Editor Component Editors

Overview

Component editors render ECS component properties in the editor's Properties panel. They use the IComponentEditor interface with static utility methods for consistent UI styling.

When to Use This Skill

• Creating a new component editor for an ECS component
• Editing vector properties (Vector2/Vector3) with axis color coding
• Editing primitive properties (int, float, bool, string)
• Need collapsible component UI with remove button
• Building custom property controls for components

---

Core Architecture

IComponentEditor Interface

// Editor/ComponentEditors/Core/IComponentEditor.cs
public interface IComponentEditor
{
    void DrawComponent(Entity entity);
}

Key Points:

• Takes Entity, not the component directly
• Component is retrieved inside using entity.GetComponent<T>()
• No return value - mutates component properties directly

---

Essential Pattern: ComponentEditorRegistry.DrawComponent()

Every component editor uses this static wrapper method for consistent UI:

ComponentEditorRegistry.DrawComponent<ComponentType>("Display Name", entity, entity =>
{
    var component = entity.GetComponent<ComponentType>();

    // Draw property editors here
});

What it provides:

• ✅ Collapsible tree node (DefaultOpen)
• ✅ Component name header
• ✅ Remove component button (-)
• ✅ Consistent padding and spacing
• ✅ Framed appearance
• ✅ Only renders if entity has the component

Implementation (ComponentEditorRegistry.cs:60-87):

• Uses ImGuiTreeNodeFlags for styling
• Adds remove button in top-right corner
• Calls your lambda only if component exists
• Handles tree pop automatically

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Property Editing Utilities

1. UIPropertyRenderer.DrawPropertyField()

Best for: Simple primitive properties (int, float, bool, string)

UIPropertyRenderer.DrawPropertyField("Label", currentValue,
    newValue => component.Property = (TypeCast)newValue);

Features:

• Automatic type detection via FieldEditorRegistry
• Consistent label/input width ratio (33%/67%)
• Supports: int, float, double, bool, string, Vector2, Vector3, Vector4
• Boxing-based (object newValue)

Example (CameraComponentEditor.cs:22-23):

UIPropertyRenderer.DrawPropertyField("Primary", cameraComponent.Primary,
    newValue => cameraComponent.Primary = (bool)newValue);

---

2. VectorPanel Static Methods

Best for: Vector properties needing axis color coding or reset buttons

Vector3 with Axis Colors

var newPosition = component.Position;
VectorPanel.DrawVec3Control("Position", ref newPosition);

if (newPosition != component.Position)
    component.Position = newPosition;

Features:

• Colored axis buttons: X (red), Y (green), Z (blue)
• Click button to reset axis to default value
• Drag float inputs for each axis
• Consistent 33%/67% label/input ratio

With Reset Value (TransformComponentEditor.cs:32):

var newScale = component.Scale;
VectorPanel.DrawVec3Control("Scale", ref newScale, resetValue: 1.0f);

if (newScale != component.Scale)
    component.Scale = newScale;

Vector2 Controls

var newSize = component.Size;
VectorPanel.DrawVec2Control("Size", ref newSize);

if (newSize != component.Size)
    component.Size = newSize;

VectorPanel.cs methods:

• DrawVec3Control(string label, ref Vector3 values, float resetValue = 0.0f)
• DrawVec2Control(string label, ref Vector2 values, float resetValue = 0.0f)

---

3. LayoutDrawer.DrawComboBox()

Best for: Enum or string selection dropdowns

private static readonly string[] ProjectionTypeStrings = { "Perspective", "Orthographic" };

LayoutDrawer.DrawComboBox("Projection",
    ProjectionTypeStrings[(int)camera.ProjectionType],
    ProjectionTypeStrings,
    selectedType =>
    {
        camera.ProjectionType = selectedType switch
        {
            "Perspective" => ProjectionType.Perspective,
            "Orthographic" => ProjectionType.Orthographic,
            _ => camera.ProjectionType
        };
    });

---

Complete Working Examples

Example 1: Simple Component Editor (Camera)

// CameraComponentEditor.cs (simplified)
using ECS;
using Editor.ComponentEditors.Core;
using Editor.UI.Drawers;
using Editor.UI.Elements;
using Engine.Scene.Components;

namespace Editor.ComponentEditors;

public class CameraComponentEditor : IComponentEditor
{
    private static readonly string[] ProjectionTypeStrings = { "Perspective", "Orthographic" };

    public void DrawComponent(Entity e)
    {
        ComponentEditorRegistry.DrawComponent<CameraComponent>("Camera", e, entity =>
        {
            var camera = entity.GetComponent<CameraComponent>().Camera;

            UIPropertyRenderer.DrawPropertyField("Size", camera.OrthographicSize,
                newValue => camera.OrthographicSize = (float)newValue);

            UIPropertyRenderer.DrawPropertyField("Near", camera.OrthographicNear,
                newValue => camera.OrthographicNear = (float)newValue);

            UIPropertyRenderer.DrawPropertyField("Far", camera.OrthographicFar,
                newValue => camera.OrthographicFar = (float)newValue);
        });
    }
}

---

Example 2: Vector Component Editor (Transform)

// TransformComponentEditor.cs (actual implementation)
using ECS;
using Editor.ComponentEditors.Core;
using Engine.Math;
using Engine.Scene.Components;

namespace Editor.ComponentEditors;

public class TransformComponentEditor : IComponentEditor
{
    public void DrawComponent(Entity e)
    {
        ComponentEditorRegistry.DrawComponent<TransformComponent>("Transform", e, entity =>
        {
            var tc = entity.GetComponent<TransformComponent>();

            // Translation
            var newTranslation = tc.Translation;
            VectorPanel.DrawVec3Control("Translation", ref newTranslation);
            if (newTranslation != tc.Translation)
                tc.Translation = newTranslation;

            // Rotation (convert radians to degrees for UI)
            var rotationRadians = tc.Rotation;
            Vector3 rotationDegrees = MathHelpers.ToDegrees(rotationRadians);
            VectorPanel.DrawVec3Control("Rotation", ref rotationDegrees);
            var newRotationRadians = MathHelpers.ToRadians(rotationDegrees);
            if (newRotationRadians != tc.Rotation)
                tc.Rotation = newRotationRadians;

            // Scale (reset to 1.0 instead of 0.0)
            var newScale = tc.Scale;
            VectorPanel.DrawVec3Control("Scale", ref newScale, resetValue: 1.0f);
            if (newScale != tc.Scale)
                tc.Scale = newScale;
        });
    }
}

Key Pattern: Copy to temp variable → modify → check if changed → assign back

---

Example 3: Complex Component with Multiple Property Types

public class MyComponentEditor : IComponentEditor
{
    public void DrawComponent(Entity e)
    {
        ComponentEditorRegistry.DrawComponent<MyComponent>("My Component", e, entity =>
        {
            var component = entity.GetComponent<MyComponent>();

            // Simple properties with UIPropertyRenderer
            UIPropertyRenderer.DrawPropertyField("Enabled", component.IsEnabled,
                newValue => component.IsEnabled = (bool)newValue);

            UIPropertyRenderer.DrawPropertyField("Speed", component.Speed,
                newValue => component.Speed = (float)newValue);

            // Vector with axis controls
            var newPosition = component.Position;
            VectorPanel.DrawVec3Control("Position", ref newPosition);
            if (newPosition != component.Position)
                component.Position = newPosition;

            // Dropdown selection
            string[] options = { "Option1", "Option2", "Option3" };
            LayoutDrawer.DrawComboBox("Mode", options[component.ModeIndex], options,
                selected =>
                {
                    component.ModeIndex = Array.IndexOf(options, selected);
                });

            // Custom UI elements with Drawers
            if (ButtonDrawer.DrawButton("Reset", ButtonDrawer.ButtonType.Primary))
            {
                component.Reset();
            }
        });
    }
}

---

Dependency Injection Registration

Component editors are registered in the DI container and injected into ComponentEditorRegistry.

Registration (Program.cs or similar)

// Register individual component editors
container.Register<TransformComponentEditor>(Reuse.Singleton);
container.Register<CameraComponentEditor>(Reuse.Singleton);
container.Register<MyComponentEditor>(Reuse.Singleton);

// ComponentEditorRegistry constructor receives all editors
container.Register<ComponentEditorRegistry>(Reuse.Singleton);

ComponentEditorRegistry Constructor Pattern

public class ComponentEditorRegistry(
    TransformComponentEditor transformComponentEditor,
    CameraComponentEditor cameraComponentEditor,
    MyComponentEditor myComponentEditor) : IComponentEditorRegistry  // Add your editor here
{
    private readonly Dictionary<Type, IComponentEditor> _editors = new()
    {
        { typeof(TransformComponent), transformComponentEditor },
        { typeof(CameraComponent), cameraComponentEditor },
        { typeof(MyComponent), myComponentEditor }  // Register component type
    };

    public void DrawAllComponents(Entity entity)
    {
        foreach (var (componentType, editor) in _editors)
        {
            editor.DrawComponent(entity);
        }
    }
}

---

Change Detection Patterns

Pattern 1: Copy-Modify-Assign (for VectorPanel)

var oldValue = component.Position;
VectorPanel.DrawVec3Control("Position", ref oldValue);

if (oldValue != component.Position)  // Value comparison
    component.Position = oldValue;

Why: VectorPanel modifies the ref parameter directly, so we need manual change detection.

---

Pattern 2: Callback Assignment (for UIPropertyRenderer)

UIPropertyRenderer.DrawPropertyField("Speed", component.Speed,
    newValue => component.Speed = (float)newValue);

Why: UIPropertyRenderer only calls callback if value changed. No manual check needed.

---

Anti-Patterns

❌ Anti-Pattern 1: Not Using DrawComponent Wrapper

// ❌ WRONG - Manual tree node management
public void DrawComponent(Entity e)
{
    if (ImGui.TreeNode("My Component"))
    {
        var component = e.GetComponent<MyComponent>();
        // ... draw properties
        ImGui.TreePop();
    }
}

// ✅ CORRECT - Use DrawComponent wrapper
public void DrawComponent(Entity e)
{
    ComponentEditorRegistry.DrawComponent<MyComponent>("My Component", e, entity =>
    {
        var component = entity.GetComponent<MyComponent>();
        // ... draw properties
    });
}

Why: DrawComponent provides consistent styling, remove button, and safety checks.

---

❌ Anti-Pattern 2: Direct ImGui Calls for Vectors

// ❌ WRONG - Raw ImGui calls
ImGui.DragFloat3("Position", ref component.Position);

// ✅ CORRECT - Use VectorPanel for axis colors and reset buttons
var newPosition = component.Position;
VectorPanel.DrawVec3Control("Position", ref newPosition);
if (newPosition != component.Position)
    component.Position = newPosition;

Why: VectorPanel provides axis color coding, reset buttons, and consistent styling.

---

❌ Anti-Pattern 3: Direct Component Property Mutation with ref

// ❌ WRONG - Modifying component property directly
VectorPanel.DrawVec3Control("Position", ref component.Position);  // May not work as expected

// ✅ CORRECT - Copy to temp variable first
var newPosition = component.Position;
VectorPanel.DrawVec3Control("Position", ref newPosition);
if (newPosition != component.Position)
    component.Position = newPosition;

Why: Component properties may be getters with backing fields or have change tracking.

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❌ Anti-Pattern 4: Forgetting DI Registration

// ❌ WRONG - Editor won't be found at runtime
public class MyComponentEditor : IComponentEditor { ... }
// (not registered in Program.cs)

// ✅ CORRECT - Register in DI container
container.Register<MyComponentEditor>(Reuse.Singleton);

// AND add to ComponentEditorRegistry constructor + dictionary

---

Workflow: Creating a New Component Editor

Step 1: Create Editor Class

// Editor/ComponentEditors/MyComponentEditor.cs
using ECS;
using Editor.ComponentEditors.Core;
using Editor.Panels;
using Editor.UI.Drawers;
using Editor.UI.Elements;
using Engine.Scene.Components;

namespace Editor.ComponentEditors;

public class MyComponentEditor : IComponentEditor
{
    public void DrawComponent(Entity e)
    {
        ComponentEditorRegistry.DrawComponent<MyComponent>("My Component", e, entity =>
        {
            var component = entity.GetComponent<MyComponent>();

            // TODO: Add property editors here
        });
    }
}

Step 2: Register in DI Container (Program.cs)

// In editor startup
container.Register<MyComponentEditor>(Reuse.Singleton);

Step 3: Add to ComponentEditorRegistry

// ComponentEditorRegistry.cs - use primary constructor
public class ComponentEditorRegistry(
    // ... existing editors
    MyComponentEditor myComponentEditor) // Add parameter
{
    private readonly Dictionary<Type, IComponentEditor> _editors = new()
    {
        // ... existing registrations
        { typeof(MyComponent), myComponentEditor }  // Add to dictionary
    };
}

Step 4: Implement Property Editors

Choose the appropriate method for each property type:

// Primitives: Use UIPropertyRenderer
UIPropertyRenderer.DrawPropertyField("Health", component.Health,
    newValue => component.Health = (int)newValue);

// Vectors: Use VectorPanel
var newPos = component.Position;
VectorPanel.DrawVec3Control("Position", ref newPos);
if (newPos != component.Position)
    component.Position = newPos;

// Enums: Use LayoutDrawer
string[] options = Enum.GetNames<MyEnum>();
LayoutDrawer.DrawComboBox("Mode", options[(int)component.Mode], options,
    selected => component.Mode = (MyEnum)Array.IndexOf(options, selected));

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Available UI Utilities

From UIPropertyRenderer

• DrawPropertyField(string label, object value, Action<object> onValueChanged)
  • Supports: int, float, double, bool, string, Vector2, Vector3, Vector4
  • Uses FieldEditorRegistry internally

From VectorPanel

• DrawVec3Control(string label, ref Vector3 values, float resetValue = 0.0f)
• DrawVec2Control(string label, ref Vector2 values, float resetValue = 0.0f)

From LayoutDrawer

• DrawComboBox(string label, string current, string[] options, Action<string> onSelected)

From ButtonDrawer

• DrawButton(string label, ButtonType type = ButtonType.Default) → returns bool
• DrawButton(string label, float width, float height, Action? onClick = null)

From TextDrawer

• DrawErrorText(string text)
• DrawWarningText(string text)
• DrawSuccessText(string text)

From ModalDrawer

• RenderConfirmationModal(string id, ref bool show, string message, Action onConfirm)

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Summary

Component Editor Checklist:

1. ✅ Implement IComponentEditor interface
2. ✅ Use ComponentEditorRegistry.DrawComponent<T>() wrapper
3. ✅ Use VectorPanel for vectors (axis colors, reset buttons)
4. ✅ Use UIPropertyRenderer for simple primitives
5. ✅ Use LayoutDrawer for dropdowns
6. ✅ Manual change detection for ref parameters
7. ✅ Register in DI container (Program.cs)
8. ✅ Add to ComponentEditorRegistry constructor + dictionary

Key Files:

• Editor/ComponentEditors/Core/IComponentEditor.cs - Interface
• Editor/ComponentEditors/Core/ComponentEditorRegistry.cs - Registry and wrapper
• Editor/Panels/VectorPanel.cs - Vector controls
• Editor/UI/Elements/UIPropertyRenderer.cs - Property field wrapper
• Editor/UI/Drawers/LayoutDrawer.cs - Combo boxes
• Editor/ComponentEditors/TransformComponentEditor.cs - Vector example
• Editor/ComponentEditors/CameraComponentEditor.cs - Mixed properties example