From f5a9bed34cb0fb8e8328a4dd7097905059dde231 Mon Sep 17 00:00:00 2001
From: Lars Brinkhoff <lars@nocrew.org>
Date: Mon, 24 Feb 2020 20:58:18 +0100
Subject: [PATCH] DISPLAY: Keep track of device using the display.

Don't let someone close the display if they're not the one having
opened it.
---
 display/display.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/display/display.c b/display/display.c
index 22efa6e3..b3c5cd13 100644
--- a/display/display.c
+++ b/display/display.c
@@ -359,6 +359,7 @@ static long queue_interval;
 #define Y(P) (((P) - points) / xpixels)
 
 static int initialized = 0;
+static void *device = NULL;  /* Current display device. */
 
 /*
  * global set by O/S display level to indicate "light pen tip switch activated"
@@ -969,6 +970,7 @@ display_init(enum display_type type, int sf, void *dptr)
 
     initialized = 1;
     init_failed = 0;            /* hey, we made it! */
+    device = dptr;
     return 1;
 
  failed:
@@ -982,10 +984,14 @@ display_close(void *dptr)
     if (!initialized)
         return;
 
+    if (device != dptr)
+        return;
+
     free (points);
     ws_shutdown();
 
     initialized = 0;
+    device = NULL;
 }
 
 void