From 1aba0073213c96af7dc6c53667ee5e14987a6278 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Fri, 2 Dec 2005 14:19:08 +0000
Subject: [PATCH] change yield so that it doesn't handle events in a
 non-handler thread(!)

svn: r1487
---
 src/mred/mred.cxx         |  5 ++++-
 src/mred/wxs/wxscheme.cxx | 22 ++++++++++++++++++----
 src/mred/wxs/wxsmred.h    |  2 ++
 3 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/src/mred/mred.cxx b/src/mred/mred.cxx
index 09dc94641f..30c468e97a 100644
--- a/src/mred/mred.cxx
+++ b/src/mred/mred.cxx
@@ -1016,7 +1016,7 @@ static int check_eventspace_inactive(void *_c)
 
 void mred_wait_eventspace(void)
 {
-  MrEdContext * volatile c;
+  MrEdContext *c;
   c = MrEdGetContext();
   if (c && (c->handler_running == scheme_current_thread)) {
     wxDispatchEventsUntilWaitable(check_eventspace_inactive, c, NULL);
@@ -1025,6 +1025,9 @@ void mred_wait_eventspace(void)
 
 int mred_current_thread_is_handler(void *ctx)
 {
+  if (!ctx)
+    ctx = MrEdGetContext();
+
   return (((MrEdContext *)ctx)->handler_running == scheme_current_thread);
 }
 
diff --git a/src/mred/wxs/wxscheme.cxx b/src/mred/wxs/wxscheme.cxx
index 5dd63d6ad7..b04ec0f6a1 100644
--- a/src/mred/wxs/wxscheme.cxx
+++ b/src/mred/wxs/wxscheme.cxx
@@ -2098,21 +2098,35 @@ static Scheme_Object *queue_callback(int argc, Scheme_Object **argv)
 
 void *wxSchemeYield(void *sema)
 {
+  int is_handler;
+
   if (!wait_symbol) {
     wxREGGLOB(wait_symbol);
     wait_symbol = scheme_intern_symbol("wait");
   }
 
+  is_handler = mred_current_thread_is_handler(NULL);
+
   if (sema == wait_symbol) {
-    mred_wait_eventspace();
-    return scheme_true;
+    if (is_handler) {
+      mred_wait_eventspace();
+      return scheme_true;
+    } else
+      return scheme_false;
   } else if (sema) {
     if (!scheme_is_evt((Scheme_Object *)sema))
       scheme_wrong_type("yield", "evt or 'wait", -1, 0, (Scheme_Object **)&sema);
 
-    return wxDispatchEventsUntilWaitable((wxDispatch_Check_Fun)NULL, NULL, (Scheme_Object *)sema);
+    if (is_handler)
+      return wxDispatchEventsUntilWaitable((wxDispatch_Check_Fun)NULL, NULL, (Scheme_Object *)sema);
+    else {
+      Scheme_Object *a[1];
+      a[0] = sema;
+      scheme_sync(1, a);
+      return scheme_false;
+    }
   } else {
-    if (wxYield())
+    if (is_handler && wxYield())
       return scheme_true;
     else
       return scheme_false;
diff --git a/src/mred/wxs/wxsmred.h b/src/mred/wxs/wxsmred.h
index 627417dba0..f8ed936263 100644
--- a/src/mred/wxs/wxsmred.h
+++ b/src/mred/wxs/wxsmred.h
@@ -41,6 +41,8 @@ extern int wxGetPreference(const char *name, int *res);
 
 extern int wxIsUserMainEventspace(Scheme_Object *o);
 
+extern int mred_current_thread_is_handler(void *ctx);
+
 void wxscheme_early_gl_init(void);
 
 #ifdef MPW_CPLUS