From 113b65dce51f37566b58fd730b206537820889e6 Mon Sep 17 00:00:00 2001
From: Thomas Zander <t.zander@nokia.com>
Date: Mon, 12 Apr 2010 14:10:28 +0200
Subject: Make debugging floating point mistakes much easier.

Its a common mistake that a floating point error, like divide by zero,
is not detected and just propagated till it breaks in curious ways elsewhere.
Like QBezier hitting an infinite loop due to operating on NaN floating points.
Adding detection of this in a debug build of Qt is sure to help a lot of these
issues be detected much faster and so Qt helps people write code even faster.

Reviewed-By: Gunnar Sletta
---
 src/gui/painting/qtransform.cpp | 43 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/src/gui/painting/qtransform.cpp b/src/gui/painting/qtransform.cpp
index 988d678..80b7520 100644
--- a/src/gui/painting/qtransform.cpp
+++ b/src/gui/painting/qtransform.cpp
@@ -47,6 +47,7 @@
 #include "qpainterpath.h"
 #include "qvariant.h"
 #include <qmath.h>
+#include <qnumeric.h>
 
 #include <private/qbezier_p.h>
 
@@ -410,6 +411,12 @@ QTransform &QTransform::translate(qreal dx, qreal dy)
 {
     if (dx == 0 && dy == 0)
         return *this;
+#ifndef QT_NO_DEBUG
+    if (qIsNaN(dx) | qIsNaN(dy)) {
+        qWarning() << "QTransform::translate with NaN called";
+        return *this;
+    }
+#endif
 
     switch(inline_type()) {
     case TxNone:
@@ -447,6 +454,12 @@ QTransform &QTransform::translate(qreal dx, qreal dy)
 */
 QTransform QTransform::fromTranslate(qreal dx, qreal dy)
 {
+#ifndef QT_NO_DEBUG
+    if (qIsNaN(dx) | qIsNaN(dy)) {
+        qWarning() << "QTransform::fromTranslate with NaN called";
+        return QTransform();
+}
+#endif
     QTransform transform(1, 0, 0, 0, 1, 0, dx, dy, 1, true);
     if (dx == 0 && dy == 0)
         transform.m_type = TxNone;
@@ -466,6 +479,12 @@ QTransform & QTransform::scale(qreal sx, qreal sy)
 {
     if (sx == 1 && sy == 1)
         return *this;
+#ifndef QT_NO_DEBUG
+    if (qIsNaN(sx) | qIsNaN(sy)) {
+        qWarning() << "QTransform::scale with NaN called";
+        return *this;
+    }
+#endif
 
     switch(inline_type()) {
     case TxNone:
@@ -501,6 +520,12 @@ QTransform & QTransform::scale(qreal sx, qreal sy)
 */
 QTransform QTransform::fromScale(qreal sx, qreal sy)
 {
+#ifndef QT_NO_DEBUG
+    if (qIsNaN(sx) | qIsNaN(sy)) {
+        qWarning() << "QTransform::fromScale with NaN called";
+        return QTransform();
+}
+#endif
     QTransform transform(sx, 0, 0, 0, sy, 0, 0, 0, 1, true);
     if (sx == 1. && sy == 1.)
         transform.m_type = TxNone;
@@ -520,6 +545,12 @@ QTransform & QTransform::shear(qreal sh, qreal sv)
 {
     if (sh == 0 && sv == 0)
         return *this;
+#ifndef QT_NO_DEBUG
+    if (qIsNaN(sh) | qIsNaN(sv)) {
+        qWarning() << "QTransform::shear with NaN called";
+        return *this;
+    }
+#endif
 
     switch(inline_type()) {
     case TxNone:
@@ -575,6 +606,12 @@ QTransform & QTransform::rotate(qreal a, Qt::Axis axis)
 {
     if (a == 0)
         return *this;
+#ifndef QT_NO_DEBUG
+    if (qIsNaN(a)) {
+        qWarning() << "QTransform::rotate with NaN called";
+        return *this;
+    }
+#endif
 
     qreal sina = 0;
     qreal cosa = 0;
@@ -660,6 +697,12 @@ QTransform & QTransform::rotate(qreal a, Qt::Axis axis)
 */
 QTransform & QTransform::rotateRadians(qreal a, Qt::Axis axis)
 {
+#ifndef QT_NO_DEBUG
+    if (qIsNaN(a)) {
+        qWarning() << "QTransform::rotateRadians with NaN called";
+        return *this;
+    }
+#endif
     qreal sina = qSin(a);
     qreal cosa = qCos(a);
 
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