Fix for Bug 223739 to get rid of floating point equality test.

Sorry for delaying this fix for months; I hadn't noticed that it had been reviewed!

1 files changed, 17 insertions, 5 deletions

diff --git a/generic/tkTextDisp.c b/generic/tkTextDisp.c
index e0d1d57..2a3cf44 100644
--- a/generic/tkTextDisp.c
+++ b/generic/tkTextDisp.c
@@ -11,7 +11,7 @@
  * See the file "license.terms" for information on usage and redistribution
  * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tkTextDisp.c,v 1.9 2000/01/06 02:18:59 hobbs Exp $
+ * RCS: @(#) $Id: tkTextDisp.c,v 1.10 2002/04/22 12:45:49 dkf Exp $
  */
 
 #include "tkPort.h"
@@ -96,6 +96,16 @@ typedef struct TextStyle {
         && ((s1)->sValuePtr->bgStipple == (s2)->sValuePtr->bgStipple))
 
 /*
+ * The following macro is used to compare two floating-point numbers
+ * to within a certain degree of scale.  Direct comparison fails on
+ * processors where the processor and memory representations of FP
+ * numbers of a particular precision is different (e.g. Intel)
+ */
+
+#define FP_EQUAL_SCALE(double1, double2, scaleFactor) \
+    (fabs((double1)-(double2))*((scaleFactor)+1.0) < 0.3)
+
+/*
  * The following structure describes one line of the display, which may
  * be either part or all of one line of the text.
  */
@@ -3865,7 +3875,7 @@ GetXView(interp, textPtr, report)
 					 * scrollbar if it has changed. */
 {
     TextDInfo *dInfoPtr = textPtr->dInfoPtr;
-    char buffer[TCL_DOUBLE_SPACE * 2];
+    char buffer[TCL_DOUBLE_SPACE * 2 + 1];
     double first, last;
     int code;
 
@@ -3886,7 +3896,8 @@ GetXView(interp, textPtr, report)
 	Tcl_SetResult(interp, buffer, TCL_VOLATILE);
 	return;
     }
-    if ((first == dInfoPtr->xScrollFirst) && (last == dInfoPtr->xScrollLast)) {
+    if (FP_EQUAL_SCALE(first, dInfoPtr->xScrollFirst, dInfoPtr->maxLength) &&
+	FP_EQUAL_SCALE(last,  dInfoPtr->xScrollLast,  dInfoPtr->maxLength)) {
 	return;
     }
     dInfoPtr->xScrollFirst = first;
@@ -3936,7 +3947,7 @@ GetYView(interp, textPtr, report)
 					 * scrollbar if it has changed. */
 {
     TextDInfo *dInfoPtr = textPtr->dInfoPtr;
-    char buffer[TCL_DOUBLE_SPACE * 2];
+    char buffer[TCL_DOUBLE_SPACE * 2 + 1];
     double first, last;
     DLine *dlPtr;
     int totalLines, code, count;
@@ -3971,7 +3982,8 @@ GetYView(interp, textPtr, report)
 	Tcl_SetResult(interp, buffer, TCL_VOLATILE);
 	return;
     }
-    if ((first == dInfoPtr->yScrollFirst) && (last == dInfoPtr->yScrollLast)) {
+    if (FP_EQUAL_SCALE(first, dInfoPtr->yScrollFirst, totalLines) &&
+	FP_EQUAL_SCALE(last,  dInfoPtr->yScrollLast,  totalLines)) {
 	return;
     }
     dInfoPtr->yScrollFirst = first;