Related: tdf#112063 validation dialog legitimally changes modality

so to keep tdf#112063 working as with...

commit e66c9aa3
Author: Caolán McNamara <caolanm@redhat.com>
Date:   Fri Sep 1 16:23:20 2017 +0100

    Related: tdf#112063 unsetting and resetting gtk modality is a problem

    for gtk3, so just set it on execute and no need to unset and reset it
    for whatever vcl nuttiness the existing code is doing

then let the proper calls to SetModalInputMode call the frame modality switch
and the hackery vcl calls the underlying vcl-specific body as ImplSetModalInputMode

Change-Id: I853ca50e0d9830ca7ba3077e243ccdee6e84e696
Reviewed-on: https://gerrit.libreoffice.org/43142Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

include/vcl/dialog.hxx

@@ -157,6 +157,7 @@ public:
 private:
     bool            ImplStartExecuteModal();
     static void     ImplEndExecuteModal();
+    void            ImplSetModalInputMode(bool bModal);
 public:
 
     // Dialog::Execute replacement API

vcl/source/window/dialog.cxx

@@ -629,8 +629,8 @@ bool Dialog::EventNotify( NotifyEvent& rNEvt )
             // have re-enabled input for our parent
             if( mbInExecute && mbModalMode )
             {
-                SetModalInputMode( false );
-                SetModalInputMode( true );
+                ImplSetModalInputMode( false );
+                ImplSetModalInputMode( true );
 
                 // #93022# def-button might have changed after show
                 if( !mnMousePositioned )
@@ -825,7 +825,6 @@ bool Dialog::ImplStartExecuteModal()
         GetParent()->CompatNotify( aNEvt );
     }
     mbInExecute = true;
-    ImplGetFrame()->SetModal(true);
     SetModalInputMode(true);
 
     // FIXME: no layouting, workaround some clipping issues
@@ -1097,7 +1096,6 @@ void Dialog::EndDialog( long nResult )
     if ( mbInExecute )
     {
         SetModalInputMode(false);
-        ImplGetFrame()->SetModal(false);
 
         // remove dialog from the list of dialogs which are being executed
         ImplSVData* pSVData = ImplGetSVData();
@@ -1181,6 +1179,15 @@ bool Dialog::AreDialogsOpen()
 }
 
 void Dialog::SetModalInputMode( bool bModal )
+{
+    if ( bModal == mbModalMode )
+        return;
+
+    ImplGetFrame()->SetModal(bModal);
+    ImplSetModalInputMode(bModal);
+}
+
+void Dialog::ImplSetModalInputMode( bool bModal )
 {
     if ( bModal == mbModalMode )
         return;
@@ -1232,8 +1239,8 @@ void Dialog::SetModalInputMode( bool bModal )
             ( pPrevModalDlg == mpPrevExecuteDlg.get()
                 || !pPrevModalDlg->IsWindowOrChild( this, true ) ) )
             {
-                mpPrevExecuteDlg->SetModalInputMode( false );
-                mpPrevExecuteDlg->SetModalInputMode( true );
+                mpPrevExecuteDlg->ImplSetModalInputMode( false );
+                mpPrevExecuteDlg->ImplSetModalInputMode( true );
             }
         }
     }