+
+// find the entry for this DC in the cache (keyed by the window)
+WXHDC wxPaintDC::FindDCInCache(wxWindow* win)
+{
+ size_t nCache = ms_cache.GetCount();
+ for ( size_t n = 0; n < nCache; n++ )
+ {
+ wxPaintDCInfo *info = &ms_cache[n];
+ if ( info->hwnd == win->GetHWND() )
+ {
+ return info->hdc;
+ }
+ }
+ return 0;
+}
+
+/*
+ * wxPaintDCEx
+ */
+
+// TODO: don't duplicate wxPaintDC code here!!
+
+wxPaintDCEx::wxPaintDCEx(wxWindow *canvas, WXHDC dc) : saveState(0)
+{
+ wxCHECK_RET( dc, wxT("wxPaintDCEx requires an existing device context") );
+
+ m_canvas = canvas;
+
+ wxPaintDCInfo *info = FindInCache();
+ if ( info )
+ {
+ m_hDC = info->hdc;
+ info->count++;
+ }
+ else // not in cache, create a new one
+ {
+ m_hDC = dc;
+ ms_cache.Add(new wxPaintDCInfo(m_canvas, this));
+ saveState = SaveDC((HDC) dc);
+ }
+}
+
+wxPaintDCEx::~wxPaintDCEx()
+{
+ size_t index;
+ wxPaintDCInfo *info = FindInCache(&index);
+
+ wxCHECK_RET( info, wxT("existing DC should have a cache entry") );
+
+ if ( --info->count == 0 )
+ {
+ RestoreDC((HDC) m_hDC, saveState);
+ ms_cache.RemoveAt(index);
+
+ // Reduce the number of bogus reports of non-freed memory
+ // at app exit
+ if (ms_cache.IsEmpty())
+ ms_cache.Clear();
+ }
+ //else: cached DC entry is still in use
+
+ // prevent the base class dtor from ReleaseDC()ing it again
+ m_hDC = 0;
+}