Custom Icons

What is it for?

ArcanumLib provides two systems for custom Cairo-drawn GUI icons:

ICustomIconRenderer — an interface for drawing a single icon at a given position and radius.
CustomIconRegistry — a global string-keyed registry of ICustomIconRenderer instances.
CustomTabIconRenderer — a static library of decorative Cairo icons (dividers, bullets, stars, shields, crowns, skulls, etc.) used by GuiElementCustomTabContent.

When to use it

You need vector-drawn icons that scale cleanly at any size.
You want to register custom icons by string key and look them up at compose/render time.
You are building tab content and want decorative section dividers and entry bullets.

Quick example

Registering a custom icon

using ArcanumLib.Gui.Icons;
using Cairo;

public class MyStarIcon : ICustomIconRenderer
{
    public void Draw(Context ctx, double cx, double cy, double radius)
    {
        ctx.SetSourceRGBA(1.0, 0.8, 0.2, 1.0);
        // Draw a 5-pointed star at (cx, cy) with the given radius.
        for (int j = 0; j < 10; j++)
        {
            double angle = j * Math.PI / 5 - Math.PI / 2;
            double r = (j % 2 == 0) ? radius : radius * 0.42;
            double px = cx + Math.Cos(angle) * r;
            double py = cy + Math.Sin(angle) * r;
            if (j == 0) ctx.MoveTo(px, py);
            else ctx.LineTo(px, py);
        }
        ctx.ClosePath();
        ctx.Fill();
    }
}

// At startup:
CustomIconRegistry.Register("mydomain:star", new MyStarIcon());

Using a registered icon

if (CustomIconRegistry.TryGet("mydomain:star", out var renderer))
{
    renderer?.Draw(ctx, centerX, centerY, 24.0);
}

Using CustomTabIconRenderer

using ArcanumLib.Gui.Icons;

// Draw a decorative section divider
CustomTabIconRenderer.DrawSectionDivider(ctx, x, y, width, ArcanumGuiTheme.BorderSilver);

// Draw a section header icon
CustomTabIconRenderer.DrawSectionHeaderIcon(ctx, cx, cy, size, ArcanumGuiTheme.Accent);

// Draw an entry bullet
CustomTabIconRenderer.DrawEntryBullet(ctx, cx, cy, size, ArcanumGuiTheme.Accent);

// Draw an active star
CustomTabIconRenderer.DrawActiveStar(ctx, cx, cy, radius, ArcanumGuiTheme.AccentBright);

API overview

ICustomIconRenderer

public interface ICustomIconRenderer
{
    void Draw(Context ctx, double cx, double cy, double radius);
}

CustomIconRegistry

Method	Description
`Register(string key, ICustomIconRenderer renderer)`	Register a renderer. Overwrites existing.
`TryGet(string key, out ICustomIconRenderer? renderer)`	Look up a renderer by key.
`Has(string key)`	Check if a renderer is registered.
`Unregister(string key)`	Remove a renderer.
`Clear()`	Remove all renderers.

CustomTabIconRenderer

Static methods for decorative Cairo icons:

Method	Description
`DrawSectionDivider`	Horizontal line with a centered diamond ornament.
`DrawSectionHeaderIcon`	Small diamond symbol for section headers.
`DrawEntryBullet`	Chevron arrow for normal entries.
`DrawActiveStar`	Five-pointed star for active entries.
`DrawSubDot`	Small dot for sub-item indentation.
`DrawRiftIcon`	Jagged vertical crack.
`DrawShieldIcon`	Shield outline with a vertical line.
`DrawCrownIcon`	Simple crown shape.
`DrawSkullIcon`	Skull and eye sockets.
`DrawHourglassIcon`	Hourglass with falling sand.
`DrawSwordIcon`	Sword with crossguard and pommel.

Notes

All icons are drawn using Cairo paths — no texture loading required.
Colours are passed as RGBA values from ArcanumLib.Gui.Theme.
CustomIconRegistry is a global static registry; register icons once at mod startup.
ItemListElement checks CustomIconRegistry for CustomIconKey before falling back to item-stack icons.