Add a set to null ('clear') to color buttons

Author: nyalldawson

python/gui/qgscolorbuttonv2.sip

@@ -151,6 +151,28 @@ class QgsColorButtonV2 : QToolButton
      */
     void setNoColorString( const QString& noColorString );
 
+     /** Sets whether a set to null (clear) option is shown in the button's drop down menu.
+     * @param showNull set to true to show a null option
+     * @note added in QGIS 2.16
+     * @see showNull()
+     * @see isNull()
+     */
+    void setShowNull( bool showNull );
+
+    /** Returns whether the set to null (clear) option is shown in the button's drop down menu.
+     * @note added in QGIS 2.16
+     * @see setShowNull()
+     * @see isNull()
+     */
+    bool showNull() const;
+
+    /** Returns true if the current color is null.
+     * @note added in QGIS 2.16
+     * @see setShowNull()
+     * @see showNull()
+     */
+    bool isNull() const;
+
     /** Returns the string used for the "no color" option in the button's drop down menu.
      * @returns string used for the "no color" menu option
      * @see setNoColorString
@@ -237,6 +259,13 @@ class QgsColorButtonV2 : QToolButton
      */
     void setToDefaultColor();
 
+    /** Sets color to null.
+     * @see setToDefaultColor()
+     * @see setToNoColor()
+     * @note added in QGIS 2.16
+     */
+    void setToNull();
+
   signals:
 
     /** Is emitted whenever a new color is set for the button. The color is always valid.

src/gui/editorwidgets/qgscolorwidgetwrapper.cpp

@@ -64,6 +64,7 @@ void QgsColorWidgetWrapper::initWidget( QWidget* editor )
     mColorButton = editor->findChild<QgsColorButtonV2*>();
   }
 
+  mColorButton->setShowNull( true );
   connect( mColorButton, SIGNAL( colorChanged( QColor ) ), this, SLOT( valueChanged() ) );
 }
 

src/gui/qgscolorbuttonv2.cpp

@@ -49,6 +49,7 @@ QgsColorButtonV2::QgsColorButtonV2( QWidget *parent, const QString& cdt, QgsColo
     , mColorSet( false )
     , mShowNoColorOption( false )
     , mNoColorString( tr( "No color" ) )
+    , mShowNull( false )
     , mPickingColor( false )
     , mMenu( nullptr )
 
@@ -155,6 +156,11 @@ void QgsColorButtonV2::setToDefaultColor()
   setColor( mDefaultColor );
 }
 
+void QgsColorButtonV2::setToNull()
+{
+  setColor( QColor() );
+}
+
 void QgsColorButtonV2::setToNoColor()
 {
   if ( mAllowAlpha )
@@ -391,6 +397,14 @@ void QgsColorButtonV2::prepareMenu()
   //menu is opened, otherwise color schemes like the recent color scheme grid are meaningless
   mMenu->clear();
 
+  if ( mShowNull )
+  {
+    QAction* nullAction = new QAction( tr( "Clear color" ), this );
+    nullAction->setIcon( createMenuIcon( Qt::transparent, false ) );
+    mMenu->addAction( nullAction );
+    connect( nullAction, SIGNAL( triggered() ), this, SLOT( setToNull() ) );
+  }
+
   //show default color option if set
   if ( mDefaultColor.isValid() )
   {
@@ -664,3 +678,18 @@ void QgsColorButtonV2::setDefaultColor( const QColor& color )
   mDefaultColor = color;
 }
 
+void QgsColorButtonV2::setShowNull( bool showNull )
+{
+  mShowNull = showNull;
+}
+
+bool QgsColorButtonV2::showNull() const
+{
+  return mShowNull;
+}
+
+bool QgsColorButtonV2::isNull() const
+{
+  return !mColor.isValid();
+}
+

src/gui/qgscolorbuttonv2.h

@@ -184,6 +184,28 @@ class GUI_EXPORT QgsColorButtonV2 : public QToolButton
      */
     void setNoColorString( const QString& noColorString ) { mNoColorString = noColorString; }
 
+    /** Sets whether a set to null (clear) option is shown in the button's drop down menu.
+     * @param showNull set to true to show a null option
+     * @note added in QGIS 2.16
+     * @see showNull()
+     * @see isNull()
+     */
+    void setShowNull( bool showNull );
+
+    /** Returns whether the set to null (clear) option is shown in the button's drop down menu.
+     * @note added in QGIS 2.16
+     * @see setShowNull()
+     * @see isNull()
+     */
+    bool showNull() const;
+
+    /** Returns true if the current color is null.
+     * @note added in QGIS 2.16
+     * @see setShowNull()
+     * @see showNull()
+     */
+    bool isNull() const;
+
     /** Returns the string used for the "no color" option in the button's drop down menu.
      * @returns string used for the "no color" menu option
      * @see setNoColorString
@@ -261,15 +283,24 @@ class GUI_EXPORT QgsColorButtonV2 : public QToolButton
     /** Sets color to a totally transparent color.
      * @note If the color button is not set to show an alpha channel in the color
      * dialog (see setColorDialogOptions) then the color will not be changed.
+     * @see setToNull()
      */
     void setToNoColor();
 
     /** Sets color to the button's default color, if set.
      * @see setDefaultColor
      * @see defaultColor
+     * @see setToNull()
      */
     void setToDefaultColor();
 
+    /** Sets color to null.
+     * @see setToDefaultColor()
+     * @see setToNoColor()
+     * @note added in QGIS 2.16
+     */
+    void setToNull();
+
   signals:
 
     /** Is emitted whenever a new color is set for the button. The color is always valid.
@@ -346,6 +377,7 @@ class GUI_EXPORT QgsColorButtonV2 : public QToolButton
 
     bool mShowNoColorOption;
     QString mNoColorString;
+    bool mShowNull;
 
     QPoint mDragStartPosition;
     bool mPickingColor;