Add a "note well" to QVectorXD re float precision.

Several bug-reports ask for clarifications/warnings in the doc for this
class, since it stores in float, but has a qreal interface (as per qt
convention).

Change-Id: I32ffcde3733866942134e881567eef367a5620f5
Task-number: QTBUG-8216
Reviewed-by: Rhys Weatherley

3 files changed, 15 insertions, 0 deletions

diff --git a/src/gui/math3d/qvector2d.cpp b/src/gui/math3d/qvector2d.cpp
index 7f5a937..1fccfc9 100644
--- a/src/gui/math3d/qvector2d.cpp
+++ b/src/gui/math3d/qvector2d.cpp
@@ -60,6 +60,11 @@ QT_BEGIN_NAMESPACE
     The QVector2D class can also be used to represent vertices in 2D space.
     We therefore do not need to provide a separate vertex class.
 
+    \bold{Note:} By design values in the QVector2D instance are stored as \c float.
+    This means that on platforms where the \c qreal arguments to QVector2D
+    functions are represented by \c double values, it is possible to
+    lose precision.
+
     \sa QVector3D, QVector4D, QQuaternion
 */
 
diff --git a/src/gui/math3d/qvector3d.cpp b/src/gui/math3d/qvector3d.cpp
index 2414b5f..7bf0400 100644
--- a/src/gui/math3d/qvector3d.cpp
+++ b/src/gui/math3d/qvector3d.cpp
@@ -63,6 +63,11 @@ QT_BEGIN_NAMESPACE
     The QVector3D class can also be used to represent vertices in 3D space.
     We therefore do not need to provide a separate vertex class.
 
+    \bold{Note:} By design values in the QVector3D instance are stored as \c float.
+    This means that on platforms where the \c qreal arguments to QVector3D
+    functions are represented by \c double values, it is possible to
+    lose precision.
+
     \sa QVector2D, QVector4D, QQuaternion
 */
 
diff --git a/src/gui/math3d/qvector4d.cpp b/src/gui/math3d/qvector4d.cpp
index 74dedc4..23befc0 100644
--- a/src/gui/math3d/qvector4d.cpp
+++ b/src/gui/math3d/qvector4d.cpp
@@ -59,6 +59,11 @@ QT_BEGIN_NAMESPACE
     The QVector4D class can also be used to represent vertices in 4D space.
     We therefore do not need to provide a separate vertex class.
 
+    \bold{Note:} By design values in the QVector4D instance are stored as \c float.
+    This means that on platforms where the \c qreal arguments to QVector4D
+    functions are represented by \c double values, it is possible to
+    lose precision.
+
     \sa QQuaternion, QVector2D, QVector3D
 */