Only warn about actual *anchors* in layout children

Do not warn if they don't actually pose a problem, such as having just

  anchors.margins: 42

in a layout child item (as demonstrated by the test)

Change-Id: I01e4515e91d7d0df3ae6bf9061cebe5c51802998
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

4 files changed, 77 insertions, 1 deletions

diff --git a/src/imports/layouts/qquicklayout.cpp b/src/imports/layouts/qquicklayout.cpp
index 7d51ec3ca9..c1e34813c6 100644
--- a/src/imports/layouts/qquicklayout.cpp
+++ b/src/imports/layouts/qquicklayout.cpp
@@ -771,7 +771,8 @@ bool QQuickLayout::shouldIgnoreItem(QQuickItem *child, QQuickLayoutAttached *&in
 
 void QQuickLayout::checkAnchors(QQuickItem *item) const
 {
-    if (QQuickItemPrivate::get(item)->_anchors)
+    QQuickAnchors *anchors = QQuickItemPrivate::get(item)->_anchors;
+    if (anchors && anchors->activeDirections())
         qmlWarning(item) << "Detected anchors on an item that is part of a layout. This is undefined behavior.";
 }
 
diff --git a/src/quick/items/qquickanchors.cpp b/src/quick/items/qquickanchors.cpp
index 45b405bd82..4367e230bc 100644
--- a/src/quick/items/qquickanchors.cpp
+++ b/src/quick/items/qquickanchors.cpp
@@ -1324,6 +1324,19 @@ QQuickAnchors::Anchors QQuickAnchors::usedAnchors() const
     return static_cast<QQuickAnchors::Anchors>(d->usedAnchors);
 }
 
+Qt::Orientations QQuickAnchors::activeDirections() const
+{
+    Q_D(const QQuickAnchors);
+    if (d->fill || d->centerIn)
+        return Qt::Horizontal | Qt::Vertical;
+    Qt::Orientations o;
+    if (d->usedAnchors & QQuickAnchors::Horizontal_Mask)
+        o |= Qt::Horizontal;
+    if (d->usedAnchors & QQuickAnchors::Vertical_Mask)
+        o |= Qt::Vertical;
+    return o;
+}
+
 bool QQuickAnchorsPrivate::checkHValid() const
 {
     if (usedAnchors & QQuickAnchors::LeftAnchor &&
diff --git a/src/quick/items/qquickanchors_p.h b/src/quick/items/qquickanchors_p.h
index f00b8b5ba7..bc1e6c10f5 100644
--- a/src/quick/items/qquickanchors_p.h
+++ b/src/quick/items/qquickanchors_p.h
@@ -174,6 +174,7 @@ public:
     void resetCenterIn();
 
     Anchors usedAnchors() const;
+    Qt::Orientations activeDirections() const;
 
     bool mirrored();
 
diff --git a/tests/auto/quick/qquicklayouts/data/tst_rowlayout.qml b/tests/auto/quick/qquicklayouts/data/tst_rowlayout.qml
index 4ff1017116..4e9e41d42e 100644
--- a/tests/auto/quick/qquicklayouts/data/tst_rowlayout.qml
+++ b/tests/auto/quick/qquicklayouts/data/tst_rowlayout.qml
@@ -1004,5 +1004,66 @@ Item {
 
             // Shouldn't crash upon destroying containerUser.
         }
+
+
+        Component {
+            id: itemsWithAnchorsLayout_Component
+            RowLayout {
+                spacing: 2
+                Item {
+                    anchors.fill: parent
+                    implicitWidth: 10
+                    implicitHeight: 10
+                }
+                Item {
+                    anchors.centerIn: parent
+                    implicitWidth: 10
+                    implicitHeight: 10
+                }
+                Item {
+                    anchors.left: parent.left
+                    implicitWidth: 10
+                    implicitHeight: 10
+                }
+                Item {
+                    anchors.right: parent.right
+                    implicitWidth: 10
+                    implicitHeight: 10
+                }
+                Item {
+                    anchors.top: parent.top
+                    implicitWidth: 10
+                    implicitHeight: 10
+                }
+                Item {
+                    anchors.bottom: parent.bottom
+                    implicitWidth: 10
+                    implicitHeight: 10
+                }
+                Item {
+                    anchors.horizontalCenter: parent.horizontalCenter
+                    anchors.verticalCenter: parent.verticalCenter
+                    implicitWidth: 10
+                    implicitHeight: 10
+                }
+                Item {
+                    anchors.margins: 42     // although silly, it should not cause a warning from the Layouts POV
+                    implicitWidth: 10
+                    implicitHeight: 10
+                }
+            }
+        }
+
+        function test_warnAboutLayoutItemsWithAnchors()
+        {
+            var fullPath = Qt.resolvedUrl("tst_rowlayout.qml")
+            for (var i = 0; i < 7; ++i) {
+                ignoreWarning(fullPath + ":" + (1013 + 5*i) +":17: QML Item: Detected anchors on an item that is part of a layout. This is undefined behavior.")
+            }
+            var layout = itemsWithAnchorsLayout_Component.createObject(container)
+            waitForRendering(layout)
+            layout.destroy()
+        }
+
     }
 }