Fix QListWidget scrolling with keys when there are hidden items

If the selected item is scrolled with keyboard keys the selected item
will go outside the visible area. The scrolling did not take hidden
items into account when calculating the amount to be scrolled.

Task-number: QTBUG-21804
Change-Id: I63da0248cec43be464898f9dc8167e739f00ccd0
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>

src/widgets/itemviews/qlistview.cpp

@@ -2533,13 +2533,21 @@ int QListModeViewBase::perItemScrollToValue(int index, int scrollValue, int view
 {
     if (index < 0)
         return scrollValue;
+
+    QVector<int> visibleFlowPositions;
+    visibleFlowPositions.reserve(flowPositions.count() - 1);
+    for (int i = 0; i < flowPositions.count() - 1; i++) { // flowPositions count is +1 larger than actual row count
+        if (!isHidden(i))
+            visibleFlowPositions.append(flowPositions.at(i));
+    }
+
     if (!wrap) {
         int topIndex = index;
         const int bottomIndex = topIndex;
-        const int bottomCoordinate = flowPositions.at(index);
+        const int bottomCoordinate = visibleFlowPositions.at(index);
 
         while (topIndex > 0 &&
-            (bottomCoordinate - flowPositions.at(topIndex-1) + itemExtent) <= (viewportSize)) {
+               (bottomCoordinate - visibleFlowPositions.at(topIndex - 1) + itemExtent) <= (viewportSize)) {
             topIndex--;
         }
 
@@ -2559,7 +2567,7 @@ int QListModeViewBase::perItemScrollToValue(int index, int scrollValue, int view
                                            ? Qt::Horizontal : Qt::Vertical);
         if (flowOrientation == orientation) { // scrolling in the "flow" direction
             // ### wrapped scrolling in the flow direction
-            return flowPositions.at(index); // ### always pixel based for now
+            return visibleFlowPositions.at(index); // ### always pixel based for now
         } else if (!segmentStartRows.isEmpty()) { // we are scrolling in the "segment" direction
             int segment = qBinarySearch<int>(segmentStartRows, index, 0, segmentStartRows.count() - 1);
             int leftSegment = segment;

tests/auto/widgets/itemviews/qlistview/tst_qlistview.cpp

@@ -136,6 +136,8 @@ private slots:
     void taskQTBUG_21115_scrollToAndHiddenItems();
     void draggablePaintPairs_data();
     void draggablePaintPairs();
+    void taskQTBUG_21804_hiddenItemsAndScrollingWithKeys_data();
+    void taskQTBUG_21804_hiddenItemsAndScrollingWithKeys();
 };
 
 // Testing get/set functions
@@ -2156,6 +2158,55 @@ void tst_QListView::draggablePaintPairs()
     }
 }
 
+void tst_QListView::taskQTBUG_21804_hiddenItemsAndScrollingWithKeys_data()
+{
+    QTest::addColumn<int>("flow");
+    QTest::newRow("flow TopToBottom") << static_cast<int>(QListView::TopToBottom);
+    QTest::newRow("flow LeftToRight") << static_cast<int>(QListView::LeftToRight);
+}
+
+void tst_QListView::taskQTBUG_21804_hiddenItemsAndScrollingWithKeys()
+{
+    QFETCH(int, flow);
+
+    // create some items to show
+    QStringListModel model;
+    QStringList list;
+    for (int i = 0; i < 60; i++)
+        list << QString::number(i);
+    model.setStringList(list);
+
+    // create listview
+    QListView lv;
+    lv.setFlow(static_cast<QListView::Flow>(flow));
+    lv.setModel(&model);
+    lv.show();
+    QTest::qWaitForWindowShown(&lv);
+
+    // hide every odd number row
+    for (int i = 1; i < model.rowCount(); i+=2)
+        lv.setRowHidden(i, true);
+
+    // scroll forward and check that selected item is visible always
+    for (int i = 0; i < model.rowCount()/2; i++) {
+        if (flow == QListView::TopToBottom)
+            QTest::keyClick(&lv, Qt::Key_Down);
+        else
+            QTest::keyClick(&lv, Qt::Key_Right);
+        QTest::qWait(100);
+        QVERIFY(lv.rect().contains(lv.visualRect(lv.currentIndex())));
+    }
+
+    // scroll backward
+    for (int i = 0; i < model.rowCount()/2; i++) {
+        if (flow == QListView::TopToBottom)
+            QTest::keyClick(&lv, Qt::Key_Up);
+        else
+            QTest::keyClick(&lv, Qt::Key_Left);
+        QTest::qWait(100);
+        QVERIFY(lv.rect().contains(lv.visualRect(lv.currentIndex())));
+    }
+}
 
 QTEST_MAIN(tst_QListView)
 #include "tst_qlistview.moc"