Fix childrenRect calculation

Because the 'bottom' and 'right' variables were both initialized to 0,
the bottom right corner of the children rect was clamped to
coordinates >= (0, 0).

Additionally, replace FLT_MAX with the more appropriate
std::numeric_limits<qreal>::max().

Task-number: QTBUG-38732
Change-Id: I073b0b44737cf1faed5e4f6a5d466dd830d451bf
Reviewed-by: Mitch Curtis <mitch.curtis@theqtcompany.com>

3 files changed, 69 insertions, 5 deletions

diff --git a/src/quick/items/qquickitem.cpp b/src/quick/items/qquickitem.cpp
index b6f35ad638..fd1b74d32d 100644
--- a/src/quick/items/qquickitem.cpp
+++ b/src/quick/items/qquickitem.cpp
@@ -72,7 +72,7 @@
 #endif
 
 #include <algorithm>
-#include <float.h>
+#include <limits>
 
 // XXX todo Check that elements that create items handle memory correctly after visual ownership change
 
@@ -217,8 +217,8 @@ bool QQuickContents::calcHeight(QQuickItem *changed)
         m_y = top;
         m_height = bottom - top;
     } else {
-        qreal top = FLT_MAX;
-        qreal bottom = 0;
+        qreal top = std::numeric_limits<qreal>::max();
+        qreal bottom = -std::numeric_limits<qreal>::max();
         QList<QQuickItem *> children = m_item->childItems();
         for (int i = 0; i < children.count(); ++i) {
             QQuickItem *child = children.at(i);
@@ -252,8 +252,8 @@ bool QQuickContents::calcWidth(QQuickItem *changed)
         m_x = left;
         m_width = right - left;
     } else {
-        qreal left = FLT_MAX;
-        qreal right = 0;
+        qreal left = std::numeric_limits<qreal>::max();
+        qreal right = -std::numeric_limits<qreal>::max();
         QList<QQuickItem *> children = m_item->childItems();
         for (int i = 0; i < children.count(); ++i) {
             QQuickItem *child = children.at(i);
diff --git a/tests/auto/quick/qquickitem2/data/childrenRectBottomRightCorner.qml b/tests/auto/quick/qquickitem2/data/childrenRectBottomRightCorner.qml
new file mode 100644
index 0000000000..0b83e20b20
--- /dev/null
+++ b/tests/auto/quick/qquickitem2/data/childrenRectBottomRightCorner.qml
@@ -0,0 +1,47 @@
+import QtQuick 2.0
+
+Item {
+    width: 300
+    height: 300
+
+    Item {
+        anchors.centerIn: parent
+
+        Rectangle {
+            objectName: "childrenRectProxy"
+            x: container.childrenRect.x
+            y: container.childrenRect.y
+            width: container.childrenRect.width
+            height: container.childrenRect.height
+            color: "red"
+            opacity: 0.5
+        }
+
+        Item {
+            id: container
+
+            Rectangle {
+                x: -100
+                y: -100
+                width: 10
+                height: 10
+                color: "red"
+            }
+
+            Rectangle {
+                x: -60
+                y: -60
+                width: 10
+                height: 10
+                color: "red"
+            }
+        }
+
+        Rectangle {
+            id: origin
+            width: 5
+            height: 5
+            color: "black"
+        }
+    }
+}
diff --git a/tests/auto/quick/qquickitem2/tst_qquickitem.cpp b/tests/auto/quick/qquickitem2/tst_qquickitem.cpp
index a31f7ab9ce..c7717b9cca 100644
--- a/tests/auto/quick/qquickitem2/tst_qquickitem.cpp
+++ b/tests/auto/quick/qquickitem2/tst_qquickitem.cpp
@@ -104,6 +104,7 @@ private slots:
     void childrenRectBug();
     void childrenRectBug2();
     void childrenRectBug3();
+    void childrenRectBottomRightCorner();
 
     void childrenProperty();
     void resourcesProperty();
@@ -2595,6 +2596,22 @@ void tst_QQuickItem::childrenRectBug3()
     delete window;
 }
 
+// QTBUG-38732
+void tst_QQuickItem::childrenRectBottomRightCorner()
+{
+    QQuickView *window = new QQuickView(0);
+    window->setSource(testFileUrl("childrenRectBottomRightCorner.qml"));
+    window->show();
+
+    QQuickItem *rect = window->rootObject()->findChild<QQuickItem*>("childrenRectProxy");
+    QCOMPARE(rect->x(), qreal(-100));
+    QCOMPARE(rect->y(), qreal(-100));
+    QCOMPARE(rect->width(), qreal(50));
+    QCOMPARE(rect->height(), qreal(50));
+
+    delete window;
+}
+
 // QTBUG-13893
 void tst_QQuickItem::transformCrash()
 {