Fix KSelectionProxyModel usage in QTableView

The proxy would initially say columnCount==0 and would then omit to notify
about the insertion of columns. Simpler to just always have columns, even
when we have 0 rows.

CCBUG: 352369
CCMAIL: steveire@gmail.com

autotests/kselectionproxymodeltest.cpp

@@ -1,37 +1,87 @@
+/*
+    Copyright (c) 2015 Stephen Kelly <steveire@gmail.com>
+    Copyright (c) 2015 David Faure <faure@kde.org>
+
+    This library is free software; you can redistribute it and/or modify it
+    under the terms of the GNU Library General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or (at your
+    option) any later version.
+
+    This library is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
+    License for more details.
+
+    You should have received a copy of the GNU Library General Public License
+    along with this library; see the file COPYING.LIB.  If not, write to the
+    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+    02110-1301, USA.
+*/
 
 #include <QTest>
 #include <QStringListModel>
 #include <QIdentityProxyModel>
 #include <QSignalSpy>
-
 #include <kselectionproxymodel.h>
 
+#include "test_model_helpers.h"
+using namespace TestModelHelpers;
+
 class KSelectionProxyModelTest : public QObject
 {
   Q_OBJECT
 public:
   KSelectionProxyModelTest(QObject* parent = 0)
-    : QObject(parent)
+    : QObject(parent),
+      days({
+          QStringLiteral("Monday"),
+          QStringLiteral("Tuesday"),
+          QStringLiteral("Wednesday"),
+          QStringLiteral("Thursday")
+      })
   {
-
   }
 
 private Q_SLOTS:
+  void columnCountShouldBeStable();
   void selectOnSourceReset();
 
 #if QT_VERSION >= QT_VERSION_CHECK(5, 5, 0)
   void selectionModelModelChange();
 #endif
+
+private:
+  const QStringList days;
 };
 
+void KSelectionProxyModelTest::columnCountShouldBeStable()
+{
+    // Given a KSelectionProxy on top of a stringlist model
+    QStringListModel strings(days);
+    QItemSelectionModel selectionModel(&strings);
+    KSelectionProxyModel proxy(&selectionModel);
+    proxy.setSourceModel(&strings);
+
+    QSignalSpy rowATBISpy(&proxy, SIGNAL(rowsAboutToBeInserted(QModelIndex,int,int)));
+    QSignalSpy rowInsertedSpy(&proxy, SIGNAL(rowsInserted(QModelIndex,int,int)));
+
+    // No selection => the proxy should have 0 rows, 1 column
+    // (if it had 0 columns, it would have to emit column insertions, too much trouble)
+    QCOMPARE(proxy.rowCount(), 0);
+    QCOMPARE(proxy.columnCount(), 1);
+    QCOMPARE(rowATBISpy.count(), 0);
+    QCOMPARE(rowInsertedSpy.count(), 0);
+
+    // Select second entry -> the proxy should have 1 rows, 1 column
+    selectionModel.select(QItemSelection(strings.index(1, 0), strings.index(1, 0)), QItemSelectionModel::Select);
+    QCOMPARE(proxy.rowCount(), 1);
+    QCOMPARE(proxy.columnCount(), 1);
+    QCOMPARE(rowSpyToText(rowATBISpy), QString("0,0"));
+    QCOMPARE(rowSpyToText(rowInsertedSpy), QString("0,0"));
+}
+
 void KSelectionProxyModelTest::selectOnSourceReset()
 {
-  QStringList days = {
-    QStringLiteral("Monday"),
-    QStringLiteral("Tuesday"),
-    QStringLiteral("Wednesday"),
-    QStringLiteral("Thursday")
-  };
   QStringListModel strings(days);
   QItemSelectionModel selectionModel(&strings);
 
@@ -65,12 +115,7 @@ void KSelectionProxyModelTest::selectOnSourceReset()
 #if QT_VERSION >= QT_VERSION_CHECK(5, 5, 0)
 void KSelectionProxyModelTest::selectionModelModelChange()
 {
-  QStringListModel strings({
+  QStringListModel strings(days);
-    QStringLiteral("Monday"),
-    QStringLiteral("Tuesday"),
-    QStringLiteral("Wednesday"),
-    QStringLiteral("Thursday")
-  });
   QItemSelectionModel selectionModel(&strings);
 
   QIdentityProxyModel identity;

autotests/test_model_helpers.h

@@ -19,6 +19,7 @@
 */
 
 #include <QString>
+#include <QStandardItem>
 
 namespace TestModelHelpers
 {

src/kselectionproxymodel.cpp

@@ -2439,16 +2439,7 @@ bool KSelectionProxyModel::hasChildren(const QModelIndex &parent) const
 
 int KSelectionProxyModel::columnCount(const QModelIndex &index) const
 {
-    Q_D(const KSelectionProxyModel);
+    if (!sourceModel() || index.column() > 0) {
-
-    if (!sourceModel() || index.column() > 0
-            // Qt 4.6 doesn't notice changes in columnCount, so we can't return 0 when
-            // it's actually 0 ,but must return what the source model says, even if we
-            // have no rows or columns.
-#if QT_VERSION >= 0x040700
-            || d->m_rootIndexList.isEmpty()
-#endif
-       ) {
         return 0;
     }