Add wxFileDialog::GetCurrentlySelectedFilterIndex() and wxEVT_UPDATE_UI event notification when the selected file type filter changes

include/wx/filedlg.h

@@ -114,6 +114,9 @@ class WXDLLIMPEXP_CORE wxFileDialogBase: public wxDialog
     virtual wxString GetCurrentlySelectedFilename() const
         { return m_currentlySelectedFilename; }
 
+    virtual int GetCurrentlySelectedFilterIndex () const
+        { return m_currentlySelectedFilterIndex; }
+
     // this function is called with wxFileDialog as parameter and should
     // create the window containing the extra controls we want to show in it
     typedef wxWindow *(*ExtraControlCreatorFunction)(wxWindow*);
@@ -153,6 +156,12 @@ class WXDLLIMPEXP_CORE wxFileDialogBase: public wxDialog
     // GetCurrentlySelectedFilename().
     wxString      m_currentlySelectedFilename;
 
+    // Currently selected, but not yet necessarily accepted by the user, file type / filter index.
+    // This should be updated whenever the selection in the control changes by
+    // the platform-specific code to provide a useful implementation of
+    // GetCurrentlySelectedFilterIndex().
+    int m_currentlySelectedFilterIndex;
+
     wxWindow*     m_extraControl;
 
     // returns true if control is created (if it already exists returns false)

include/wx/msw/filedlg.h

@@ -44,6 +44,9 @@ class WXDLLIMPEXP_CORE wxFileDialog: public wxFileDialogBase
     // called from the hook procedure on CDN_SELCHANGE.
     void MSWOnSelChange(WXHWND hDlg);
 
+    // called from the hook procedure on CDN_TYPECHANGE.
+    void MSWOnTypeChange(WXHWND hDlg, int nFilterIndex);
+
 protected:
 
     virtual void DoMoveWindow(int x, int y, int width, int height) wxOVERRIDE;

interface/wx/filedlg.h

@@ -210,6 +210,28 @@ class wxFileDialog : public wxDialog
     */
     virtual wxString GetCurrentlySelectedFilename() const;
 
+    /**
+        Returns the file type filter index currently selected in dialog.
+
+        Notice that this file type filter is not necessarily going to be the one finally accepted by the
+        user, so calling this function mostly makes sense from an update UI
+        event handler of a custom file dialog extra control to update its state
+        depending on the currently selected file type filter.
+
+        Currently this function is fully implemented under MSW only and
+        returns an undefined value elsewhere.
+
+        @since 3.1.3
+
+        @return The 0-based index of the currently selected file type filter or wxNOT_FOUND if
+            nothing is selected.
+
+        @see SetExtraControlCreator()
+        @see GetFilterIndex()
+        @see SetFilterIndex()
+    */
+    virtual int GetCurrentlySelectedFilterIndex () const;
+
     /**
         Returns the default directory.
     */

src/msw/filedlg.cpp

@@ -47,6 +47,7 @@
 #include "wx/scopeguard.h"
 #include "wx/tokenzr.h"
 #include "wx/modalhook.h"
+#include <wx/scopeguard.h>
 
 // ----------------------------------------------------------------------------
 // constants
@@ -185,6 +186,10 @@ wxFileDialogHookFunction(HWND      hDlg,
                         case CDN_SELCHANGE:
                             dialog->MSWOnSelChange((WXHWND)hDlg);
                             break;
+
+                        case CDN_TYPECHANGE:
+                            dialog->MSWOnTypeChange((WXHWND)hDlg, pNotifyCode->lpOFN->nFilterIndex -1);
+                            break;
                     }
                 }
             }
@@ -330,7 +335,7 @@ void wxFileDialog::MSWOnInitDone(WXHWND hDlg)
         SetPosition(gs_rectDialog.GetPosition());
     }
 
-    // Call selection change handler so that update handler will be
+    // Call selection change handlers so that update handlers will be
     // called once with no selection.
     MSWOnSelChange(hDlg);
 }
@@ -350,6 +355,14 @@ void wxFileDialog::MSWOnSelChange(WXHWND hDlg)
         m_extraControl->UpdateWindowUI(wxUPDATE_UI_RECURSE);
 }
 
+void wxFileDialog::MSWOnTypeChange(WXHWND hDlg, int nFilterIndex)
+{
+        m_currentlySelectedFilterIndex = nFilterIndex;
+
+    if ( m_extraControl )
+        m_extraControl->UpdateWindowUI(wxUPDATE_UI_RECURSE);
+}
+
 // helper used below in ShowCommFileDialog(): style is used to determine
 // whether to show the "Save file" dialog (if it contains wxFD_SAVE bit) or
 // "Open file" one; returns true on success or false on failure in which case
@@ -566,6 +579,7 @@ int wxFileDialog::ShowModal()
 
     of.lpstrFilter  = filterBuffer.t_str();
     of.nFilterIndex = m_filterIndex + 1;
+    m_currentlySelectedFilterIndex = m_filterIndex;
 
     //=== Setting defaultFileName >>=========================================
 
@@ -619,7 +633,7 @@ int wxFileDialog::ShowModal()
 
     if ( !ShowCommFileDialog(&of, m_windowStyle) )
         return wxID_CANCEL;
-
+    
     m_fileNames.Empty();
 
     if ( ( HasFdFlag(wxFD_MULTIPLE) ) &&