From 6721be522c279e1343d675072819bd1671b40fe8 Mon Sep 17 00:00:00 2001
From: dgp <dgp@users.sourceforge.net>
Date: Sat, 11 May 2019 20:53:22 +0000
Subject: Fix for the [button ... -textvariable] parts of [5d991b822e].

---
 generic/tkButton.c | 29 ++++++++++++++++++++++++++++-
 tests/button.test  |  2 +-
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/generic/tkButton.c b/generic/tkButton.c
index b7e314e..0e1a4e9 100644
--- a/generic/tkButton.c
+++ b/generic/tkButton.c
@@ -1709,7 +1709,34 @@ ButtonTextVarProc(
      */
 
     if (flags & TCL_TRACE_UNSETS) {
-	if ((flags & TCL_TRACE_DESTROYED) && !(flags & TCL_INTERP_DESTROYED)) {
+	if (!Tcl_InterpDeleted(interp) && butPtr->textVarNamePtr != NULL) {
+
+	    /*
+	     * An unset trace on some variable brought us here, but is it
+	     * the variable we have stored in butPtr->textVarNamePtr ? 
+	     */
+
+	    ClientData probe = NULL;
+
+	    do {
+		probe = Tcl_VarTraceInfo(interp,
+			Tcl_GetString(butPtr->textVarNamePtr),
+			TCL_GLOBAL_ONLY|TCL_TRACE_WRITES|TCL_TRACE_UNSETS,
+			ButtonTextVarProc, probe);
+		if (probe == (ClientData)butPtr) {
+		    break;
+		}
+	    } while (probe);
+	    if (probe) {
+		/* 
+		 * We were able to fetch the unset trace for our
+		 * textVarNamePtr, which means it is not unset and not
+		 * the cause of this unset trace. Instead some outdated
+		 * former textvariable must be, and we should ignore it.
+		 */
+		return NULL;
+	    }
+
 	    Tcl_ObjSetVar2(interp, butPtr->textVarNamePtr, NULL,
 		    butPtr->textPtr, TCL_GLOBAL_ONLY);
 	    Tcl_TraceVar2(interp, Tcl_GetString(butPtr->textVarNamePtr),
diff --git a/tests/button.test b/tests/button.test
index 21ccf8f..edc5a42 100644
--- a/tests/button.test
+++ b/tests/button.test
@@ -3978,7 +3978,7 @@ test button-15.2 {Bug [5d991b822e]} {
 	.b configure -textvariable new
     }}}
     pack .b
-    bind .b <Configure> {unset var}
+    bind .b <Configure> {unset -nocomplain var}
     update
     destroy .b
     unset new
-- 
cgit v0.12