From 8713f22372b7aa63ecafbe87214b8994203fac5f Mon Sep 17 00:00:00 2001
From: Christian Ehrlicher <ch.ehrlicher@gmx.de>
Date: Sun, 4 Nov 2018 18:43:00 +0100
Subject: [PATCH] QHeaderView: Fix updating hidden sections during
 initializeSections()

QHeaderView::initializeSections() was calling updateHiddenSections()
with wrong parameters which lead to an inconsistency in the hidden
section handling.
updateHiddenSections() needs the first and last index which got removed.
Therefore we must pass the new section count for logicalFirst.

Fixes: QTBUG-55461
Change-Id: Ica06125cf19bdd500f55fd9cd59ace1795f3703f
Reviewed-by: David Faure <david.faure@kdab.com>
---
 src/widgets/itemviews/qheaderview.cpp         |  5 +-
 .../itemviews/qheaderview/tst_qheaderview.cpp | 55 ++++++++++++++++---
 2 files changed, 50 insertions(+), 10 deletions(-)

diff --git a/src/widgets/itemviews/qheaderview.cpp b/src/widgets/itemviews/qheaderview.cpp
index b7de69d63a..e9091ca1a2 100644
--- a/src/widgets/itemviews/qheaderview.cpp
+++ b/src/widgets/itemviews/qheaderview.cpp
@@ -2321,9 +2321,10 @@ void QHeaderView::initializeSections()
         if (stretchLastSection())   // we've already gotten the size hint
             d->maybeRestorePrevLastSectionAndStretchLast();
 
-        //make sure we update the hidden sections
+        // make sure we update the hidden sections
+        // simulate remove from newCount to oldCount
         if (newCount < oldCount)
-            d->updateHiddenSections(0, newCount-1);
+            d->updateHiddenSections(newCount, oldCount);
     }
 }
 
diff --git a/tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp b/tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp
index b6932d4892..9d3770064f 100644
--- a/tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp
+++ b/tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp
@@ -253,11 +253,12 @@ protected:
     void calculateAndCheck(int cppline, const int precalced_comparedata[]);
     void testMinMaxSectionSize(bool stretchLastSection);
 
-    QWidget *topLevel;
-    QHeaderView *view;
-    QStandardItemModel *model;
-    QTableView *m_tableview;
-    bool m_using_reset_model;
+    QWidget *topLevel = nullptr;
+    QHeaderView *view = nullptr;
+    QStandardItemModel *model = nullptr;
+    QTableView *m_tableview = nullptr;
+    bool m_using_reset_model = false;
+    bool m_special_prepare = false;
     QElapsedTimer timer;
 };
 
@@ -614,6 +615,27 @@ void tst_QHeaderView::hidden()
     view->setSectionHidden(1, false);
     QCOMPARE(view->isSectionHidden(0), false);
     QCOMPARE(view->sectionSize(0), view->defaultSectionSize());
+
+    // d->hiddenSectionSize could go out of sync when a new model
+    // was set which has fewer sections than before and some of them
+    // were hidden
+    QStandardItemModel model2(model->rowCount() - 1, model->columnCount());
+
+    for (int i = 0; i < model->rowCount(); ++i)
+        view->setSectionHidden(i, true);
+    view->setModel(&model2);
+    QVERIFY(view->sectionsHidden());
+    for (int i = 0; i < model2.rowCount(); ++i) {
+        QVERIFY(view->isSectionHidden(i));
+    }
+
+    view->setModel(model);
+    for (int i = 0; i < model2.rowCount(); ++i) {
+        QVERIFY(view->isSectionHidden(i));
+    }
+    QCOMPARE(view->isSectionHidden(model->rowCount() - 1), false);
+    for (int i = 0; i < model->rowCount(); ++i)
+        view->setSectionHidden(i, false);
 }
 
 void tst_QHeaderView::stretch()
@@ -2822,6 +2844,7 @@ void tst_QHeaderView::additionalInit()
     QFETCH(bool, reset_model);
 
     m_using_reset_model = reset_model;
+    m_special_prepare = special_prepare;
 
     if (m_using_reset_model) {
         XResetModel *m = new XResetModel();
@@ -3035,18 +3058,34 @@ void tst_QHeaderView::mixedTests()
     view->moveSection(0, 5);
 
     for (int u = model->rowCount(); u >= 0; --u) {
-        if (u % 5 != 0)
+        if (u % 5 != 0) {
             view->hideSection(u);
-        if (u % 3 != 0)
+            QVERIFY(view->isSectionHidden(u));
+        }
+        if (u % 3 != 0) {
             view->showSection(u);
+            QVERIFY(!view->isSectionHidden(u));
+        }
     }
 
     model->insertRows(3, 7);
     model->removeRows(8, 3);
     model->setRowCount(model->rowCount() - 10);
 
+    // the upper is not visible (when m_using_reset_model is true)
+    // the lower 11 are modified due to insert/removeRows
+    for (int u = model->rowCount() - 1; u >= 11; --u) {
+        // when using reset, the hidden rows will *not* move
+        const int calcMod = m_using_reset_model ? u : u - 4;    // 7 added, 3 removed
+        if (calcMod % 5 != 0 && calcMod % 3 == 0) {
+            QVERIFY(view->isSectionHidden(u));
+        }
+        if (calcMod % 3 != 0) {
+            QVERIFY(!view->isSectionHidden(u));
+        }
+    }
     if (m_using_reset_model) {
-        const int precalced_results[] = { 898296472, 337096378, -543340640, 1, -1251526424, -568618976, 9250 };
+        const int precalced_results[] = { 898296472, 337096378, -543340640, -1964432121, -1251526424, -568618976, 9250 };
         calculateAndCheck(__LINE__, precalced_results);
     } else {
         const int precalced_results[] = { 1911338224, 1693514365, -613398968, -1912534953, 1582159424, -1851079000, 9300 };