From 69a682ce34a9660cfaad5112682972d4a3e0b40a Mon Sep 17 00:00:00 2001
From: Nikos Tsipinakis <nikos@tsipinakis.com>
Date: Wed, 19 Jun 2019 10:55:23 +0300
Subject: [PATCH] Fix call to draw when no notifications are available

Draw should not be called when there are no notifications in the queue.
This for unknown reasons causes a crash the next time we attempt to get
the currently active window with a BadValue error from
XGetWindowProperty.

Fixes #630.
---
 src/draw.c  | 1 +
 src/x11/x.c | 5 ++++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/draw.c b/src/draw.c
index 7dbe55f..80468b5 100644
--- a/src/draw.c
+++ b/src/draw.c
@@ -611,6 +611,7 @@ static void calc_window_pos(int width, int height, int *ret_x, int *ret_y)
 
 void draw(void)
 {
+        assert(queues_length_displayed() > 0);
 
         GSList *layouts = create_layouts(x_win_get_context(win));
 
diff --git a/src/x11/x.c b/src/x11/x.c
index e5f8177..5606762 100644
--- a/src/x11/x.c
+++ b/src/x11/x.c
@@ -341,7 +341,10 @@ gboolean x_mainloop_fd_dispatch(GSource *source, GSourceFunc callback, gpointer
                                 LOG_D("XEvent: processing PropertyNotify for Resource manager");
                                 XRM_update_db();
                                 screen_dpi_xft_cache_purge();
-                                draw();
+
+                                if (win->visible) {
+                                        draw();
+                                }
                                 break;
                         }
                         /* Explicitly fallthrough. Other PropertyNotify events, e.g. catching