function name is calculated automatically if leaving blanc

svn path=/trunk/kdeedu/kmplot/; revision=295868

kmplot/keditfunction.cpp

@@ -136,12 +136,17 @@ void KEditFunction::setWidgets()
 
 void KEditFunction::accept()
 {
+	// if we are editing an existing function, first delete the old one
 	if( m_index != -1 ) 
 	{
 		m_parser->delfkt( m_index );
 		m_index = -1;
 	}
 	
+	// find a name not allready used 
+	if( kLineEditName->text().isEmpty() )
+		kLineEditName->setText( newName() );
+	
 	int index = m_parser->addfkt( yFunction() );
 	if( index == -1 ) 
 	{
@@ -191,6 +196,33 @@ void KEditFunction::accept()
 	QEditFunction::accept();
 }
 
+QString KEditFunction::newName()
+{
+	int i = 0;
+	QString name;
+	// prepend the correct prefix
+	switch( m_type )
+	{
+		case Function:
+			name = "f%1";
+			break;
+		case Parametric:
+			name = "xf%1";
+			break;
+		case Polar:
+			name = "rf%1";
+	}
+	do
+	{
+		i++;
+	} while( m_parser->getfix( name.arg( i ) ) != -1 );
+	
+	// cut of prefix again, will be added later again
+	if( m_type == Parametric || m_type == Polar )
+		name = name.right( name.length()-1 );
+	return name.arg( i );
+}
+
 QString KEditFunction::xFunction()
 {
 	return "x" + kLineEditName->text() + "(t)=" + kLineEditXFunction->text();

kmplot/keditfunction.h

@@ -48,6 +48,7 @@ class KEditFunction : public QEditFunction
 		void setVisibleWidgets();
 		void clearWidgets();
 		void setWidgets();
+		QString newName();
 		void splitEquation( const QString equation, QString &name, QString &expression );
 		FunctionType m_type;
 		XParser* m_parser;

kmplot/qeditfunction.ui

@@ -8,8 +8,8 @@
         <rect>
             <x>0</x>
             <y>0</y>
-            <width>282</width>
-            <height>484</height>
+            <width>293</width>
+            <height>486</height>
         </rect>
     </property>
     <property name="sizePolicy">
@@ -71,7 +71,8 @@
                         <string>enter the expression</string>
                     </property>
                     <property name="whatsThis" stdset="0">
-                        <string>Enter an expression for the function.</string>
+                        <string>Enter an expression for the function. The dummy variable is t.
+Example: t^2</string>
                     </property>
                 </widget>
                 <widget class="KLineEdit" row="0" column="1">
@@ -85,7 +86,8 @@
                         <string>name of the function</string>
                     </property>
                     <property name="whatsThis" stdset="0">
-                        <string>Enter the name of the function.</string>
+                        <string>Enter the name of the function.
+The name of a function must be unique. If you leave this line empty KmPlot will set a default name. You can change it later.</string>
                     </property>
                 </widget>
                 <widget class="QLayoutWidget" row="2" column="0">