Fix sentinel value for HWND on WIN32 (STR #862)

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.1@4362 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

CHANGES

@@ -2,6 +2,7 @@ CHANGES IN FLTK 1.1.7
 
 	- Documentation fixes (STR #648, STR #692, STR #730, STR
 	  #744, STR #745)
+	- Changed initializations on WIN32 (STR #862)
 	- Fl_Preferences::getUserdataPath() didn't work for
 	  sub-groups (STR #872)
 	- Fixed some redraw issues on Windows XP.

src/Fl_win32.cxx

@@ -1219,12 +1219,12 @@ Fl_Window *Fl_Window::current_;
 HDC fl_gc = 0;
 // the current window handle, initially set to -1 so we can correctly
 // allocate fl_GetDC(0)
-HWND fl_window = (HWND)-1;
+HWND fl_window = NULL;
 
 // Here we ensure only one GetDC is ever in place.
 HDC fl_GetDC(HWND w) {
   if (fl_gc) {
-    if (w == fl_window) return fl_gc;
+    if (w == fl_window  &&  fl_window != NULL) return fl_gc;
     ReleaseDC(fl_window, fl_gc);
   }
   fl_gc = GetDC(w);