroy()
 {
     mutex.lock();
     for (const auto& id : ids) {
         g_source_remove(id.second);
+        if (id.first->deleter) {
+            id.first->deleter(id.first->data);
+        }
         delete id.first;
     }
     ids.clear();
@@ -1278,7 +1253,7 @@ MyFileChooserButton::MyFileChooserButton(const Glib::ustring &title, Gtk::FileCh
     if (GTK_MINOR_VERSION < 20) {
         set_border_width(2); // margin doesn't work on GTK < 3.20
     }
-    
+
     set_name("MyFileChooserButton");
 }
 
@@ -1368,7 +1343,7 @@ std::vector<Glib::RefPtr<Gtk::FileFilter>> MyFileChooserButton::list_filters()
     return file_filters_;
 }
 
-    
+
 bool MyFileChooserButton::set_current_folder(const std::string &filename)
 {
     current_folder_ = filename;
diff --git a/rtgui/guiutils.h b/rtgui/guiutils.h
index 8816eca4f..2cb7ca77e 100644
--- a/rtgui/guiutils.h
+++ b/rtgui/guiutils.h
@@ -50,7 +50,54 @@ class IdleRegister final :
 public:
     ~IdleRegister();
 
-    void add(GSourceFunc function, gpointer data, gint priority = G_PRIORITY_DEFAULT_IDLE);
+    template<typename DATA>
+    void add(bool (*function)(DATA*), DATA* data, bool delete_data, gint priority = G_PRIORITY_DEFAULT_IDLE)
+    {
+        const auto dispatch =
+            [](gpointer data) -> gboolean
+            {
+                DataWrapper* const data_wrapper = static_cast<DataWrapper*>(data);
+
+                // This is safe as per https://en.cppreference.com/w/cpp/language/reinterpret_cast item 7)
+                if (!reinterpret_cast<bool (*)(DATA*)>(data_wrapper->function)(static_cast<DATA*>(data_wrapper->data))) {
+                    data_wrapper->self->mutex.lock();
+                    data_wrapper->self->ids.erase(data_wrapper);
+                    data_wrapper->self->mutex.unlock();
+
+                    if (data_wrapper->deleter) {
+                        data_wrapper->deleter(data_wrapper->data);
+                    }
+
+                    delete data_wrapper;
+                    return FALSE;
+                }
+
+                return TRUE;
+            };
+
+        DataWrapper* const data_wrapper = new DataWrapper{
+            this,
+            reinterpret_cast<GSourceFunc>(function),
+            data,
+            [delete_data]() -> GSourceFunc
+            {
+                if (delete_data) {
+                    return
+                        [](gpointer data) -> gboolean
+                        {
+                            delete static_cast<DATA*>(data);
+                            return TRUE;
+                        };
+                }
+                return nullptr;
+            }()
+        };
+
+        mutex.lock();
+        ids[data_wrapper] = gdk_threads_add_idle_full(priority, dispatch, data_wrapper, nullptr);
+        mutex.unlock();
+    }
+
     void destroy();
 
 private:
@@ -58,6 +105,7 @@ private:
         IdleRegister* const self;
         GSourceFunc function;
         gpointer data;
+        GSourceFunc deleter;
     };
 
     std::map<const DataWrapper*, guint> ids;
@@ -399,7 +447,7 @@ public:
 
     sigc::signal<void> &signal_selection_changed();
     sigc::signal<void> &signal_file_set();
-    
+
     std::string get_filename() const;
     bool set_filename(const std::string &filename);
 
@@ -407,7 +455,7 @@ public:
     void remove_filter(const Glib::RefPtr<Gtk::FileFilter> &filter);
     void set_filter(const Glib::RefPtr<Gtk::FileFilter> &filter);
     std::vector<Glib::RefPtr<Gtk::FileFilter>> list_filters();
-    
+
     bool set_current_folder(const std::string &filename);
     std::string get_current_folder() const;
 
diff --git a/rtgui/histogrampanel.cc b/rtgui/histogrampanel.cc
index 7c136cbfe..007e1187d 100644
--- a/rtgui/histogrampanel.cc
+++ b/rtgui/histogrampanel.cc
@@ -44,11 +44,11 @@ HistogramPanel::HistogramPanel ()
 
     histogramArea = Gtk::manage (new HistogramArea (this));
     setExpandAlignProperties(histogramArea, true, true, Gtk::ALIGN_FILL, Gtk::ALIGN_FILL);
-    
+
     histogramRGBArea = Gtk::manage (new HistogramRGBArea ());
     setExpandAlignProperties(histogramRGBArea, true, false, Gtk::ALIGN_FILL, Gtk::ALIGN_END);
     histogramRGBArea->show();
-    
+
     // connecting the two childs
     histogramArea->signal_factor_changed().connect( sigc::mem_fun(*histogramRGBArea, &HistogramRGBArea::factorChanged) );
 
@@ -78,7 +78,7 @@ HistogramPanel::HistogramPanel ()
     chroImage_g  = new RTImage ("histogram-gold-off-small.png");
     rawImage_g   = new RTImage ("histogram-bayer-off-small.png");
     barImage_g   = new RTImage ("histogram-bar-off-small.png");
-	
+
     mode0Image  = new RTImage ("histogram-mode-linear-small.png");
     mode1Image  = new RTImage ("histogram-mode-logx-small.png");
     mode2Image  = new RTImage ("histogram-mode-logxy-small.png");
@@ -226,9 +226,9 @@ void HistogramPanel::resized (Gtk::Allocation& req)
     histogramRGBArea->updateBackBuffer(-1, -1, -1);
     histogramRGBArea->queue_draw ();
 
-    // Store current height of the histogram 
+    // Store current height of the histogram
     options.histogramHeight = get_height();
-    
+
 }
 
 void HistogramPanel::red_toggled ()
@@ -346,7 +346,7 @@ void HistogramPanel::reorder (Gtk::PositionType align)
 
 // DrawModeListener interface:
 void HistogramPanel::toggleButtonMode ()
-{   
+{
     if (options.histogramDrawMode == 0)
         showMode->set_image(*mode0Image);
     else if (options.histogramDrawMode == 1)
@@ -562,28 +562,28 @@ void HistogramRGBArea::update (int valh, int rh, int  gh, int bh)
 
     harih->pending++;
 
-    const auto func = [](gpointer data) -> gboolean {
-        HistogramRGBAreaIdleHelper* const harih = static_cast<HistogramRGBAreaIdleHelper*>(data);
+    const auto func =
+        [](HistogramRGBAreaIdleHelper* harih) -> bool
+        {
+            if (harih->destroyed) {
+                if (harih->pending == 1) {
+                    delete harih;
+                } else {
+                    harih->pending--;
+                }
 
-        if (harih->destroyed) {
-            if (harih->pending == 1) {
-                delete harih;
-            } else {
-                harih->pending--;
+                return false;
             }
 
-            return 0;
-        }
+            harih->harea->updateBackBuffer(-1, -1, -1);
+            harih->harea->queue_draw ();
 
-        harih->harea->updateBackBuffer(-1, -1, -1);
-        harih->harea->queue_draw ();
+            harih->pending--;
 
-        harih->pending--;
+            return false;
+        };
 
-        return FALSE;
-    };
-
-    idle_register.add(func, harih);
+    idle_register.add<HistogramRGBAreaIdleHelper>(func, harih, false);
 }
 
 void HistogramRGBArea::updateOptions (bool r, bool g, bool b, bool l, bool c, bool raw, bool bar)
@@ -655,7 +655,7 @@ void HistogramRGBArea::factorChanged (double newFactor)
 //
 //
 // HistogramArea
-HistogramArea::HistogramArea (DrawModeListener *fml) : 
+HistogramArea::HistogramArea (DrawModeListener *fml) :
     valid(false), drawMode(options.histogramDrawMode), myDrawModeListener(fml),
     oldwidth(-1), oldheight(-1),
     needRed(options.histogramRed), needGreen(options.histogramGreen), needBlue(options.histogramBlue),
@@ -703,14 +703,14 @@ void HistogramArea::get_preferred_height_vfunc (int &minimum_height, int &natura
 
 void HistogramArea::get_preferred_width_vfunc (int &minimum_width, int &natural_width) const
 {
-    
+
     minimum_width = 200;
     natural_width = 400;
 }
 
 void HistogramArea::get_preferred_height_for_width_vfunc (int width, int &minimum_height, int &natural_height) const
 {
-    
+
     minimum_height = 0;
     natural_height = 0;
 }
@@ -722,7 +722,7 @@ void HistogramArea::get_preferred_width_for_height_vfunc (int height, int &minim
 
 void HistogramArea::updateOptions (bool r, bool g, bool b, bool l, bool c, bool raw, int mode)
 {
-    
+
     options.histogramRed      = needRed    = r;
     options.histogramGreen    = needGreen  = g;
     options.histogramBlue     = needBlue   = b;
@@ -761,29 +761,29 @@ void HistogramArea::update(
 
     haih->pending++;
     // Can be done outside of the GUI thread
-    const auto func = [](gpointer data) -> gboolean {
-        HistogramAreaIdleHelper* const haih = static_cast<HistogramAreaIdleHelper*>(data);
+    const auto func =
+        [](HistogramAreaIdleHelper* haih) -> bool
+        {
+            if (haih->destroyed) {
+                if (haih->pending == 1) {
+                    delete haih;
+                } else {
+                    haih->pending--;
+                }
 
-        if (haih->destroyed) {
-            if (haih->pending == 1) {
-                delete haih;
-            } else {
-                haih->pending--;
+                return false;
             }
 
-            return 0;
-        }
+            haih->harea->setDirty (true);
+            haih->harea->updateBackBuffer ();
+            haih->harea->queue_draw ();
 
-        haih->harea->setDirty (true);
-        haih->harea->updateBackBuffer ();
-        haih->harea->queue_draw ();
+            haih->pending--;
 
-        haih->pending--;
+            return false;
+        };
 
-        return FALSE;
-    };
-
-    idle_register.add(func, haih);
+    idle_register.add<HistogramAreaIdleHelper>(func, haih, false);
 }
 
 void HistogramArea::updateBackBuffer ()
@@ -889,7 +889,7 @@ void HistogramArea::updateBackBuffer ()
 
         // Compute the highest point of the histogram for scaling
         // Values at far left and right end (0 and 255) are handled differently
-        
+
         unsigned int histheight = 0;
 
         for (int i = 1; i < 255; i++) {
@@ -915,7 +915,7 @@ void HistogramArea::updateBackBuffer ()
         }
 
         int realhistheight = histheight;
-        
+
         if (realhistheight < winh - 2) {
             realhistheight = winh - 2;
         }
@@ -960,7 +960,7 @@ void HistogramArea::updateBackBuffer ()
             cr->stroke ();
             drawMarks(cr, bhchanged, realhistheight, w, ui, oi);
         }
-        
+
     }
 
     // Draw the frame's border
@@ -1044,16 +1044,16 @@ bool HistogramArea::on_button_press_event (GdkEventButton* event)
 {
     isPressed = true;
     movingPosition = event->x;
-    
+
     if (event->type == GDK_2BUTTON_PRESS && event->button == 1) {
-        
+
         drawMode = (drawMode + 1) % 3;
         options.histogramDrawMode = (options.histogramDrawMode + 1) % 3;
-        
+
         if (myDrawModeListener) {
             myDrawModeListener->toggleButtonMode ();
         }
-        
+
         updateBackBuffer ();
         queue_draw ();
     }
@@ -1072,19 +1072,19 @@ bool HistogramArea::on_motion_notify_event (GdkEventMotion* event)
     if (isPressed)
     {
         double mod = 1 + (event->x - movingPosition) / get_width();
-        
+
         factor /= mod;
         if (factor < 1.0)
             factor = 1.0;
         if (factor > 100.0)
             factor = 100.0;
-        
+
         sigFactorChanged.emit(factor);
-        
+
         setDirty(true);
         queue_draw ();
     }
-    
+
     return true;
 }
 
diff --git a/rtgui/mydiagonalcurve.cc b/rtgui/mydiagonalcurve.cc
index 0bc58f28e..d07ce5943 100644
--- a/rtgui/mydiagonalcurve.cc
+++ b/rtgui/mydiagonalcurve.cc
@@ -1516,28 +1516,28 @@ void MyDiagonalCurve::updateBackgroundHistogram (LUTu & hist)
 
     mcih->pending++;
 
-    const auto func = [](gpointer data) -> gboolean {
-        MyCurveIdleHelper* const mcih = static_cast<MyCurveIdleHelper*>(data);
+    const auto func =
+        [](MyCurveIdleHelper* mcih) -> bool
+        {
+            if (mcih->destroyed) {
+                if (mcih->pending == 1) {
+                    delete mcih;
+                } else {
+                    mcih->pending--;
+                }
 
-        if (mcih->destroyed) {
-            if (mcih->pending == 1) {
-                delete mcih;
-            } else {
-                mcih->pending--;
+                return false;
             }
 
-            return 0;
-        }
+            mcih->clearPixmap ();
+            mcih->myCurve->queue_draw ();
 
-        mcih->clearPixmap ();
-        mcih->myCurve->queue_draw ();
+            mcih->pending--;
 
-        mcih->pending--;
+            return false;
+        };
 
-        return FALSE;
-    };
-
-    idle_register.add(func, mcih);
+    idle_register.add<MyCurveIdleHelper>(func, mcih, false);
 }
 
 void MyDiagonalCurve::reset(const std::vector<double> &resetCurve, double identityValue)
diff --git a/rtgui/previewhandler.cc b/rtgui/previewhandler.cc
index a251986bf..5029397a0 100644
--- a/rtgui/previewhandler.cc
+++ b/rtgui/previewhandler.cc
@@ -67,40 +67,38 @@ void PreviewHandler::setImage(rtengine::IImage8* i, double scale, const rtengine
     iap->scale      = scale;
     iap->cp         = cp;
 
-    const auto func = [](gpointer data) -> gboolean {
-        iaimgpar* const iap = static_cast<iaimgpar*>(data);
-        PreviewHandlerIdleHelper* const pih = iap->pih;
+    const auto func =
+        [](iaimgpar* iap) -> bool
+        {
+            PreviewHandlerIdleHelper* const pih = iap->pih;
 
-        if (pih->destroyed) {
-            if (pih->pending == 1) {
-                delete pih;
-            } else {
-                pih->pending--;
+            if (pih->destroyed) {
+                if (pih->pending == 1) {
+                    delete pih;
+                } else {
+                    pih->pending--;
+                }
+
+                return false;
             }
 
-            delete iap;
+            if (pih->phandler->image) {
+                IImage8* const oldImg = pih->phandler->image;
+                oldImg->getMutex().lock ();
+                pih->phandler->image = iap->image;
+                oldImg->getMutex().unlock ();
+            } else {
+                pih->phandler->image = iap->image;
+            }
 
-            return FALSE;
-        }
+            pih->phandler->cropParams = iap->cp;
+            pih->phandler->previewScale = iap->scale;
+            pih->pending--;
 
-        if (pih->phandler->image) {
-            IImage8* const oldImg = pih->phandler->image;
-            oldImg->getMutex().lock ();
-            pih->phandler->image = iap->image;
-            oldImg->getMutex().unlock ();
-        } else {
-            pih->phandler->image = iap->image;
-        }
+            return false;
+        };
 
-        pih->phandler->cropParams = iap->cp;
-        pih->phandler->previewScale = iap->scale;
-        pih->pending--;
-        delete iap;
-
-        return FALSE;
-    };
-
-    idle_register.add(func, iap);
+    idle_register.add<iaimgpar>(func, iap, true);
 }
 
 
@@ -112,41 +110,39 @@ void PreviewHandler::delImage(IImage8* i)
     iap->image    = i;
     iap->pih = pih;
 
-    const auto func = [](gpointer data) -> gboolean {
-        iaimgpar* iap = static_cast<iaimgpar*>(data);
-        PreviewHandlerIdleHelper* pih = iap->pih;
+    const auto func =
+        [](iaimgpar* iap) -> bool
+        {
+            PreviewHandlerIdleHelper* const pih = iap->pih;
 
-        if (pih->destroyed) {
-            if (pih->pending == 1) {
-                delete pih;
-            } else {
-                pih->pending--;
+            if (pih->destroyed) {
+                if (pih->pending == 1) {
+                    delete pih;
+                } else {
+                    pih->pending--;
+                }
+
+                return false;
             }
 
-            delete iap;
+            if (pih->phandler->image) {
+                IImage8* oldImg = pih->phandler->image;
+                oldImg->getMutex().lock ();
+                pih->phandler->image = nullptr;
+                oldImg->getMutex().unlock ();
+            }
 
-            return FALSE;
-        }
+            iap->image->free ();
+            pih->phandler->previewImgMutex.lock ();
+            pih->phandler->previewImg.clear ();
+            pih->phandler->previewImgMutex.unlock ();
 
-        if (pih->phandler->image) {
-            IImage8* oldImg = pih->phandler->image;
-            oldImg->getMutex().lock ();
-            pih->phandler->image = nullptr;
-            oldImg->getMutex().unlock ();
-        }
+            pih->pending--;
 
-        iap->image->free ();
-        pih->phandler->previewImgMutex.lock ();
-        pih->phandler->previewImg.clear ();
-        pih->phandler->previewImgMutex.unlock ();
+            return false;
+        };
 
-        pih->pending--;
-        delete iap;
-
-        return FALSE;
-    };
-
-    idle_register.add(func, iap);
+    idle_register.add<iaimgpar>(func, iap, true);
 }
 
 void PreviewHandler::imageReady(const rtengine::procparams::CropParams& cp)
@@ -156,34 +152,32 @@ void PreviewHandler::imageReady(const rtengine::procparams::CropParams& cp)
     iap->pih      = pih;
     iap->cp       = cp;
 
-    const auto func = [](gpointer data) -> gboolean {
-        iaimgpar* const iap = static_cast<iaimgpar*>(data);
-        PreviewHandlerIdleHelper* pih = iap->pih;
+    const auto func =
+        [](iaimgpar* iap) -> bool
+        {
+            PreviewHandlerIdleHelper* const pih = iap->pih;
 
-        if (pih->destroyed) {
-            if (pih->pending == 1) {
-                delete pih;
-            } else {
-                pih->pending--;
+            if (pih->destroyed) {
+                if (pih->pending == 1) {
+                    delete pih;
+                } else {
+                    pih->pending--;
+                }
+
+                return false;
             }
 
-            delete iap;
+            pih->phandler->previewImgMutex.lock ();
+            pih->phandler->previewImg = Gdk::Pixbuf::create_from_data (pih->phandler->image->getData(), Gdk::COLORSPACE_RGB, false, 8, pih->phandler->image->getWidth(), pih->phandler->image->getHeight(), 3 * pih->phandler->image->getWidth());
+            pih->phandler->previewImgMutex.unlock ();
+            pih->phandler->cropParams = iap->cp;
+            pih->phandler->previewImageChanged ();
+            pih->pending--;
 
-            return FALSE;
-        }
+            return false;
+        };
 
-        pih->phandler->previewImgMutex.lock ();
-        pih->phandler->previewImg = Gdk::Pixbuf::create_from_data (pih->phandler->image->getData(), Gdk::COLORSPACE_RGB, false, 8, pih->phandler->image->getWidth(), pih->phandler->image->getHeight(), 3 * pih->phandler->image->getWidth());
-        pih->phandler->previewImgMutex.unlock ();
-        pih->phandler->cropParams = iap->cp;
-        pih->phandler->previewImageChanged ();
-        pih->pending--;
-        delete iap;
-
-        return FALSE;
-    };
-
-    idle_register.add(func, iap);
+    idle_register.add<iaimgpar>(func, iap, true);
 }
 
 Glib::RefPtr<Gdk::Pixbuf> PreviewHandler::getRoughImage (int x, int y, int w, int h, double zoom)
diff --git a/rtgui/resize.cc b/rtgui/resize.cc
index 0de1f7db0..c57ff236a 100644
--- a/rtgui/resize.cc
+++ b/rtgui/resize.cc
@@ -95,7 +95,7 @@ Resize::Resize () : FoldableToolPanel(this, "resize", M("TP_RESIZE_LABEL"), fals
     allowUpscaling = Gtk::manage(new Gtk::CheckButton(M("TP_RESIZE_ALLOW_UPSCALING")));
     sizeBox->pack_start(*allowUpscaling);
     allowUpscaling->signal_toggled().connect(sigc::mem_fun(*this, &Resize::allowUpscalingChanged));
-    
+
     sizeBox->show_all ();
     sizeBox->reference ();
 
@@ -366,76 +366,76 @@ void Resize::sizeChanged(int mw, int mh, int ow, int oh)
 
 void Resize::setDimensions ()
 {
-    const auto func = [](gpointer data) -> gboolean {
-        Resize* const self = static_cast<Resize*>(data);
+    const auto func =
+        [](Resize* self) -> bool
+        {
+            self->wconn.block(true);
+            self->hconn.block(true);
+            self->scale->block(true);
 
-        self->wconn.block(true);
-        self->hconn.block(true);
-        self->scale->block(true);
+            int refw, refh;
 
-        int refw, refh;
-
-        if (self->appliesTo->get_active_row_number() == 0 && self->cropw) {
-            // Applies to Cropped area
-            refw = self->cropw;
-            refh = self->croph;
-        } else {
-            // Applies to Full image or crop is disabled
-            refw = self->maxw;
-            refh = self->maxh;
-        }
-
-        self->w->set_range(32, MAX_SCALE * refw);
-        self->h->set_range(32, MAX_SCALE * refh);
-
-        switch (self->spec->get_active_row_number()) {
-            case 0: {
-                // Scale mode
-                self->w->set_value(static_cast<double>(static_cast<int>(static_cast<double>(refw) * self->scale->getValue() + 0.5)));
-                self->h->set_value(static_cast<double>(static_cast<int>(static_cast<double>(refh) * self->scale->getValue() + 0.5)));
-                break;
+            if (self->appliesTo->get_active_row_number() == 0 && self->cropw) {
+                // Applies to Cropped area
+                refw = self->cropw;
+                refh = self->croph;
+            } else {
+                // Applies to Full image or crop is disabled
+                refw = self->maxw;
+                refh = self->maxh;
             }
 
-            case 1: {
-                // Width mode
-                const double tmp_scale = self->w->get_value() / static_cast<double>(refw);
-                self->scale->setValue(tmp_scale);
-                self->h->set_value(static_cast<double>(static_cast<int>(static_cast<double>(refh) * tmp_scale + 0.5)));
-                break;
+            self->w->set_range(32, MAX_SCALE * refw);
+            self->h->set_range(32, MAX_SCALE * refh);
+
+            switch (self->spec->get_active_row_number()) {
+                case 0: {
+                    // Scale mode
+                    self->w->set_value(static_cast<double>(static_cast<int>(static_cast<double>(refw) * self->scale->getValue() + 0.5)));
+                    self->h->set_value(static_cast<double>(static_cast<int>(static_cast<double>(refh) * self->scale->getValue() + 0.5)));
+                    break;
+                }
+
+                case 1: {
+                    // Width mode
+                    const double tmp_scale = self->w->get_value() / static_cast<double>(refw);
+                    self->scale->setValue(tmp_scale);
+                    self->h->set_value(static_cast<double>(static_cast<int>(static_cast<double>(refh) * tmp_scale + 0.5)));
+                    break;
+                }
+
+                case 2: {
+                    // Height mode
+                    const double tmp_scale = self->h->get_value() / static_cast<double>(refh);
+                    self->scale->setValue(tmp_scale);
+                    self->w->set_value(static_cast<double>(static_cast<int>(static_cast<double>(refw) * tmp_scale + 0.5)));
+                    break;
+                }
+
+                case 3: {
+                    // Bounding box mode
+                    const double tmp_scale =
+                        self->w->get_value() / self->h->get_value() < static_cast<double>(refw) / static_cast<double>(refh)
+                            ? self->w->get_value() / static_cast<double>(refw)
+                            : self->h->get_value() / static_cast<double>(refh);
+
+                    self->scale->setValue(tmp_scale);
+                    break;
+                }
+
+                default: {
+                    break;
+                }
             }
 
-            case 2: {
-                // Height mode
-                const double tmp_scale = self->h->get_value() / static_cast<double>(refh);
-                self->scale->setValue(tmp_scale);
-                self->w->set_value(static_cast<double>(static_cast<int>(static_cast<double>(refw) * tmp_scale + 0.5)));
-                break;
-            }
+            self->scale->block(false);
+            self->wconn.block(false);
+            self->hconn.block(false);
 
-            case 3: {
-                // Bounding box mode
-                const double tmp_scale =
-                    self->w->get_value() / self->h->get_value() < static_cast<double>(refw) / static_cast<double>(refh)
-                        ? self->w->get_value() / static_cast<double>(refw)
-                        : self->h->get_value() / static_cast<double>(refh);
+            return false;
+        };
 
-                self->scale->setValue(tmp_scale);
-                break;
-            }
-
-            default: {
-                break;
-            }
-        }
-
-        self->scale->block(false);
-        self->wconn.block(false);
-        self->hconn.block(false);
-
-        return FALSE;
-    };
-
-    idle_register.add(func, this);
+    idle_register.add<Resize>(func, this, false);
 }
 
 void Resize::fitBoxScale()
diff --git a/rtgui/retinex.cc b/rtgui/retinex.cc
index 08883708e..0e2bddbda 100644
--- a/rtgui/retinex.cc
+++ b/rtgui/retinex.cc
@@ -673,14 +673,16 @@ void Retinex::minmaxChanged (double cdma, double cdmin, double mini, double maxi
     nextminT = Tmin;
     nextmaxT = Tmax;
 
-    const auto func = [] (gpointer data) -> gboolean {
-        GThreadLock lock; // All GUI access from idle_add callbacks or separate thread HAVE to be protected
-        static_cast<Retinex*> (data)->minmaxComputed_();
+    const auto func =
+        [](Retinex* self) -> bool
+        {
+            GThreadLock lock; // All GUI access from idle_add callbacks or separate thread HAVE to be protected
+            // FIXME: The above can't be true?!
+            self->minmaxComputed_();
+            return false;
+        };
 
-        return FALSE;
-    };
-
-    idle_register.add (func, this);
+    idle_register.add<Retinex>(func, this, false);
 }
 
 bool Retinex::minmaxComputed_ ()
diff --git a/rtgui/tonecurve.cc b/rtgui/tonecurve.cc
index 06abe1fd2..d4c9e8ab6 100644
--- a/rtgui/tonecurve.cc
+++ b/rtgui/tonecurve.cc
@@ -45,7 +45,7 @@ ToneCurve::ToneCurve () : FoldableToolPanel(this, "tonecurve", M("TP_EXPOSURE_LA
     pack_start(*clampOOG);
     pack_start (*Gtk::manage (new  Gtk::HSeparator()));
     clampOOG->signal_toggled().connect(sigc::mem_fun(*this, &ToneCurve::clampOOGChanged));
-    
+
 //----------- Auto Levels ----------------------------------
     abox = Gtk::manage (new Gtk::HBox ());
     abox->set_spacing (10);
@@ -238,7 +238,7 @@ void ToneCurve::read (const ProcParams* pp, const ParamsEdited* pedited)
     if (!black->getAddMode() && !batchMode) {
         shcompr->set_sensitive(!((int)black->getValue () == 0));    //at black=0 shcompr value has no effect
     }
-    
+
     if (!hlcompr->getAddMode() && !batchMode) {
         hlcomprthresh->set_sensitive(!((int)hlcompr->getValue () == 0));    //at hlcompr=0 hlcomprthresh value has no effect
     }
@@ -604,7 +604,7 @@ void ToneCurve::adjusterChanged(Adjuster* a, double newval)
     if (a != expcomp && a != hlcompr && a != hlcomprthresh) {
         setHistmatching(false);
     }
-    
+
     Glib::ustring costr;
 
     if (a == expcomp) {
@@ -629,7 +629,7 @@ void ToneCurve::adjusterChanged(Adjuster* a, double newval)
         listener->panelChanged (EvSaturation, costr);
     } else if (a == hlcompr) {
         listener->panelChanged (EvHLCompr, costr);
-        
+
         if (!hlcompr->getAddMode() && !batchMode) {
             hlcomprthresh->set_sensitive(!((int)hlcompr->getValue () == 0));    //at hlcompr=0 hlcomprthresh value has no effect
         }
@@ -650,7 +650,7 @@ void ToneCurve::neutral_pressed ()
 // and sets neutral values to params in exposure panel
 
     setHistmatching(false);
-    
+
     if (batchMode) {
         autolevels->set_inconsistent (false);
         autoconn.block (true);
@@ -680,7 +680,7 @@ void ToneCurve::neutral_pressed ()
     if (!black->getAddMode() && !batchMode) {
         shcompr->set_sensitive(!((int)black->getValue () == 0));    //at black=0 shcompr value has no effect
     }
-    
+
     if (!hlcompr->getAddMode() && !batchMode) {
         hlcomprthresh->set_sensitive(!((int)hlcompr->getValue () == 0));    //at hlcompr=0 hlcomprthresh value has no effect
     }
@@ -754,7 +754,7 @@ void ToneCurve::autolevels_toggled ()
             if (!black->getAddMode()) {
                 shcompr->set_sensitive(!((int)black->getValue () == 0));    //at black=0 shcompr value has no effect
             }
-            
+
             if (!hlcompr->getAddMode() && !batchMode) {
                 hlcomprthresh->set_sensitive(!((int)hlcompr->getValue () == 0));    //at hlcompr=0 hlcomprthresh value has no effect
             }
@@ -857,7 +857,7 @@ bool ToneCurve::autoExpComputed_ ()
     if (!black->getAddMode() && !batchMode) {
         shcompr->set_sensitive(!((int)black->getValue () == 0));    //at black=0 shcompr value has no effect
     }
-    
+
     if (!hlcompr->getAddMode() && !batchMode) {
         hlcomprthresh->set_sensitive(!((int)hlcompr->getValue () == 0));    //at hlcompr=0 hlcomprthresh value has no effect
     }
@@ -979,7 +979,7 @@ bool ToneCurve::histmatchingComputed()
     if (!black->getAddMode() && !batchMode) {
         shcompr->set_sensitive(!((int)black->getValue() == 0));
     }
-    
+
     if (!hlcompr->getAddMode() && !batchMode) {
         hlcomprthresh->set_sensitive(!((int)hlcompr->getValue () == 0));    //at hlcompr=0 hlcomprthresh value has no effect
     }
@@ -1013,13 +1013,14 @@ void ToneCurve::autoExpChanged(double expcomp, int bright, int contr, int black,
     nextHlcomprthresh = hlcomprthresh;
     nextHLRecons = hlrecons;
 
-    const auto func = [](gpointer data) -> gboolean {
-        static_cast<ToneCurve*>(data)->autoExpComputed_();
+    const auto func =
+        [](ToneCurve* self) -> bool
+        {
+            self->autoExpComputed_();
+            return false;
+        };
 
-        return FALSE;
-    };
-
-    idle_register.add(func, this);
+    idle_register.add<ToneCurve>(func, this, false);
 }
 
 void ToneCurve::autoMatchedToneCurveChanged(rtengine::procparams::ToneCurveParams::TcMode curveMode, const std::vector<double>& curve)
@@ -1027,11 +1028,12 @@ void ToneCurve::autoMatchedToneCurveChanged(rtengine::procparams::ToneCurveParam
     nextToneCurveMode = curveMode;
     nextToneCurve = curve;
 
-    const auto func = [](gpointer data) -> gboolean {
-        static_cast<ToneCurve*>(data)->histmatchingComputed();
+    const auto func =
+        [](ToneCurve* self) -> bool
+        {
+            self->histmatchingComputed();
+            return false;
+        };
 
-        return FALSE;
-    };
-
-    idle_register.add(func, this);
+    idle_register.add<ToneCurve>(func, this, false);
 }
diff --git a/rtgui/toolpanelcoord.cc b/rtgui/toolpanelcoord.cc
index 43aaeecd2..1c9b17a5a 100644
--- a/rtgui/toolpanelcoord.cc
+++ b/rtgui/toolpanelcoord.cc
@@ -263,74 +263,74 @@ void ToolPanelCoordinator::imageTypeChanged (bool isRaw, bool isBayer, bool isXt
 {
     if (isRaw) {
         if (isBayer) {
-            const auto func = [](gpointer data) -> gboolean {
-                ToolPanelCoordinator* const self = static_cast<ToolPanelCoordinator*>(data);
+            const auto func =
+                [](ToolPanelCoordinator* self) -> bool
+                {
+                    self->rawPanelSW->set_sensitive (true);
+                    self->sensorxtrans->FoldableToolPanel::hide();
+                    self->sensorbayer->FoldableToolPanel::show();
+                    self->preprocess->FoldableToolPanel::show();
+                    self->flatfield->FoldableToolPanel::show();
+                    self->retinex->FoldableToolPanel::setGrayedOut(false);
 
-                self->rawPanelSW->set_sensitive (true);
-                self->sensorxtrans->FoldableToolPanel::hide();
-                self->sensorbayer->FoldableToolPanel::show();
-                self->preprocess->FoldableToolPanel::show();
-                self->flatfield->FoldableToolPanel::show();
-                self->retinex->FoldableToolPanel::setGrayedOut(false);
-
-                return FALSE;
-            };
-            idle_register.add(func, this);
+                    return false;
+                };
+            idle_register.add<ToolPanelCoordinator>(func, this, false);
         }
         else if (isXtrans) {
-            const auto func = [](gpointer data) -> gboolean {
-                ToolPanelCoordinator* const self = static_cast<ToolPanelCoordinator*>(data);
+            const auto func =
+                [](ToolPanelCoordinator* self) -> bool
+                {
+                    self->rawPanelSW->set_sensitive (true);
+                    self->sensorxtrans->FoldableToolPanel::show();
+                    self->sensorbayer->FoldableToolPanel::hide();
+                    self->preprocess->FoldableToolPanel::show();
+                    self->flatfield->FoldableToolPanel::show();
+                    self->retinex->FoldableToolPanel::setGrayedOut(false);
 
-                self->rawPanelSW->set_sensitive (true);
-                self->sensorxtrans->FoldableToolPanel::show();
-                self->sensorbayer->FoldableToolPanel::hide();
-                self->preprocess->FoldableToolPanel::show();
-                self->flatfield->FoldableToolPanel::show();
-                self->retinex->FoldableToolPanel::setGrayedOut(false);
-
-                return FALSE;
-            };
-            idle_register.add(func, this);
+                    return false;
+                };
+            idle_register.add<ToolPanelCoordinator>(func, this, false);
         }
         else if (isMono) {
-            const auto func = [](gpointer data) -> gboolean {
-                ToolPanelCoordinator* const self = static_cast<ToolPanelCoordinator*>(data);
+            const auto func =
+                [](ToolPanelCoordinator* self) -> bool
+                {
+                    self->rawPanelSW->set_sensitive (true);
+                    self->sensorbayer->FoldableToolPanel::hide();
+                    self->sensorxtrans->FoldableToolPanel::hide();
+                    self->preprocess->FoldableToolPanel::hide();
+                    self->flatfield->FoldableToolPanel::show();
+                    self->retinex->FoldableToolPanel::setGrayedOut(false);
 
-                self->rawPanelSW->set_sensitive (true);
-                self->sensorbayer->FoldableToolPanel::hide();
-                self->sensorxtrans->FoldableToolPanel::hide();
-                self->preprocess->FoldableToolPanel::hide();
-                self->flatfield->FoldableToolPanel::show();
-                self->retinex->FoldableToolPanel::setGrayedOut(false);
-
-                return FALSE;
-            };
-            idle_register.add(func, this);
+                    return false;
+                };
+            idle_register.add<ToolPanelCoordinator>(func, this, false);
         } else {
-            const auto func = [](gpointer data) -> gboolean {
-                ToolPanelCoordinator* const self = static_cast<ToolPanelCoordinator*>(data);
+            const auto func =
+                [](ToolPanelCoordinator* self) -> bool
+                {
+                    self->rawPanelSW->set_sensitive (true);
+                    self->sensorbayer->FoldableToolPanel::hide();
+                    self->sensorxtrans->FoldableToolPanel::hide();
+                    self->preprocess->FoldableToolPanel::hide();
+                    self->flatfield->FoldableToolPanel::hide();
+                    self->retinex->FoldableToolPanel::setGrayedOut(false);
 
-                self->rawPanelSW->set_sensitive (true);
-                self->sensorbayer->FoldableToolPanel::hide();
-                self->sensorxtrans->FoldableToolPanel::hide();
-                self->preprocess->FoldableToolPanel::hide();
-                self->flatfield->FoldableToolPanel::hide();
-                self->retinex->FoldableToolPanel::setGrayedOut(false);
-
-                return FALSE;
-            };
-            idle_register.add(func, this);
+                    return false;
+                };
+            idle_register.add<ToolPanelCoordinator>(func, this, false);
         }
     } else {
-        const auto func = [](gpointer data) -> gboolean {
-            ToolPanelCoordinator* const self = static_cast<ToolPanelCoordinator*>(data);
+        const auto func =
+            [](ToolPanelCoordinator* self) -> bool
+            {
+                self->rawPanelSW->set_sensitive (false);
+                self->retinex->FoldableToolPanel::setGrayedOut(true);
 
-            self->rawPanelSW->set_sensitive (false);
-            self->retinex->FoldableToolPanel::setGrayedOut(true);
-
-            return FALSE;
-        };
-        idle_register.add(func, this);
+                return false;
+            };
+        idle_register.add<ToolPanelCoordinator>(func, this, false);
     }
 
 }
diff --git a/rtgui/wavelet.cc b/rtgui/wavelet.cc
index 7aa03050a..5b395fc91 100644
--- a/rtgui/wavelet.cc
+++ b/rtgui/wavelet.cc
@@ -888,22 +888,22 @@ void Wavelet::wavChanged (double nlevel)
 {
     if (!batchMode) {
         struct Data {
-            Wavelet *me;
+            Wavelet *self;
             double nlevel;
         };
 
-        const auto func = [](gpointer data) -> gboolean {
-            Data *d = static_cast<Data *>(data);
-            Wavelet *me = d->me;
-            me->wavLabels->set_text(
-            Glib::ustring::compose(M("TP_WAVELET_LEVLABEL"),
-                                   Glib::ustring::format(std::fixed, std::setprecision(0), d->nlevel))
-            );
-            delete d;
-            return FALSE;
-        };
+        const auto func =
+            [](Data* data) -> bool
+            {
+                Wavelet* self = data->self;
+                self->wavLabels->set_text(
+                Glib::ustring::compose(M("TP_WAVELET_LEVLABEL"),
+                                       Glib::ustring::format(std::fixed, std::setprecision(0), data->nlevel))
+                );
+                return false;
+            };
 
-        idle_register.add(func, new Data { this, nlevel });
+        idle_register.add<Data>(func, new Data{this, nlevel}, true);
     }
 }
 
diff --git a/rtgui/whitebalance.cc b/rtgui/whitebalance.cc
index 1257a9c58..fcd983618 100644
--- a/rtgui/whitebalance.cc
+++ b/rtgui/whitebalance.cc
@@ -695,7 +695,7 @@ void WhiteBalance::read (const ProcParams* pp, const ParamsEdited* pedited)
     }
 
     green->setLogScale(10, green->getValue(), true);
-    
+
     methconn.block (false);
     enableListener ();
 }
@@ -915,22 +915,23 @@ void WhiteBalance::WBChanged(double temperature, double greenVal)
         double green_val;
     };
 
-    const auto func = [](gpointer data) -> gboolean {
-        WhiteBalance* const self = static_cast<WhiteBalance*>(static_cast<Data*>(data)->self);
-        const double temperature = static_cast<Data*>(data)->temperature;
-        const double green_val = static_cast<Data*>(data)->green_val;
-        delete static_cast<Data*>(data);
+    const auto func =
+        [](Data* data) -> bool
+        {
+            WhiteBalance* const self = static_cast<WhiteBalance*>(data->self);
+            const double temperature = data->temperature;
+            const double green_val = data->green_val;
 
-        self->disableListener();
-        self->setEnabled(true);
-        self->temp->setValue(temperature);
-        self->green->setValue(green_val);
-        self->temp->setDefault(temperature);
-        self->green->setDefault(green_val);
-        self->enableListener();
+            self->disableListener();
+            self->setEnabled(true);
+            self->temp->setValue(temperature);
+            self->green->setValue(green_val);
+            self->temp->setDefault(temperature);
+            self->green->setDefault(green_val);
+            self->enableListener();
 
-        return FALSE;
-    };
+            return false;
+        };
 
-    idle_register.add(func, new Data{this, temperature, greenVal});
+    idle_register.add<Data>(func, new Data{this, temperature, greenVal}, true);
 }
diff --git a/rtgui/xtransprocess.cc b/rtgui/xtransprocess.cc
index 47556e54f..72a2db2b0 100644
--- a/rtgui/xtransprocess.cc
+++ b/rtgui/xtransprocess.cc
@@ -255,18 +255,19 @@ void XTransProcess::checkBoxToggled (CheckBox* c, CheckValue newval)
 void XTransProcess::autoContrastChanged (double autoContrast)
 {
     struct Data {
-        XTransProcess *me;
+        XTransProcess* self;
         double autoContrast;
     };
-    const auto func = [](gpointer data) -> gboolean {
-        Data *d = static_cast<Data *>(data);
-        XTransProcess *me = d->me;
-        me->disableListener();
-        me->dualDemosaicContrast->setValue(d->autoContrast);
-        me->enableListener();
-        delete d;
-        return FALSE;
-    };
 
-    idle_register.add(func, new Data { this, autoContrast });
+    const auto func =
+        [](Data* data) -> bool
+        {
+            XTransProcess* self = data->self;
+            self->disableListener();
+            self->dualDemosaicContrast->setValue(data->autoContrast);
+            self->enableListener();
+            return false;
+        };
+
+    idle_register.add<Data>(func, new Data{this, autoContrast}, true);
 }