From: Tang Haixiang <[email protected]>
Date: Mon, May 31 13:24:30 2021 +0800
Subject: Fix PageDown behavior and PageUP
Upstream: https://codereview.qt-project.org/c/qt/qtbase/+/351728

---

Index: qtbase-opensource-src/src/widgets/itemviews/qlistview.cpp
===================================================================
--- qtbase-opensource-src.orig/src/widgets/itemviews/qlistview.cpp
+++ qtbase-opensource-src/src/widgets/itemviews/qlistview.cpp
@@ -1155,13 +1155,25 @@ QModelIndex QListView::moveCursor(Cursor
             d->removeCurrentAndDisabled(&intersectVector, current);
         }
         return d->closestIndex(initialRect, intersectVector);
-    case MovePageUp:
-        // move current by (visibileRowCount - 1) items.
-        // rect.translate(0, -rect.height()); will happen in the switch fallthrough for MoveUp.
-        rect.moveTop(rect.top() - d->viewport->height() + 2 * rect.height());
-        if (rect.top() < rect.height())
-            rect.moveTop(rect.height());
-        Q_FALLTHROUGH();
+    case MovePageUp: {
+        rect.moveTop(rect.top() - d->viewport->height() + 1 );
+        if (rect.top() < rect.height()) {
+            rect.setTop(0);
+            rect.setBottom(1);
+        }
+        QModelIndex findindex = current;
+        while (intersectVector.isEmpty()
+               || rectForIndex(findindex).top() <= (rectForIndex(current).bottom() - d->viewport->rect().height())
+               || rect.top() <= 0) {
+            rect.translate(0, 1);
+            if (rect.bottom() <= 0) {
+                return current;
+            }
+            intersectVector = d->intersectingSet(rect);
+            findindex = d->closestIndex(initialRect, intersectVector);
+        }
+        return findindex;
+    }
     case MovePrevious:
     case MoveUp:
         while (intersectVector.isEmpty()) {
@@ -1184,13 +1196,26 @@ QModelIndex QListView::moveCursor(Cursor
             d->removeCurrentAndDisabled(&intersectVector, current);
         }
         return d->closestIndex(initialRect, intersectVector);
-    case MovePageDown:
-        // move current by (visibileRowCount - 1) items.
-        // rect.translate(0, rect.height()); will happen in the switch fallthrough for MoveDown.
-        rect.moveTop(rect.top() + d->viewport->height() - 2 * rect.height());
-        if (rect.bottom() > contents.height() - rect.height())
-            rect.moveBottom(contents.height() - rect.height());
-        Q_FALLTHROUGH();
+    case MovePageDown: {
+        rect.moveTop(rect.top() + d->viewport->height() - 1 );
+        if (rect.bottom() > contents.height() - rect.height()){
+            rect.setTop(contents.height() - 1);
+            rect.setBottom(contents.height());
+        }
+        QModelIndex index = current;
+        // index's bottom() - current's top() always <=  (d->viewport->rect().height()
+        while (intersectVector.isEmpty()
+               || rectForIndex(index).bottom() >= (d->viewport->rect().height() + rectForIndex(current).top())
+               || rect.bottom() > contents.height()) {
+            rect.translate(0, -1);
+            if (rect.top() >= contents.height()) {
+                return current;
+            }
+            intersectVector = d->intersectingSet(rect);
+            index = d->closestIndex(initialRect, intersectVector);
+        }
+        return index;
+    }
     case MoveNext:
     case MoveDown:
         while (intersectVector.isEmpty()) {
Index: qtbase-opensource-src/tests/auto/widgets/itemviews/qlistview/tst_qlistview.cpp
===================================================================
--- qtbase-opensource-src.orig/tests/auto/widgets/itemviews/qlistview/tst_qlistview.cpp
+++ qtbase-opensource-src/tests/auto/widgets/itemviews/qlistview/tst_qlistview.cpp
@@ -93,6 +93,7 @@ private slots:
     void moveCursor();
     void moveCursor2();
     void moveCursor3();
+    void moveCursor4();
     void indexAt();
     void clicked();
     void singleSelectionRemoveRow();
@@ -559,6 +560,56 @@ void tst_QListView::moveCursor3()
     QCOMPARE(view.selectionModel()->currentIndex(), model.index(0, 0));
 }
 
+void tst_QListView::moveCursor4()
+{
+    int indexCount = 100;
+    PublicListView listView;
+    QStandardItemModel model;
+    for (int i = 0; i < 100; i++)
+    {
+        QStandardItem* item = new QStandardItem(QString("item 0%0").arg(i));
+        QFont font = item->font();
+        font.setPixelSize(14);
+        item->setFont(font);
+        model.appendRow(item);
+    }
+    QFont font = model.item(0)->font();
+    font.setPixelSize(50);
+    font.setBold(true);
+    model.item(0)->setFont(font);
+    listView.setModel(&model);
+    listView.setFixedSize(200, 200);
+    listView.setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
+    listView.setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
+    listView.show();
+    listView.selectionModel()->setCurrentIndex(model.index(0, 0), QItemSelectionModel::SelectCurrent);
+
+    QModelIndex idx = listView.moveCursor(PublicListView::MovePageDown, Qt::NoModifier);
+
+    int actualIndex = 0;
+    int indexHeight = 0;
+    while (indexHeight <= listView.viewport()->height()) {
+        indexHeight +=  listView.visualRect(model.item(actualIndex)->index()).height();
+        actualIndex++;
+    }
+    QTRY_COMPARE(idx, model.index(actualIndex - 2, 0));
+    idx = listView.moveCursor(PublicListView::MoveUp, Qt::NoModifier);
+    QTRY_COMPARE(idx, model.index(0, 0));
+
+    listView.setCurrentIndex(model.index(indexCount - 2, 0));
+    idx = listView.moveCursor(PublicListView::MovePageDown, Qt::NoModifier);
+    QTRY_COMPARE(idx, model.index(99, 0));
+
+    listView.setCurrentIndex(model.index(3, 0));
+    actualIndex = 3;
+    indexHeight = 0;
+    while (indexHeight <= listView.viewport()->height()) {
+        indexHeight +=  listView.visualRect(model.item(actualIndex)->index()).height();
+        actualIndex++;
+    }
+    idx = listView.moveCursor(PublicListView::MovePageDown, Qt::NoModifier);
+    QTRY_COMPARE(idx, model.index(actualIndex - 2, 0));
+}
 
 class QListViewShowEventListener : public QListView
 {