In MergeView, replace QTableWidget with QTableView with custom model (#266,#217)

QTableWidget was a major bottleneck for large merge sources (#217).  This is because a QTableWidgetItem needed to be created for every field in every record of the merge data, whether they are being displayed or not.  This was not a problem for small merge sources (only a few dozen records max), however for larger data sets this would severely affect performance and make the application unresponsive.  QTableView only renders the fields and records currently visible.

glabels/CMakeLists.txt

@@ -21,6 +21,7 @@ set (glabels_sources
   Help.cpp
   LabelEditor.cpp
   MainWindow.cpp
+  MergeTableModel.cpp
   MergeView.cpp
   MiniPreviewPixmap.cpp
   NotebookUtil.cpp
@@ -57,6 +58,7 @@ set (glabels_qobject_headers
   File.h
   LabelEditor.h
   MainWindow.h
+  MergeTableModel.h
   MergeView.h
   ObjectEditor.h
   PreferencesDialog.h

glabels/MergeTableModel.cpp

@@ -0,0 +1,178 @@
+/*  MergeTableModel.cpp
+ *
+ *  Copyright (C) 2025  Jaye Evins <evins@snaught.com>
+ *
+ *  This file is part of gLabels-qt.
+ *
+ *  gLabels-qt is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  gLabels-qt 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 General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with gLabels-qt.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+
+#include "MergeTableModel.h"
+
+#include <QDebug>
+
+
+namespace glabels
+{
+
+	///
+	/// Constructor
+	///
+	MergeTableModel::MergeTableModel( merge::Merge* merge, QObject* parent )
+		: QAbstractTableModel( parent ),
+		  mMerge( merge )
+	{
+		// Copy keys, make sure primary key is first
+		mDisplayKeys.push_back( mMerge->primaryKey() );
+		for ( auto& key : mMerge->keys() )
+		{
+			if ( key != mMerge->primaryKey() )
+			{
+				mDisplayKeys.push_back( key );
+			}
+		}
+
+		connect( mMerge, SIGNAL(selectionChanged()),
+		         this, SLOT(onSelectionChanged()) );
+	}
+
+
+	///
+	/// Row count
+	///
+	int MergeTableModel::rowCount( const QModelIndex& parent ) const
+	{
+		return mMerge->recordList().size();
+	}
+
+
+	///
+	/// Column count
+	///
+	int MergeTableModel::columnCount( const QModelIndex& parent ) const
+	{
+		return mDisplayKeys.size() + 1;
+	}
+
+
+	///
+	/// Header data
+	///
+	QVariant MergeTableModel::headerData( int section, Qt::Orientation orientation, int role ) const
+	{
+		if ( orientation == Qt::Vertical )
+		{
+			return QAbstractTableModel::headerData( section, orientation, role );
+		}
+
+		if ( (role != Qt::DisplayRole) || section >= mDisplayKeys.size() )
+		{
+			return QVariant();
+		}
+
+		return mDisplayKeys[ section ];
+	}
+
+
+	///
+	/// Data
+	///
+	QVariant MergeTableModel::data( const QModelIndex& index, int role ) const
+	{
+		if ( !index.isValid() )
+		{
+			return QVariant();
+		}
+
+		if ( (index.row() >= mMerge->recordList().size()) ||
+		     (index.column() >= mDisplayKeys.size()) )
+		{
+			return QVariant();
+		}
+
+
+		if ( (role == Qt::CheckStateRole) && (index.column() == 0) )
+		{
+			auto record = mMerge->recordList()[ index.row() ];
+			return record.isSelected() ? Qt::Checked : Qt::Unchecked;
+		}
+
+		if ( role == Qt::DisplayRole )
+		{
+			auto record = mMerge->recordList()[ index.row() ];
+			auto key = mDisplayKeys[ index.column() ];
+
+			if ( record.contains( key ) )
+			{
+				return record[ key ];
+			}
+		}
+
+		return QVariant();
+	}
+
+
+	///
+	/// Set data
+	///
+	bool MergeTableModel::setData( const QModelIndex& index, const QVariant& value, int role )
+	{
+		if ( !index.isValid() || (index.column() != 0) || (role != Qt::CheckStateRole) )
+		{
+			return false;
+		}
+
+		bool isChecked = static_cast<Qt::CheckState>(value.toInt()) != Qt::Unchecked;
+		
+		mMerge->blockSignals( true );
+		mMerge->setSelected( index.row(), isChecked );
+		mMerge->blockSignals( false );
+		return true;
+	}
+
+
+	///
+	/// Flags
+	///
+	Qt::ItemFlags MergeTableModel::flags( const QModelIndex& index ) const
+	{
+		if ( !index.isValid() )
+		{
+			return Qt::NoItemFlags;
+		}
+
+		if ( index.column() == 0 )
+		{
+			return Qt::ItemIsEnabled | Qt::ItemIsUserCheckable;
+		}
+
+		return Qt::ItemIsEnabled;
+	}
+
+
+	///
+	/// Selection changed handler
+	///
+	void MergeTableModel::onSelectionChanged()
+	{
+		for ( int iRow = 0; iRow < mMerge->recordList().size(); iRow++ )
+		{
+			auto index = createIndex( iRow, 0 );
+			emit dataChanged( index, index, {Qt::CheckStateRole} );
+		}
+	}
+
+
+} // namespace glabels

glabels/MergeTableModel.h

@@ -0,0 +1,80 @@
+/*  MergeTableModel.h
+ *
+ *  Copyright (C) 2025  Jaye Evins <evins@snaught.com>
+ *
+ *  This file is part of gLabels-qt.
+ *
+ *  gLabels-qt is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  gLabels-qt 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 General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with gLabels-qt.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef MergeTableModel_h
+#define MergeTableModel_h
+
+
+#include "merge/Merge.h"
+
+#include <QAbstractTableModel>
+
+
+namespace glabels
+{
+
+	///
+	/// MergeTable proxy model
+	///
+	class MergeTableModel : public QAbstractTableModel
+	{
+		Q_OBJECT
+
+		/////////////////////////////////
+		// Life Cycle
+		/////////////////////////////////
+	public:
+		MergeTableModel( merge::Merge* merge, QObject* parent = nullptr );
+
+
+		/////////////////////////////////
+		// Public methods
+		/////////////////////////////////
+	public:
+		int rowCount( const QModelIndex& parent = QModelIndex() ) const override;
+		int columnCount( const QModelIndex &parent = QModelIndex() ) const override;
+
+		QVariant headerData( int section, Qt::Orientation orientation, int role = Qt::DisplayRole ) const override;
+		QVariant data( const QModelIndex& index, int role = Qt::DisplayRole ) const override;
+		bool setData( const QModelIndex& index, const QVariant& value, int role = Qt::EditRole ) override;
+		Qt::ItemFlags flags( const QModelIndex& index ) const override;
+		
+
+		/////////////////////////////////
+		// Private slots
+		/////////////////////////////////
+	private slots:
+		void onSelectionChanged();
+
+
+		/////////////////////////////////
+		// Private Members
+		/////////////////////////////////
+	private:
+		merge::Merge* mMerge;
+
+		QStringList mDisplayKeys;
+		
+	};
+
+}
+
+
+#endif // MergeTableModel_h

glabels/MergeView.cpp

@@ -21,6 +21,8 @@
 
 #include "MergeView.h"
 
+#include "MergeTableModel.h"
+
 #include "merge/Factory.h"
 
 #include "model/FileUtil.h"
@@ -38,7 +40,7 @@ namespace glabels
 	/// Constructor
 	///
 	MergeView::MergeView( QWidget *parent )
-		: QWidget(parent), mModel(nullptr), mUndoRedoModel(nullptr), mBlock(false), mOldFormatComboIndex(0)
+		: QWidget(parent), mModel(nullptr), mUndoRedoModel(nullptr), mOldFormatComboIndex(0)
 	{
 		setupUi( this );
 
@@ -98,19 +100,11 @@ namespace glabels
 			break;
 		}
 
-		recordsTable->clear();
+		recordsTableView->setModel( new MergeTableModel( mModel->merge() ) );
-		recordsTable->setColumnCount( 0 );
+		recordsTableView->resizeColumnsToContents();
-		loadHeaders( mModel->merge() );
-		loadTable( mModel->merge() );
 
 		connect( mModel->merge(), SIGNAL(sourceChanged()),
 		         this, SLOT(onMergeSourceChanged()) );
-		
-		connect( mModel->merge(), SIGNAL(selectionChanged()),
-		         this, SLOT(onMergeSelectionChanged()) );
-
-		connect( recordsTable, SIGNAL(cellChanged(int,int)),
-		         this, SLOT(onCellChanged(int,int)) );
 	}
 
 
@@ -122,32 +116,8 @@ namespace glabels
 		QString fn = model::FileUtil::makeRelativeIfInDir( mModel->dir(), mModel->merge()->source() );
 		locationLineEdit->setText( fn );
 
-		recordsTable->clear();
+		recordsTableView->setModel( new MergeTableModel( mModel->merge() ) );
-		recordsTable->setColumnCount( 0 );
+		recordsTableView->resizeColumnsToContents();
-		loadHeaders( mModel->merge() );
-		loadTable( mModel->merge() );
-	}
-
-
-	///
-	/// Merge selection changed handler
-	///
-	void MergeView::onMergeSelectionChanged()
-	{
-		mBlock = true;  // Don't recurse
-	
-		auto& records = mModel->merge()->recordList();
-
-		int iRow = 0;
-		for ( auto& record : records )
-		{
-			QTableWidgetItem* item = recordsTable->item( iRow, 0 );
-			item->setCheckState( record.isSelected() ? Qt::Checked : Qt::Unchecked );
-
-			iRow++;
-		}
-
-		mBlock = false;
 	}
 
 
@@ -212,118 +182,6 @@ namespace glabels
 	}
 
 
-	///
-	/// Cell changed handler
-	///
-	void MergeView::onCellChanged( int iRow, int iCol )
-	{
-		if ( !mBlock )
-		{
-			QTableWidgetItem* item = recordsTable->item( iRow, 0 );
-			bool state = (item->checkState() == Qt::Unchecked) ? false : true;
-		
-			mModel->merge()->setSelected( iRow, state );
-		}
-	}
-
-
-	///
-	/// Load headers
-	///
-	void MergeView::loadHeaders( merge::Merge* merge )
-	{
-		mPrimaryKey = merge->primaryKey();
-		mKeys = merge->keys();
-
-		if ( mKeys.size() > 0 )
-		{
-			recordsTable->setColumnCount( mKeys.size() + 1 );  // Include extra column
-
-			// First column = primary Key
-			auto* item = new QTableWidgetItem( mPrimaryKey );
-			item->setFlags( Qt::ItemIsEnabled );
-			recordsTable->setHorizontalHeaderItem( 0, item );
-
-			// Starting on second column, one column per key, skip primary Key
-			int iCol = 1;
-			foreach ( QString key, mKeys )
-			{
-				if ( key != mPrimaryKey )
-				{
-					auto* item = new QTableWidgetItem( key );
-					item->setFlags( Qt::ItemIsEnabled );
-					recordsTable->setHorizontalHeaderItem( iCol, item );
-
-					iCol++;
-				}
-
-			}
-
-			// Extra dummy column to fill any extra horizontal space
-			auto* fillItem = new QTableWidgetItem();
-			fillItem->setFlags( Qt::NoItemFlags );
-			recordsTable->setHorizontalHeaderItem( iCol, fillItem );
-			recordsTable->horizontalHeader()->setStretchLastSection( true );
-		}
-	}
-
-
-	///
-	/// Load table
-	///
-	void MergeView::loadTable( merge::Merge* merge )
-	{
-		mBlock = true;
-
-		auto& records = merge->recordList();
-		recordsTable->setRowCount( records.size() );
-
-		int iRow = 0;
-		for ( auto record : records )
-		{
-			// First column for primary field
-			auto* item = new QTableWidgetItem();
-			if ( record.contains( mPrimaryKey ) )
-			{
-				auto text = printableTextForView( record[mPrimaryKey] );
-				item->setText( text );
-			}
-			item->setFlags( Qt::ItemIsEnabled | Qt::ItemIsUserCheckable );
-			item->setCheckState( record.isSelected() ? Qt::Checked : Qt::Unchecked );
-			recordsTable->setItem( iRow, 0, item );
-			recordsTable->resizeColumnToContents( 0 );
-
-			// Starting on 2nd column, 1 column per field, skip primary field
-			int iCol = 1;
-			for ( auto& key : mKeys )
-			{
-				if ( key != mPrimaryKey )
-				{
-					if ( record.contains( key ) )
-					{
-						auto text = printableTextForView( record[key] );
-						auto* item = new QTableWidgetItem( text );
-						item->setFlags( Qt::ItemIsEnabled );
-						recordsTable->setItem( iRow, iCol, item );
-						recordsTable->resizeColumnToContents( iCol );
-					}
-
-					iCol++;
-				}
-			}
-
-			// Extra dummy column to fill any extra horizontal space
-			auto* fillItem = new QTableWidgetItem();
-			fillItem->setFlags( Qt::NoItemFlags );
-			recordsTable->setItem( iRow, iCol, fillItem );
-
-			iRow++;
-		}
-
-		mBlock = false;
-	}
-
-
 	///
 	/// modify text to be printable e.g. replace newlines
 	///
@@ -337,4 +195,6 @@ namespace glabels
 
 		return text;
 	}
+
+
 } // namespace glabels

glabels/MergeView.h

@@ -64,22 +64,18 @@ namespace glabels
 	private slots:
 		void onMergeChanged();
 		void onMergeSourceChanged();
-		void onMergeSelectionChanged();
 
 		void onFormatComboActivated();
 		void onLocationBrowseButtonClicked();
 		void onSelectAllButtonClicked();
 		void onUnselectAllButtonClicked();
 		void onReloadButtonClicked();
-		void onCellChanged( int iRow, int iCol );
 
 
 		/////////////////////////////////
 		// Private methods
 		/////////////////////////////////
 	private:
-		void loadHeaders( merge::Merge* merge );
-		void loadTable( merge::Merge* merge );
 		static QString printableTextForView( QString text );
 
 
@@ -97,7 +93,6 @@ namespace glabels
 
 		QString mCwd;
 
-		bool mBlock;
 		int  mOldFormatComboIndex;
 
 	};

glabels/ui/MergeView.ui

@@ -95,13 +95,6 @@
         <string>Records</string>
        </property>
        <layout class="QGridLayout" name="gridLayout_4">
-        <item row="0" column="0">
-         <widget class="QTableWidget" name="recordsTable">
-          <property name="focusPolicy">
-           <enum>Qt::NoFocus</enum>
-          </property>
-         </widget>
-        </item>
         <item row="1" column="0">
          <layout class="QHBoxLayout" name="horizontalLayout">
           <item>
@@ -140,6 +133,28 @@
           </item>
          </layout>
         </item>
+        <item row="0" column="0">
+         <widget class="QTableView" name="recordsTableView">
+          <property name="focusPolicy">
+           <enum>Qt::NoFocus</enum>
+          </property>
+          <property name="selectionMode">
+           <enum>QAbstractItemView::NoSelection</enum>
+          </property>
+          <property name="textElideMode">
+           <enum>Qt::ElideRight</enum>
+          </property>
+          <attribute name="horizontalHeaderCascadingSectionResizes">
+           <bool>true</bool>
+          </attribute>
+          <attribute name="horizontalHeaderStretchLastSection">
+           <bool>true</bool>
+          </attribute>
+          <attribute name="verticalHeaderStretchLastSection">
+           <bool>false</bool>
+          </attribute>
+         </widget>
+        </item>
        </layout>
       </widget>
      </item>