From 9e852e5e879084155aadf5a7d8f41bc227be1a26 Mon Sep 17 00:00:00 2001
From: Matt Parker <61717342+MattParkerDev@users.noreply.github.com>
Date: Tue, 27 Jan 2026 22:39:22 +1000
Subject: [PATCH] Fix rendering error underlines

---
 .../Features/CodeEditor/SharpIdeCodeEdit.cs   | 10 +++-
 .../Features/CodeEditor/SharpIdeCodeEdit.tscn |  6 +++
 src/SharpIDE.Godot/NodeExtensions.cs          | 47 +++++++++++++++++++
 3 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/src/SharpIDE.Godot/Features/CodeEditor/SharpIdeCodeEdit.cs b/src/SharpIDE.Godot/Features/CodeEditor/SharpIdeCodeEdit.cs
index c7307d0..8c36bac 100644
--- a/src/SharpIDE.Godot/Features/CodeEditor/SharpIdeCodeEdit.cs
+++ b/src/SharpIDE.Godot/Features/CodeEditor/SharpIdeCodeEdit.cs
@@ -35,6 +35,8 @@ public partial class SharpIdeCodeEdit : CodeEdit
 	
 	private CustomHighlighter _syntaxHighlighter = new();
 	private PopupMenu _popupMenu = null!;
+	private CanvasItem _aboveCanvasItem = null!;
+	private Rid? _aboveCanvasItemRid = null!;
 
 	private ImmutableArray<SharpIdeDiagnostic> _fileDiagnostics = [];
 	private ImmutableArray<SharpIdeDiagnostic> _fileAnalyzerDiagnostics = [];
@@ -63,6 +65,9 @@ public partial class SharpIdeCodeEdit : CodeEdit
 	{
 		SyntaxHighlighter = _syntaxHighlighter;
 		_popupMenu = GetNode<PopupMenu>("CodeFixesMenu");
+		_aboveCanvasItem = GetNode<CanvasItem>("%AboveCanvasItem");
+		_aboveCanvasItemRid = _aboveCanvasItem.GetCanvasItem();
+		RenderingServer.Singleton.CanvasItemSetParent(_aboveCanvasItemRid.Value, GetCanvasItem());
 		_popupMenu.IdPressed += OnCodeFixSelected;
 		CustomCodeCompletionRequested.Subscribe(OnCodeCompletionRequested);
 		CodeFixesRequested += OnCodeFixesRequested;
@@ -363,8 +368,9 @@ public partial class SharpIdeCodeEdit : CodeEdit
 		{
 			endPos.X += 10;
 		}
-		DrawDashedLine(startPos, endPos, color, thickness);
-		//DrawLine(startPos, endPos, color, thickness);
+		
+		RenderingServer.Singleton.CanvasItemClear(_aboveCanvasItemRid!.Value);
+		RenderingServer.Singleton.DrawDashedLine(_aboveCanvasItemRid!.Value, startPos, endPos, color, thickness);
 	}
 	public override void _Draw()
 	{
diff --git a/src/SharpIDE.Godot/Features/CodeEditor/SharpIdeCodeEdit.tscn b/src/SharpIDE.Godot/Features/CodeEditor/SharpIdeCodeEdit.tscn
index 07bb8ea..f6ea40c 100644
--- a/src/SharpIDE.Godot/Features/CodeEditor/SharpIdeCodeEdit.tscn
+++ b/src/SharpIDE.Godot/Features/CodeEditor/SharpIdeCodeEdit.tscn
@@ -43,3 +43,9 @@ size = Vector2i(217, 100)
 item_count = 1
 item_0/text = "Getting Context Actions..."
 item_0/id = 0
+
+[node name="AboveCanvasItem" type="Control" parent="." unique_id=650087366]
+unique_name_in_owner = true
+anchors_preset = 0
+offset_right = 40.0
+offset_bottom = 40.0
diff --git a/src/SharpIDE.Godot/NodeExtensions.cs b/src/SharpIDE.Godot/NodeExtensions.cs
index 6482871..94d721a 100644
--- a/src/SharpIDE.Godot/NodeExtensions.cs
+++ b/src/SharpIDE.Godot/NodeExtensions.cs
@@ -40,6 +40,53 @@ public class RequiresGodotUiThreadAttribute : Attribute
 
 public static class NodeExtensions
 {
+    extension(RenderingServerInstance renderingServerInstance)
+    {
+        // https://github.com/godotengine/godot/blob/a4bbad2ba8a8ecd4e756e49de5c83666f12a9bd5/scene/main/canvas_item.cpp#L717
+        public void DrawDashedLine(Rid canvasItemRid, Vector2 from, Vector2 to, Color color, float width = -1.0f, float dash = 2.0f, bool aligned = true, bool antialiased = false)
+        {
+            if (dash <= 0.0f)
+            {
+                GD.PushError("draw_dashed_line: dash length must be greater than 0");
+                return;
+            }
+
+            var length = (to - from).Length();
+            var step = dash * (to - from).Normalized();
+
+            if (length < dash || step == Vector2.Zero)
+            {
+                renderingServerInstance.CanvasItemAddLine(canvasItemRid, from, to, color, width, antialiased);
+                return;
+            }
+
+            int steps = aligned ? Mathf.CeilToInt(length / dash) : Mathf.FloorToInt(length / dash);
+            if (steps % 2 == 0)
+            {
+                steps--;
+            }
+
+            var off = from;
+            if (aligned)
+            {
+                off += (to - from).Normalized() * (length - steps * dash) / 2.0f;
+            }
+
+            //Span<Vector2> points = steps <= 128 ? stackalloc Vector2[steps + 1] : new Vector2[steps + 1];
+            Span<Vector2> points = stackalloc Vector2[steps + 1];
+            for (var i = 0; i < steps; i += 2)
+            {
+                points[i] = (i == 0) ? from : off;
+                points[i + 1] = (aligned && i == steps - 1) ? to : (off + step);
+                off += step * 2;
+            }
+
+            ReadOnlySpan<Color> colors = stackalloc Color[1] { color };
+
+            renderingServerInstance.CanvasItemAddMultiline(canvasItemRid, points, colors, width, antialiased);
+        }
+    }
+
     extension(TreeItem treeItem)
     {
         public T? GetTypedMetadata<T>(int column) where T : RefCounted?