run the scrolling detection code with "real video" if detection is on…

… since it may get it wrong

git-svn-id: https://xpra.org/svn/Xpra/trunk@13799 3bb7dfac-3a0b-4e04-842a-767bc560f471

src/xpra/server/window/window_video_source.py

@@ -1467,7 +1467,8 @@ def do_video_encode(self, encoding, image, options):
             self.pixel_format = src_format
 
         #check for scrolling, unless there's already a b-frame pending, or in strict mode:
-        if self.supports_scrolling and not self.b_frame_flush_timer and not STRICT_MODE:
+        # or when a true video region exists and detection is turned off
+        if self.supports_scrolling and not self.b_frame_flush_timer and not STRICT_MODE and (self.video_subregion.detection or not self.subregion_is_video()):
             try:
                 start = time.time()
                 lsd = self.scroll_data