Attribute Management

Most icons in a project share the same size, stroke width, or base class. Instead of repeating those attributes on every call, set them once and let the five-layer merge handle the rest.

The five-layer merge

When manager.Get() resolves an icon, the IconRenderer merges attributes from five sources. Higher layers override lower ones. The class attribute is concatenated rather than replaced at every layer.

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Layer 1 (lowest)    Icon's own attributes
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                    (from SVG file parse or Iconify JSON)
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                    e.g. viewBox="0 0 24 24", width="24", height="24"
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Layer 2             Global DefaultAttributes
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                    e.g. stroke="currentColor", stroke-width="2", fill="none"
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Layer 3             PrefixAttributes for the resolved prefix
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                    e.g. tabler → stroke-width="1.5"
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Layer 4             PrefixSuffix for the resolved prefix + icon name suffix
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                    e.g. heroicons + "-solid" → fill="currentColor"
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Layer 5 (highest)   Caller-provided attributes
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                    e.g. manager.Get("home", map{"class": "icon", "width": "16"})

Configuring each layer

Layer 2 (global defaults):

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import swarmicons "github.com/frostybee/go-swarm-icons"
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manager, _ := swarmicons.NewConfig().
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    AddProvider("lucide", lucide.Provider()).
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    DefaultAttributes(map[string]string{
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        "fill":         "none",
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        "stroke":       "currentColor",
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        "stroke-width": "2",
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    }).
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    Build()

Calling DefaultAttributes() multiple times is additive. Later calls merge into earlier ones.

Layer 3 (per-prefix):

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import swarmicons "github.com/frostybee/go-swarm-icons"
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manager, _ := swarmicons.NewConfig().
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    AddProvider("tabler", tablerProvider).
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    PrefixAttributes("tabler", map[string]string{
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        "stroke-width": "1.5",
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    }).
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    Build()

These attributes apply only to icons resolved from the "tabler" prefix.

Layer 4 (suffix matching):

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import swarmicons "github.com/frostybee/go-swarm-icons"
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manager, _ := swarmicons.NewConfig().
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    AddProvider("heroicons", heroiconsProvider).
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    PrefixSuffix("heroicons", "solid", map[string]string{
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        "fill": "currentColor",
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    }).
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    PrefixSuffix("heroicons", "outline", map[string]string{
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        "fill":   "none",
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        "stroke": "currentColor",
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    }).
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    PrefixSuffix("heroicons", "", map[string]string{
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        "fill": "currentColor",
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    }).
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    Build()

The renderer checks if the icon name ends with -{suffix}. When multiple suffixes match, the longest suffix wins. An empty suffix ("") acts as a catch-all for icons that match no other suffix.

Layer 5 (caller attributes):

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icon, _ := manager.Get("home", map[string]string{
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    "class": "nav-icon",
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    "id":    "home-btn",
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})

Merge rules

class: concatenated from all layers, space-separated. No deduplication.
All other attributes: last layer wins. A value set at layer 4 overrides the same key from layer 3.
Empty-string values: skipped entirely. Passing "fill": "" at layer 5 does not clear a fill set at layer 2.

Full example

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import (
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    "fmt"
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    swarmicons "github.com/frostybee/go-swarm-icons"
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    "github.com/frostybee/go-swarm-icons/lucide"
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)
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func main() {
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    manager, _ := swarmicons.NewConfig().
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        AddProvider("lucide", lucide.Provider()).
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        DefaultPrefix("lucide").
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        DefaultAttributes(map[string]string{
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            "fill":   "none",
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            "stroke": "currentColor",
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            "class":  "icon",
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        }).
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        Build()
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    icon, _ := manager.Get("home", map[string]string{
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        "class": "nav-icon",
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        "id":    "home-link",
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    })
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    fmt.Println(icon.ToHTML())
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    // class includes both "icon" (from layer 2) and "nav-icon" (from layer 5)
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    // fill="none" and stroke="currentColor" from layer 2
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    // id="home-link" from layer 5
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}

ARIA injection

After the five-layer merge, the renderer injects ARIA attributes for accessibility. The behavior depends on which attributes are already present:

Decorative icons (default)

If no aria-label, aria-labelledby, or role attribute is present:

aria-hidden="true" is set (unless already present).
focusable="false" is set (unless already present).

This marks the icon as decorative and hidden from screen readers.

Labeled icons

If aria-label, aria-labelledby, or role is present:

role="img" is set (unless role is already set to another value).
aria-hidden and focusable are not injected.

Existing values are preserved

The renderer never overwrites an attribute that is already set. For example:

An icon with aria-hidden="false" keeps that value.
An icon with role="button" keeps role="button" even when aria-label is present.
An icon with focusable="true" keeps focusable="true".

Interaction with `Title()`

The Title() fluent method prepends a <title> element to the SVG content but does not set aria-label automatically. To make a titled icon accessible, pass aria-label or aria-labelledby as a caller attribute:

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icon.Title("Home").Attr(map[string]string{"aria-label": "Home"})
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// Result: role="img" is injected, aria-hidden is NOT set.