Draw last (half-) segment of stroke to make drawing feel smoother

Also, clarified the difference between received and drawn points
in UBGraphicsStroke

src/domain/UBGraphicsScene.cpp

@@ -335,6 +335,7 @@ UBGraphicsScene::UBGraphicsScene(UBDocumentProxy* parent, bool enableUndoRedoSta
     , mZLayerController(new UBZLayerController(this))
     , mpLastPolygon(NULL)
     , mCurrentPolygon(0)
+    , mTempPolygon(NULL)
     , mSelectionFrame(0)
 {
     UBCoreGraphicsScene::setObjectName("BoardScene");
@@ -561,6 +562,23 @@ bool UBGraphicsScene::inputDeviceMove(const QPointF& scenePos, const qreal& pres
                 if (newPoints.length() > 1) {
                     drawCurve(newPoints, mPreviousWidth, width);
                 }
+
+                if (interpolator == UBInterpolator::Bezier) {
+                    // Bezier curves aren't drawn all the way to the scenePos (they stop halfway between the previous and
+                    // current scenePos), so we add a line from the last drawn position in the stroke and the
+                    // scenePos, to make the drawing feel more responsive. This line is then deleted if a new segment is
+                    // added to the stroke. (Or it is added to the stroke when we stop drawing)
+
+                    if (mTempPolygon) {
+                        removeItem(mTempPolygon);
+                        mTempPolygon = NULL;
+                    }
+
+                    QPointF lastDrawnPoint = newPoints.last();
+
+                    mTempPolygon = lineToPolygonItem(QLineF(lastDrawnPoint, scenePos), mPreviousWidth, width);
+                    addItem(mTempPolygon);
+                }
             }
         }
         else if (currentTool == UBStylusTool::Eraser)
@@ -629,6 +647,13 @@ bool UBGraphicsScene::inputDeviceRelease()
             mDrawWithCompass = false;
         }
         else if (mCurrentStroke){
+            if (mTempPolygon) {
+                UBGraphicsPolygonItem * poly = dynamic_cast<UBGraphicsPolygonItem*>(mTempPolygon->deepCopy());
+                removeItem(mTempPolygon);
+                mTempPolygon = NULL;
+                addPolygonItemToCurrentStroke(poly);
+            }
+
             UBGraphicsStrokesGroup* pStrokes = new UBGraphicsStrokesGroup();
 
             // Remove the strokes that were just drawn here and replace them by a stroke item

src/domain/UBGraphicsScene.h

@@ -442,6 +442,7 @@ public slots:
 
         UBZLayerController *mZLayerController;
         UBGraphicsPolygonItem* mpLastPolygon;
+        UBGraphicsPolygonItem* mTempPolygon;
 
         bool mDrawWithCompass;
         UBGraphicsPolygonItem *mCurrentPolygon;

src/domain/UBGraphicsStroke.cpp

@@ -70,18 +70,18 @@ QList<UBGraphicsPolygonItem*> UBGraphicsStroke::polygons() const
  */
 QList<QPointF> UBGraphicsStroke::addPoint(const QPointF& point, UBInterpolator::InterpolationMethod interpolationMethod)
 {
-    int n = mDrawnPoints.size();
+    int n = mReceivedPoints.size();
 
     if (n == 0) {
+        mReceivedPoints << point;
         mDrawnPoints << point;
-        mAllPoints << point;
         return QList<QPointF>();
     }
 
     if (interpolationMethod == UBInterpolator::NoInterpolation) {
-        QPointF lastPoint = mDrawnPoints.last();
+        QPointF lastPoint = mReceivedPoints.last();
+        mReceivedPoints << point;
         mDrawnPoints << point;
-        mAllPoints << point;
         return QList<QPointF>() << lastPoint << point;
     }
 
@@ -91,23 +91,24 @@ QList<QPointF> UBGraphicsStroke::addPoint(const QPointF& point, UBInterpolator::
 
         // Don't draw segments smaller than a certain length. This can help with performance
         // (less polygons in a stroke) but mostly with keeping the curve smooth.
-        qreal MIN_DISTANCE = 3*mAntiScaleRatio;
-        qreal distance = QLineF(mDrawnPoints.last(), point).length();
+        qreal MIN_DISTANCE = 5*mAntiScaleRatio;
+        qreal distance = QLineF(mReceivedPoints.last(), point).length();
 
         if (distance < MIN_DISTANCE) {
-            return QList<QPointF>();
+            return QList<QPointF>() << mDrawnPoints.last();
         }
 
         // The first segment is just a straight line to the first midway point
         if (n == 1) {
-            QPointF lastPoint = mDrawnPoints[0];
-            mDrawnPoints << point;
+            QPointF lastPoint = mReceivedPoints[0];
+            mReceivedPoints << point;
+            mDrawnPoints << QPointF((lastPoint + point)/2.0);
 
             return QList<QPointF>() << lastPoint << ((lastPoint + point)/2.0);
         }
 
-        QPointF p0 = mDrawnPoints[mDrawnPoints.size() - 2];
-        QPointF p1 = mDrawnPoints[mDrawnPoints.size() - 1];
+        QPointF p0 = mReceivedPoints[mReceivedPoints.size() - 2];
+        QPointF p1 = mReceivedPoints[mReceivedPoints.size() - 1];
         QPointF p2 = point;
 
         UBQuadraticBezier bz;
@@ -119,11 +120,15 @@ QList<QPointF> UBGraphicsStroke::addPoint(const QPointF& point, UBInterpolator::
 
         QList<QPointF> newPoints = bz.getPoints(10);
 
+        // avoid adding duplicates
+        if (newPoints.first() == mDrawnPoints.last())
+            mDrawnPoints.removeLast();
+
         foreach(QPointF p, newPoints) {
-            mAllPoints << p;
+            mDrawnPoints << p;
         }
 
-        mDrawnPoints << point;
+        mReceivedPoints << point;
         return newPoints;
     }
 

src/domain/UBGraphicsStroke.h

@@ -59,7 +59,7 @@ class UBGraphicsStroke
 
         QList<QPointF> addPoint(const QPointF& point, UBInterpolator::InterpolationMethod interpolationMethod = UBInterpolator::NoInterpolation);
 
-        const QList<QPointF>& points() { return mAllPoints; }
+        const QList<QPointF>& points() { return mDrawnPoints; }
 
     protected:
         void addPolygon(UBGraphicsPolygonItem* pol);
@@ -68,11 +68,11 @@ class UBGraphicsStroke
 
         QList<UBGraphicsPolygonItem*> mPolygons;
 
-        /// Points that were drawn by the user (actually received through input device)
-        QList<QPointF> mDrawnPoints;
+        /// Points that were drawn by the user (i.e, actually received through input device)
+        QList<QPointF> mReceivedPoints;
 
         /// All the points (including interpolated) that are used to draw the stroke
-        QList<QPointF> mAllPoints;
+        QList<QPointF> mDrawnPoints;
 
         qreal mAntiScaleRatio;
 };