Merge pull request #5179 from opengisch/drawing_undo

Implement undo mechanism for drawing canvas

src/core/drawingcanvas.cpp

@@ -31,6 +31,8 @@ DrawingCanvas::DrawingCanvas( QQuickItem *parent )
 
 void DrawingCanvas::createBlankCanvas( int width, int height, QColor backgroundColor )
 {
+  clear();
+
   mBackgroundImage = QImage( QSize( width, height ), QImage::Format_ARGB32 );
   mBackgroundImage.fill( backgroundColor );
 
@@ -44,6 +46,8 @@ void DrawingCanvas::createBlankCanvas( int width, int height, QColor backgroundC
 
 void DrawingCanvas::createCanvasFromImage( const QString &path )
 {
+  clear();
+
   QImageReader imageReader( path.startsWith( QStringLiteral( "file://" ) ) ? path.mid( 7 ) : path );
   imageReader.setAutoTransform( true );
   mBackgroundImage = imageReader.read();
@@ -71,6 +75,8 @@ void DrawingCanvas::createCanvasFromImage( const QString &path )
 
 void DrawingCanvas::clear()
 {
+  mStrokes.clear();
+
   mBackgroundImage = QImage();
   mDrawingImage = QImage();
 
@@ -257,13 +263,15 @@ void DrawingCanvas::strokeEnd( const QPointF &point )
   painter.setRenderHint( QPainter::Antialiasing, true );
   drawStroke( &painter, mCurrentStroke );
 
+  mStrokes << mCurrentStroke;
   mCurrentStroke.points.clear();
 
   setIsDirty( true );
+
   update();
 }
 
-void DrawingCanvas::drawStroke( QPainter *painter, Stroke &stroke, bool onCanvas )
+void DrawingCanvas::drawStroke( QPainter *painter, const Stroke &stroke, bool onCanvas ) const
 {
   QPainterPath path( onCanvas ? stroke.points.at( 0 ) : canvasToItem( stroke.points.at( 0 ) ) );
   for ( int i = 1; i < stroke.points.size(); i++ )
@@ -279,15 +287,38 @@ void DrawingCanvas::drawStroke( QPainter *painter, Stroke &stroke, bool onCanvas
   painter->drawPath( path );
 }
 
-QPointF DrawingCanvas::itemToCanvas( const QPointF &point )
+void DrawingCanvas::undo()
+{
+  if ( !mStrokes.isEmpty() )
+  {
+    // Clear current stroke in the off chance an ongoing stroke had not yet ended
+    mCurrentStroke.points.clear();
+    mStrokes.removeLast();
+
+    // Reset image and redraw remaining strokes
+    mDrawingImage.fill( Qt::transparent );
+    for ( const Stroke &stroke : std::as_const( mStrokes ) )
+    {
+      QPainter painter( &mDrawingImage );
+      painter.setRenderHint( QPainter::Antialiasing, true );
+      drawStroke( &painter, stroke );
+    }
+
+    setIsDirty( !mStrokes.isEmpty() );
+
+    update();
+  }
+}
+
+QPointF DrawingCanvas::itemToCanvas( const QPointF &point ) const
 {
   const QPointF canvasTopLeft( size().width() / 2 - ( mBackgroundImage.size().width() * mZoomFactor / 2 ) + mOffset.x(),
                                size().height() / 2 - ( mBackgroundImage.size().height() * mZoomFactor / 2 ) + mOffset.y() );
   return QPointF( ( point.x() - canvasTopLeft.x() ) / mZoomFactor,
                   ( point.y() - canvasTopLeft.y() ) / mZoomFactor );
 }
 
-QPointF DrawingCanvas::canvasToItem( const QPointF &point )
+QPointF DrawingCanvas::canvasToItem( const QPointF &point ) const
 {
   const QPointF canvasTopLeft( size().width() / 2 - ( mBackgroundImage.size().width() * mZoomFactor / 2 ) + mOffset.x(),
                                size().height() / 2 - ( mBackgroundImage.size().height() * mZoomFactor / 2 ) + mOffset.y() );

src/core/drawingcanvas.h

@@ -112,6 +112,12 @@ class DrawingCanvas : public QQuickPaintedItem
      */
     Q_INVOKABLE void clear();
 
+    /**
+     * Undos the last drawing operation.
+     * \see isDirty()
+     */
+    Q_INVOKABLE void undo();
+
     /**
      * Saves the drawing canvas to a temporary location.
      * \returns the temporary file path of the saved image.
@@ -168,10 +174,10 @@ class DrawingCanvas : public QQuickPaintedItem
         QList<QPointF> points;
     };
 
-    void drawStroke( QPainter *painter, Stroke &stroke, bool onCanvas = true );
+    void drawStroke( QPainter *painter, const Stroke &stroke, bool onCanvas = true ) const;
 
-    QPointF itemToCanvas( const QPointF &point );
-    QPointF canvasToItem( const QPointF &point );
+    QPointF itemToCanvas( const QPointF &point ) const;
+    QPointF canvasToItem( const QPointF &point ) const;
 
     bool mIsEmpty = true;
     bool mIsDirty = false;
@@ -183,6 +189,7 @@ class DrawingCanvas : public QQuickPaintedItem
     QImage mBackgroundImage;
     QImage mDrawingImage;
 
+    QList<Stroke> mStrokes;
     Stroke mCurrentStroke;
 };
 

src/qml/QFieldSketcher.qml

@@ -47,7 +47,7 @@ Popup {
 
     DragHandler {
       id: stylusDragHandler
-      enabled: sketcher.visible
+      enabled: sketcher.visible && !drawingCanvas.isEmpty
       target: null
       acceptedButtons: Qt.NoButton | Qt.LeftButton | Qt.RightButton
       acceptedDevices: PointerDevice.Stylus | PointerDevice.Mouse
@@ -82,7 +82,7 @@ Popup {
 
     DragHandler {
       id: dragHandler
-      enabled: sketcher.visible
+      enabled: sketcher.visible && !drawingCanvas.isEmpty
       target: null
       acceptedButtons: Qt.NoButton | Qt.LeftButton
       acceptedDevices: PointerDevice.TouchScreen
@@ -107,7 +107,7 @@ Popup {
 
     PinchHandler {
       id: pinchHandler
-      enabled: sketcher.visible
+      enabled: sketcher.visible && !drawingCanvas.isEmpty
       acceptedButtons: Qt.NoButton | Qt.LeftButton
       acceptedDevices: PointerDevice.TouchScreen
       dragThreshold: 2
@@ -129,7 +129,7 @@ Popup {
 
     WheelHandler {
       id: wheelHandler
-      enabled: sketcher.visible
+      enabled: sketcher.visible && !drawingCanvas.isEmpty
       target: null
       grabPermissions: PointerHandler.CanTakeOverFromHandlersOfDifferentType | PointerHandler.ApprovesTakeOverByItems
 
@@ -281,6 +281,25 @@ Popup {
       }
     }
 
+    QfToolButton {
+      id: undoButton
+      visible: drawingCanvas.isDirty
+
+      anchors.right: saveButton.left
+      anchors.rightMargin: 5
+      anchors.top: parent.top
+      anchors.topMargin: mainWindow.sceneTopMargin + 5
+
+      iconSource: Theme.getThemeVectorIcon( "ic_undo_black_24dp" )
+      iconColor: "white"
+      bgcolor: Theme.darkGraySemiOpaque
+      round: true
+
+      onClicked: {
+        drawingCanvas.undo()
+      }
+    }
+
     QfToolButton {
       id: saveButton
       visible: !drawingCanvas.isEmpty
@@ -290,7 +309,7 @@ Popup {
       anchors.top: parent.top
       anchors.topMargin: mainWindow.sceneTopMargin + 5
 
-      iconSource: Theme.getThemeIcon( 'ic_check_white_48dp' )
+      iconSource: Theme.getThemeIcon( "ic_check_white_48dp" )
       iconColor: "white"
       bgcolor: drawingCanvas.isDirty ? Theme.mainColor : Theme.darkGraySemiOpaque
       round: true