JKQTPlotter: improved plotting speed for line-graphs by drawing a series of single lines instead of a polyline in some cases

doc/dox/whatsnew.dox

@@ -33,6 +33,7 @@ Changes, compared to  \ref page_whatsnew_V4_0_0 "v4.0.0" include:
     <li>NEW/BREAKING CHANGE: changed JKQTPColorDerivationMode into a struct, which extends its capabilities above the previously available few enum-items</li>
     <li>NEW: added debug-feature to show boxes around text in the plot</li>
     <li>BREAKING: Print-Support can now be switched off with a CMAKE-option JKQtPlotter_BUILD_FORCE_NO_PRINTER_SUPPORT=ON. This also switches off PDF and SVG export, partly solves issue <a href="https://github.com/jkriege2/JKQtPlotter/issues/81">#81</a>, many thanks to <a href="https://github.com/sufuk">user:sufuk</a> for contributing part of the code and supplying the idea!  </li>
+    <li>NEW: improved plotting speed for line-graphs by drawing a series of single lines instead of a polyline in some cases</li>
     <li>NEW: improved plotting speed for line-graphs by a compression algorithm (see JKQTPGraphLinesCompressionMixin) that removes overlaying lines (e.g. in JKQTPXYLineGraph)</li>
     <li>NEW: improved plotting speed for line-graphs by a clipping algorithm (applies to JKQTPXYLineGraph, JKQTPGraphErrorStyleMixin, JKQTPSpecialLineHorizontalGraph, JKQTPSpecialLineVerticalGraph and others)</li>
     <li>NEW: improved plotting speed for scatter-graphs by not calling draw functions for symbols outside the plot window (e.g. in JKQTPXYLineGraph)</li>

examples/speed/speedtestplot.cpp

@@ -41,13 +41,16 @@ SpeedTestPlot::SpeedTestPlot():
     graph->setYColumn(columnY);
     graph->setTitle(QObject::tr("live sin() graph"));
     graph->setLineWidth(1);
+    graph->setSymbolType(JKQTPNoSymbol);
     addGraph(graph);
 
     graph2=new JKQTPXYLineGraph(this);
     graph2->setXColumn(columnX);
     graph2->setYColumn(columnY2);
     graph2->setTitle(QObject::tr("live cos() graph"));
-    graph2->setLineWidth(1);
+    graph2->setLineWidth(2);
+    graph2->setSymbolType(JKQTPNoSymbol);
+
     addGraph(graph2);
 
     // 6. scale the plot so the graph is contained
@@ -87,7 +90,7 @@ SpeedTestPlot::SpeedTestPlot():
 
     actSymbols=new QAction(QObject::tr("Show Graph Symbols"));
     actSymbols->setCheckable(true);
-    actSymbols->setChecked(true);
+    actSymbols->setChecked(false);
     connect(actSymbols, &QAction::toggled, std::bind([](bool enabled, JKQTPXYLineGraph* g, JKQTPXYLineGraph* g2,SpeedTestPlot* p){
                 g->setSymbolType(enabled?JKQTPCross:JKQTPNoSymbol);
                 g2->setSymbolType(enabled?JKQTPCircle:JKQTPNoSymbol);

lib/jkqtcommon/jkqtpenhancedpainter.cpp

@@ -23,7 +23,8 @@
 
 
 JKQTPEnhancedPainter::JKQTPEnhancedPainter(QPaintDevice *device):
-    QPainter(device)
+    QPainter(device),
+    m_flags(DefaultPaintMode)
 {
     initQEnhacedPainter();
 }
@@ -34,6 +35,51 @@ JKQTPEnhancedPainter::JKQTPEnhancedPainter():
     initQEnhacedPainter();
 }
 
+void JKQTPEnhancedPainter::setPainterFlag(PainterFlag flag, bool enabled)
+{
+    if (!enabled && m_flags.testFlag(flag)) m_flags &= ~flag;
+    else if (enabled && !m_flags.testFlag(flag)) m_flags |= flag;
+}
+
+void JKQTPEnhancedPainter::setPainterFlag(PainterFlags flags)
+{
+    m_flags=flags;
+}
+
+void JKQTPEnhancedPainter::drawPolylineFast(const QPointF *points, int pointCount)
+{
+    if (!points || pointCount<2) return;
+    if (m_flags.testFlag(VectorPainting) || pen().style()!=Qt::SolidLine || pen().widthF()>device()->devicePixelRatioF()+0.01 || pen().widthF()<device()->devicePixelRatioF()*0.8) {
+        //qDebug()<<"drawFastPolyline(): widthF="<<pen().widthF();
+        drawPolyline(points, pointCount);
+    } else {
+        //qDebug()<<"drawFastPolyline()";
+        // we use a specialized algorithm only in a very defined circumstances
+        for (int i=1; i<pointCount; i++) {
+            QLineF l(points[i-1], points[i]);
+            if (!l.isNull() && l.length()>0) drawLine(l);
+        }
+    }
+}
+
+void JKQTPEnhancedPainter::drawPolylineFast(const QPoint *points, int pointCount)
+{
+    if (!points || pointCount<2) return;
+    if (m_flags.testFlag(VectorPainting) || pen().style()!=Qt::SolidLine || pen().widthF()>1.01) {
+        drawPolyline(points, pointCount);
+    } else {
+        // we use a specialized algorithm only in a very defined circumstances
+        for (int i=1; i<pointCount; i++) {
+            QLine l(points[i-1], points[i]);
+            if (!l.isNull() && (l.dx()>0||l.dy()>0)) drawLine(l);
+        }
+    }
+}
+
+JKQTPEnhancedPainter::PainterFlags JKQTPEnhancedPainter::painterFlags() const {
+    return m_flags;
+}
+
 
 void JKQTPEnhancedPainter::initQEnhacedPainter()
 {

lib/jkqtcommon/jkqtpenhancedpainter.h

@@ -32,17 +32,46 @@
 */
 class JKQTCOMMON_LIB_EXPORT JKQTPEnhancedPainter : public QPainter {
     public:
+
+        enum PainterFlag { DefaultPaintMode = 0x00, /*!< \brief the default  mode, the JKQTPEnhancedPainter draws on a pixel-device */
+                           VectorPainting   = 0x01, /*!< \brief if set, the JKQTPEnhancedPainter draws onto a vector-device, like a printer, PDF or SVG-output */
+                         };
+        Q_ENUMS(PainterFlag)
+        Q_FLAGS(PainterFlags)
+        Q_DECLARE_FLAGS(PainterFlags, PainterFlag)
+
         JKQTPEnhancedPainter(QPaintDevice* device);
         JKQTPEnhancedPainter();
+        /** \copydoc m_flags */
+        PainterFlags painterFlags() const ;
+        /** \copydoc m_flags */
+        void setPainterFlag(PainterFlag flag, bool enabled=true);
+        /** \copydoc m_flags */
+        void setPainterFlag(PainterFlags flags);
 
+        /** \brief faster variant of QPainter::drawPolyline(),it turns out that drawing single lines is way faster than drawing with drawPolyLine()
+         *
+         *  At least for thin (1 Pixel) lines on non-vector-devices, this does not make much difference in appearance
+         */
+        void drawPolylineFast(const QPointF *points, int pointCount);
+        inline void drawPolylineFast(const QPolygonF &polyline) {
+            drawPolylineFast(polyline.constData(), int(polyline.size()));
+        }
+        void drawPolylineFast(const QPoint *points, int pointCount);
+        inline void drawPolylineFast(const QPolygon &polyline) {
+            drawPolylineFast(polyline.constData(), int(polyline.size()));
+        }
 
     protected:
         void initQEnhacedPainter();
     private:
-
+        /** \brief flags, specifying how the JKQTPEnhancedPainter works
+         *
+         *  \see PainterFlags */
+        PainterFlags m_flags;
 };
 
-
+Q_DECLARE_OPERATORS_FOR_FLAGS(JKQTPEnhancedPainter::PainterFlags)
 
 
 

lib/jkqtplotter/graphs/jkqtpcontour.cpp

@@ -126,7 +126,7 @@ void JKQTPContourPlot::draw(JKQTPEnhancedPainter &painter)
                 //qDebug()<<lineTranformed;
             }
             for (const QPolygonF& poly: contourLinesTransformedSingleLevel) {
-                painter.drawPolyline(poly);
+                painter.drawPolylineFast(poly);
             }
         }
     }

lib/jkqtplotter/graphs/jkqtpevaluatedfunction.cpp

@@ -299,14 +299,14 @@ void JKQTPEvaluatedFunctionWithErrorsGraphDrawingBase::drawXGraph(JKQTPEnhancedP
         if (getDrawLine()) {
             painter.save(); auto __finalpaintline=JKQTPFinally([&painter]() {painter.restore();});
             painter.setPen(p);
-            painter.drawPolyline(linePolygon);
+            painter.drawPolylineFast(linePolygon);
         }
 
         if (drawErrorLines && (static_cast<bool>(errorPlotFunction))) {
             painter.save(); auto __finalpainterrline=JKQTPFinally([&painter]() {painter.restore();});
             painter.setPen(ep);
-            painter.drawPolyline(errorLineTop);
+            painter.drawPolylineFast(errorLineTop);
-            painter.drawPolyline(errorLineBottom);
+            painter.drawPolylineFast(errorLineBottom);
         }
 
 
@@ -425,14 +425,14 @@ void JKQTPEvaluatedFunctionWithErrorsGraphDrawingBase::drawYGraph(JKQTPEnhancedP
         if (getDrawLine()) {
             painter.save(); auto __finalpaintline=JKQTPFinally([&painter]() {painter.restore();});
             painter.setPen(p);
-            painter.drawPolyline(linePolygon);
+            painter.drawPolylineFast(linePolygon);
         }
 
         if (drawErrorLines && (static_cast<bool>(errorPlotFunction))) {
             painter.save(); auto __finalpainterrline=JKQTPFinally([&painter]() {painter.restore();});
             painter.setPen(ep);
-            painter.drawPolyline(errorLineTop);
+            painter.drawPolylineFast(errorLineTop);
-            painter.drawPolyline(errorLineBottom);
+            painter.drawPolylineFast(errorLineBottom);
         }
 
 

lib/jkqtplotter/graphs/jkqtpevaluatedparametriccurve.cpp

@@ -108,7 +108,7 @@ void JKQTPXYFunctionLineGraphBase::draw(JKQTPEnhancedPainter& painter) {
         {
             painter.save(); auto __finalpaintline=JKQTPFinally([&painter]() {painter.restore();});
             painter.setPen(p);
-            painter.drawPolyline(data);
+            painter.drawPolylineFast(data);
         }
 
 

lib/jkqtplotter/graphs/jkqtpfilledcurve.cpp

@@ -466,14 +466,14 @@ void JKQTPFilledVerticalRangeGraph::draw(JKQTPEnhancedPainter &painter)
                 if (isHighlighted()) {
 
                     painter.setPen(ps);
-                    painter.drawPolyline(phigh);
+                    painter.drawPolylineFast(phigh);
-                    painter.drawPolyline(plow);
+                    painter.drawPolylineFast(plow);
                 }
 
 
                 painter.setPen(p);
-                painter.drawPolyline(phigh);
+                painter.drawPolylineFast(phigh);
-                painter.drawPolyline(plow);
+                painter.drawPolylineFast(plow);
 
             }
         }
@@ -581,14 +581,14 @@ void JKQTPFilledHorizontalRangeGraph::draw(JKQTPEnhancedPainter &painter)
                 if (isHighlighted()) {
 
                     painter.setPen(ps);
-                    painter.drawPolyline(phigh);
+                    painter.drawPolylineFast(phigh);
-                    painter.drawPolyline(plow);
+                    painter.drawPolylineFast(plow);
                 }
 
 
                 painter.setPen(p);
-                painter.drawPolyline(phigh);
+                painter.drawPolylineFast(phigh);
-                painter.drawPolyline(plow);
+                painter.drawPolylineFast(plow);
 
             }
         }

lib/jkqtplotter/graphs/jkqtpgeolines.cpp

@@ -142,7 +142,7 @@ void JKQTPGeoLine::draw(JKQTPEnhancedPainter& painter) {
                     if (drawHead) JKQTPPlotLineDecorator(painter, xx2.x(), xx2.y(), angle2, getHeadDecoratorStyle(), calcHeadDecoratorSize(getLinePen(painter, getParent()).widthF()));//, &lx2);
                     //points[0]=lx1;
                     //points[points.size()-1]=lx2;
-                    painter.drawPolyline(points.data(), points.size());
+                    painter.drawPolylineFast(points.data(), points.size());
                     /*for (auto& p: points) {
                         JKQTPPlotSymbol(painter, p.x(), p.y(), JKQTPPlus, 5, 1, QColor("green"), QColor("darkgreen"));
                     }*/
@@ -421,7 +421,7 @@ void JKQTPGeoInfiniteLine::draw(JKQTPEnhancedPainter& painter) {
                     xx1=points[0];
                     const QPointF xx1p=points[1];
                     angle1=atan2(xx1p.y()-xx1.y(), xx1p.x()-xx1.x());
-                    painter.drawPolyline(points.data(), points.size());
+                    painter.drawPolylineFast(points.data(), points.size());
                     /*for (auto& p: points) {
                         JKQTPPlotSymbol(painter, p.x(), p.y(), JKQTPPlus, 5, 1, QColor("green"), QColor("darkgreen"));
                     }*/
@@ -592,7 +592,7 @@ void JKQTPGeoPolyLines::draw(JKQTPEnhancedPainter& painter) {
             xx1=path[0];
             xx2=path[path.size()-1];
             // draw corrected line
-            painter.drawPolyline(path.data(), path.size());
+            painter.drawPolylineFast(path.data(), path.size());
             doDrawDecorator=true;
         } else {
             // for non-linear axes, a line might not be drawn as a line, so we need to segment the line (i.e. linear function in coordinate space)
@@ -607,7 +607,7 @@ void JKQTPGeoPolyLines::draw(JKQTPEnhancedPainter& painter) {
                 xx2=points_poly[points_poly.size()-1];
                 const QPointF xx2p=points_poly[points_poly.size()-2];
                 angle2=atan2(xx2p.y()-xx2.y(), xx2p.x()-xx2.x());
-                painter.drawPolyline(points_poly.data(), points_poly.size());
+                painter.drawPolylineFast(points_poly.data(), points_poly.size());
                 doDrawDecorator=true;
                 /*for (auto& p: points_poly) {
                     JKQTPPlotSymbol(painter, p.x(), p.y(), JKQTPPlus, 5, 1, QColor("green"), QColor("darkgreen"));
@@ -719,7 +719,7 @@ void JKQTPGeoArc::draw(JKQTPEnhancedPainter& painter) {
 
     painter.save(); auto __finalpaint=JKQTPFinally([&painter]() {painter.restore();});
     painter.setPen(getLinePen(painter, parent));
-    painter.drawPolyline(rect);
+    painter.drawPolylineFast(rect);
 }
 
 void JKQTPGeoArc::setAngleStart(double __value)

lib/jkqtplotter/graphs/jkqtplines.cpp

@@ -134,10 +134,10 @@ void JKQTPXYLineGraph::draw(JKQTPEnhancedPainter& painter) {
                     if (linesP.size()>0) {
                         if (isHighlighted()) {
                             painter.setPen(penSelection);
-                            painter.drawPolyline(linesP);
+                            painter.drawPolylineFast(linesP);
                         }
                         painter.setPen(p);
-                        painter.drawPolyline(linesP);
+                        painter.drawPolylineFast(linesP);
                     }
                 }
             }

lib/jkqtplotter/graphs/jkqtpscatter.cpp

@@ -393,7 +393,7 @@ void JKQTPXYParametrizedScatterGraph::draw(JKQTPEnhancedPainter &painter)
                 } else {
                     pp.setColor(getHighlightingLineColor());
                     painter.setPen(pp);
-                    painter.drawPolyline(linesP);
+                    painter.drawPolylineFast(linesP);
                 }
             }
             QPen pp=p;
@@ -407,7 +407,7 @@ void JKQTPXYParametrizedScatterGraph::draw(JKQTPEnhancedPainter &painter)
             } else {
                 pp.setColor(getHighlightingLineColor());
                 painter.setPen(pp);
-                painter.drawPolyline(linesP);
+                painter.drawPolylineFast(linesP);
             }
 
         }

lib/jkqtplotter/graphs/jkqtpspecialline.cpp

@@ -276,7 +276,7 @@ void JKQTPSpecialLineHorizontalGraph::draw(JKQTPEnhancedPainter& painter) {
             painter.setBrush(Qt::NoBrush);
             painter.setPen(ph);
             for (const QPolygonF& lines : pl_fordrawing) {
-                painter.drawPolyline(lines);
+                painter.drawPolylineFast(lines);
             }
         }
 
@@ -284,7 +284,7 @@ void JKQTPSpecialLineHorizontalGraph::draw(JKQTPEnhancedPainter& painter) {
             painter.setBrush(Qt::NoBrush);
             painter.setPen(p);
             for (const QPolygonF& lines : pl_fordrawing) {
-                painter.drawPolyline(lines);
+                painter.drawPolylineFast(lines);
             }
         }
 
@@ -464,7 +464,7 @@ void JKQTPSpecialLineVerticalGraph::draw(JKQTPEnhancedPainter& painter) {
             painter.setBrush(Qt::NoBrush);
             painter.setPen(ph);
             for (const QPolygonF& lines : pl_fordrawing) {
-                painter.drawPolyline(lines);
+                painter.drawPolylineFast(lines);
             }
         }
 
@@ -472,7 +472,7 @@ void JKQTPSpecialLineVerticalGraph::draw(JKQTPEnhancedPainter& painter) {
             painter.setBrush(Qt::NoBrush);
             painter.setPen(p);
             for (const QPolygonF& lines : pl_fordrawing) {
-                painter.drawPolyline(lines);
+                painter.drawPolylineFast(lines);
             }
         }
 

lib/jkqtplotter/jkqtpbaseplotter.cpp

@@ -1965,6 +1965,7 @@ void JKQTBasePlotter::printpreviewPaintRequested(QPrinter* printer) {
     }
 
     JKQTPEnhancedPainter painter;
+    painter.setPainterFlag(JKQTPEnhancedPainter::VectorPainting);
     painter.begin(printer);
     if (!printSetAbsolutePageSize) {
 #ifdef SHOW_JKQTPLOTTER_DEBUG
@@ -2065,6 +2066,7 @@ void JKQTBasePlotter::printpreviewPaintRequestedNewPaintDevice(QPaintDevice *pai
     if (printer) painter.begin(printer);
     else if (svg) painter.begin(svg);
     else painter.begin(paintDevice);
+    if (printer||svg) painter.setPainterFlag(JKQTPEnhancedPainter::VectorPainting);
 #else
     painter.begin(paintDevice);
 #endif
@@ -3916,6 +3918,7 @@ void JKQTBasePlotter::copyPixelImage(bool showPreview) {
                 svg->setSize(size);
                 svg->setOutputDevice(&buffer);
                 JKQTPEnhancedPainter painter;
+                painter.setPainterFlag(JKQTPEnhancedPainter::VectorPainting);
                 painter.begin(svg);
                 painter.scale(factor,factor);
                 printAspect=printSizeY_Millimeter/printSizeX_Millimeter;