diff --git a/lcl/interfaces/gtk/gtkcallback.inc b/lcl/interfaces/gtk/gtkcallback.inc
index dc4868362a..120e659826 100644
--- a/lcl/interfaces/gtk/gtkcallback.inc
+++ b/lcl/interfaces/gtk/gtkcallback.inc
@@ -1976,6 +1976,7 @@ function gtksize_allocateCB(widget: PGtkWidget; size: pGtkAllocation;
 var
   w, h: Gint;
 {$ENDIF}
+
 begin
   Result := CallBackDefaultReturn;
 
@@ -1992,6 +1993,18 @@ begin
     RaiseGDBException('');
     exit;
   end;
+  {$IFDEF Gtk2}
+  // do not send msg to LCL if we are shown after hide, setVisible will
+  // do that.
+  if TObject(Data) is TForm then
+  begin
+    with GetWidgetInfo(Widget)^.FormSavedPos do
+    begin
+      if (X <> -10000) and (Y <> -10000) then
+        exit;
+    end;
+  end;
+  {$ENDIF}
 
   {$IFDEF VerboseSizeMsg}
   w:=0; h:=0;
@@ -2037,7 +2050,8 @@ begin
   Result := CallBackDefaultReturn;
 
   if (Widget=nil) or (Size=nil) then ;
-  if (TObject(Data) is TWinControl) then begin
+  if (TObject(Data) is TWinControl) then
+  begin
     {$IFDEF VerboseSizeMsg}
     DebugLn('gtksize_allocate_client: ',
       TControl(Data).Name,':',TControl(Data).ClassName,
diff --git a/lcl/interfaces/gtk/gtkdef.pp b/lcl/interfaces/gtk/gtkdef.pp
index 4ee7828efe..823d97ec3d 100644
--- a/lcl/interfaces/gtk/gtkdef.pp
+++ b/lcl/interfaces/gtk/gtkdef.pp
@@ -481,6 +481,8 @@ type
     UserData: Pointer;
     FormBorderStyle: Integer;         // used only by forms
     FormWindowState: TGdkEventWindowState; // used only by forms to stop infinite loops eg. issue #16505
+    FormSavedPos: TPoint;            // used only by forms - saved LCL Left & Top if form hidden eg. issue #15417
+                                     // so later when we call show, it's restored to it's original position
   end;
   
   //TODO: remove
diff --git a/lcl/interfaces/gtk/gtkwidgetset.inc b/lcl/interfaces/gtk/gtkwidgetset.inc
index 33e901ead0..0eea2508ee 100644
--- a/lcl/interfaces/gtk/gtkwidgetset.inc
+++ b/lcl/interfaces/gtk/gtkwidgetset.inc
@@ -3699,7 +3699,8 @@ begin
     LM_WINDOWPOSCHANGED: //LM_SIZEALLOCATE, LM_RESIZE :
     begin
       ConnectSenderSignal(gObject, 'size-allocate', @gtksize_allocateCB);
-      if gObject<>gFixed then begin
+      if gObject<>gFixed then
+      begin
         ConnectSenderSignal(gFixed, 'size-allocate', @gtksize_allocate_client);
       end;
     end;
@@ -4350,6 +4351,10 @@ var
   AWindow: PGdkWindow;
   ACustomForm: TCustomForm;
   {$IFDEF GTK2}
+  {$IFDEF VerboseFormPositioning}
+  X1, Y1: gint; // current gdk_window_root_origin
+  {$ENDIF}
+  SavedOrigin: TPoint;
   CurWindowState: TWindowState;
   {$ENDIF}
 begin
@@ -4431,7 +4436,41 @@ begin
     if gtk_widget_visible(SenderWidget) then
       exit;
 
+    {$IFDEF GTK2}
+    // we must restore Left & Top coords here to prevent flickering
+    if (ACustomForm <> nil) and
+       (ACustomForm.Parent = nil) and
+       (ACustomForm.ParentWindow = 0) and
+       (ACustomForm is TForm) and // be sure that we are not THintWindow !
+       (ACustomForm.BorderStyle <> bsNone) and
+       not (ACustomForm.FormStyle in [fsMDIChild, fsSplash]) then
+    begin
+      if (ACustomForm.WindowState <> wsMinimized) then
+      begin
+        SavedOrigin := GetWidgetInfo(SenderWidget)^.FormSavedPos;
+        if (SavedOrigin.X <> -10000) and (SavedOrigin.Y <> -10000) then
+        begin
+          {$IFDEF VerboseFormPositioning}
+          gdk_window_get_root_origin(SenderWidget^.window, @X1, @Y1);
+          DebugLn('VFP [TGtkWidgetSet.ShowHide] B ',
+             LCLControl.Name,':',LCLControl.ClassName,
+            ' Window=',dbgs(GetControlWindow(SenderWidget)<>nil),
+          ' RESTORE FORMSAVEDPOS CURRENT X=',dbgs(X1),' Y=',dbgs(Y1),
+          ' SAVED X=',dbgs(SavedOrigin.X),' Y=',dbgs(SavedOrigin.Y));
+          {$ENDIF}
+          with SavedOrigin do
+            gtk_window_move(PGtkWindow(SenderWidget), X, Y);
+          SavedOrigin.X := -10000;
+          SavedOrigin.Y := -10000;
+          GetWidgetInfo(SenderWidget)^.FormSavedPos := SavedOrigin;
+        end;
+      end;
+
+    end;
+    {$ENDIF}
+
     gtk_widget_show(SenderWidget);
+
     {$IFDEF GTK2}
     if (ACustomForm <> nil) and 
        (ACustomForm.Parent = nil) and 
@@ -4453,13 +4492,30 @@ begin
     {$ENDIF}
   end
   else begin
-    if (ACustomForm<>nil) then begin
+
+    if (ACustomForm<>nil) then
       UnshareWindowAccelGroups(SenderWidget);
-    end;
 
     if not gtk_widget_visible(SenderWidget) then
       exit;
 
+    {$IFDEF GTK2}
+    // save previous position
+    if ACustomForm <> nil then
+    begin
+      if (ACustomForm is TForm) and
+        not (ACustomForm.FormStyle in [fsMDIChild, fsSplash])
+        and (ACustomForm.BorderStyle <> bsNone) then
+      begin
+        with GetWidgetInfo(SenderWidget)^.FormSavedPos do
+        begin
+          X := ACustomForm.Left;
+          Y := ACustomForm.Top;
+        end;
+      end;
+    end;
+    {$ENDIF}
+
     gtk_widget_hide(SenderWidget);
 
     if GtkWidgetIsA(SenderWidget,GTK_TYPE_WINDOW) then begin
diff --git a/lcl/interfaces/gtk2/gtk2wsforms.pp b/lcl/interfaces/gtk2/gtk2wsforms.pp
index f383104a47..f0644c9c62 100644
--- a/lcl/interfaces/gtk2/gtk2wsforms.pp
+++ b/lcl/interfaces/gtk2/gtk2wsforms.pp
@@ -317,6 +317,14 @@ begin
   FillChar(WidgetInfo^.FormWindowState, SizeOf(WidgetInfo^.FormWindowState), #0);
   WidgetInfo^.FormWindowState.new_window_state := GDK_WINDOW_STATE_WITHDRAWN;
 
+  // FormRootOrigin is used only to save and restore LCL's Left & Top
+  // in case when form is hidden and then shown again !
+  with WidgetInfo^.FormSavedPos do
+  begin
+    X := -10000;
+    Y := -10000;
+  end;
+
   Box := CreateFormContents(ACustomForm, P, WidgetInfo);
   gtk_container_add(PGtkContainer(P), Box);