[chronojump] Nicer code on Cairo grid

[Xavier de Blas <xaviblas src gnome org>]

commit 7df3fe8b3e9da7e0c013d2e7f0967da10a86ce95
Author: Xavier de Blas <xaviblas gmail com>
Date:   Thu Jan 2 17:01:15 2020 +0100

    Nicer code on Cairo grid

 src/gui/cairo/xy.cs | 71 ++++++++++++++++++++++++++++-------------------------
 1 file changed, 37 insertions(+), 34 deletions(-)
---
diff --git a/src/gui/cairo/xy.cs b/src/gui/cairo/xy.cs
index cda8dbf8..75df46fd 100644
--- a/src/gui/cairo/xy.cs
+++ b/src/gui/cairo/xy.cs
@@ -141,9 +141,7 @@ public abstract class CairoXY
                printText(2, Convert.ToInt32(outerMargins/2), 0, textHeight, "Height (cm)", g, false);
                printText(graphWidth - Convert.ToInt32(outerMargins/2), graphHeight - outerMargins, 0, 
textHeight, axisRightLabel, g, false);
 
-               //2 paint grid: horizontal, vertical
-               paintGrid (minY, absoluteMaxY, 5, true);
-               paintGrid (minX, absoluteMaxX, 5, false);
+               paintGrid (minX, absoluteMaxX, minY, absoluteMaxY, 5);
        }
 
        protected void plotPredictedLine()
@@ -281,14 +279,44 @@ public abstract class CairoXY
        }
 
        //TODO: fix if min == max (crashes)
-       protected void paintGrid (double min, double max, int seps, bool horiz)
+       protected void paintGrid (double minX, double maxX, double minY, double maxY, int seps)
        {
-               LogB.Information(string.Format("paintGrid: {0}, {1}, {2}, {3}", min, max, seps, horiz));
+               //LogB.Information(string.Format("paintGrid: {0}, {1}, {2}, {3}", min, max, seps, horiz));
 
-               //TODO: improve this
-               if(min == max)
-                       return;
+               double stepX = getGridStep(minX, maxX, seps);
+               double stepY = getGridStep(minY, maxY, seps);
 
+               g.Save();
+               g.SetDash(new double[]{1, 2}, 0);
+               // i <= max*1.5 to allow to have grid just above the maxpoint if it's below innermargins
+               // see: if(ytemp < outerMargins) continue;
+               for(double i = minX; i <= maxX *1.5 ; i += stepX)
+               {
+                       int xtemp = Convert.ToInt32(calculatePaintX(i, graphWidth, maxX, minX, outerMargins + 
innerMargins, outerMargins + innerMargins));
+                       if(xtemp < outerMargins || xtemp > graphWidth - outerMargins)
+                               continue;
+
+                       g.MoveTo(xtemp, graphHeight - outerMargins);
+                       g.LineTo(xtemp, outerMargins);
+                       printText(xtemp, graphHeight - Convert.ToInt32(outerMargins/2), 0, textHeight, 
Util.TrimDecimals(i, 1), g, true);
+               }
+
+               for(double i = minY; i <= maxY *1.5 ; i += stepY)
+               {
+                       int ytemp = Convert.ToInt32(calculatePaintY(i, graphHeight, maxY, minY, outerMargins 
+ innerMargins, outerMargins + innerMargins));
+                       if(ytemp < outerMargins || ytemp > graphHeight - outerMargins)
+                               continue;
+
+                       g.MoveTo(outerMargins, ytemp);
+                       g.LineTo(graphWidth - outerMargins, ytemp);
+                       printText(Convert.ToInt32(outerMargins/2), ytemp, 0, textHeight, Util.TrimDecimals(i, 
1), g, true);
+               }
+               g.Stroke ();
+               g.Restore();
+       }
+
+       private double getGridStep(double min, double max, int seps)
+       {
                //show 5 steps positive, 5 negative (if possible)
                double temp = Util.DivideSafe(max - min, seps);
                double step = temp;
@@ -309,32 +337,7 @@ public abstract class CairoXY
                if(step == 0)
                        step = 1;
 
-               g.Save();
-               g.SetDash(new double[]{1, 2}, 0);
-               // i <= max*1.5 to allow to have grid just above the maxpoint if it's below innermargins
-               // see: if(ytemp < outerMargins) continue;
-               for(double i = min; i <= max *1.5 ; i += step)
-               {
-                       //LogB.Information("i: " + i.ToString());
-                       if(horiz)
-                       {
-                               int ytemp = Convert.ToInt32(calculatePaintY(i, graphHeight, max, min, 
outerMargins + innerMargins, outerMargins + innerMargins));
-                               if(ytemp < outerMargins || ytemp > graphHeight - outerMargins)
-                                       continue;
-                               g.MoveTo(outerMargins, ytemp);
-                               g.LineTo(graphWidth - outerMargins, ytemp);
-                               printText(Convert.ToInt32(outerMargins/2), ytemp, 0, textHeight, 
Util.TrimDecimals(i, 1), g, true);
-                       } else {
-                               int xtemp = Convert.ToInt32(calculatePaintX(i, graphWidth, max, min, 
outerMargins + innerMargins, outerMargins + innerMargins));
-                               if(xtemp < outerMargins || xtemp > graphWidth - outerMargins)
-                                       continue;
-                               g.MoveTo(xtemp, graphHeight - outerMargins);
-                               g.LineTo(xtemp, outerMargins);
-                               printText(xtemp, graphHeight - Convert.ToInt32(outerMargins/2), 0, 
textHeight, Util.TrimDecimals(i, 1), g, true);
-                       }
-               }
-               g.Stroke ();
-               g.Restore();
+               return step;
        }
 
        protected double calculatePaintX(double currentValue, int ancho, double maxValue, double minValue, 
int rightMargin, int leftMargin)