diff --git a/rtengine/improccoordinator.cc b/rtengine/improccoordinator.cc
index 6d49dfab5..8f40c6979 100644
--- a/rtengine/improccoordinator.cc
+++ b/rtengine/improccoordinator.cc
@@ -187,7 +187,7 @@ void ImProcCoordinator::updatePreviewImage(int todo, bool panningRelatedChange)
         }
     }
 
-    if (((todo & ALL) == ALL) || panningRelatedChange || (highDetailNeeded && options.prevdemo != PD_Sidecar)) {
+    if (((todo & ALL) == ALL) || (todo & M_MONITOR) || panningRelatedChange || (highDetailNeeded && options.prevdemo != PD_Sidecar)) {
         bwAutoR = bwAutoG = bwAutoB = -9000.f;
 
         if (todo == CROP && ipf.needsPCVignetting()) {
@@ -1022,11 +1022,11 @@ void ImProcCoordinator::updatePreviewImage(int todo, bool panningRelatedChange)
 
 // process crop, if needed
     for (size_t i = 0; i < crops.size(); i++)
-        if (crops[i]->hasListener() && (panningRelatedChange || crops[i]->get_skip() == 1)) {
+        if (crops[i]->hasListener() && (panningRelatedChange || (todo & M_MONITOR) || crops[i]->get_skip() == 1)) {
             crops[i]->update(todo);     // may call ourselves
         }
 
-    if (panningRelatedChange) {
+    if (panningRelatedChange || (todo & M_MONITOR)) {
         progress("Conversion to RGB...", 100 * readyphase / numofphases);
 
         if ((todo != CROP && todo != MINUPDATE) || (todo & M_MONITOR)) {
@@ -1575,7 +1575,6 @@ void ImProcCoordinator::process()
             || params.raw != nextParams.raw
             || params.retinex != nextParams.retinex
             || params.wavelet != nextParams.wavelet
-            
             || params.dirpyrequalizer != nextParams.dirpyrequalizer;
 
         params = nextParams;
diff --git a/rtgui/batchqueuepanel.cc b/rtgui/batchqueuepanel.cc
index 1a9e08b94..b73fb2f6f 100644
--- a/rtgui/batchqueuepanel.cc
+++ b/rtgui/batchqueuepanel.cc
@@ -363,15 +363,12 @@ void BatchQueuePanel::pathFolderButtonPressed ()
 // since these settings are shared with editorpanel :
 void BatchQueuePanel::pathFolderChanged ()
 {
-
     options.savePathFolder = outdirFolder->get_filename();
 }
 
-void BatchQueuePanel::formatChanged (Glib::ustring f)
+void BatchQueuePanel::formatChanged(const Glib::ustring& format)
 {
-
-    options.saveFormatBatch = saveFormatPanel->getFormat ();
-
+    options.saveFormatBatch = saveFormatPanel->getFormat();
 }
 
 bool BatchQueuePanel::handleShortcutKey (GdkEventKey* event)
diff --git a/rtgui/batchqueuepanel.h b/rtgui/batchqueuepanel.h
index 497bc166e..d765e23dc 100644
--- a/rtgui/batchqueuepanel.h
+++ b/rtgui/batchqueuepanel.h
@@ -72,7 +72,7 @@ public:
     void saveOptions ();
     void pathFolderChanged ();
     void pathFolderButtonPressed ();
-    void formatChanged (Glib::ustring f);
+    void formatChanged(const Glib::ustring& format) override;
     void updateTab (int qsize, int forceOrientation = 0); // forceOrientation=0: base on options / 1: horizontal / 2: vertical
 
     bool handleShortcutKey (GdkEventKey* event);
diff --git a/rtgui/cropwindow.cc b/rtgui/cropwindow.cc
index 69d7a98b4..374b755ae 100644
--- a/rtgui/cropwindow.cc
+++ b/rtgui/cropwindow.cc
@@ -267,15 +267,22 @@ void CropWindow::flawnOver (bool isFlawnOver)
     this->isFlawnOver = isFlawnOver;
 }
 
-void CropWindow::scroll (int state, GdkScrollDirection direction, int x, int y)
+void CropWindow::scroll (int state, GdkScrollDirection direction, int x, int y, double deltaX, double deltaY)
 {
+    double delta = 0.0;
+    if (abs(deltaX) > abs(deltaY)) {
+        delta = deltaX;
+    } else {
+        delta = deltaY;
+    }
+    bool isUp = direction == GDK_SCROLL_UP || (direction == GDK_SCROLL_SMOOTH && delta < 0.0);
     if ((state & GDK_CONTROL_MASK) && onArea(ColorPicker, x, y)) {
         // resizing a color picker
-        if (direction == GDK_SCROLL_UP) {
+        if (isUp) {
             hoveredPicker->incSize();
             updateHoveredPicker();
             iarea->redraw ();
-        }else if (direction == GDK_SCROLL_DOWN) {
+        } else {
             hoveredPicker->decSize();
             updateHoveredPicker();
             iarea->redraw ();
@@ -287,9 +294,9 @@ void CropWindow::scroll (int state, GdkScrollDirection direction, int x, int y)
 
         screenCoordToImage(newCenterX, newCenterY, newCenterX, newCenterY);
 
-        if (direction == GDK_SCROLL_UP && !isMaxZoom()) {
+        if (isUp && !isMaxZoom()) {
             zoomIn (true, newCenterX, newCenterY);
-        } else if (direction == GDK_SCROLL_DOWN && !isMinZoom()) {
+        } else if (!isUp && !isMinZoom()) {
             zoomOut (true, newCenterX, newCenterY);
         }
     }
diff --git a/rtgui/cropwindow.h b/rtgui/cropwindow.h
index 9f0dfb7f4..66f9b9097 100644
--- a/rtgui/cropwindow.h
+++ b/rtgui/cropwindow.h
@@ -187,7 +187,7 @@ public:
     bool isInside    (int x, int y);
 
 
-    void scroll        (int state, GdkScrollDirection direction, int x, int y);
+    void scroll        (int state, GdkScrollDirection direction, int x, int y, double deltaX=0.0, double deltaY=0.0);
     void buttonPress   (int button, int num, int state, int x, int y);
     void buttonRelease (int button, int num, int state, int x, int y);
     void pointerMoved  (int bstate, int x, int y);
diff --git a/rtgui/guiutils.cc b/rtgui/guiutils.cc
index 980b94765..a2b38760b 100644
--- a/rtgui/guiutils.cc
+++ b/rtgui/guiutils.cc
@@ -945,6 +945,9 @@ bool MyScrolledWindow::on_scroll_event (GdkEventScroll* event)
         double step  = adjust->get_step_increment();
         double value2 = 0.;
 
+        printf("MyScrolledwindow::on_scroll_event / delta_x=%.5f, delta_y=%.5f, direction=%d, type=%d, send_event=%d\n",
+                event->delta_x, event->delta_y, (int)event->direction, (int)event->type, event->send_event);
+
         if (event->direction == GDK_SCROLL_DOWN) {
             value2 = value + step;
 
@@ -962,6 +965,13 @@ bool MyScrolledWindow::on_scroll_event (GdkEventScroll* event)
                 value2 = lower;
             }
 
+            if (value2 != value) {
+                scroll->set_value(value2);
+            }
+        } else if (event->direction == GDK_SCROLL_SMOOTH) {
+            if (abs(event->delta_y) > 0.1) {
+                value2 = rtengine::LIM<double>(value + (event->delta_y > 0 ? step : -step), lower, upper);
+            }
             if (value2 != value) {
                 scroll->set_value(value2);
             }
@@ -1010,6 +1020,9 @@ bool MyScrolledToolbar::on_scroll_event (GdkEventScroll* event)
         double step  = adjust->get_step_increment() * 2;
         double value2 = 0.;
 
+        printf("MyScrolledToolbar::on_scroll_event / delta_x=%.5f, delta_y=%.5f, direction=%d, type=%d, send_event=%d\n",
+                event->delta_x, event->delta_y, (int)event->direction, (int)event->type, event->send_event);
+
         if (event->direction == GDK_SCROLL_DOWN) {
             value2 = rtengine::min<double>(value + step, upper);
             if (value2 != value) {
@@ -1057,11 +1070,14 @@ MyComboBoxText::MyComboBoxText (bool has_entry) : Gtk::ComboBoxText(has_entry)
     minimumWidth = naturalWidth = 70;
     Gtk::CellRendererText* cellRenderer = dynamic_cast<Gtk::CellRendererText*>(get_first_cell());
     cellRenderer->property_ellipsize() = Pango::ELLIPSIZE_MIDDLE;
+    add_events(Gdk::SCROLL_MASK|Gdk::SMOOTH_SCROLL_MASK);
 }
 
 bool MyComboBoxText::on_scroll_event (GdkEventScroll* event)
 {
 
+    printf("MyComboboxText::on_scroll_event / delta_x=%.5f, delta_y=%.5f, direction=%d, type=%d, send_event=%d\n",
+            event->delta_x, event->delta_y, (int)event->direction, (int)event->type, event->send_event);
     // If Shift is pressed, the widget is modified
     if (event->state & GDK_SHIFT_MASK) {
         Gtk::ComboBoxText::on_scroll_event(event);
@@ -1219,6 +1235,8 @@ bool MySpinButton::on_scroll_event (GdkEventScroll* event)
 bool MyHScale::on_scroll_event (GdkEventScroll* event)
 {
 
+    printf("MyHScale::on_scroll_event / delta_x=%.5f, delta_y=%.5f, direction=%d, type=%d, send_event=%d\n",
+            event->delta_x, event->delta_y, (int)event->direction, (int)event->type, event->send_event);
     // If Shift is pressed, the widget is modified
     if (event->state & GDK_SHIFT_MASK) {
         Gtk::HScale::on_scroll_event(event);
@@ -1343,7 +1361,7 @@ void MyFileChooserButton::set_filter(const Glib::RefPtr<Gtk::FileFilter> &filter
 {
     cur_filter_ = filter;
 }
-    
+
 
 std::vector<Glib::RefPtr<Gtk::FileFilter>> MyFileChooserButton::list_filters()
 {
diff --git a/rtgui/imagearea.cc b/rtgui/imagearea.cc
index b2b938139..cd148acff 100644
--- a/rtgui/imagearea.cc
+++ b/rtgui/imagearea.cc
@@ -77,7 +77,7 @@ void ImageArea::on_realize()
     // This workaround should be removed when bug is fixed in GTK2 or when migrating to GTK3
     add_events(Gdk::EXPOSURE_MASK | Gdk::POINTER_MOTION_MASK | Gdk::BUTTON_PRESS_MASK | Gdk::BUTTON_RELEASE_MASK | Gdk::SCROLL_MASK);
 #else
-    add_events(Gdk::EXPOSURE_MASK | Gdk::POINTER_MOTION_MASK | Gdk::POINTER_MOTION_HINT_MASK | Gdk::BUTTON_PRESS_MASK | Gdk::BUTTON_RELEASE_MASK | Gdk::SCROLL_MASK);
+    add_events(Gdk::EXPOSURE_MASK | Gdk::POINTER_MOTION_MASK | Gdk::POINTER_MOTION_HINT_MASK | Gdk::BUTTON_PRESS_MASK | Gdk::BUTTON_RELEASE_MASK | Gdk::SCROLL_MASK | Gdk::SMOOTH_SCROLL_MASK);
 #endif
 
     Cairo::FontOptions cfo;
@@ -302,9 +302,12 @@ bool ImageArea::on_button_press_event (GdkEventButton* event)
 bool ImageArea::on_scroll_event (GdkEventScroll* event)
 {
 
+    printf("ImageArea::on_scroll_event / delta_x=%.5f, delta_y=%.5f, direction=%d, type=%d, send_event=%d\n",
+            event->delta_x, event->delta_y, (int)event->direction, (int)event->type, event->send_event);
+
     CropWindow* cw = getCropWindow (event->x, event->y);
     if (cw) {
-        cw->scroll (event->state, event->direction, event->x, event->y);
+        cw->scroll (event->state, event->direction, event->x, event->y, event->delta_x, event->delta_y);
     }
 
     return true;
diff --git a/rtgui/options.cc b/rtgui/options.cc
index c0a9e06bc..1444fffc0 100644
--- a/rtgui/options.cc
+++ b/rtgui/options.cc
@@ -1354,17 +1354,10 @@ void Options::readFromFile(Glib::ustring fname)
                     FileBrowserToolbarSingleRow = keyFile.get_boolean ("GUI", "FileBrowserToolbarSingleRow");
                 }
 
-#if defined(__linux__) && ((GTK_MAJOR_VERSION == 3 && GTK_MINOR_VERSION > 18) || GTK_MAJOR_VERSION > 3)
-                // Cannot scroll toolbox with mousewheel when HideTPVScrollbar=true #3413
-                hideTPVScrollbar = false;
-#else
-
                 if (keyFile.has_key("GUI", "HideTPVScrollbar")) {
                     hideTPVScrollbar = keyFile.get_boolean("GUI", "HideTPVScrollbar");
                 }
 
-#endif
-
                 if (keyFile.has_key("GUI", "HistogramWorking")) {
                     rtSettings.HistogramWorking = keyFile.get_boolean("GUI", "HistogramWorking");
                 }
diff --git a/rtgui/preferences.cc b/rtgui/preferences.cc
index f00d2f1c1..6f651a4a8 100644
--- a/rtgui/preferences.cc
+++ b/rtgui/preferences.cc
@@ -932,11 +932,6 @@ Gtk::Widget* Preferences::getGeneralPanel()
     setExpandAlignProperties(hb4label, false, false, Gtk::ALIGN_START, Gtk::ALIGN_BASELINE);
     ckbHideTPVScrollbar = Gtk::manage(new Gtk::CheckButton(M("PREFERENCES_TP_VSCROLLBAR")));
     setExpandAlignProperties(ckbHideTPVScrollbar, false, false, Gtk::ALIGN_START, Gtk::ALIGN_BASELINE);
-#if defined(__linux__) && ((GTK_MAJOR_VERSION == 3 && GTK_MINOR_VERSION > 18) || GTK_MAJOR_VERSION > 3)
-    // Cannot scroll toolbox with mousewheel when HideTPVScrollbar=true #3413
-    ckbHideTPVScrollbar->set_active(false);
-    ckbHideTPVScrollbar->set_sensitive(false);
-#endif
     workflowGrid->attach_next_to(*hb4label, *ckbFileBrowserToolbarSingleRow, Gtk::POS_BOTTOM, 1, 1);
     workflowGrid->attach_next_to(*ckbHideTPVScrollbar, *hb4label, Gtk::POS_RIGHT, 1, 1);
     ckbAutoSaveTpOpen = Gtk::manage(new Gtk::CheckButton(M("PREFERENCES_AUTOSAVE_TP_OPEN")));
diff --git a/rtgui/previewwindow.cc b/rtgui/previewwindow.cc
index 5c7cce997..f9dba53ac 100644
--- a/rtgui/previewwindow.cc
+++ b/rtgui/previewwindow.cc
@@ -34,7 +34,7 @@ void PreviewWindow::on_realize ()
 {
 
     Gtk::DrawingArea::on_realize ();
-    add_events(Gdk::POINTER_MOTION_MASK | Gdk::BUTTON_PRESS_MASK | Gdk::BUTTON_RELEASE_MASK | Gdk::SCROLL_MASK);
+    add_events(Gdk::POINTER_MOTION_MASK | Gdk::BUTTON_PRESS_MASK | Gdk::BUTTON_RELEASE_MASK);
 }
 
 void PreviewWindow::getObservedFrameArea (int& x, int& y, int& w, int& h)
diff --git a/rtgui/saveasdlg.cc b/rtgui/saveasdlg.cc
index 7067e8ed1..f2a7206b9 100644
--- a/rtgui/saveasdlg.cc
+++ b/rtgui/saveasdlg.cc
@@ -16,15 +16,36 @@
  *  You should have received a copy of the GNU General Public License
  *  along with RawTherapee.  If not, see <http://www.gnu.org/licenses/>.
  */
+#include <functional>
+
 #include "saveasdlg.h"
-#include "multilangmgr.h"
+
 #include "guiutils.h"
+#include "multilangmgr.h"
 #include "rtimage.h"
 
 #include "../rtengine/utils.h"
 
 extern Options options;
 
+namespace
+{
+
+Glib::ustring getCurrentFilename(const Gtk::FileChooserWidget* fchooser)
+{
+    Glib::ustring res = fchooser->get_filename();
+
+    // NB: There seem to be a bug in Gtkmm2.22 / FileChooserWidget : if you suppress the filename entry and
+    //     click on a folder in the list, the filename field is empty but get_filename will return the folder's path :/
+    if (Glib::file_test(res, Glib::FILE_TEST_IS_DIR)) {
+        res = fchooser->get_current_name();
+    }
+
+    return res;
+}
+
+}
+
 SaveAsDialog::SaveAsDialog (const Glib::ustring &initialDir, Gtk::Window* parent)
     : Gtk::Dialog (M("GENERAL_SAVE"), *parent)
 {
@@ -219,13 +240,7 @@ SaveFormat SaveAsDialog::getFormat ()
 
 void SaveAsDialog::okPressed ()
 {
-    fname = fchooser->get_filename();
-
-    // NB: There seem to be a bug in Gtkmm2.22 / FileChooserWidget : if you suppress the filename entry and
-    //     click on a folder in the list, the filename field is empty but get_filename will return the folder's path :/
-    if (Glib::file_test(fname, Glib::FILE_TEST_IS_DIR)) {
-        fname = fchooser->get_current_name();
-    }
+    fname = getCurrentFilename(fchooser);
 
     // Checking if the filename field is empty. The user have to click Cancel if he don't want to specify a filename
     if (fname.empty()) {
@@ -246,9 +261,18 @@ void SaveAsDialog::okPressed ()
         // Extension is either empty or unfamiliar
         fname += '.' + formatOpts->getFormat().format;
     } else if (
-        !rtengine::hasJpegExtension(fname)
-        && !rtengine::hasTiffExtension(fname)
-        && !rtengine::hasPngExtension(fname)
+        (
+            formatOpts->getFormat().format == "jpg"
+            && !rtengine::hasJpegExtension(fname)
+        )
+        || (
+            formatOpts->getFormat().format == "tif"
+            && !rtengine::hasTiffExtension(fname)
+        )
+        || (
+            formatOpts->getFormat().format == "png"
+            && !rtengine::hasPngExtension(fname)
+        )
     ) {
         // Create dialog to warn user that the filename may have two extensions on the end
         Gtk::MessageDialog msgd(
@@ -283,15 +307,42 @@ void SaveAsDialog::cancelPressed ()
     response (Gtk::RESPONSE_CANCEL);
 }
 
-void SaveAsDialog::formatChanged (Glib::ustring f)
+void SaveAsDialog::formatChanged(const Glib::ustring& format)
 {
+    const auto sanitize_suffix =
+        [this, format](const std::function<bool (const Glib::ustring&)>& has_suffix)
+        {
+            const Glib::ustring name = getCurrentFilename(fchooser);
 
-    if (f == "jpg") {
+            if (!has_suffix(name)) {
+                fchooser->set_current_name(removeExtension(Glib::path_get_basename(name)) + '.' + format);
+            }
+        };
+
+    if (format == "jpg") {
         fchooser->set_filter (filter_jpg);
-    } else if (f == "png") {
+        sanitize_suffix(
+            [](const Glib::ustring& filename)
+            {
+                return rtengine::hasJpegExtension(filename);
+            }
+        );
+    } else if (format == "png") {
         fchooser->set_filter (filter_png);
-    } else if (f == "tif") {
+        sanitize_suffix(
+            [](const Glib::ustring& filename)
+            {
+                return rtengine::hasPngExtension(filename);
+            }
+        );
+    } else if (format == "tif") {
         fchooser->set_filter (filter_tif);
+        sanitize_suffix(
+            [](const Glib::ustring& filename)
+            {
+                return rtengine::hasTiffExtension(filename);
+            }
+        );
     }
 }
 
diff --git a/rtgui/saveasdlg.h b/rtgui/saveasdlg.h
index 073be23f4..e02be340f 100644
--- a/rtgui/saveasdlg.h
+++ b/rtgui/saveasdlg.h
@@ -62,7 +62,7 @@ public:
 
     void okPressed ();
     void cancelPressed ();
-    void formatChanged (Glib::ustring f);
+    void formatChanged(const Glib::ustring& format) override;
     bool keyPressed (GdkEventKey* event);
 };
 
diff --git a/rtgui/saveformatpanel.h b/rtgui/saveformatpanel.h
index 47011be18..7c4dbf33f 100644
--- a/rtgui/saveformatpanel.h
+++ b/rtgui/saveformatpanel.h
@@ -28,8 +28,8 @@ class FormatChangeListener
 {
 
 public:
-    virtual ~FormatChangeListener () {}
-    virtual void formatChanged (Glib::ustring f) {}
+    virtual ~FormatChangeListener() = default;
+    virtual void formatChanged(const Glib::ustring& format) = 0;
 };
 
 class SaveFormatPanel : public Gtk::Grid, public AdjusterListener
diff --git a/rtgui/thumbbrowserbase.cc b/rtgui/thumbbrowserbase.cc
index 829aec9f7..814c3e53e 100644
--- a/rtgui/thumbbrowserbase.cc
+++ b/rtgui/thumbbrowserbase.cc
@@ -68,26 +68,59 @@ void ThumbBrowserBase::scrollChanged ()
     }
 }
 
-void ThumbBrowserBase::scroll (int direction)
+void ThumbBrowserBase::scroll (int direction, double deltaX, double deltaY)
 {
+    double delta = 0.0;
+    if (abs(deltaX) > abs(deltaY)) {
+        delta = deltaX;
+    } else {
+        delta = deltaY;
+    }
+    double coef = direction == GDK_SCROLL_DOWN || (direction == GDK_SCROLL_SMOOTH && delta > 0.0) ? +1.0 : -1.0;
+
     // GUI already acquired when here
-    if (direction == GDK_SCROLL_UP || direction == GDK_SCROLL_DOWN) {
+    if (direction == GDK_SCROLL_UP || direction == GDK_SCROLL_DOWN || direction == GDK_SCROLL_SMOOTH) {
         if (arrangement == TB_Vertical) {
-            vscroll.set_value (vscroll.get_value() + (direction == GDK_SCROLL_DOWN ? +1 : -1) * vscroll.get_adjustment()->get_step_increment());
+            double currValue = vscroll.get_value();
+            double newValue = rtengine::LIM<double>(currValue + coef * vscroll.get_adjustment()->get_step_increment(),
+                                                    vscroll.get_adjustment()->get_lower (),
+                                                    vscroll.get_adjustment()->get_upper());
+            if (newValue != currValue) {
+                vscroll.set_value (newValue);
+            }
         } else {
-            hscroll.set_value (hscroll.get_value() + (direction == GDK_SCROLL_DOWN ? +1 : -1) * hscroll.get_adjustment()->get_step_increment());
+            double currValue = hscroll.get_value();
+            double newValue = rtengine::LIM<double>(currValue + coef * hscroll.get_adjustment()->get_step_increment(),
+                                                    hscroll.get_adjustment()->get_lower(),
+                                                    hscroll.get_adjustment()->get_upper());
+            if (newValue != currValue) {
+                hscroll.set_value (newValue);
+            }
         }
     }
 }
 
 void ThumbBrowserBase::scrollPage (int direction)
 {
+    // GUI already acquired when here
     // GUI already acquired when here
     if (direction == GDK_SCROLL_UP || direction == GDK_SCROLL_DOWN) {
         if (arrangement == TB_Vertical) {
-            vscroll.set_value (vscroll.get_value() + (direction == GDK_SCROLL_DOWN ? +1 : -1) * vscroll.get_adjustment()->get_page_increment());
+            double currValue = vscroll.get_value();
+            double newValue = rtengine::LIM<double>(currValue + (direction == GDK_SCROLL_DOWN ? +1 : -1) * vscroll.get_adjustment()->get_page_increment(),
+                                                    vscroll.get_adjustment()->get_lower(),
+                                                    vscroll.get_adjustment()->get_upper());
+            if (newValue != currValue) {
+                vscroll.set_value (newValue);
+            }
         } else {
-            hscroll.set_value (hscroll.get_value() + (direction == GDK_SCROLL_DOWN ? +1 : -1) * hscroll.get_adjustment()->get_page_increment());
+            double currValue = hscroll.get_value();
+            double newValue = rtengine::LIM<double>(currValue + (direction == GDK_SCROLL_DOWN ? +1 : -1) * hscroll.get_adjustment()->get_page_increment(),
+                                                    hscroll.get_adjustment()->get_lower(),
+                                                    hscroll.get_adjustment()->get_upper());
+            if (newValue != currValue) {
+                hscroll.set_value (newValue);
+            }
         }
     }
 }
@@ -682,7 +715,7 @@ void ThumbBrowserBase::Internal::on_realize()
     bgs = style->get_background_color(Gtk::STATE_FLAG_SELECTED);
 
     set_can_focus(true);
-    add_events(Gdk::EXPOSURE_MASK | Gdk::BUTTON_PRESS_MASK | Gdk::BUTTON_RELEASE_MASK | Gdk::POINTER_MOTION_MASK | Gdk::SCROLL_MASK | Gdk::KEY_PRESS_MASK);
+    add_events(Gdk::EXPOSURE_MASK | Gdk::BUTTON_PRESS_MASK | Gdk::BUTTON_RELEASE_MASK | Gdk::POINTER_MOTION_MASK | Gdk::SCROLL_MASK | Gdk::SMOOTH_SCROLL_MASK | Gdk::KEY_PRESS_MASK);
     set_has_tooltip (true);
     signal_query_tooltip().connect( sigc::mem_fun(*this, &ThumbBrowserBase::Internal::on_query_tooltip) );
 }
@@ -920,7 +953,10 @@ bool ThumbBrowserBase::Internal::on_scroll_event (GdkEventScroll* event)
 {
     // Gtk signals automatically acquire the GUI (i.e. this method is enclosed by gdk_thread_enter and gdk_thread_leave)
 
-    parent->scroll (event->direction);
+    printf("ThumbBrowserBase::Internal::on_scroll_event / delta_x=%.5f, delta_y=%.5f, direction=%d, type=%d, send_event=%d\n",
+            event->delta_x, event->delta_y, (int)event->direction, (int)event->type, event->send_event);
+
+    parent->scroll (event->direction, event->delta_x, event->delta_y);
     return true;
 }
 
diff --git a/rtgui/thumbbrowserbase.h b/rtgui/thumbbrowserbase.h
index d4d7e63e2..02bea3646 100644
--- a/rtgui/thumbbrowserbase.h
+++ b/rtgui/thumbbrowserbase.h
@@ -138,7 +138,7 @@ public:
     enum Arrangement {TB_Horizontal, TB_Vertical};
     void configScrollBars ();
     void scrollChanged ();
-    void scroll (int direction);
+    void scroll (int direction, double deltaX=0.0, double deltaY=0.0);
     void scrollPage (int direction);
 
 private: