From 123ebf1d957e48227b0819d8236cba57aa52a0d2 Mon Sep 17 00:00:00 2001
From: Craig Watson <craig@watsons.ch>
Date: Sat, 9 Sep 2017 13:30:51 -0400
Subject: [PATCH] Improved drawing of end of current stroke

Distance between the last drawn point and the current point is
calculated to be able to discard very short stroke segments (i.e we only
add to the current stroke if the input device has moved more than a
certain distance since the last drawn point).

This commit moves this code from the stroke to the scene, which allows
to calculate distance more accurately: it is now calculated as the
total, absolute distance traveled since the last point, rather than simply the
length of a line between the last point and current one.
---
 src/domain/UBGraphicsScene.cpp  | 21 +++++++++++++++++----
 src/domain/UBGraphicsScene.h    |  1 +
 src/domain/UBGraphicsStroke.cpp |  8 --------
 3 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/src/domain/UBGraphicsScene.cpp b/src/domain/UBGraphicsScene.cpp
index 9b6a1958..4327a495 100644
--- a/src/domain/UBGraphicsScene.cpp
+++ b/src/domain/UBGraphicsScene.cpp
@@ -561,9 +561,22 @@ bool UBGraphicsScene::inputDeviceMove(const QPointF& scenePos, const qreal& pres
                     interpolator = UBInterpolator::Bezier;
                 }
 
-                QList<QPair<QPointF, qreal> > newPoints = mCurrentStroke->addPoint(scenePos, width, interpolator);
-                if (newPoints.length() > 1) {
-                    drawCurve(newPoints);
+
+                // Don't draw segments smaller than a certain length. This can help with performance
+                // (less polygons to draw) but mostly with making the curve look smooth.
+
+                qreal antiScaleRatio = 1./(UBApplication::boardController->systemScaleFactor() * UBApplication::boardController->currentZoom());
+                qreal MIN_DISTANCE = 10*antiScaleRatio; // arbitrary. Move to settings if relevant.
+                qreal distance = QLineF(mPreviousPoint, scenePos).length();
+
+                mDistanceFromLastStrokePoint += distance;
+
+                if (mDistanceFromLastStrokePoint > MIN_DISTANCE) {
+                    QList<QPair<QPointF, qreal> > newPoints = mCurrentStroke->addPoint(scenePos, width, interpolator);
+                    if (newPoints.length() > 1)
+                        drawCurve(newPoints);
+
+                    mDistanceFromLastStrokePoint = 0;
                 }
 
                 if (interpolator == UBInterpolator::Bezier) {
@@ -577,7 +590,7 @@ bool UBGraphicsScene::inputDeviceMove(const QPointF& scenePos, const qreal& pres
                         mTempPolygon = NULL;
                     }
 
-                    QPointF lastDrawnPoint = newPoints.last().first;
+                    QPointF lastDrawnPoint = mCurrentStroke->points().last().first;
 
                     mTempPolygon = lineToPolygonItem(QLineF(lastDrawnPoint, scenePos), mPreviousWidth, width);
                     addItem(mTempPolygon);
diff --git a/src/domain/UBGraphicsScene.h b/src/domain/UBGraphicsScene.h
index 18a8c05a..84d01514 100644
--- a/src/domain/UBGraphicsScene.h
+++ b/src/domain/UBGraphicsScene.h
@@ -429,6 +429,7 @@ public slots:
 
         QPointF mPreviousPoint;
         qreal mPreviousWidth;
+        qreal mDistanceFromLastStrokePoint;
 
         QList<UBGraphicsPolygonItem*> mPreviousPolygonItems;
 
diff --git a/src/domain/UBGraphicsStroke.cpp b/src/domain/UBGraphicsStroke.cpp
index 8218624d..4456b26d 100644
--- a/src/domain/UBGraphicsStroke.cpp
+++ b/src/domain/UBGraphicsStroke.cpp
@@ -102,14 +102,6 @@ QList<QPair<QPointF, qreal> > UBGraphicsStroke::addPoint(const QPointF& point, q
         // The curve we are interpolating is not between two drawn points;
         // it is between the midway points of the second-to-last and last point, and last and current point.
 
-        // Don't draw segments smaller than a certain length. This can help with performance
-        // (less polygons to draw) but mostly with keeping the curve smooth.
-        qreal MIN_DISTANCE = 3*mAntiScaleRatio;
-        qreal distance = QLineF(mReceivedPoints.last().first, newPoint.first).length();
-
-        if (distance < MIN_DISTANCE) {
-            return QList<strokePoint>() << mDrawnPoints.last();
-        }
 
         // The first segment is just a straight line to the first midway point
         if (n == 1) {