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
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
Reviewed-by: Paul Wicking <paul.wicking@qt.io>
(cherry picked from commit cca62a7360a117880eea5821fd7403d68a1431c8)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

3 files changed, 37 insertions, 8 deletions

diff --git a/src/corelib/tools/qpoint.cpp b/src/corelib/tools/qpoint.cpp
index 432fb33297..5b9ae5314d 100644
--- a/src/corelib/tools/qpoint.cpp
+++ b/src/corelib/tools/qpoint.cpp
@@ -762,14 +762,26 @@ QDebug operator<<(QDebug dbg, const QPointF &p)
     \fn bool operator==(const QPointF &p1, const QPointF &p2)
     \relates QPointF
 
-    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 operator!=(const QPointF &p1, const QPointF &p2);
     \relates QPointF
 
-    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 6f120b9d10..2d4c55ad85 100644
--- a/src/corelib/tools/qrect.cpp
+++ b/src/corelib/tools/qrect.cpp
@@ -2391,8 +2391,13 @@ 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
 */
 
 
@@ -2400,8 +2405,11 @@ 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 2cbaae117d..1bc7d4c15b 100644
--- a/src/corelib/tools/qsize.cpp
+++ b/src/corelib/tools/qsize.cpp
@@ -751,15 +751,24 @@ QSizeF QSizeF::scaled(const QSizeF &s, Qt::AspectRatioMode mode) const noexcept
     \fn bool operator==(const QSizeF &s1, const QSizeF &s2)
     \relates QSizeF
 
-    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 operator!=(const QSizeF &s1, const QSizeF &s2)
     \relates QSizeF
 
-    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.
 */
 
 /*!