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manarutoswharden
manaruto
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swharden
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DataStreamer: add area fill support (ScottPlot#5023)
* add area fill support to DataStreamer - Add FillY properties matching Scatter class API (FillY, FillYValue, FillYAboveColor, FillYBelowColor) - Implement two-tone fill rendering for areas above/below baseline - Add GetSegments() method to IDataStreamerView interface - Update Wipe and Scroll renderers to expose segment structure - Handle partial buffers correctly during initial streaming BREAKING CHANGE: IDataStreamerView interface now requires GetSegments() method implementation * Update CHANGELOG.md --------- Co-authored-by: Scott W Harden <swharden@gmail.com>
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Lines changed: 142 additions & 28 deletions

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‎CHANGELOG.md‎

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@@ -22,6 +22,7 @@ _Not yet on NuGet..._
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* Labels: Added styling options for underline with customizable thickness and offset (#4893) @manaruto
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* Legend: Added the ability to customize default marker shape for legend items (#5005, #5006) @aespitia
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* Pie: Added a `Radius` property (instead of forcing `1.0`) and improved rendering and SVG export (#5020) @CoderPM2011 @aespitia
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* Data Streamer: Added `FillY` and related properties so streaming plots support filled ares (#4948, #5023) @manaruto @Stephanowicz
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## ScottPlot 5.0.55
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_Published on [NuGet](https://www.nuget.org/profiles/ScottPlot) on 2025-03-22_

‎src/ScottPlot5/ScottPlot5/DataViews/IDataStreamerView.cs‎

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@@ -9,4 +9,5 @@ public interface IDataStreamerView
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{
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DataStreamer Streamer { get; }
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void Render(RenderPack rp);
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IReadOnlyList<Pixel[]> GetSegments(RenderPack rp);
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}

‎src/ScottPlot5/ScottPlot5/DataViews/Scroll.cs‎

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@@ -16,24 +16,55 @@ public Scroll(DataStreamer streamer, bool newOnRight)
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public void Render(RenderPack rp)
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{
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int dataLength = Streamer.Data.Length;
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int dataNextIndex = Streamer.Data.NextIndex;
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int oldPointCount = dataLength - dataNextIndex;
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using SKPaint paint = new();
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foreach (Pixel[] seg in GetSegments(rp))
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{
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Drawing.DrawLines(rp.Canvas, paint, seg, Streamer.LineStyle);
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Drawing.DrawMarkers(rp.Canvas, paint, seg, Streamer.MarkerStyle);
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}
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}
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23-
Pixel[] points = new Pixel[dataLength];
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public IReadOnlyList<Pixel[]> GetSegments(RenderPack rp)
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{
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int cap = Streamer.Data.Length;
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int samples = Math.Min(Streamer.Data.CountTotal, cap);
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if (samples < 2)
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return Array.Empty<Pixel[]>();
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int nextIdx = Streamer.Data.NextIndex;
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bool wrapped = samples == cap;
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int oldCnt = wrapped ? cap - nextIdx : 0;
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25-
for (int i = 0; i < dataLength; i++)
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Span<double> vals = stackalloc double[samples];
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int dst = 0;
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if (wrapped && oldCnt > 0)
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{
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bool isNewPoint = i < oldPointCount;
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int sourceIndex = isNewPoint ? dataNextIndex + i : i - oldPointCount;
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int targetIndex = NewOnRight ? i : dataLength - 1 - i;
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points[targetIndex] = new(
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x: Streamer.Axes.GetPixelX(targetIndex * Streamer.Data.SamplePeriod + Streamer.Data.OffsetX),
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y: Streamer.Axes.GetPixelY(Streamer.Data.Data[sourceIndex] + Streamer.Data.OffsetY));
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for (int i = 0; i < oldCnt; i++, dst++)
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vals[dst] = Streamer.Data.Data[nextIdx + i];
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}
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using SKPaint paint = new();
36-
Drawing.DrawLines(rp.Canvas, paint, points, Streamer.LineStyle);
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Drawing.DrawMarkers(rp.Canvas, paint, points, Streamer.MarkerStyle);
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for (int i = 0; i < nextIdx && dst < samples; i++, dst++)
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vals[dst] = Streamer.Data.Data[i];
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int xShift = NewOnRight ? cap - samples : 0;
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Pixel[] px = new Pixel[samples];
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for (int screenX = 0; screenX < samples; screenX++)
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{
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int valIdx = NewOnRight
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? screenX
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: samples - 1 - screenX;
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int plotIdx = screenX + xShift;
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double xVal = plotIdx * Streamer.Data.SamplePeriod + Streamer.Data.OffsetX;
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double yVal = vals[valIdx] + Streamer.Data.OffsetY;
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px[screenX] = new Pixel(
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Streamer.Axes.GetPixelX(xVal),
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Streamer.Axes.GetPixelY(yVal));
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}
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return new[] { px };
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}
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}

‎src/ScottPlot5/ScottPlot5/DataViews/Wipe.cs‎

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Original file line numberDiff line numberDiff line change
@@ -17,6 +17,16 @@ public Wipe(DataStreamer streamer, bool wipeRight)
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}
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public void Render(RenderPack rp)
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{
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using SKPaint paint = new();
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foreach (Pixel[] seg in GetSegments(rp))
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{
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Drawing.DrawLines(rp.Canvas, paint, seg, Streamer.LineStyle);
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Drawing.DrawMarkers(rp.Canvas, paint, seg, Streamer.MarkerStyle);
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}
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}
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public IReadOnlyList<Pixel[]> GetSegments(RenderPack rp)
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{
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int newestCount = Streamer.Data.NextIndex;
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int oldestCount = Streamer.Data.Data.Length - newestCount;
@@ -31,36 +41,49 @@ public void Render(RenderPack rp)
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double xPos = i * Streamer.Data.SamplePeriod + Streamer.Data.OffsetX;
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float x = Streamer.Axes.GetPixelX(WipeRight ? xPos : xMax - xPos);
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float y = Streamer.Axes.GetPixelY(Streamer.Data.Data[i] + Streamer.Data.OffsetY);
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newest[i] = new(x, y);
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newest[i] = new Pixel(x, y);
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}
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for (int i = 0; i < oldest.Length; i++)
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{
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double xPos = (i + newestCount) * Streamer.Data.SamplePeriod + Streamer.Data.OffsetX;
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float x = Streamer.Axes.GetPixelX(WipeRight ? xPos : xMax - xPos);
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float y = Streamer.Axes.GetPixelY(Streamer.Data.Data[i + newestCount] + Streamer.Data.OffsetY);
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oldest[i] = new(x, y);
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oldest[i] = new Pixel(x, y);
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}
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if (BlankFraction > 0)
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{
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int blankPoints = (int)(BlankFraction * Streamer.Data.Length);
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int blank = (int)(BlankFraction * Streamer.Data.Length);
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49-
if (blankPoints <= oldest.Length)
50-
{
51-
oldest = oldest.Skip(blankPoints).ToArray();
52-
}
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if (blank <= oldest.Length)
60+
oldest = oldest.Skip(blank).ToArray();
5361
else
5462
{
55-
oldest = [];
56-
newest = newest.Skip(blankPoints - oldest.Length).ToArray();
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newest = newest.Skip(blank - oldest.Length).ToArray();
64+
oldest = Array.Empty<Pixel>();
5765
}
5866
}
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60-
using SKPaint paint = new();
61-
Drawing.DrawLines(rp.Canvas, paint, oldest, Streamer.LineStyle);
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Drawing.DrawLines(rp.Canvas, paint, newest, Streamer.LineStyle);
63-
Drawing.DrawMarkers(rp.Canvas, paint, oldest, Streamer.MarkerStyle);
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Drawing.DrawMarkers(rp.Canvas, paint, newest, Streamer.MarkerStyle);
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if (!WipeRight)
69+
{
70+
System.Array.Reverse(newest);
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System.Array.Reverse(oldest);
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}
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var list = new List<Pixel[]>();
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if (WipeRight)
77+
{
78+
if (oldest.Length > 1) list.Add(oldest);
79+
if (newest.Length > 1) list.Add(newest);
80+
}
81+
else
82+
{
83+
if (newest.Length > 1) list.Add(newest);
84+
if (oldest.Length > 1) list.Add(oldest);
85+
}
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87+
return list;
6588
}
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}

‎src/ScottPlot5/ScottPlot5/Plottables/DataStreamer.cs‎

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@@ -1,5 +1,6 @@
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using ScottPlot.AxisLimitManagers;
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using ScottPlot.DataSources;
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using ScottPlot.DataViews;
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45
namespace ScottPlot.Plottables;
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@@ -25,6 +26,11 @@ public class DataStreamer : IPlottable, IManagesAxisLimits, IHasLine, IHasLegend
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public Color MarkerLineColor { get => MarkerStyle.LineColor; set => MarkerStyle.LineColor = value; }
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public Color MarkerColor { get => MarkerStyle.MarkerColor; set => MarkerStyle.MarkerColor = value; }
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public float MarkerLineWidth { get => MarkerStyle.LineWidth; set => MarkerStyle.LineWidth = value; }
29+
public bool FillY { get; set; } = false;
30+
public double FillYValue { get; set; } = 0;
31+
public Color FillYAboveColor { get; set; } = Colors.Blue.WithAlpha(.2);
32+
public Color FillYBelowColor { get; set; } = Colors.Blue.WithAlpha(.2);
33+
public Color FillYColor { get => FillYAboveColor; set { FillYAboveColor = value; FillYBelowColor = value; } }
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2935
public Color Color
3036
{
@@ -184,7 +190,59 @@ public void UpdateAxisLimits(Plot plot)
184190

185191
public virtual void Render(RenderPack rp)
186192
{
193+
if (Renderer is not IDataStreamerView viewWithSegs)
194+
{
195+
Renderer.Render(rp);
196+
return;
197+
}
198+
199+
var segs = viewWithSegs.GetSegments(rp);
200+
if (segs.Count == 0)
201+
return;
202+
203+
if (FillY)
204+
{
205+
float yBasePx = Axes.YAxis.GetPixel(FillYValue + Data.OffsetY, rp.DataRect);
206+
207+
using SKPaint paint = new();
208+
foreach (Pixel[] seg in segs)
209+
{
210+
using SKPath path = new();
211+
path.MoveTo(seg[0].X, seg[0].Y);
212+
for (int i = 1; i < seg.Length; i++)
213+
path.LineTo(seg[i].X, seg[i].Y);
214+
215+
PixelRect rect = new(seg);
216+
using SKPath fill = new(path);
217+
fill.LineTo(rect.Right, yBasePx);
218+
fill.LineTo(rect.Left, yBasePx);
219+
220+
// above
221+
if (yBasePx > rect.Top)
222+
{
223+
PixelRect clip = new(rp.DataRect.Left, rp.DataRect.Right, rp.DataRect.Top, yBasePx);
224+
FillStyle fs = new() { IsVisible = true, Color = FillYAboveColor };
225+
rp.CanvasState.Save();
226+
rp.CanvasState.Clip(clip);
227+
Drawing.FillPath(rp.Canvas, paint, fill, fs, clip);
228+
rp.CanvasState.Restore();
229+
}
230+
231+
// below
232+
if (yBasePx < rect.Bottom)
233+
{
234+
PixelRect clip = new(rp.DataRect.Left, rp.DataRect.Right, yBasePx, rp.DataRect.Bottom);
235+
FillStyle fs = new() { IsVisible = true, Color = FillYBelowColor };
236+
rp.CanvasState.Save();
237+
rp.CanvasState.Clip(clip);
238+
Drawing.FillPath(rp.Canvas, paint, fill, fs, clip);
239+
rp.CanvasState.Restore();
240+
}
241+
}
242+
}
243+
187244
Renderer.Render(rp);
245+
188246
Data.CountTotalOnLastRender = Data.CountTotal;
189247
}
190248
}

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