From 26211cca19666e5cb6d85dbb895b04cc22d55a1a Mon Sep 17 00:00:00 2001
From: Chen Bin <chenbin@uniontech.com>
Date: Fri, 2 Apr 2021 13:40:08 +0800
Subject: [PATCH] Check scrollbar visibility when computing QListView margins

When the listview setWordWrap is true and ScrollBarPolicy is
ScrollBarAsNeeded, if the text needs a newline display and the
vbar is not shown, the width of the item was subtracted from
the width of the scrollbar.

In most cases, the listview needs to reserve the size of the scrollbar.
But if the flow is TopToBottom and the vertical scrollbar is not
visible, the width of the vertical scrollbar cannot be reserved.

Fixes: QTBUG-92366
Change-Id: I73cce691099a253d409019dbb3fe9a16e1830bb1
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit aeef92c3c33e4ebcb7e5d8dd955020f4f4600e84)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/widgets/itemviews/qlistview.cpp           |  2 +-
 .../itemviews/qlistview/tst_qlistview.cpp     | 54 +++++++++++++++++++
 2 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/src/widgets/itemviews/qlistview.cpp b/src/widgets/itemviews/qlistview.cpp
index ce7b98d7806..35bc2aac9b4 100644
--- a/src/widgets/itemviews/qlistview.cpp
+++ b/src/widgets/itemviews/qlistview.cpp
@@ -1791,7 +1791,7 @@ void QListViewPrivate::prepareItemsLayout()
     // maximumViewportSize() already takes scrollbar into account if policy is
     // Qt::ScrollBarAlwaysOn but scrollbar extent must be deduced if policy
     // is Qt::ScrollBarAsNeeded
-    int verticalMargin = vbarpolicy==Qt::ScrollBarAsNeeded
+    int verticalMargin = (vbarpolicy == Qt::ScrollBarAsNeeded) && (flow == QListView::LeftToRight || vbar->isVisible())
         ? q->style()->pixelMetric(QStyle::PM_ScrollBarExtent, nullptr, vbar) + frameAroundContents
         : 0;
     int horizontalMargin =  hbarpolicy==Qt::ScrollBarAsNeeded
diff --git a/tests/auto/widgets/itemviews/qlistview/tst_qlistview.cpp b/tests/auto/widgets/itemviews/qlistview/tst_qlistview.cpp
index 98dec7ded9b..3768acade70 100644
--- a/tests/auto/widgets/itemviews/qlistview/tst_qlistview.cpp
+++ b/tests/auto/widgets/itemviews/qlistview/tst_qlistview.cpp
@@ -169,6 +169,7 @@ private slots:
     void itemAlignment();
     void internalDragDropMove_data();
     void internalDragDropMove();
+    void spacingWithWordWrap();
 };
 
 // Testing get/set functions
@@ -2710,6 +2711,59 @@ void tst_QListView::internalDragDropMove()
     }
 }
 
+/*!
+    Verify fix for QTBUG-92366
+*/
+void tst_QListView::spacingWithWordWrap()
+{
+    const int listViewResizeCount = 200;
+    QWidget window;
+    window.resize(300, 200);
+    QListView lv(&window);
+
+    lv.setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
+    lv.setVerticalScrollBarPolicy(Qt::ScrollBarAsNeeded);
+    lv.setFlow(QListView::TopToBottom);
+    lv.setWordWrap(true);
+    lv.setSpacing(0);
+    lv.setGeometry(0, 0, 200, 150);
+
+    QStandardItem *it1 = new QStandardItem("qqqqqqqqqqqqqqqqqqqqq-ttttttttttttttttt");
+    QStandardItem *it2 = new QStandardItem("qqqqqqqqqqqqqqqq-tttttttttttt");
+    QStandardItemModel model;
+    lv.setModel(&model);
+    model.appendRow(it1);
+    model.appendRow(it2);
+
+    window.show();
+    QVERIFY(QTest::qWaitForWindowExposed(&window));
+
+    QVERIFY(!lv.verticalScrollBar()->isVisible());
+    for (int i = 0; i < listViewResizeCount; ++i) {
+        lv.resize(lv.width() + 1, lv.height());
+        QRect rectForRowOne = lv.visualRect(model.index(0, 0));
+        QRect rectForRowTwo = lv.visualRect(model.index(1, 0));
+
+        QCOMPARE(rectForRowOne.y() + rectForRowOne.height(), rectForRowTwo.y());
+    }
+
+    lv.resize(200, 150);
+    const QStringList &stringList = generateList(QStringLiteral("Test_Abnormal_Spacing"), 30);
+    for (const QString &item_string : stringList) {
+        QStandardItem *item = new QStandardItem(item_string);
+        model.appendRow(item);
+    }
+
+    // test whether the height of item is correct if the vbar is shown.
+    QTRY_VERIFY(lv.verticalScrollBar()->isVisible());
+    for (int i = 0; i < listViewResizeCount; ++i) {
+        lv.resize(lv.width() + 1, lv.height());
+        QRect rectForRowOne = lv.visualRect(model.index(0, 0));
+        QRect rectForRowTwo = lv.visualRect(model.index(1, 0));
+
+        QCOMPARE(rectForRowOne.y() + rectForRowOne.height(), rectForRowTwo.y());
+    }
+}
 
 QTEST_MAIN(tst_QListView)
 #include "tst_qlistview.moc"