Fix LTM trend line

.. broken on All Dates selections.

It must be time to introduce a polynomial fit or somesuch
as the linear regress is a little simplistic for most cases.

src/LTMPlot.cpp

@@ -536,8 +536,8 @@ LTMPlot::setData(LTMSettings *set)
 
             // cosmetics
             QPen cpen = QPen(metricDetail.penColor.darker(200));
-            cpen.setWidth(width*2); // double thickness for trend lines
-            cpen.setStyle(Qt::DotLine);
+            cpen.setWidth(2); // double thickness for trend lines
+            cpen.setStyle(Qt::SolidLine);
             trend->setPen(cpen);
             if (appsettings->value(this, GC_ANTIALIAS, false).toBool()==true)
                 trend->setRenderHint(QwtPlotItem::RenderAntialiased);
@@ -547,6 +547,11 @@ LTMPlot::setData(LTMSettings *set)
 
             // perform linear regression
             LTMTrend regress(xdata.data(), ydata.data(), count);
+
+            // override class variable as doing it temporarily for trend line only
+            double maxX = 0.5 + groupForDate(settings->end.date(), settings->groupBy) -
+                groupForDate(settings->start.date(), settings->groupBy);
+
             double xtrend[2], ytrend[2];
             xtrend[0] = 0.0;
             ytrend[0] = regress.getYforX(0.0);

src/LTMTrend.cpp

@@ -29,6 +29,10 @@ LTMTrend::LTMTrend(double *xdata, double *ydata, int count) :
     if (count <= 2) return;
 
     for (int i = 0; i < count; i++) {
+
+        // ignore zero points
+        if (ydata[i] == 0.00) continue;
+
         points++;
         sumX += xdata[i];
         sumY += ydata[i];

src/LTMTrend.h

@@ -26,6 +26,8 @@ class LTMTrend
         // Constructor using arrays of x values and y values
         LTMTrend(double *, double *, int);
         double getYforX(double x) const { return (a + b * x); }
+        double intercept() { return a; }
+        double slope() { return b; }
 
     protected:
         long points;