QGIS API Documentation  3.13.0-Master (b73bd58cfb)
qgsfieldexpressionwidget.cpp
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1 
2 /***************************************************************************
3  qgsfieldexpressionwidget.cpp
4  --------------------------------------
5  Date : 01.04.2014
6  Copyright : (C) 2014 Denis Rouzaud
7  Email : [email protected]
8 ***************************************************************************
9 * *
10 * This program is free software; you can redistribute it and/or modify *
11 * it under the terms of the GNU General Public License as published by *
12 * the Free Software Foundation; either version 2 of the License, or *
13 * (at your option) any later version. *
14 * *
15 ***************************************************************************/
16 
17 #include <QHBoxLayout>
18 #include <QObject>
19 #include <QKeyEvent>
20 
21 #include "qgsapplication.h"
24 #include "qgsfieldproxymodel.h"
25 #include "qgsdistancearea.h"
26 #include "qgsfieldmodel.h"
27 #include "qgsvectorlayer.h"
28 #include "qgsproject.h"
31 
33  : QWidget( parent )
34  , mExpressionDialogTitle( tr( "Expression Dialog" ) )
35  , mDistanceArea( nullptr )
36 
37 {
38  QHBoxLayout *layout = new QHBoxLayout( this );
39  layout->setContentsMargins( 0, 0, 0, 0 );
40 
41  mCombo = new QComboBox( this );
42  mCombo->setEditable( true );
43  mCombo->setSizePolicy( QSizePolicy::MinimumExpanding, QSizePolicy::Minimum );
44  int width = mCombo->minimumSizeHint().width();
45  mCombo->setMinimumWidth( width );
46 
47  mFieldProxyModel = new QgsFieldProxyModel( mCombo );
48  mFieldProxyModel->sourceFieldModel()->setAllowExpression( true );
49  mCombo->setModel( mFieldProxyModel );
50 
51  mButton = new QToolButton( this );
52  mButton->setSizePolicy( QSizePolicy::Minimum, QSizePolicy::Minimum );
53  mButton->setIcon( QgsApplication::getThemeIcon( QStringLiteral( "/mIconExpression.svg" ) ) );
54 
55  layout->addWidget( mCombo );
56  layout->addWidget( mButton );
57 
58  // give focus to the combo
59  // hence if the widget is used as a delegate
60  // it will allow pressing on the expression dialog button
61  setFocusProxy( mCombo );
62 
63  connect( mCombo->lineEdit(), &QLineEdit::textEdited, this, &QgsFieldExpressionWidget::expressionEdited );
64  connect( mCombo->lineEdit(), &QLineEdit::editingFinished, this, &QgsFieldExpressionWidget::expressionEditingFinished );
65  connect( mCombo, static_cast < void ( QComboBox::* )( int ) > ( &QComboBox::activated ), this, &QgsFieldExpressionWidget::currentFieldChanged );
66  connect( mButton, &QAbstractButton::clicked, this, &QgsFieldExpressionWidget::editExpression );
67  connect( mFieldProxyModel, &QAbstractItemModel::modelAboutToBeReset, this, &QgsFieldExpressionWidget::beforeResetModel );
68  connect( mFieldProxyModel, &QAbstractItemModel::modelReset, this, &QgsFieldExpressionWidget::afterResetModel );
69 
70  mExpressionContext = QgsExpressionContext();
71  mExpressionContext << QgsExpressionContextUtils::globalScope()
73 
74  mCombo->installEventFilter( this );
75 }
76 
78 {
79  mExpressionDialogTitle = title;
80 }
81 
82 void QgsFieldExpressionWidget::setFilters( QgsFieldProxyModel::Filters filters )
83 {
84  mFieldProxyModel->setFilters( filters );
85 }
86 
88 {
89  mCombo->lineEdit()->setClearButtonEnabled( allowEmpty );
90  mFieldProxyModel->sourceFieldModel()->setAllowEmptyFieldName( allowEmpty );
91 }
92 
94 {
95  return mFieldProxyModel->sourceFieldModel()->allowEmptyFieldName();
96 }
97 
99 {
100  QHBoxLayout *layout = dynamic_cast<QHBoxLayout *>( this->layout() );
101  if ( !layout )
102  return;
103 
104  if ( isLeft )
105  {
106  QLayoutItem *item = layout->takeAt( 1 );
107  layout->insertWidget( 0, item->widget() );
108  }
109  else
110  layout->addWidget( mCombo );
111 }
112 
114 {
115  mDistanceArea = std::shared_ptr<const QgsDistanceArea>( new QgsDistanceArea( da ) );
116 }
117 
119 {
120  return mCombo->currentText();
121 }
122 
124 {
126 }
127 
129 {
130  return asExpression();
131 }
132 
133 bool QgsFieldExpressionWidget::isValidExpression( QString *expressionError ) const
134 {
135  QString temp;
136  return QgsExpression::checkExpression( currentText(), &mExpressionContext, expressionError ? *expressionError : temp );
137 }
138 
140 {
141  return !mFieldProxyModel->sourceFieldModel()->isField( currentText() );
142 }
143 
144 QString QgsFieldExpressionWidget::currentField( bool *isExpression, bool *isValid ) const
145 {
146  QString text = currentText();
147  bool valueIsExpression = this->isExpression();
148  if ( isValid )
149  {
150  // valid if not an expression (ie, set to a field), or set to an expression and expression is valid
151  *isValid = !valueIsExpression || isValidExpression();
152  }
153  if ( isExpression )
154  {
155  *isExpression = valueIsExpression;
156  }
157  return text;
158 }
159 
161 {
162  return mFieldProxyModel->sourceFieldModel()->layer();
163 }
164 
166 {
167  mExpressionContextGenerator = generator;
168 }
169 
171 {
172  QgsVectorLayer *vl = qobject_cast< QgsVectorLayer * >( layer );
173 
174  if ( mFieldProxyModel->sourceFieldModel()->layer() )
175  disconnect( mFieldProxyModel->sourceFieldModel()->layer(), &QgsVectorLayer::updatedFields, this, &QgsFieldExpressionWidget::reloadLayer );
176 
177  if ( vl )
178  mExpressionContext = vl->createExpressionContext();
179  else
180  mExpressionContext = QgsProject::instance()->createExpressionContext();
181 
182  mFieldProxyModel->sourceFieldModel()->setLayer( vl );
183 
184  if ( mFieldProxyModel->sourceFieldModel()->layer() )
185  connect( mFieldProxyModel->sourceFieldModel()->layer(), &QgsVectorLayer::updatedFields, this, &QgsFieldExpressionWidget::reloadLayer, Qt::UniqueConnection );
186 }
187 
188 void QgsFieldExpressionWidget::setField( const QString &fieldName )
189 {
190  if ( fieldName.isEmpty() )
191  {
192  setRow( -1 );
193  emit fieldChanged( QString() );
194  emit fieldChanged( QString(), true );
195  return;
196  }
197 
198  QModelIndex idx = mFieldProxyModel->sourceFieldModel()->indexFromName( fieldName );
199  if ( !idx.isValid() )
200  {
201  // try to remove quotes and white spaces
202  QString simpleFieldName = fieldName.trimmed();
203  if ( simpleFieldName.startsWith( '"' ) && simpleFieldName.endsWith( '"' ) )
204  {
205  simpleFieldName.remove( 0, 1 ).chop( 1 );
206  idx = mFieldProxyModel->sourceFieldModel()->indexFromName( simpleFieldName );
207  }
208 
209  if ( !idx.isValid() )
210  {
211  // new expression
212  mFieldProxyModel->sourceFieldModel()->setExpression( fieldName );
213  idx = mFieldProxyModel->sourceFieldModel()->indexFromName( fieldName );
214  }
215  }
216  QModelIndex proxyIndex = mFieldProxyModel->mapFromSource( idx );
217  mCombo->setCurrentIndex( proxyIndex.row() );
219 }
220 
222 {
223  mFieldProxyModel->sourceFieldModel()->setFields( fields );
224 }
225 
227 {
228  setField( expression );
229 }
230 
232 {
233  QString currentExpression = currentText();
234  QgsVectorLayer *vl = layer();
235 
236  QgsExpressionContext context = mExpressionContextGenerator ? mExpressionContextGenerator->createExpressionContext() : mExpressionContext;
237 
238  QgsExpressionBuilderDialog dlg( vl, currentExpression, this, QStringLiteral( "generic" ), context );
239  if ( mDistanceArea )
240  {
241  dlg.setGeomCalculator( *mDistanceArea );
242  }
243  dlg.setWindowTitle( mExpressionDialogTitle );
244  dlg.setAllowEvalErrors( mAllowEvalErrors );
245 
246  if ( !vl )
247  dlg.expressionBuilder()->expressionTree()->loadFieldNames( mFieldProxyModel->sourceFieldModel()->fields() );
248 
249  if ( dlg.exec() )
250  {
251  QString newExpression = dlg.expressionText();
252  setField( newExpression );
253  }
254 }
255 
257 {
258  updateLineEditStyle( expression );
259  emit fieldChanged( expression, isValidExpression() );
260 }
261 
263 {
264  const QString expression = mCombo->lineEdit()->text();
265  mFieldProxyModel->sourceFieldModel()->setExpression( expression );
266  QModelIndex idx = mFieldProxyModel->sourceFieldModel()->indexFromName( expression );
267  QModelIndex proxyIndex = mFieldProxyModel->mapFromSource( idx );
268  mCombo->setCurrentIndex( proxyIndex.row() );
270 }
271 
273 {
274  if ( event->type() == QEvent::EnabledChange )
275  {
277  }
278 }
279 
280 void QgsFieldExpressionWidget::reloadLayer()
281 {
282  setLayer( mFieldProxyModel->sourceFieldModel()->layer() );
283 }
284 
285 void QgsFieldExpressionWidget::beforeResetModel()
286 {
287  // Backup expression
288  mBackupExpression = mCombo->currentText();
289 }
290 
291 void QgsFieldExpressionWidget::afterResetModel()
292 {
293  // Restore expression
294  mCombo->lineEdit()->setText( mBackupExpression );
295 }
296 
297 bool QgsFieldExpressionWidget::eventFilter( QObject *watched, QEvent *event )
298 {
299  if ( watched == mCombo && event->type() == QEvent::KeyPress )
300  {
301  QKeyEvent *keyEvent = static_cast<QKeyEvent *>( event );
302  if ( keyEvent->key() == Qt::Key_Enter || keyEvent->key() == Qt::Key_Return )
303  {
305  return true;
306  }
307  }
308  return QObject::eventFilter( watched, event );
309 }
310 
312 {
313  return mAllowEvalErrors;
314 }
315 
317 {
318  if ( allowEvalErrors == mAllowEvalErrors )
319  return;
320 
321  mAllowEvalErrors = allowEvalErrors;
322  emit allowEvalErrorsChanged();
323 }
324 
326 {
328 
329  bool isExpression, isValid;
330  QString fieldName = currentField( &isExpression, &isValid );
331 
332  // display tooltip if widget is shorter than expression
333  QFontMetrics metrics( mCombo->lineEdit()->font() );
334  if ( metrics.boundingRect( fieldName ).width() > mCombo->lineEdit()->width() )
335  {
336  mCombo->setToolTip( fieldName );
337  }
338  else
339  {
340  mCombo->setToolTip( QString() );
341  }
342 
343  emit fieldChanged( fieldName );
344  emit fieldChanged( fieldName, isValid );
345 }
346 
348 {
349  QString stylesheet;
350  if ( !isEnabled() )
351  {
352  stylesheet = QStringLiteral( "QLineEdit { color: %1; }" ).arg( QColor( Qt::gray ).name() );
353  }
354  else
355  {
356  bool isExpression, isValid;
357  if ( !expression.isEmpty() )
358  {
359  isExpression = true;
360  isValid = isExpressionValid( expression );
361  }
362  else
363  {
364  currentField( &isExpression, &isValid );
365  }
366  QFont font = mCombo->lineEdit()->font();
367  font.setItalic( isExpression );
368  mCombo->lineEdit()->setFont( font );
369 
370  if ( isExpression && !isValid )
371  {
372  stylesheet = QStringLiteral( "QLineEdit { color: %1; }" ).arg( QColor( Qt::red ).name() );
373  }
374  }
375  mCombo->lineEdit()->setStyleSheet( stylesheet );
376 }
377 
378 bool QgsFieldExpressionWidget::isExpressionValid( const QString &expressionStr )
379 {
380  QgsExpression expression( expressionStr );
381  expression.prepare( &mExpressionContext );
382  return !expression.hasParserError();
383 }
384 
386 {
387  mExpressionContext.appendScope( scope );
388 }
Class for parsing and evaluation of expressions (formerly called "search strings").
bool hasParserError() const
Returns true if an error occurred when parsing the input expression.
Base class for all map layer types.
Definition: qgsmaplayer.h:81
void setExpression(const QString &expression)
Sets the current expression text and if applicable also the field.
void setAllowEmptyFieldName(bool allowEmpty)
Sets whether an optional empty field ("not set") option is shown in the combo box.
QgsFieldModel * sourceFieldModel()
Returns the QgsFieldModel used in this QSortFilterProxyModel.
static QString quotedColumnRef(QString name)
Returns a quoted column reference (in double quotes)
void setLayer(QgsMapLayer *layer)
Sets the layer used to display the fields and expression.
void changeEvent(QEvent *event) override
QString asExpression() const
Returns the currently selected field or expression.
QgsExpressionContext createExpressionContext() const override
This method needs to be reimplemented in all classes which implement this interface and return an exp...
QgsExpressionBuilderWidget * expressionBuilder()
The builder widget that is used by the dialog.
bool allowEmptyFieldName
Definition: qgsfieldmodel.h:43
void setExpression(const QString &expression)
Sets a single expression to be added after the fields at the end of the model.
Container of fields for a vector layer.
Definition: qgsfields.h:42
void editExpression()
open the expression dialog to edit the current or add a new expression
static QIcon getThemeIcon(const QString &name)
Helper to get a theme icon.
QgsFieldProxyModel * setFilters(QgsFieldProxyModel::Filters filters)
Set flags that affect how fields are filtered in the model.
static QgsExpressionContextScope * projectScope(const QgsProject *project)
Creates a new scope which contains variables and functions relating to a QGIS project.
void setAllowEvalErrors(bool allowEvalErrors)
Allow accepting expressions with evaluation errors.
void setFields(const QgsFields &fields)
Manually sets the fields to use for the model.
QgsFieldProxyModel::Filters filters() const
currently used filter on list of fields
static bool checkExpression(const QString &text, const QgsExpressionContext *context, QString &errorMessage)
Tests whether a string is a valid expression.
virtual QgsExpressionContext createExpressionContext() const =0
This method needs to be reimplemented in all classes which implement this interface and return an exp...
static QgsExpressionContextScope * globalScope()
Creates a new scope which contains variables and functions relating to the global QGIS context...
void expressionEdited(const QString &expression)
when expression is edited by the user in the line edit, it will be checked for validity ...
void setAllowEmptyFieldName(bool allowEmpty)
Sets whether an optional empty field ("not set") option is present in the model.
The QgsFieldProxyModel class provides an easy to use model to display the list of fields of a layer...
bool isExpression() const
If the content is not just a simple field this method will return true.
Expression contexts are used to encapsulate the parameters around which a QgsExpression should be eva...
bool isValidExpression(QString *expressionError=nullptr) const
Returns true if the current expression is valid.
void setLayer(QgsVectorLayer *layer)
Set the layer from which fields are displayed.
void registerExpressionContextGenerator(const QgsExpressionContextGenerator *generator)
Register an expression context generator class that will be used to retrieve an expression context fo...
QgsFields fields() const
Returns the fields currently shown in the model.
void setGeomCalculator(const QgsDistanceArea &da)
Sets geometry calculator used in distance/area calculations.
void appendScope(QgsExpressionContextScope *scope)
Appends a scope to the current expression context.
void setAllowExpression(bool allowExpression)
Sets whether custom expressions are accepted and displayed in the model.
bool isExpressionValid(const QString &expressionStr)
void setGeomCalculator(const QgsDistanceArea &da)
Sets the geometry calculator used in the expression dialog.
Single scope for storing variables and functions for use within a QgsExpressionContext.
QgsExpressionContext createExpressionContext() const FINAL
This method needs to be reimplemented in all classes which implement this interface and return an exp...
Abstract interface for generating an expression context.
QString expression() const
Returns the currently selected field or expression.
bool allowEmptyFieldName() const
Returns true if the combo box allows the empty field ("not set") choice.
bool eventFilter(QObject *watched, QEvent *event) override
void fieldChanged(const QString &fieldName)
Emitted when the currently selected field changes.
bool allowEvalErrors() const
Allow accepting expressions with evaluation errors.
QgsVectorLayer layer
Definition: qgsfieldmodel.h:44
A general purpose distance and area calculator, capable of performing ellipsoid based calculations...
void allowEvalErrorsChanged()
Allow accepting expressions with evaluation errors.
void setAllowEvalErrors(bool allowEvalErrors)
Allow accepting expressions with evaluation errors.
void expressionEditingFinished()
when expression has been edited (finished) it will be added to the model
void setRow(int row)
sets the current row in the widget
void setExpressionDialogTitle(const QString &title)
define the title used in the expression dialog
QgsVectorLayer * layer() const
Returns the layer currently associated with the widget.
void setFilters(QgsFieldProxyModel::Filters filters)
setFilters allows filtering according to the type of field
bool prepare(const QgsExpressionContext *context)
Gets the expression ready for evaluation - find out column indexes.
bool isField(const QString &expression) const
Returns true if a string represents a field reference, or false if it is an expression consisting of ...
void appendScope(QgsExpressionContextScope *scope)
Appends a scope to the end of the context.
static QgsProject * instance()
Returns the QgsProject singleton instance.
Definition: qgsproject.cpp:458
void setField(const QString &fieldName)
sets the current field or expression in the widget
void setFields(const QgsFields &fields)
Sets the fields used in the widget to fields, this allows the widget to work without a layer...
QgsExpressionTreeView * expressionTree() const
Returns the expression tree.
void updateLineEditStyle(const QString &expression=QString())
updateLineEditStyle will re-style (color/font) the line edit depending on content and status ...
void loadFieldNames(const QgsFields &fields)
This allows loading fields without specifying a layer.
QModelIndex indexFromName(const QString &fieldName)
Returns the index corresponding to a given fieldName.
Represents a vector layer which manages a vector based data sets.
void updatedFields()
Emitted whenever the fields available from this layer have been changed.
A generic dialog for building expression strings.
QgsFieldExpressionWidget(QWidget *parent=nullptr)
QgsFieldExpressionWidget creates a widget with a combo box to display the fields and expression and a...
QString currentText() const
Returns the current text that is set in the expression area.
QString currentField(bool *isExpression=nullptr, bool *isValid=nullptr) const
currentField returns the currently selected field or expression if allowed