QRectF/QPointF/QSizeF: document that operator== and != are fuzzy

This has been the case for a _very_ long time, and I can't
believe this hasn't been documented anywhere.

Change-Id: Ib157edf14e87a6f546c155496f70a760ab218cca
Pick-to: 5.15 5.12
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

3 files changed, 37 insertions, 8 deletions

diff --git a/src/corelib/tools/qpoint.cpp b/src/corelib/tools/qpoint.cpp
index e02fe2e41c..942ae995d5 100644
--- a/src/corelib/tools/qpoint.cpp
+++ b/src/corelib/tools/qpoint.cpp
@@ -755,13 +755,25 @@ size_t qHash(QPoint key, size_t seed) noexcept
 /*!
     \fn bool QPointF::operator==(const QPointF &p1, const QPointF &p2)
 
-    Returns \c true if \a p1 is equal to \a p2; otherwise returns \c false.
+    Returns \c true if \a p1 is approximately equal to \a p2; otherwise
+    returns \c false.
+
+    \warning This function does not check for strict equality; instead,
+    it uses a fuzzy comparison to compare the points' coordinates.
+
+    \sa qFuzzyCompare
 */
 
 /*!
     \fn bool QPointF::operator!=(const QPointF &p1, const QPointF &p2);
 
-    Returns \c true if \a p1 is not equal to \a p2; otherwise returns \c false.
+    Returns \c true if \a p1 is sufficiently different from \a p2;
+    otherwise returns \c false.
+
+    \warning This function does not check for strict inequality; instead,
+    it uses a fuzzy comparison to compare the points' coordinates.
+
+    \sa qFuzzyCompare
 */
 
 #ifndef QT_NO_DATASTREAM
diff --git a/src/corelib/tools/qrect.cpp b/src/corelib/tools/qrect.cpp
index 69dc24b5e7..326b0c0cd8 100644
--- a/src/corelib/tools/qrect.cpp
+++ b/src/corelib/tools/qrect.cpp
@@ -2371,8 +2371,13 @@ QRect QRectF::toAlignedRect() const noexcept
     \fn bool operator==(const QRectF &r1, const QRectF &r2)
     \relates QRectF
 
-    Returns \c true if the rectangles \a r1 and \a r2 are equal,
+    Returns \c true if the rectangles \a r1 and \a r2 are \b approximately equal,
     otherwise returns \c false.
+
+    \warning This function does not check for strict equality; instead,
+    it uses a fuzzy comparison to compare the rectangles' coordinates.
+
+    \sa qFuzzyCompare
 */
 
 
@@ -2380,8 +2385,11 @@ QRect QRectF::toAlignedRect() const noexcept
     \fn bool operator!=(const QRectF &r1, const QRectF &r2)
     \relates QRectF
 
-    Returns \c true if the rectangles \a r1 and \a r2 are different, otherwise
-    returns \c false.
+    Returns \c true if the rectangles \a r1 and \a r2 are sufficiently
+    different, otherwise returns \c false.
+
+    \warning This function does not check for strict inequality; instead,
+    it uses a fuzzy comparison to compare the rectangles' coordinates.
 */
 
 /*!
diff --git a/src/corelib/tools/qsize.cpp b/src/corelib/tools/qsize.cpp
index 57b2cc0319..788356002c 100644
--- a/src/corelib/tools/qsize.cpp
+++ b/src/corelib/tools/qsize.cpp
@@ -743,14 +743,23 @@ QSizeF QSizeF::scaled(const QSizeF &s, Qt::AspectRatioMode mode) const noexcept
 /*!
     \fn bool QSizeF::operator==(const QSizeF &s1, const QSizeF &s2)
 
-    Returns \c true if \a s1 and \a s2 are equal; otherwise returns
-    false.
+    Returns \c true if \a s1 and \a s2 are approximately equal; otherwise
+    returns false.
+
+    \warning This function does not check for strict equality; instead,
+    it uses a fuzzy comparison to compare the sizes' extents.
+
+    \sa qFuzzyCompare
 */
 
 /*!
     \fn bool QSizeF::operator!=(const QSizeF &s1, const QSizeF &s2)
 
-    Returns \c true if \a s1 and \a s2 are different; otherwise returns \c false.
+    Returns \c true if \a s1 and \a s2 are sufficiently different; otherwise
+    returns \c false.
+
+    \warning This function does not check for strict inequality; instead,
+    it uses a fuzzy comparison to compare the sizes' extents.
 */
 
 /*!