Update images when DPI changes in wxBookCtrlBase-derived classes

Just pretend that the images themselves have changed, this should be
enough to recreate wxImageList from the bundle using the new scale
factor in UpdateImageListIfNecessary().

include/wx/bookctrl.h

@@ -360,6 +360,10 @@ private:
     // common part of all ctors
     void Init();
 
+    // update the images if we use them on DPI change
+    void WXHandleDPIChanged(wxDPIChangedEvent& event);
+
+
     // internal border
     unsigned int m_internalBorder;
 

src/common/bookctrl.cpp

@@ -41,6 +41,8 @@ wxBEGIN_EVENT_TABLE(wxBookCtrlBase, wxControl)
 #if wxUSE_HELP
     EVT_HELP(wxID_ANY, wxBookCtrlBase::OnHelp)
 #endif // wxUSE_HELP
+
+    EVT_DPI_CHANGED(wxBookCtrlBase::WXHandleDPIChanged)
 wxEND_EVENT_TABLE()
 
 // ----------------------------------------------------------------------------
@@ -291,6 +293,16 @@ wxSize wxBookCtrlBase::GetControllerSize() const
 // miscellaneous stuff
 // ----------------------------------------------------------------------------
 
+void wxBookCtrlBase::WXHandleDPIChanged(wxDPIChangedEvent& event)
+{
+    if ( HasImages() )
+    {
+        OnImagesChanged();
+    }
+
+    event.Skip();
+}
+
 #if wxUSE_HELP
 
 void wxBookCtrlBase::OnHelp(wxHelpEvent& event)