Use wxClientDC::CanBeUsedForDrawing() in wxSplitterWindow

No real changes, just simplify the code by using the just added
wxClientDC function instead of reproducing its logic here.

src/generic/splitter.cpp

@@ -74,25 +74,12 @@ static bool IsLive(wxSplitterWindow* wnd)
     // with wxSP_LIVE_UPDATE style the splitter windows are always resized
     // following the mouse movement while it drags the sash, without it we only
     // draw the sash at the new position but only resize the windows when the
-    // dragging is finished
-#if defined( __WXMAC__ ) && defined(TARGET_API_MAC_OSX) && TARGET_API_MAC_OSX == 1
-    return true; // Mac can't paint outside paint event - always need live mode
-#else
-    // wxClientDC doesn't work with Wayland either, so check if we're using it.
-    #if defined(__WXGTK3__) && defined(__UNIX__)
-        switch ( wxGetDisplayInfo().type )
-        {
-            case wxDisplayNone:
-            case wxDisplayX11:
-                break;
-
-            case wxDisplayWayland:
-                return true;
-        }
-    #endif // wxGTK3
+    // dragging is finished -- but drawing the sash is done using wxClientDC,
+    // so check if we can use it and always use live resizing if we can't
+    if ( !wxClientDC::CanBeUsedForDrawing(wnd) )
+        return true;
 
     return wnd->HasFlag(wxSP_LIVE_UPDATE);
-#endif
 }
 
 bool wxSplitterWindow::Create(wxWindow *parent, wxWindowID id,