Send wxEVT_COLOUR_CHANGED from wxColourDialog under MSW

Add support for a new event sent by wxColourDialog, currently only under
MSW, when the colour currently selected in it changes.

Based on work by Trylz, see https://github.com/wxWidgets/wxWidgets/pull/1219

include/wx/colordlg.h

@@ -31,6 +31,52 @@
     #define wxColourDialog wxGenericColourDialog
 #endif
 
+// Under some platforms (currently only wxMSW) wxColourDialog can send events
+// of this type while it is shown.
+//
+// Notice that this class is almost identical to wxColourPickerEvent but it
+// doesn't really sense to reuse the same class for both controls.
+class WXDLLIMPEXP_CORE wxColourDialogEvent : public wxCommandEvent
+{
+public:
+    wxColourDialogEvent()
+    {
+    }
+
+    wxColourDialogEvent(wxEventType evtType,
+                        wxColourDialog* dialog,
+                        const wxColour& colour)
+        : wxCommandEvent(evtType, dialog->GetId()),
+          m_colour(colour)
+    {
+        SetEventObject(dialog);
+    }
+
+    // default copy ctor and dtor are ok
+
+    wxColour GetColour() const { return m_colour; }
+    void SetColour(const wxColour& colour) { m_colour = colour; }
+
+    virtual wxEvent *Clone() const wxOVERRIDE
+    {
+        return new wxColourDialogEvent(*this);
+    }
+
+private:
+    wxColour m_colour;
+
+    wxDECLARE_DYNAMIC_CLASS_NO_ASSIGN(wxColourDialogEvent);
+};
+
+wxDECLARE_EXPORTED_EVENT(WXDLLIMPEXP_CORE, wxEVT_COLOUR_CHANGED, wxColourDialogEvent);
+
+#define wxColourDialogEventHandler(func) \
+    wxEVENT_HANDLER_CAST(wxColourDialogEventFunction, func)
+
+#define EVT_COLOUR_CHANGED(id, fn) \
+    wx__DECLARE_EVT1(wxEVT_COLOUR_CHANGED, id, wxColourDialogEventHandler(fn))
+
+
 // get the colour from user and return it
 WXDLLIMPEXP_CORE wxColour wxGetColourFromUser(wxWindow *parent = NULL,
                                               const wxColour& colInit = wxNullColour,

include/wx/msw/colordlg.h

@@ -44,6 +44,9 @@ public:
     // called from the hook procedure on WM_INITDIALOG reception
     virtual void MSWOnInitDone(WXHWND hDlg);
 
+    // called from the hook procedure
+    void MSWCheckIfCurrentChanged(WXCOLORREF currentCol);
+
 protected:
     // common part of all ctors
     void Init();
@@ -57,6 +60,9 @@ protected:
     wxColourData        m_colourData;
     wxString            m_title;
 
+    // Currently selected colour, used while the dialog is being shown.
+    WXCOLORREF m_currentCol;
+
     // indicates that the dialog should be centered in this direction if non 0
     // (set by DoCentre(), used by MSWOnInitDone())
     int m_centreDir;