added wxWindow::IsDoubleBuffered() and improve wxBufferedDC (patch 1565330)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@41810 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/changes.txt

@@ -76,6 +76,7 @@ All (GUI):
   consistency with wxRichTextCtrl.
 - wxRichTextCtrl: fixed range out-by-one bug to be consistent with wxTextCtrl API,
   fixed some attribute bugs and added wxRichTextStyleComboCtrl.
+- Added wxWindow::IsDoubleBuffered()
 
 wxMSW:
 

docs/latex/wx/window.tex

@@ -1495,6 +1495,19 @@ to the dialog via validators.
 Resets the cached best size value so it will be recalculated the next time it is needed.
 
 
+\membersection{wxWindow::IsDoubleBuffered}\label{wxwindowisdoublebuffered}
+
+\constfunc{virtual bool}{IsDoubleBuffered}{\void}
+
+Returns \true if the window contents is double-buffered by the system, i.e. if
+any drawing done on the window is really done on a temporary backing surface
+and transferred to the screen all at once later.
+
+\wxheading{See also}
+
+\helpref{wxBufferedDC}{wxbuffereddc}
+
+
 \membersection{wxWindow::IsEnabled}\label{wxwindowisenabled}
 
 \constfunc{virtual bool}{IsEnabled}{\void}