/// <summary>
/// Plots grid lines onto the graph.
/// </summary>
/// <param name="graphics">The GDI+ drawing surface to use for plotting this IPlottable.</param>
/// <param name="graphSize">The size of the Graph on the screen. This is a property of the display rather than the
/// graph and is thus not included in the graph's parameters.</param>
/// <param name="plotParams">The parameters used to plot this IPlottable.</param>
/// <param name="originX">The X position of the origin on the screen.</param>
/// <param name="originY">The Y position of the origin on the screen.</param>
private void PlotGridLinesOnto(Graph graph, Graphics graphics, Size graphSize, PlottableParameters plotParams, int originX, int originY)
{
using (Pen majorPen = new Pen(plotParams.PlotColor.ColorAlpha(0.25)))
using (Pen minorPen = new Pen(plotParams.PlotColor.ColorAlpha(0.15)))
using (Brush valueBrush = new SolidBrush(plotParams.PlotColor.ColorAlpha(0.5)))
{
// the increment, in pixels, of each grid space
double incrementX = HorizontalType.AxisTypeGridScale() * GridSize / graph.Parameters.HorizontalPixelScale,
incrementY = VerticalType.AxisTypeGridScale() * GridSize / graph.Parameters.VerticalPixelScale;
// draw the variable names onto the axis
graphics.DrawString(graph.Parameters.VerticalAxis.ToString(), SystemFonts.DefaultFont, valueBrush, (int)originX, 2);
graphics.DrawString(graph.Parameters.HorizontalAxis.ToString(), SystemFonts.DefaultFont, valueBrush, (int)graphSize.Width - 16, (int)originY);
// the unit suffix of the grid labels, for example the little circle for degrees
string horizontalAxisSuffix = HorizontalType.AxisTypeExtension();
string verticalAxisSuffix = VerticalType.AxisTypeExtension();
// the axis label scale for the numbers along each axis
// for example, axes plotted in degree mode are scaled such that 2*pi is displayed
// as 360 degrees instead
double horizontalAxisScale = GridSize * HorizontalType.AxisTypeLabelScale() * HorizontalType.AxisTypeGridScale();
double verticalAxisScale = GridSize * VerticalType.AxisTypeLabelScale() * VerticalType.AxisTypeGridScale();
// the remainder of the code in this method plots the gridlines from the origin outward.
// this is potentially not the most efficient method of doing it, but it avoids floating-
// point rounding errors resulting in axis labels like 2.00000000000017 without adding in
// even more horrible code.
// some of this code looks redundant, and it is. However as drawing the grid lines is a
// (surprisingly) CPU intensive operation this method needs to be as fast as possible as
// the grid is drawn every time the graph is
double value = originX;
int index = 0;
// plot horizontal grid lines from the origin to the right of the page
while (value < graphSize.Width)
{
bool major = index % MajorInterval == 0;
if (major)
{
graphics.DrawLine(majorPen,
(int)value, 0, (int)value, graphSize.Height);
graphics.DrawString(
String.Format("{0:0.####}{1}", index * horizontalAxisScale, horizontalAxisSuffix),
SystemFonts.DefaultFont,
valueBrush, (int)value, (int)originY);
}
else
{
graphics.DrawLine(minorPen,
(int)value, 0, (int)value, graphSize.Height);
}
value += incrementX; index++;
}
value = originX; index = 0;
// plot hoz grid from origin to left of page
while (value >= 0)
{
bool major = index % MajorInterval == 0;
if (major)
{
graphics.DrawLine(majorPen,
(int)value, 0, (int)value, graphSize.Height);
graphics.DrawString(
String.Format("{0:0.####}{1}", index * horizontalAxisScale, horizontalAxisSuffix),
SystemFonts.DefaultFont,
valueBrush,
(int)value, (int)originY);
}
else
{
graphics.DrawLine(minorPen,
(int)value, 0, (int)value, graphSize.Height);
}
value -= incrementX; index++;
}
value = originY; index = 0;
// plot vertical grid lines from origin to bottom of page
while (value < graphSize.Height)
{
bool major = index % MajorInterval == 0;
if (major)
{
graphics.DrawLine(majorPen,
0, (int)value, graphSize.Width, (int)value);
graphics.DrawString(
String.Format("{0:0.####}{1}", index * verticalAxisScale, verticalAxisSuffix),
SystemFonts.DefaultFont,
valueBrush,
(int)originX, (int)value);
}
else
{
graphics.DrawLine(minorPen,
0, (int)value, graphSize.Width, (int)value);
}
value += incrementY; index++;
}
value = originY; index = 0;
// plot vert grid from origin to top of page
while (value >= 0)
{
bool major = index % MajorInterval == 0;
if (major)
{
graphics.DrawLine(majorPen,
0, (int)value, graphSize.Width, (int)value);
double vertical = graph.Parameters.VerticalPixelScale * index;
graphics.DrawString(
String.Format("{0:0.####}{1}", index * verticalAxisScale, verticalAxisSuffix),
SystemFonts.DefaultFont,
valueBrush,
(int)originX, (int)value);
}
else
{
graphics.DrawLine(minorPen,
0, (int)value, graphSize.Width, (int)value);
}
value -= incrementY; index++;
}
}
}
