[Feature] Allow custom expression functions in expression widget

Author: NathanW2

src/gui/qgsexpressionbuilderwidget.cpp

@@ -18,6 +18,7 @@
 #include "qgsexpression.h"
 #include "qgsmessageviewer.h"
 #include "qgsapplication.h"
+#include "qgspythonrunner.h"
 
 #include <QSettings>
 #include <QMenu>
@@ -112,6 +113,11 @@ QgsExpressionBuilderWidget::QgsExpressionBuilderWidget( QWidget *parent )
   splitter_2->restoreState( settings.value( "/windows/QgsExpressionBuilderWidget/splitter2" ).toByteArray() );
 
   txtExpressionString->setFoldingVisible( false );
+  customFunctionBotton->setVisible( QgsPythonRunner::isValid() );
+  txtPython->setVisible( false );
+  txtPython->setText("@qgsfunction(args=-1, group='Custom')\n"
+                     "def func(values, feature, parent):\n"
+                     "    return str(values)");
 }
 
 
@@ -292,6 +298,10 @@ void QgsExpressionBuilderWidget::setGeomCalculator( const QgsDistanceArea & da )
 
 QString QgsExpressionBuilderWidget::expressionText()
 {
+  if ( QgsPythonRunner::isValid() ) {
+      QString pythontext = txtPython->text();
+      QgsPythonRunner::run( pythontext );
+  }
   return txtExpressionString->text();
 }
 
@@ -302,7 +312,7 @@ void QgsExpressionBuilderWidget::setExpressionText( const QString& expression )
 
 void QgsExpressionBuilderWidget::on_txtExpressionString_textChanged()
 {
-  QString text = txtExpressionString->text();
+  QString text = expressionText();
 
   // If the string is empty the expression will still "fail" although
   // we don't show the user an error as it will be confusing.
@@ -316,8 +326,6 @@ void QgsExpressionBuilderWidget::on_txtExpressionString_textChanged()
     return;
   }
 
-
-
   QgsExpression exp( text );
 
   if ( mLayer )

src/ui/qgsexpressionbuilder.ui

@@ -6,8 +6,8 @@
    <rect>
     <x>0</x>
     <y>0</y>
-    <width>418</width>
-    <height>447</height>
+    <width>538</width>
+    <height>535</height>
    </rect>
   </property>
   <property name="sizePolicy">
@@ -453,7 +453,7 @@
           <property name="bottomMargin">
            <number>0</number>
           </property>
-          <item row="1" column="0">
+          <item row="3" column="0">
            <widget class="QLabel" name="label_2">
             <property name="sizePolicy">
              <sizepolicy hsizetype="Fixed" vsizetype="Fixed">
@@ -469,7 +469,7 @@
             </property>
            </widget>
           </item>
-          <item row="1" column="1">
+          <item row="3" column="1">
            <widget class="QLabel" name="lblPreview">
             <property name="sizePolicy">
              <sizepolicy hsizetype="Preferred" vsizetype="Preferred">
@@ -514,9 +514,25 @@
             </property>
            </widget>
           </item>
-          <item row="0" column="0" colspan="2">
+          <item row="2" column="0" colspan="2">
            <widget class="QgsCodeEditorSQL" name="txtExpressionString" native="true"/>
           </item>
+          <item row="1" column="0" colspan="2">
+           <widget class="QgsCodeEditorPython" name="txtPython" native="true"/>
+          </item>
+          <item row="0" column="0" colspan="2">
+           <widget class="QToolButton" name="customFunctionBotton">
+            <property name="text">
+             <string>Define custom function</string>
+            </property>
+            <property name="checkable">
+             <bool>true</bool>
+            </property>
+            <property name="autoRaise">
+             <bool>true</bool>
+            </property>
+           </widget>
+          </item>
          </layout>
         </widget>
        </item>
@@ -544,7 +560,30 @@
    <header>qgscodeeditorsql.h</header>
    <container>1</container>
   </customwidget>
+  <customwidget>
+   <class>QgsCodeEditorPython</class>
+   <extends>QWidget</extends>
+   <header>qgscodeeditorpython.h</header>
+   <container>1</container>
+  </customwidget>
  </customwidgets>
  <resources/>
- <connections/>
+ <connections>
+  <connection>
+   <sender>customFunctionBotton</sender>
+   <signal>toggled(bool)</signal>
+   <receiver>txtPython</receiver>
+   <slot>setVisible(bool)</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>74</x>
+     <y>468</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>116</x>
+     <y>485</y>
+    </hint>
+   </hints>
+  </connection>
+ </connections>
 </ui>