8 files changed, 255 insertions, 180 deletions
diff --git a/src/corelib/tools/qline.h b/src/corelib/tools/qline.h
index 8970a084bbf..05d73f45b43 100644
--- a/src/corelib/tools/qline.h
+++ b/src/corelib/tools/qline.h
@@ -114,12 +114,12 @@ constexpr inline QPoint QLine::p2() const
 
 constexpr inline int QLine::dx() const
 {
-    return pt2.x() - pt1.x();
+    return (pt2 - pt1).x();
 }
 
 constexpr inline int QLine::dy() const
 {
-    return pt2.y() - pt1.y();
+    return (pt2 - pt1).y();
 }
 
 constexpr inline void QLine::translate(const QPoint &point)
diff --git a/src/corelib/tools/qmargins.h b/src/corelib/tools/qmargins.h
index 8782b147afc..fb3d70f64fe 100644
--- a/src/corelib/tools/qmargins.h
+++ b/src/corelib/tools/qmargins.h
@@ -4,6 +4,7 @@
 #ifndef QMARGINS_H
 #define QMARGINS_H
 
+#include <QtCore/qcheckedint_impl.h>
 #include <QtCore/qcompare.h>
 #include <QtCore/qnamespace.h>
 
@@ -50,11 +51,34 @@ public:
 
     [[nodiscard]] constexpr inline QMarginsF toMarginsF() const noexcept;
 
+    friend constexpr inline QMargins operator+(const QMargins &m1, const QMargins &m2) noexcept;
+    friend constexpr inline QMargins operator-(const QMargins &m1, const QMargins &m2) noexcept;
+    friend constexpr inline QMargins operator+(const QMargins &lhs, int rhs) noexcept;
+    friend constexpr inline QMargins operator+(int lhs, const QMargins &rhs) noexcept;
+    friend constexpr inline QMargins operator-(const QMargins &lhs, int rhs) noexcept;
+    friend constexpr inline QMargins operator*(const QMargins &margins, int factor) noexcept;
+    friend constexpr inline QMargins operator*(int factor, const QMargins &margins) noexcept;
+    friend constexpr inline QMargins operator*(const QMargins &margins, qreal factor) noexcept;
+    friend constexpr inline QMargins operator*(qreal factor, const QMargins &margins) noexcept;
+    friend constexpr inline QMargins operator/(const QMargins &margins, int divisor);
+    friend constexpr inline QMargins operator/(const QMargins &margins, qreal divisor);
+    friend constexpr inline QMargins operator|(const QMargins &m1, const QMargins &m2) noexcept;
+
 private:
-    int m_left;
-    int m_top;
-    int m_right;
-    int m_bottom;
+    using Representation = QtPrivate::QCheckedIntegers::QCheckedInt<int>;
+
+    constexpr QMargins(Representation left,
+                       Representation top,
+                       Representation right,
+                       Representation bottom) noexcept
+        : m_left(left), m_top(top), m_right(right), m_bottom(bottom)
+    {
+    }
+
+    Representation m_left;
+    Representation m_top;
+    Representation m_right;
+    Representation m_bottom;
 
     friend constexpr bool comparesEqual(const QMargins &lhs, const QMargins &rhs) noexcept
     {
@@ -72,13 +96,13 @@ private:
     friend constexpr decltype(auto) get(M &&m) noexcept
     {
         if constexpr (I == 0)
-            return q23::forward_like<M>(m.m_left);
+            return q23::forward_like<M>(m.m_left).as_underlying();
         else if constexpr (I == 1)
-            return q23::forward_like<M>(m.m_top);
+            return q23::forward_like<M>(m.m_top).as_underlying();
         else if constexpr (I == 2)
-            return q23::forward_like<M>(m.m_right);
+            return q23::forward_like<M>(m.m_right).as_underlying();
         else if constexpr (I == 3)
-            return q23::forward_like<M>(m.m_bottom);
+            return q23::forward_like<M>(m.m_bottom).as_underlying();
     }
 };
 
@@ -105,74 +129,75 @@ constexpr inline bool QMargins::isNull() const noexcept
 { return m_left==0 && m_top==0 && m_right==0 && m_bottom==0; }
 
 constexpr inline int QMargins::left() const noexcept
-{ return m_left; }
+{ return m_left.value(); }
 
 constexpr inline int QMargins::top() const noexcept
-{ return m_top; }
+{ return m_top.value(); }
 
 constexpr inline int QMargins::right() const noexcept
-{ return m_right; }
+{ return m_right.value(); }
 
 constexpr inline int QMargins::bottom() const noexcept
-{ return m_bottom; }
+{ return m_bottom.value(); }
 
 
 constexpr inline void QMargins::setLeft(int aleft) noexcept
-{ m_left = aleft; }
+{ m_left.setValue(aleft); }
 
 constexpr inline void QMargins::setTop(int atop) noexcept
-{ m_top = atop; }
+{ m_top.setValue(atop); }
 
 constexpr inline void QMargins::setRight(int aright) noexcept
-{ m_right = aright; }
+{ m_right.setValue(aright); }
 
 constexpr inline void QMargins::setBottom(int abottom) noexcept
-{ m_bottom = abottom; }
+{ m_bottom.setValue(abottom); }
 
 constexpr inline QMargins operator+(const QMargins &m1, const QMargins &m2) noexcept
 {
-    return QMargins(m1.left() + m2.left(), m1.top() + m2.top(),
-                    m1.right() + m2.right(), m1.bottom() + m2.bottom());
+    return QMargins(m1.m_left + m2.m_left, m1.m_top + m2.m_top,
+                    m1.m_right + m2.m_right, m1.m_bottom + m2.m_bottom);
 }
 
 constexpr inline QMargins operator-(const QMargins &m1, const QMargins &m2) noexcept
 {
-    return QMargins(m1.left() - m2.left(), m1.top() - m2.top(),
-                    m1.right() - m2.right(), m1.bottom() - m2.bottom());
+    return QMargins(m1.m_left - m2.m_left, m1.m_top - m2.m_top,
+                    m1.m_right - m2.m_right, m1.m_bottom - m2.m_bottom);
 }
 
 constexpr inline QMargins operator+(const QMargins &lhs, int rhs) noexcept
 {
-    return QMargins(lhs.left() + rhs, lhs.top() + rhs,
-                    lhs.right() + rhs, lhs.bottom() + rhs);
+    return QMargins(lhs.m_left + rhs, lhs.m_top + rhs,
+                    lhs.m_right + rhs, lhs.m_bottom + rhs);
 }
 
 constexpr inline QMargins operator+(int lhs, const QMargins &rhs) noexcept
 {
-    return QMargins(rhs.left() + lhs, rhs.top() + lhs,
-                    rhs.right() + lhs, rhs.bottom() + lhs);
+    return QMargins(rhs.m_left + lhs, rhs.m_top + lhs,
+                    rhs.m_right + lhs, rhs.m_bottom + lhs);
 }
 
 constexpr inline QMargins operator-(const QMargins &lhs, int rhs) noexcept
 {
-    return QMargins(lhs.left() - rhs, lhs.top() - rhs,
-                    lhs.right() - rhs, lhs.bottom() - rhs);
+    return QMargins(lhs.m_left - rhs, lhs.m_top - rhs,
+                    lhs.m_right - rhs, lhs.m_bottom - rhs);
 }
 
 constexpr inline QMargins operator*(const QMargins &margins, int factor) noexcept
 {
-    return QMargins(margins.left() * factor, margins.top() * factor,
-                    margins.right() * factor, margins.bottom() * factor);
+    return QMargins(margins.m_left * factor, margins.m_top * factor,
+                    margins.m_right * factor, margins.m_bottom * factor);
 }
 
 constexpr inline QMargins operator*(int factor, const QMargins &margins) noexcept
 {
-    return QMargins(margins.left() * factor, margins.top() * factor,
-                    margins.right() * factor, margins.bottom() * factor);
+    return QMargins(margins.m_left * factor, margins.m_top * factor,
+                    margins.m_right * factor, margins.m_bottom * factor);
 }
 
 constexpr inline QMargins operator*(const QMargins &margins, qreal factor) noexcept
 {
+    // Deliberately using left(), top() etc. (checked ints don't have FP arithmetic)
     return QMargins(qRound(margins.left() * factor), qRound(margins.top() * factor),
                     qRound(margins.right() * factor), qRound(margins.bottom() * factor));
 }
@@ -185,20 +210,21 @@ constexpr inline QMargins operator*(qreal factor, const QMargins &margins) noexc
 
 constexpr inline QMargins operator/(const QMargins &margins, int divisor)
 {
-    return QMargins(margins.left() / divisor, margins.top() / divisor,
-                    margins.right() / divisor, margins.bottom() / divisor);
+    return QMargins(margins.m_left / divisor, margins.m_top / divisor,
+                    margins.m_right / divisor, margins.m_bottom / divisor);
 }
 
 constexpr inline QMargins operator/(const QMargins &margins, qreal divisor)
 {
+    Q_ASSERT(!qFuzzyIsNull(divisor));
     return QMargins(qRound(margins.left() / divisor), qRound(margins.top() / divisor),
                     qRound(margins.right() / divisor), qRound(margins.bottom() / divisor));
 }
 
 constexpr inline QMargins operator|(const QMargins &m1, const QMargins &m2) noexcept
 {
-    return QMargins(qMax(m1.left(), m2.left()), qMax(m1.top(), m2.top()),
-                    qMax(m1.right(), m2.right()), qMax(m1.bottom(), m2.bottom()));
+    return QMargins(qMax(m1.m_left, m2.m_left), qMax(m1.m_top, m2.m_top),
+                    qMax(m1.m_right, m2.m_right), qMax(m1.m_bottom, m2.m_bottom));
 }
 
 constexpr inline QMargins &QMargins::operator+=(const QMargins &margins) noexcept
diff --git a/src/corelib/tools/qpoint.h b/src/corelib/tools/qpoint.h
index d9a0fa53235..c652ef1daf8 100644
--- a/src/corelib/tools/qpoint.h
+++ b/src/corelib/tools/qpoint.h
@@ -4,6 +4,7 @@
 #ifndef QPOINT_H
 #define QPOINT_H
 
+#include <QtCore/qcheckedint_impl.h>
 #include <QtCore/qcompare.h>
 #include <QtCore/qnamespace.h>
 #include <QtCore/qnumeric.h>
@@ -21,6 +22,7 @@ QT_ENABLE_P0846_SEMANTICS_FOR(get)
 
 class QDataStream;
 class QPointF;
+class QRect;
 
 class QPoint
 {
@@ -52,7 +54,7 @@ public:
     constexpr inline QPoint &operator/=(qreal divisor);
 
     constexpr static inline int dotProduct(const QPoint &p1, const QPoint &p2)
-    { return p1.xp * p2.xp + p1.yp * p2.yp; }
+    { return int(p1.xp * p2.xp + p1.yp * p2.yp); }
 
 private:
     friend constexpr bool comparesEqual(const QPoint &p1, const QPoint &p2) noexcept
@@ -63,15 +65,15 @@ private:
     friend constexpr inline QPoint operator-(const QPoint &p1, const QPoint &p2) noexcept
     { return QPoint(p1.xp - p2.xp, p1.yp - p2.yp); }
     friend constexpr inline QPoint operator*(const QPoint &p, float factor)
-    { return QPoint(qRound(p.xp * factor), qRound(p.yp * factor)); }
+    { return QPoint(qRound(p.x() * factor), qRound(p.y() * factor)); }
     friend constexpr inline QPoint operator*(const QPoint &p, double factor)
-    { return QPoint(qRound(p.xp * factor), qRound(p.yp * factor)); }
+    { return QPoint(qRound(p.x() * factor), qRound(p.y() * factor)); }
     friend constexpr inline QPoint operator*(const QPoint &p, int factor) noexcept
     { return QPoint(p.xp * factor, p.yp * factor); }
     friend constexpr inline QPoint operator*(float factor, const QPoint &p)
-    { return QPoint(qRound(p.xp * factor), qRound(p.yp * factor)); }
+    { return QPoint(qRound(p.x() * factor), qRound(p.y() * factor)); }
     friend constexpr inline QPoint operator*(double factor, const QPoint &p)
-    { return QPoint(qRound(p.xp * factor), qRound(p.yp * factor)); }
+    { return QPoint(qRound(p.x() * factor), qRound(p.y() * factor)); }
     friend constexpr inline QPoint operator*(int factor, const QPoint &p) noexcept
     { return QPoint(p.xp * factor, p.yp * factor); }
     friend constexpr inline QPoint operator+(const QPoint &p) noexcept
@@ -79,7 +81,10 @@ private:
     friend constexpr inline QPoint operator-(const QPoint &p) noexcept
     { return QPoint(-p.xp, -p.yp); }
     friend constexpr inline QPoint operator/(const QPoint &p, qreal c)
-    { return QPoint(qRound(p.xp / c), qRound(p.yp / c)); }
+    {
+        Q_ASSERT(!qFuzzyIsNull(c));
+        return QPoint(qRound(p.x() / c), qRound(p.y() / c));
+    }
 
 public:
 #if defined(Q_OS_DARWIN) || defined(Q_QDOC)
@@ -88,9 +93,14 @@ public:
     [[nodiscard]] constexpr inline QPointF toPointF() const noexcept;
 
 private:
-    friend class QTransform;
-    int xp;
-    int yp;
+    using Representation = QtPrivate::QCheckedIntegers::QCheckedInt<int>;
+
+    friend class QRect;
+    constexpr QPoint(Representation xpos, Representation ypos) noexcept
+        : xp(xpos), yp(ypos) {}
+
+    Representation xp;
+    Representation yp;
 
     template <std::size_t I,
               typename P,
@@ -99,9 +109,9 @@ private:
     friend constexpr decltype(auto) get(P &&p) noexcept
     {
         if constexpr (I == 0)
-            return q23::forward_like<P>(p.xp);
+            return q23::forward_like<P>(p.xp).as_underlying();
         else if constexpr (I == 1)
-            return q23::forward_like<P>(p.yp);
+            return q23::forward_like<P>(p.yp).as_underlying();
     }
 };
 
@@ -130,37 +140,37 @@ constexpr inline bool QPoint::isNull() const noexcept
 
 constexpr inline int QPoint::x() const noexcept
 {
-    return xp;
+    return xp.value();
 }
 
 constexpr inline int QPoint::y() const noexcept
 {
-    return yp;
+    return yp.value();
 }
 
 constexpr inline void QPoint::setX(int xpos) noexcept
 {
-    xp = xpos;
+    xp.setValue(xpos);
 }
 
 constexpr inline void QPoint::setY(int ypos) noexcept
 {
-    yp = ypos;
+    yp.setValue(ypos);
 }
 
 inline int constexpr QPoint::manhattanLength() const
 {
-    return qAbs(x()) + qAbs(y());
+    return (qAbs(xp) + qAbs(yp)).value();
 }
 
 constexpr inline int &QPoint::rx() noexcept
 {
-    return xp;
+    return xp.as_underlying();
 }
 
 constexpr inline int &QPoint::ry() noexcept
 {
-    return yp;
+    return yp.as_underlying();
 }
 
 constexpr inline QPoint &QPoint::operator+=(const QPoint &p)
@@ -179,15 +189,15 @@ constexpr inline QPoint &QPoint::operator-=(const QPoint &p)
 
 constexpr inline QPoint &QPoint::operator*=(float factor)
 {
-    xp = qRound(xp * factor);
-    yp = qRound(yp * factor);
+    xp.setValue(qRound(x() * factor));
+    yp.setValue(qRound(y() * factor));
     return *this;
 }
 
 constexpr inline QPoint &QPoint::operator*=(double factor)
 {
-    xp = qRound(xp * factor);
-    yp = qRound(yp * factor);
+    xp.setValue(qRound(x() * factor));
+    yp.setValue(qRound(y() * factor));
     return *this;
 }
 
@@ -200,8 +210,9 @@ constexpr inline QPoint &QPoint::operator*=(int factor)
 
 constexpr inline QPoint &QPoint::operator/=(qreal c)
 {
-    xp = qRound(xp / c);
-    yp = qRound(yp / c);
+    Q_ASSERT(!qFuzzyIsNull(c));
+    xp.setValue(qRound(int(xp) / c));
+    yp.setValue(qRound(int(yp) / c));
     return *this;
 }
 
diff --git a/src/corelib/tools/qrect.cpp b/src/corelib/tools/qrect.cpp
index a82183bc804..6ca3caa0f44 100644
--- a/src/corelib/tools/qrect.cpp
+++ b/src/corelib/tools/qrect.cpp
@@ -788,7 +788,7 @@ QRect QRect::normalized() const noexcept
 
 bool QRect::contains(const QPoint &p, bool proper) const noexcept
 {
-    int l, r;
+    Representation l, r;
     if (x2 < x1 - 1) {
         l = x2 + 1;
         r = x1 - 1;
@@ -803,7 +803,7 @@ bool QRect::contains(const QPoint &p, bool proper) const noexcept
         if (p.x() < l || p.x() > r)
             return false;
     }
-    int t, b;
+    Representation t, b;
     if (y2 < y1 - 1) {
         t = y2 + 1;
         b = y1 - 1;
@@ -855,15 +855,15 @@ bool QRect::contains(const QRect &r, bool proper) const noexcept
     if (isNull() || r.isNull())
         return false;
 
-    int l1 = x1;
-    int r1 = x1 - 1;
+    Representation l1 = x1;
+    Representation r1 = x1 - 1;
     if (x2 < x1 - 1)
         l1 = x2 + 1;
     else
         r1 = x2;
 
-    int l2 = r.x1;
-    int r2 = r.x1 - 1;
+    Representation l2 = r.x1;
+    Representation r2 = r.x1 - 1;
     if (r.x2 < r.x1 - 1)
         l2 = r.x2 + 1;
     else
@@ -877,15 +877,15 @@ bool QRect::contains(const QRect &r, bool proper) const noexcept
             return false;
     }
 
-    int t1 = y1;
-    int b1 = y1 - 1;
+    Representation t1 = y1;
+    Representation b1 = y1 - 1;
     if (y2 < y1 - 1)
         t1 = y2 + 1;
     else
         b1 = y2;
 
-    int t2 = r.y1;
-    int b2 = r.y1 - 1;
+    Representation t2 = r.y1;
+    Representation b2 = r.y1 - 1;
     if (r.y2 < r.y1 - 1)
         t2 = r.y2 + 1;
     else
@@ -935,29 +935,29 @@ QRect QRect::operator|(const QRect &r) const noexcept
     if (r.isNull())
         return *this;
 
-    int l1 = x1;
-    int r1 = x1 - 1;
+    Representation l1 = x1;
+    Representation r1 = x1 - 1;
     if (x2 < x1 - 1)
         l1 = x2 + 1;
     else
         r1 = x2;
 
-    int l2 = r.x1;
-    int r2 = r.x1 - 1;
+    Representation l2 = r.x1;
+    Representation r2 = r.x1 - 1;
     if (r.x2 < r.x1 - 1)
         l2 = r.x2 + 1;
     else
         r2 = r.x2;
 
-    int t1 = y1;
-    int b1 = y1 - 1;
+    Representation t1 = y1;
+    Representation b1 = y1 - 1;
     if (y2 < y1 - 1)
         t1 = y2 + 1;
     else
         b1 = y2;
 
-    int t2 = r.y1;
-    int b2 = r.y1 - 1;
+    Representation t2 = r.y1;
+    Representation b2 = r.y1 - 1;
     if (r.y2 < r.y1 - 1)
         t2 = r.y2 + 1;
     else
@@ -997,15 +997,15 @@ QRect QRect::operator&(const QRect &r) const noexcept
     if (isNull() || r.isNull())
         return QRect();
 
-    int l1 = x1;
-    int r1 = x2;
+    Representation l1 = x1;
+    Representation r1 = x2;
     if (x2 < x1 - 1) {
         l1 = x2 + 1;
         r1 = x1 - 1;
     }
 
-    int l2 = r.x1;
-    int r2 = r.x2;
+    Representation l2 = r.x1;
+    Representation r2 = r.x2;
     if (r.x2 < r.x1 - 1) {
         l2 = r.x2 + 1;
         r2 = r.x1 - 1;
@@ -1014,15 +1014,15 @@ QRect QRect::operator&(const QRect &r) const noexcept
     if (l1 > r2 || l2 > r1)
         return QRect();
 
-    int t1 = y1;
-    int b1 = y2;
+    Representation t1 = y1;
+    Representation b1 = y2;
     if (y2 < y1 - 1) {
         t1 = y2 + 1;
         b1 = y1 - 1;
     }
 
-    int t2 = r.y1;
-    int b2 = r.y2;
+    Representation t2 = r.y1;
+    Representation b2 = r.y2;
     if (r.y2 < r.y1 - 1) {
         t2 = r.y2 + 1;
         b2 = r.y1 - 1;
@@ -1069,15 +1069,15 @@ bool QRect::intersects(const QRect &r) const noexcept
     if (isNull() || r.isNull())
         return false;
 
-    int l1 = x1;
-    int r1 = x2;
+    Representation l1 = x1;
+    Representation r1 = x2;
     if (x2 < x1 - 1) {
         l1 = x2 + 1;
         r1 = x1 - 1;
     }
 
-    int l2 = r.x1;
-    int r2 = r.x2;
+    Representation l2 = r.x1;
+    Representation r2 = r.x2;
     if (r.x2 < r.x1 - 1) {
         l2 = r.x2 + 1;
         r2 = r.x1 - 1;
@@ -1086,15 +1086,15 @@ bool QRect::intersects(const QRect &r) const noexcept
     if (l1 > r2 || l2 > r1)
         return false;
 
-    int t1 = y1;
-    int b1 = y2;
+    Representation t1 = y1;
+    Representation b1 = y2;
     if (y2 < y1 - 1) {
         t1 = y2 + 1;
         b1 = y1 - 1;
     }
 
-    int t2 = r.y1;
-    int b2 = r.y2;
+    Representation t2 = r.y1;
+    Representation b2 = r.y2;
     if (r.y2 < r.y1 - 1) {
         t2 = r.y2 + 1;
         b2 = r.y1 - 1;
diff --git a/src/corelib/tools/qrect.h b/src/corelib/tools/qrect.h
index fb938b00560..04f3b9a6d67 100644
--- a/src/corelib/tools/qrect.h
+++ b/src/corelib/tools/qrect.h
@@ -4,6 +4,7 @@
 #ifndef QRECT_H
 #define QRECT_H
 
+#include <QtCore/qcheckedint_impl.h>
 #include <QtCore/qhashfunctions.h>
 #include <QtCore/qmargins.h>
 #include <QtCore/qsize.h>
@@ -132,10 +133,20 @@ public:
     [[nodiscard]] constexpr inline QRectF toRectF() const noexcept;
 
 private:
-    int x1;
-    int y1;
-    int x2;
-    int y2;
+    using Representation = QtPrivate::QCheckedIntegers::QCheckedInt<int>;
+
+    constexpr QRect(Representation aleft,
+                    Representation atop,
+                    Representation awidth,
+                    Representation aheight) noexcept
+        : x1(aleft), y1(atop),
+          x2(aleft + awidth - 1), y2(atop + aheight - 1)
+    {}
+
+    Representation x1;
+    Representation y1;
+    Representation x2;
+    Representation y2;
 };
 Q_DECLARE_TYPEINFO(QRect, Q_RELOCATABLE_TYPE);
 
@@ -153,16 +164,24 @@ Q_CORE_EXPORT QDataStream &operator>>(QDataStream &, QRect &);
  *****************************************************************************/
 
 constexpr inline QRect::QRect(int aleft, int atop, int awidth, int aheight) noexcept
-    : x1(aleft), y1(atop), x2(aleft + awidth - 1), y2(atop + aheight - 1) {}
+    : QRect(Representation(aleft), Representation(atop), Representation(awidth), Representation(aheight)) {}
 
 constexpr inline QRect::QRect(const QPoint &atopLeft, const QPoint &abottomRight) noexcept
     : x1(atopLeft.x()), y1(atopLeft.y()), x2(abottomRight.x()), y2(abottomRight.y()) {}
 
 constexpr inline QRect::QRect(const QPoint &atopLeft, const QSize &asize) noexcept
-    : x1(atopLeft.x()), y1(atopLeft.y()), x2(atopLeft.x()+asize.width() - 1), y2(atopLeft.y()+asize.height() - 1) {}
+    : x1(atopLeft.x()), y1(atopLeft.y()), x2(x1 + asize.width() - 1), y2(y1 + asize.height() - 1) {}
 
 constexpr inline bool QRect::isNull() const noexcept
-{ return x2 == x1 - 1 && y2 == y1 - 1; }
+{
+    // This strange behavior is here for backwards compatibility -- a
+    // rectangle spanning from INT_MIN to INT_MAX is considered null.
+    constexpr Representation minInt((std::numeric_limits<int>::min)());
+    constexpr Representation maxInt((std::numeric_limits<int>::max)());
+    const auto adjustedX1 = Q_UNLIKELY(x1 == minInt) ? maxInt : x1 - 1;
+    const auto adjustedY1 = Q_UNLIKELY(y1 == minInt) ? maxInt : y1 - 1;
+    return x2 == adjustedX1 && y2 == adjustedY1;
+}
 
 constexpr inline bool QRect::isEmpty() const noexcept
 { return x1 > x2 || y1 > y2; }
@@ -171,52 +190,52 @@ constexpr inline bool QRect::isValid() const noexcept
 { return x1 <= x2 && y1 <= y2; }
 
 constexpr inline int QRect::left() const noexcept
-{ return x1; }
+{ return x1.value(); }
 
 constexpr inline int QRect::top() const noexcept
-{ return y1; }
+{ return y1.value(); }
 
 constexpr inline int QRect::right() const noexcept
-{ return x2; }
+{ return x2.value(); }
 
 constexpr inline int QRect::bottom() const noexcept
-{ return y2; }
+{ return y2.value(); }
 
 constexpr inline int QRect::x() const noexcept
-{ return x1; }
+{ return x1.value(); }
 
 constexpr inline int QRect::y() const noexcept
-{ return y1; }
+{ return y1.value(); }
 
 constexpr inline void QRect::setLeft(int pos) noexcept
-{ x1 = pos; }
+{ x1.setValue(pos); }
 
 constexpr inline void QRect::setTop(int pos) noexcept
-{ y1 = pos; }
+{ y1.setValue(pos); }
 
 constexpr inline void QRect::setRight(int pos) noexcept
-{ x2 = pos; }
+{ x2.setValue(pos); }
 
 constexpr inline void QRect::setBottom(int pos) noexcept
-{ y2 = pos; }
+{ y2.setValue(pos); }
 
 constexpr inline void QRect::setTopLeft(const QPoint &p) noexcept
-{ x1 = p.x(); y1 = p.y(); }
+{ x1.setValue(p.x()); y1.setValue(p.y()); }
 
 constexpr inline void QRect::setBottomRight(const QPoint &p) noexcept
-{ x2 = p.x(); y2 = p.y(); }
+{ x2.setValue(p.x()); y2.setValue(p.y()); }
 
 constexpr inline void QRect::setTopRight(const QPoint &p) noexcept
-{ x2 = p.x(); y1 = p.y(); }
+{ x2.setValue(p.x()); y1.setValue(p.y()); }
 
 constexpr inline void QRect::setBottomLeft(const QPoint &p) noexcept
-{ x1 = p.x(); y2 = p.y(); }
+{ x1.setValue(p.x()); y2.setValue(p.y()); }
 
 constexpr inline void QRect::setX(int ax) noexcept
-{ x1 = ax; }
+{ x1.setValue(ax); }
 
 constexpr inline void QRect::setY(int ay) noexcept
-{ y1 = ay; }
+{ y1.setValue(ay); }
 
 constexpr inline QPoint QRect::topLeft() const noexcept
 { return QPoint(x1, y1); }
@@ -231,13 +250,17 @@ constexpr inline QPoint QRect::bottomLeft() const noexcept
 { return QPoint(x1, y2); }
 
 constexpr inline QPoint QRect::center() const noexcept
-{ return QPoint(int((qint64(x1)+x2)/2), int((qint64(y1)+y2)/2)); } // cast avoids overflow on addition
+{
+    // cast avoids overflow on addition
+    return QPoint(int((qint64(x1.value()) + x2.value()) / 2),
+                  int((qint64(y1.value()) + y2.value()) / 2));
+}
 
 constexpr inline int QRect::width() const noexcept
-{ return  x2 - x1 + 1; }
+{ return (x2 - x1 + 1).value(); }
 
 constexpr inline int QRect::height() const noexcept
-{ return  y2 - y1 + 1; }
+{ return (y2 - y1 + 1).value(); }
 
 constexpr inline QSize QRect::size() const noexcept
 { return QSize(width(), height()); }
@@ -269,36 +292,38 @@ constexpr inline QRect QRect::transposed() const noexcept
 
 constexpr inline void QRect::moveTo(int ax, int ay) noexcept
 {
-    x2 += ax - x1;
-    y2 += ay - y1;
-    x1 = ax;
-    y1 = ay;
+    Representation rax(ax);
+    Representation ray(ay);
+    x2 += rax - x1;
+    y2 += ray - y1;
+    x1 = rax;
+    y1 = ray;
 }
 
 constexpr inline void QRect::moveTo(const QPoint &p) noexcept
 {
-    x2 += p.x() - x1;
-    y2 += p.y() - y1;
-    x1 = p.x();
-    y1 = p.y();
+    x2 += Representation(p.x()) - x1;
+    y2 += Representation(p.y()) - y1;
+    x1 = Representation(p.x());
+    y1 = Representation(p.y());
 }
 
 constexpr inline void QRect::moveLeft(int pos) noexcept
-{ x2 += (pos - x1); x1 = pos; }
+{ x2 += (pos - x1); x1.setValue(pos); }
 
 constexpr inline void QRect::moveTop(int pos) noexcept
-{ y2 += (pos - y1); y1 = pos; }
+{ y2 += (pos - y1); y1.setValue(pos); }
 
 constexpr inline void QRect::moveRight(int pos) noexcept
 {
     x1 += (pos - x2);
-    x2 = pos;
+    x2.setValue(pos);
 }
 
 constexpr inline void QRect::moveBottom(int pos) noexcept
 {
     y1 += (pos - y2);
-    y2 = pos;
+    y2.setValue(pos);
 }
 
 constexpr inline void QRect::moveTopLeft(const QPoint &p) noexcept
@@ -327,8 +352,8 @@ constexpr inline void QRect::moveBottomLeft(const QPoint &p) noexcept
 
 constexpr inline void QRect::moveCenter(const QPoint &p) noexcept
 {
-    int w = x2 - x1;
-    int h = y2 - y1;
+    auto w = x2 - x1;
+    auto h = y2 - y1;
     x1 = p.x() - w/2;
     y1 = p.y() - h/2;
     x2 = x1 + w;
@@ -337,34 +362,34 @@ constexpr inline void QRect::moveCenter(const QPoint &p) noexcept
 
 constexpr inline void QRect::getRect(int *ax, int *ay, int *aw, int *ah) const
 {
-    *ax = x1;
-    *ay = y1;
-    *aw = x2 - x1 + 1;
-    *ah = y2 - y1 + 1;
+    *ax = x1.value();
+    *ay = y1.value();
+    *aw = (x2 - x1 + 1).value();
+    *ah = (y2 - y1 + 1).value();
 }
 
 constexpr inline void QRect::setRect(int ax, int ay, int aw, int ah) noexcept
 {
-    x1 = ax;
-    y1 = ay;
-    x2 = (ax + aw - 1);
-    y2 = (ay + ah - 1);
+    x1.setValue(ax);
+    y1.setValue(ay);
+    x2 = (x1 + aw - 1);
+    y2 = (y1 + ah - 1);
 }
 
 constexpr inline void QRect::getCoords(int *xp1, int *yp1, int *xp2, int *yp2) const
 {
-    *xp1 = x1;
-    *yp1 = y1;
-    *xp2 = x2;
-    *yp2 = y2;
+    *xp1 = x1.value();
+    *yp1 = y1.value();
+    *xp2 = x2.value();
+    *yp2 = y2.value();
 }
 
 constexpr inline void QRect::setCoords(int xp1, int yp1, int xp2, int yp2) noexcept
 {
-    x1 = xp1;
-    y1 = yp1;
-    x2 = xp2;
-    y2 = yp2;
+    x1.setValue(xp1);
+    y1.setValue(yp1);
+    x2.setValue(xp2);
+    y2.setValue(yp2);
 }
 
 constexpr inline QRect QRect::adjusted(int xp1, int yp1, int xp2, int yp2) const noexcept
@@ -648,7 +673,10 @@ constexpr inline QRectF::QRectF(const QPointF &atopLeft, const QPointF &abottomR
 }
 
 constexpr inline QRectF::QRectF(const QRect &r) noexcept
-    : xp(r.x()), yp(r.y()), w(r.width()), h(r.height())
+    : xp(r.x()),
+      yp(r.y()),
+      w(qint64(r.right()) - r.left() + 1),
+      h(qint64(r.bottom()) - r.top() + 1)
 {
 }
 
diff --git a/src/corelib/tools/qsize.cpp b/src/corelib/tools/qsize.cpp
index 27ff1d164d1..08e89748ac7 100644
--- a/src/corelib/tools/qsize.cpp
+++ b/src/corelib/tools/qsize.cpp
@@ -192,19 +192,19 @@ QSize QSize::scaled(const QSize &s, Qt::AspectRatioMode mode) const noexcept
         return s;
     } else {
         bool useHeight;
-        qint64 rw = qint64(s.ht) * qint64(wd) / qint64(ht);
+        qint64 rw = qint64(s.height()) * qint64(width()) / qint64(height());
 
         if (mode == Qt::KeepAspectRatio) {
-            useHeight = (rw <= s.wd);
+            useHeight = (rw <= s.width());
         } else { // mode == Qt::KeepAspectRatioByExpanding
-            useHeight = (rw >= s.wd);
+            useHeight = (rw >= s.width());
         }
 
         if (useHeight) {
-            return QSize(rw, s.ht);
+            return QSize(int(rw), s.height());
         } else {
-            return QSize(s.wd,
-                         qint32(qint64(s.wd) * qint64(ht) / qint64(wd)));
+            return QSize(s.width(),
+                         qint32(qint64(s.width()) * qint64(height()) / qint64(width())));
         }
     }
 }
diff --git a/src/corelib/tools/qsize.h b/src/corelib/tools/qsize.h
index 67f7146201c..75f1f8e70fb 100644
--- a/src/corelib/tools/qsize.h
+++ b/src/corelib/tools/qsize.h
@@ -4,6 +4,7 @@
 #ifndef QSIZE_H
 #define QSIZE_H
 
+#include <QtCore/qcheckedint_impl.h>
 #include <QtCore/qnamespace.h>
 #include <QtCore/qhashfunctions.h>
 #include <QtCore/qmargins.h>
@@ -47,9 +48,9 @@ public:
     [[nodiscard]] constexpr inline QSize boundedTo(const QSize &) const noexcept;
 
     [[nodiscard]] constexpr QSize grownBy(QMargins m) const noexcept
-    { return {width() + m.left() + m.right(), height() + m.top() + m.bottom()}; }
+    { return {wd + m.left() + m.right(), ht + m.top() + m.bottom()}; }
     [[nodiscard]] constexpr QSize shrunkBy(QMargins m) const noexcept
-    { return {width() - m.left() - m.right(), height() - m.top() - m.bottom()}; }
+    { return {wd - m.left() - m.right(), ht - m.top() - m.bottom()}; }
 
     constexpr inline int &rwidth() noexcept;
     constexpr inline int &rheight() noexcept;
@@ -68,11 +69,14 @@ private:
     friend inline constexpr QSize operator-(const QSize &s1, const QSize &s2) noexcept
     { return QSize(s1.wd - s2.wd, s1.ht - s2.ht); }
     friend inline constexpr QSize operator*(const QSize &s, qreal c) noexcept
-    { return QSize(qRound(s.wd * c), qRound(s.ht * c)); }
+    { return QSize(qRound(s.width() * c), qRound(s.height() * c)); }
     friend inline constexpr QSize operator*(qreal c, const QSize &s) noexcept
     { return s * c; }
     friend inline QSize operator/(const QSize &s, qreal c)
-    { Q_ASSERT(!qFuzzyIsNull(c)); return QSize(qRound(s.wd / c), qRound(s.ht / c)); }
+    {
+        Q_ASSERT(!qFuzzyIsNull(c));
+        return QSize(qRound(s.width() / c), qRound(s.height() / c));
+    }
     friend inline constexpr size_t qHash(const QSize &, size_t) noexcept;
 
 public:
@@ -83,8 +87,14 @@ public:
     [[nodiscard]] inline constexpr QSizeF toSizeF() const noexcept;
 
 private:
-    int wd;
-    int ht;
+    using Representation = QtPrivate::QCheckedIntegers::QCheckedInt<int>;
+
+    constexpr QSize(Representation w, Representation h) noexcept
+        : wd(w), ht(h)
+    {}
+
+    Representation wd;
+    Representation ht;
 
     template <std::size_t I,
               typename S,
@@ -93,9 +103,9 @@ private:
     friend constexpr decltype(auto) get(S &&s) noexcept
     {
         if constexpr (I == 0)
-            return q23::forward_like<S>(s.wd);
+            return q23::forward_like<S>(s.wd).as_underlying();
         else if constexpr (I == 1)
-            return q23::forward_like<S>(s.ht);
+            return q23::forward_like<S>(s.ht).as_underlying();
     }
 };
 Q_DECLARE_TYPEINFO(QSize, Q_RELOCATABLE_TYPE);
@@ -128,16 +138,16 @@ constexpr inline bool QSize::isValid() const noexcept
 { return wd >= 0 && ht >= 0; }
 
 constexpr inline int QSize::width() const noexcept
-{ return wd; }
+{ return wd.value(); }
 
 constexpr inline int QSize::height() const noexcept
-{ return ht; }
+{ return ht.value(); }
 
 constexpr inline void QSize::setWidth(int w) noexcept
-{ wd = w; }
+{ wd.setValue(w); }
 
 constexpr inline void QSize::setHeight(int h) noexcept
-{ ht = h; }
+{ ht.setValue(h); }
 
 constexpr inline QSize QSize::transposed() const noexcept
 { return QSize(ht, wd); }
@@ -152,10 +162,10 @@ inline QSize QSize::scaled(int w, int h, Qt::AspectRatioMode mode) const noexcep
 { return scaled(QSize(w, h), mode); }
 
 constexpr inline int &QSize::rwidth() noexcept
-{ return wd; }
+{ return wd.as_underlying(); }
 
 constexpr inline int &QSize::rheight() noexcept
-{ return ht; }
+{ return ht.as_underlying(); }
 
 constexpr inline QSize &QSize::operator+=(const QSize &s) noexcept
 {
@@ -173,19 +183,19 @@ constexpr inline QSize &QSize::operator-=(const QSize &s) noexcept
 
 constexpr inline QSize &QSize::operator*=(qreal c) noexcept
 {
-    wd = qRound(wd * c);
-    ht = qRound(ht * c);
+    wd.setValue(qRound(width() * c));
+    ht.setValue(qRound(height() * c));
     return *this;
 }
 
 constexpr inline size_t qHash(const QSize &s, size_t seed = 0) noexcept
-{ return qHashMulti(seed, s.wd, s.ht); }
+{ return qHashMulti(seed, s.width(), s.height()); }
 
 inline QSize &QSize::operator/=(qreal c)
 {
     Q_ASSERT(!qFuzzyIsNull(c));
-    wd = qRound(wd / c);
-    ht = qRound(ht / c);
+    wd.setValue(qRound(width() / c));
+    ht.setValue(qRound(height() / c));
     return *this;
 }
 
diff --git a/src/gui/painting/qtransform.cpp b/src/gui/painting/qtransform.cpp
index 768e92a15bf..1ea63f40965 100644
--- a/src/gui/painting/qtransform.cpp
+++ b/src/gui/painting/qtransform.cpp
@@ -1281,7 +1281,7 @@ QPolygonF QTransform::map(const QPolygonF &a) const
     QPointF *dp = p.data();
 
     for(i = 0; i < size; ++i) {
-        do_map(da[i].xp, da[i].yp, dp[i].xp, dp[i].yp);
+        do_map(da[i].x(), da[i].y(), dp[i].rx(), dp[i].ry());
     }
     return p;
 }
@@ -1309,9 +1309,9 @@ QPolygon QTransform::map(const QPolygon &a) const
 
     for(i = 0; i < size; ++i) {
         qreal nx = 0, ny = 0;
-        do_map(da[i].xp, da[i].yp, nx, ny);
-        dp[i].xp = qRound(nx);
-        dp[i].yp = qRound(ny);
+        do_map(da[i].x(), da[i].y(), nx, ny);
+        dp[i].rx() = qRound(nx);
+        dp[i].ry() = qRound(ny);
     }
     return p;
 }