localize button click routines

Keep state local into click_*() for routines relating to button clicks
than in global variables around frame.c and main.c

screen.c

@@ -418,3 +418,38 @@ Scrn *getscreenbyroot(Window w)
 {
   return getscreenbyrootext(w, 0);
 }
+
+void click_screendepth(Scrn *s, Time time)
+{
+  extern void redrawmenubar(Scrn *, Window);
+  extern void get_drag_event(XEvent *event);
+  extern Scrn *mbdclick;
+  int status;
+
+  XSync(dpy, False);
+  status = XGrabPointer(dpy, s->menubardepth, True, ButtonPressMask|ButtonReleaseMask,
+                        GrabModeAsync, GrabModeAsync, False, None, time);
+  if (status != AlreadyGrabbed && status != GrabSuccess)
+    return;
+  mbdclick = s;
+  redrawmenubar(s, s->menubardepth);
+  for (;;) {
+    XEvent event;
+
+    get_drag_event(&event);
+    if (event.type == ButtonRelease || event.type == ButtonPress) {
+      mbdclick = NULL;
+      redrawmenubar(s, s->menubardepth);
+      XUngrabPointer(dpy, event.xbutton.time);
+      if (event.type == ButtonPress)
+        return;
+      if (event.xbutton.x < 0 || event.xbutton.y < 0)
+        return;   /* pointer to left/top of button */
+      if (event.xbutton.x >= 23 || event.xbutton.y >= s->bh)
+        return;   /* pointer to right/bottom of button */
+      if(event.xbutton.window == s->menubardepth)
+        screentoback();
+      return;
+    }
+  }
+}