From: Taylor R Campbell <campbell@mumble.net>
Date: Tue, 28 Aug 2012 04:26:04 +0000 (+0000)
Subject: Ask Xlib for events before blocking on the display in x11graph.scm.
X-Git-Tag: release-9.2.0~230
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=c34646cdfa3184920e12186865063f631d9a4408;p=mit-scheme.git

Ask Xlib for events before blocking on the display in x11graph.scm.

Fixes race whereby Xlib may have queued up events already before we
ask the OS about I/O on the underlying file descriptor.  This can
cause us to fail to notice an event until a second one comes along,
so that, e.g., a newly created window will hang until you move the
mouse over it or similar.
---

diff --git a/src/runtime/x11graph.scm b/src/runtime/x11graph.scm
index f273c898d..fd879179c 100644
--- a/src/runtime/x11graph.scm
+++ b/src/runtime/x11graph.scm
@@ -314,12 +314,13 @@ USA.
 
 (define (%read-and-process-event display)
   (let ((event
-	 (and (eq? 'READ
-		   (test-for-io-on-descriptor
-		    (x-display-descriptor (x-display/xd display))
-		    #t
-		    'READ))
-	      (x-display-process-events (x-display/xd display) 1))))
+	 (or (x-display-process-events (x-display/xd display) 2)
+	     (and (eq? 'READ
+		       (test-for-io-on-descriptor
+			(x-display-descriptor (x-display/xd display))
+			#t
+			'READ))
+		  (x-display-process-events (x-display/xd display) 1)))))
     (if event
 	(process-event display event))))