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 amout to be scrolled.

Backported from Qt5 commit:
d4385e48b8566a5587048a3c6d8b2396ba587ed5

Task-number: QTBUG-21804
Change-Id: I81a82ed56bb0e4c0229fd117784790e1234aacca
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>

2 files changed, 63 insertions, 3 deletions

diff --git a/src/gui/itemviews/qlistview.cpp b/src/gui/itemviews/qlistview.cpp
index 6db979c..e6949fd 100644
--- a/src/gui/itemviews/qlistview.cpp
+++ b/src/gui/itemviews/qlistview.cpp
@@ -2558,13 +2558,21 @@ 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--;
         }
 
@@ -2584,7 +2592,7 @@ 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;
diff --git a/tests/auto/qlistview/tst_qlistview.cpp b/tests/auto/qlistview/tst_qlistview.cpp
index 5623ecb..a97296f 100644
--- a/tests/auto/qlistview/tst_qlistview.cpp
+++ b/tests/auto/qlistview/tst_qlistview.cpp
@@ -130,6 +130,8 @@ private slots:
     void taskQTBUG_12308_wrongFlowLayout();
     void taskQTBUG_21115_scrollToAndHiddenItems_data();
     void taskQTBUG_21115_scrollToAndHiddenItems();
+    void taskQTBUG_21804_hiddenItemsAndScrollingWithKeys_data();
+    void taskQTBUG_21804_hiddenItemsAndScrollingWithKeys();
 };
 
 // Testing get/set functions
@@ -2108,5 +2110,55 @@ void tst_QListView::taskQTBUG_21115_scrollToAndHiddenItems()
     QCOMPARE(lv.visualRect(index), firstItemRect);
 }
 
+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"