Allow size hint changes during a rearrange.

Previously, we marked the layout as not dirty straight after a
rearrange was done. However, in the case of when a size hint changed
during a rearrange that would block the pending rearrange (since it
only perform the actual rearrange if its dirty).

Instead, mark the layout as not dirty *before* the rearrange.

This will allow bindings such as
  implicitWidth: height
to execute the pending rearrange.
(Although such bindings are not encouraged)

Task-number: QTBUG-36169
Change-Id: I75bd821a0ca4302026bd5dac01287ca3359d471b
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>

2 files changed, 39 insertions, 1 deletions

diff --git a/src/layouts/qquicklinearlayout.cpp b/src/layouts/qquicklinearlayout.cpp
index 554ce10c..c15f2ed4 100644
--- a/src/layouts/qquicklinearlayout.cpp
+++ b/src/layouts/qquicklinearlayout.cpp
@@ -499,9 +499,11 @@ void QQuickGridLayoutBase::rearrange(const QSizeF &size)
         qSwap(left, right);
     */
 
+    // Set m_dirty to false in case size hint changes during arrangement.
+    // This could happen if there is a binding like implicitWidth: height
+    QQuickLayout::rearrange(size);
     d->engine.setGeometries(QRectF(QPointF(0,0), size));
 
-    QQuickLayout::rearrange(size);
 }
 
 bool QQuickGridLayoutBase::shouldIgnoreItem(QQuickItem *child, QQuickLayoutAttached *&info, QSizeF *sizeHints)
diff --git a/tests/auto/controls/data/tst_rowlayout.qml b/tests/auto/controls/data/tst_rowlayout.qml
index c82a16d4..9db6c803 100644
--- a/tests/auto/controls/data/tst_rowlayout.qml
+++ b/tests/auto/controls/data/tst_rowlayout.qml
@@ -536,6 +536,42 @@ Item {
 
             layout.destroy()
         }
+
+        Component {
+            id: layout_change_implicitWidth_during_rearrange
+            ColumnLayout {
+                width: 100
+                height: 20
+                RowLayout {
+                    spacing: 0
+                    Rectangle {
+                        Layout.fillHeight: true
+                        Layout.fillWidth: false
+                        implicitWidth: height
+                        color: "red"
+                    }
+                    Rectangle {
+                        Layout.fillHeight: true
+                        Layout.fillWidth: true
+                        color: "blue"
+                    }
+                }
+            }
+        }
+
+        function test_change_implicitWidth_during_rearrange() {
+            var layout = layout_change_implicitWidth_during_rearrange.createObject(container)
+            var red = layout.children[0].children[0]
+            var blue = layout.children[0].children[1]
+            waitForRendering(layout);
+            tryCompare(red, 'width', 20)
+            tryCompare(blue, 'width', 80)
+            layout.height = 40
+            tryCompare(red, 'width', 40)
+            tryCompare(blue, 'width', 60)
+            layout.destroy()
+        }
+
         Component {
             id: layout_addIgnoredItem_Component
             RowLayout {