GridView: Set content position when changing cell size

Content size was calculated before the new data was applied.
This caused problems when calculating the column count while
resizing the window.

Pick-to: 5.15
Pick-to: 6.2
Fixes: QTBUG-92998
Change-Id: Ia4401c0e34cd11dc9e6c24a0320dbf0ca2f59ab9
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

src/quick/items/qquickgridview.cpp

@@ -1649,6 +1649,7 @@ void QQuickGridView::setCellWidth(qreal cellWidth)
         d->updateViewport();
         emit cellWidthChanged();
         d->forceLayoutPolish();
+        QQuickFlickable::setContentX(d->contentXForPosition(d->position()));
     }
 }
 
@@ -1666,6 +1667,7 @@ void QQuickGridView::setCellHeight(qreal cellHeight)
         d->updateViewport();
         emit cellHeightChanged();
         d->forceLayoutPolish();
+        QQuickFlickable::setContentY(d->contentYForPosition(d->position()));
     }
 }
 /*!

tests/auto/quick/qquickgridview/data/qtbug92998.qml

@@ -0,0 +1,53 @@
+import QtQuick 2.12
+import QtQuick.Window 2.12
+
+Item {
+    width: 450
+    height: 650
+    GridView {
+        objectName: "gridview"
+        id: gridView
+        width: 450
+        height: 650
+        layoutDirection: Qt.RightToLeft
+        property int cells: calcCells(width)
+        cellWidth: width / cells
+        cellHeight: cellWidth
+
+        delegate: Component {
+            Item {
+                width: gridView.cellWidth
+                height: gridView.cellHeight
+                Rectangle {
+                    anchors {
+                        fill: parent
+                        margins: 10
+                    }
+                    color: "green"
+                }
+            }
+        }
+        model: [
+           { number: "1" },
+           { number: "2" },
+           { number: "3" },
+           { number: "4" },
+           { number: "5" },
+           { number: "6" },
+           { number: "7" },
+           { number: "8" },
+           { number: "9" },
+           { number: "10" },
+           { number: "11" },
+           { number: "12" },
+           { number: "13" },
+           { number: "14" },
+           { number: "15" },
+           { number: "16" }];
+        function calcCells(w) {
+            var rw = 120;
+            var c = Math.max(1, Math.round(w / rw));
+            return c;
+        }
+    }
+}

tests/auto/quick/qquickgridview/tst_qquickgridview.cpp

@@ -214,6 +214,7 @@ private slots:
     void QTBUG_49218();
     void QTBUG_48870_fastModelUpdates();
     void QTBUG_86255();
+    void resizeDynamicCellWidthRtL();
 
     void keyNavigationEnabled();
     void releaseItems();
@@ -6810,6 +6811,25 @@ void tst_QQuickGridView::QTBUG_86255()
     QTRY_COMPARE(view->isFlicking(), false);
 }
 
+void tst_QQuickGridView::resizeDynamicCellWidthRtL()
+{
+    QScopedPointer<QQuickView> window(createView());
+    QTRY_VERIFY(window);
+    window->setSource(testFileUrl("qtbug92998.qml"));
+    window->show();
+    QVERIFY(QTest::qWaitForWindowExposed(window.data()));
+
+    QQuickGridView *gridview = findItem<QQuickGridView>(window->rootObject(), "gridview");
+    QTRY_VERIFY(gridview != nullptr);
+    QVERIFY(QQuickTest::qWaitForItemPolished(gridview));
+    gridview->setWidth(460);
+    QVERIFY(QQuickTest::qWaitForItemPolished(gridview));
+    QTRY_COMPARE(gridview->contentX(), 0.f);
+    gridview->setWidth(360);
+    QVERIFY(QQuickTest::qWaitForItemPolished(gridview));
+    QTRY_COMPARE(gridview->contentX(), 0.f);
+}
+
 void tst_QQuickGridView::releaseItems()
 {
     QScopedPointer<QQuickView> view(createView());