Legend: default marker style (ScottPlot#5006)

* changing default shape of legend marker

* logic updates for defaults

* legend logic updates

* formatting

* Update CHANGELOG.md

---------

Co-authored-by: Scott W Harden <swharden@gmail.com>

Author: aespitia

CHANGELOG.md

@@ -20,6 +20,7 @@ _Not yet on NuGet..._
 * Maui: Improve behavior for interactive plots when their user input processor is disabled (#4990, #4989) @Adam--
 * Fonts: Added new styling options for weight, slant, density, etc. (#5013, #4873) @aespitia @Christoph-Wagner
 * Labels: Added styling options for underline with customizable thickness and offset (#4893) @manaruto
+* Legend: Added the ability to customize default marker shape for legend items (#5005, #5006) @aespitia
 
 ## ScottPlot 5.0.55
 _Published on [NuGet](https://www.nuget.org/profiles/ScottPlot) on 2025-03-22_

src/ScottPlot5/ScottPlot5 Cookbook/Recipes/General/Legend.cs

@@ -49,7 +49,7 @@ public override void Execute()
     public class ManualLegend : RecipeBase
     {
         public override string Name => "Manual Legend Items";
-        public override string Description => "Legends may be constructed manually.";
+        public override string Description => "Legends may be constructed manually and markers customized.";
 
         [Test]
         public override void Execute()
@@ -63,6 +63,7 @@ public override void Execute()
                 LineColor = Colors.Magenta,
                 MarkerFillColor = Colors.Magenta,
                 MarkerLineColor = Colors.Magenta,
+                MarkerShape = MarkerShape.Cross,
                 LineWidth = 2,
                 LabelText = "Alpha"
             };
@@ -106,11 +107,49 @@ public override void Execute()
             myPlot.Legend.ShadowColor = Colors.Blue.WithOpacity(.2);
             myPlot.Legend.ShadowOffset = new(10, 10);
 
-            myPlot.Legend.FontSize = 32;
+            myPlot.Legend.FontSize = 22;
             myPlot.Legend.FontName = Fonts.Serif;
         }
     }
 
+    public class LegendOverrideSymbol : RecipeBase
+    {
+        public override string Name => "Legend Default Marker";
+        public override string Description => @"You can override the default rectangular marker used when rendering the legend.  It also maintains the desired marker for manually added items.";
+
+        [Test]
+        public override void Execute()
+        {
+            var sig1 = myPlot.Add.Signal(Generate.Sin(51));
+            sig1.LegendText = "Sin";
+
+            var sig2 = myPlot.Add.Signal(Generate.Cos(51));
+            sig2.LegendText = "Cos";
+
+            myPlot.Legend.MarkerShapeDefault = MarkerShape.FilledCircle;
+
+
+            LegendItem item1 = new()
+            {
+                MarkerColor = Colors.Red,
+                MarkerShape = MarkerShape.Cross,
+                LabelText = "Alpha"
+            };
+
+            LegendItem item2 = new()
+            {
+                MarkerColor = Colors.Green,
+                MarkerShape = MarkerShape.FilledSquare,
+                LabelText = "Beta"
+            };
+
+            myPlot.Legend.ManualItems.Add(item1);
+            myPlot.Legend.ManualItems.Add(item2);
+
+            myPlot.ShowLegend();
+        }
+    }
+
     public class LegendOrientation : RecipeBase
     {
         public override string Name => "Legend Orientation";

src/ScottPlot5/ScottPlot5/Primitives/Legend.cs

@@ -114,6 +114,8 @@ public class Legend(Plot plot) : IPlottable, IHasOutline, IHasBackground, IHasSh
     public IEnumerable<LegendItem> LegendItems => LegendItem.None;
     public AxisLimits GetAxisLimits() => AxisLimits.NoLimits;
 
+    public MarkerShape MarkerShapeDefault { get; set; } = MarkerShape.None;
+
     public bool DisplayPlottableLegendItems { get; set; } = true;
 
     /// <summary>
@@ -292,6 +294,12 @@ private void RenderLayout(SKCanvas canvas, LegendLayout layout)
             PixelRect symbolFillOutlineRect = symbolFillRect.Expand(1 - item.OutlineWidth);
             PixelLine symbolLine = new(symbolRect.RightCenter, symbolRect.LeftCenter);
 
+            if (item.MarkerShape == MarkerShape.None && item.MarkerStyle.Shape == MarkerShape.None)
+            {
+                item.MarkerShape = MarkerShapeDefault != MarkerShape.None ? MarkerShapeDefault : MarkerShape.None;
+                item.MarkerColor = item.MarkerColor == Colors.Transparent ? Colors.Black : item.MarkerColor;
+            }
+
             item.LabelStyle.Render(canvas, labelRect.LeftCenter, paint, true);
 
             if (ShowItemRectangles_DEBUG)
@@ -300,9 +308,33 @@ private void RenderLayout(SKCanvas canvas, LegendLayout layout)
                 Drawing.DrawRectangle(canvas, labelRect, Colors.Magenta.WithAlpha(.2));
             }
 
-            item.LineStyle.Render(canvas, symbolLine, paint);
-            item.FillStyle.Render(canvas, symbolFillRect, paint);
-            item.OutlineStyle.Render(canvas, symbolFillOutlineRect, paint);
+            if (MarkerShapeDefault != MarkerShape.None)
+            {
+                item.MarkerStyle.Shape = item.MarkerShape != MarkerShape.None ? item.MarkerShape : MarkerShapeDefault;
+
+                //NOTE: tried this but size seems to be defaulting something to something small, so you can barely see the shape, defaulting to font size for now
+                //item.MarkerStyle.Size = item.MarkerStyle.Size != 0 ? item.MarkerStyle.Size : item.LabelFontSize;
+                item.MarkerStyle.Size = item.LabelFontSize;
+            }
+            else
+            {
+                item.MarkerStyle.Shape = item.MarkerShape;
+
+                // If the marker size is not set, use the label font size as a fallback
+                //NOTE: Same as above, tried it, but somehow the default is really small, setting to font size for now.
+                //item.MarkerStyle.Size = item.MarkerStyle.Shape != MarkerShape.None && item.MarkerStyle.Size != 0? item.MarkerStyle.Size : item.LabelFontSize;
+
+                item.MarkerStyle.Size = item.LabelFontSize;
+
+                if (item.MarkerShape == MarkerShape.None && item.MarkerStyle.Shape == MarkerShape.None)
+                {
+                    item.LineStyle.Render(canvas, symbolLine, paint);
+                }
+
+                item.FillStyle.Render(canvas, symbolFillRect, paint);
+                item.OutlineStyle.Render(canvas, symbolFillOutlineRect, paint);
+            }
+
             item.MarkerStyle.Render(canvas, symbolRect.Center, paint);
             item.ArrowStyle.Render(canvas, symbolLine, paint);