make IsEnabled() return false even if the window parent, and not the window itself, is disabled and added IsThisEnabled() implementing the old IsEnabled() behaviour; also significantly simplify the window state management code in all ports by factoring out the common parts in wxWindowBase

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@45031 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/latex/wx/window.tex

@@ -1532,7 +1532,13 @@ and transferred to the screen all at once later.
 
 \constfunc{virtual bool}{IsEnabled}{\void}
 
-Returns {\tt true} if the window is enabled for input, {\tt false} otherwise.
+Returns \true if the window is enabled, i.e. if it accepts user input, \false 
+otherwise.
+
+Notice that this method can return \false even if this window itself hadn't
+been explicitly disabled when one of its parent windows is disabled. To get the
+intrinsic status of this window, use 
+\helpref{IsThisEnabled}{wxwindowisthisenabled}
 
 \wxheading{See also}
 
@@ -1608,6 +1614,16 @@ is shown and all its parents up to the toplevel window are shown as well.
 \helpref{wxWindow::IsShown}{wxwindowisshown}
 
 
+\membersection{wxWindow::IsThisEnabled}\label{wxwindowisthisenabled}
+
+\constfunc{bool}{IsThisEnabled}{\void}
+
+Returns \true if this window is intrinsically enabled, \false otherwise, i.e.
+if \helpref{Enable(false)}{wxwindowenable} had been called. This method is
+mostly used for wxWidgets itself, user code should normally use 
+\helpref{IsEnabled}{wxwindowisenabled} instead.
+
+
 \membersection{wxWindow::IsTopLevel}\label{wxwindowistoplevel}
 
 \constfunc{bool}{IsTopLevel}{\void}