Original Skin Creation Guide

This guide covers creating custom skins for NullPlayer's Original UI mode. The implementation retains the modern name internally for compatibility.

Overview

Original skins are built on the ModernSkin Engine (its internal compatibility name), a theme-agnostic system that renders UI elements from:

1. JSON configuration (skin.json) -- colors, fonts, layout, animations
2. PNG image assets -- optional per-element images
3. Programmatic fallback -- elements without images are drawn using palette colors

You can create a skin with just a skin.json (pure programmatic) or provide custom images for every element.

Skin Directory Structure

MySkin/
├── skin.json              # Required: skin configuration
├── images/                # Optional: PNG assets
│   ├── btn_play_normal.png
│   ├── btn_play_pressed.png
│   ├── btn_play_normal@2x.png    # Optional Retina
│   └── background.png
└── fonts/                 # Optional: custom fonts
    └── MyFont.ttf

skin.json Schema

{
    "meta": {
        "name": "My Skin",
        "author": "Your Name",
        "version": "1.0",
        "description": "A custom Original skin"
    },
    "palette": {
        "primary": "#00ffcc",
        "secondary": "#00aaff",
        "accent": "#ff00aa",
        "highlight": "#00ffee",
        "background": "#0a0a12",
        "surface": "#0d1117",
        "text": "#00ffcc",
        "textDim": "#006655",
        "positive": "#00ff88",
        "negative": "#ff3366",
        "warning": "#ffaa00",
        "border": "#00ffcc",
        "timeColor": "#d9d900",
        "marqueeColor": "#d9d900",
        "dataColor": "#d9d900",
        "eqLow": "#00d900",
        "eqMid": "#d9d900",
        "eqHigh": "#d92600"
    },
    "fonts": {
        "primaryName": "DepartureMono-Regular",
        "fallbackName": "Menlo",
        "titleSize": 8,
        "bodySize": 9,
        "smallSize": 7,
        "timeSize": 20,
        "infoSize": 6.5,
        "eqLabelSize": 7,
        "eqValueSize": 6,
        "marqueeSize": 12.7,
        "playlistSize": 8
    },
    // NOTE: "primaryName": "DepartureMono-Regular" (the lo-fi default) now resolves to the
    // macOS system font — the Original/Metal UI no longer uses the retro bitmap font. Only a
    // real custom font name is rendered verbatim. See advanced-features.md → Font Configuration.
    "background": {
        "image": "background.png",
        "grid": {
            "color": "#0a2a2a",
            "spacing": 20,
            "angle": 75,
            "opacity": 0.15,
            "perspective": true
        }
    },
    "glow": {
        "enabled": true,
        "radius": 8,
        "intensity": 0.6,
        "threshold": 0.7,
        "color": "#00ffcc",
        "elementBlur": 1.0
    },
    "window": {
        "borderWidth": 1,
        "borderColor": "#00ffcc",
        "cornerRadius": 8,
        "scale": 1.25,
        "opacity": 0.9,
        "textOpacity": 1.0,
        "mainSpectrumOpacity": 1.0,
        "spectrumTransparentBackground": false,
        "waveformWindowOpacity": 0.85,
        "seamlessDocking": 1.0
    },
    "marquee": {
        "scrollSpeed": 30,
        "scrollGap": 50
    },
    "titleText": {
        "mode": "image",
        "charSpacing": 1,
        "charHeight": 10,
        "alignment": "center",
        "tintColor": "#d4cfc0"
    },
    "elements": {
        "play_controls":       { "color": "#00ffcc" },
        "seek_fill":           { "color": "#00ffcc" },
        "volume_fill":         { "color": "#00ffcc" },
        "minicontrol_buttons": { "color": "#00ffcc" },
        "playlist_text":       { "color": "#009977" },
        "tab_outline":         { "color": "#00ffcc" },
        "tab_text":            { "color": "#00ffcc" },
        "btn_play": {
            "color": "#00ff00",
            "x": 33, "y": 8, "width": 23, "height": 20
        }
    },
    "animations": {
        "seek_fill": {
            "type": "glow",
            "duration": 3.0,
            "minValue": 0.4,
            "maxValue": 1.0
        }
    }
}

Color Palette

17 named colors used throughout the UI:

Key	Required	Purpose
primary	Yes	Main accent (buttons, text, indicators)
secondary	Yes	Secondary accent
accent	Yes	Highlight accent (spectrum, volume gradient)
highlight	No	Bright highlight (falls back to primary)
background	Yes	Window fill
surface	Yes	Panel/recessed areas
text	Yes	Primary text
textDim	Yes	Dimmed/inactive text
positive	No	Positive state indicator (default green)
negative	No	Negative state indicator (default red)
warning	No	Warning indicator (default amber)
border	No	Window border (falls back to primary)
timeColor	No	Time display digits (default #d9d900)
marqueeColor	No	Scrolling title text (default #d9d900)
dataColor	No	Track numbers, info fields (default #d9d900)
eqLow	No	EQ color at -12dB (default #00d900)
eqMid	No	EQ color at 0dB (default #d9d900)
eqHigh	No	EQ color at +12dB (default #d92600)

Element-Level Color Overrides

Some UI sections have dedicated elements color keys that override the palette:

Element key	Controls	Fallback chain
play_controls	All transport button icon colors	palette.primary
btn_prev … btn_next	Individual transport button (overrides play_controls)	play_controls → palette.primary
seek_fill	Seek bar fill + thumb	palette.primary
volume_fill	Volume bar fill + thumb	seek_fill.color → palette.primary
playlist_text	Normal (non-current, non-selected) track text in playlist	palette.textDim
tab_outline	Active tab border + glow color in library browser tab bar	palette.accent
tab_text	Active tab label text color in library browser tab bar	palette.accent
minicontrol_buttons	ON state color for main window toggle buttons (EQ, PL, SP, etc.)	palette.accent

Image Naming Convention

Images go in the images/ subdirectory:

{element_id}_{state}.png       # State-specific
{element_id}.png               # All states
{element_id}_{state}@2x.png   # Retina (optional)

Examples:

• btn_play_normal.png -- Play button, normal state
• btn_play_pressed.png -- Play button, pressed state
• time_digit_5.png -- Digit "5" for time display

Time Display Rendering

The Original main-window timer supports two rendering paths:

• Sprite-based rendering for the default 7-segment set: time_digit_0 through time_digit_9, time_colon, and time_minus
• Font-based fallback rendering for alternate timer number systems when matching sprites are not present

The timer keeps the full minutes-and-seconds value for long tracks. Its normal digit metrics are unchanged while the readout fits; longer strings such as -158:43 scale all digit, colon, gap, and height metrics uniformly into a content width inset by 3 points on each side of the LCD. Do not clamp to the panel's full width, because that makes the outer glyph touch the border. Font-fallback glyphs must also reduce their configured time font when the measured character is wider than its assigned cell.

This means skins can keep the existing LED-style decimal timer sprites, while alternate numeral systems and radix modes still render using the configured time font.

The engine automatically checks for @2x variants on Retina displays.

Creating a Minimal Skin

The simplest skin is just a skin.json with palette colors:

{
    "meta": { "name": "Minimal", "author": "Me", "version": "1.0" },
    "palette": {
        "primary": "#ff6600",
        "accent": "#ff0066",
        "background": "#1a1a2e",
        "surface": "#16213e",
        "text": "#ff6600",
        "textDim": "#664400"
    },
    "fonts": { "primaryName": "DepartureMono-Regular", "fallbackName": "Menlo" },
    "background": { "grid": { "color": "#332200", "spacing": 15, "angle": 80, "opacity": 0.1 } },
    "glow": { "enabled": true, "radius": 6, "intensity": 0.5, "threshold": 0.6 },
    "window": {
        "borderWidth": 1,
        "cornerRadius": 6,
        "opacity": 0.9,
        "textOpacity": 1.0,
        "mainSpectrumOpacity": 1.0,
        "seamlessDocking": 1.0
    }
}

All elements render programmatically using the palette colors.

Original-Metal mode uses the same Original skin engine but a separate family namespace (.metal render style, metalSkinName key, user skins under MetalSkins). Its appearance is code-driven, not palette-driven: every metal skin draws the same surfaces, with per-finish colors supplied by a MetalMaterial preset (ModernSkin/MetalMaterial.swift).

Seven built-in metal finishes ship in code (ModernSkinLoader.createBuiltInMetalSkin(named:), listed by builtInMetalSkinNames): Brushed Steel (default), Aluminum, Gunmetal, Anodized Black, Brass, Bronze, Copper. They appear automatically in the Skins → Original-Metal menu and load by name (path-nil SkinInfo).

Display vs. chrome contrast: the main-window time/track panels and EQ curve graph render on a backlit-green LCD (material.displayFill); text on the LCD uses material.lcdInk (dark in every finish), while on-chrome text uses the skin palette text/textDim/dataColor (light on dark finishes, dark on light). timeColor/marqueeColor stay dark for all finishes since they sit on the green LCD. EQ faders use a brightness value ramp (material.faderLow/faderMid/faderHigh), not a hue scale.

Dockable sub-windows (EQ, Playlist, Spectrum, Audio Analysis, Flow, PeppyMeter, Waveform, Visualizations, Library) use ModernSkinElements.auxiliaryWindowBorderWidth for their chrome/content inset. In standard Original skins this preserves the established thicker inset; in Metal skins it collapses to the renderer's thin window-border width so every dockable sub-window presents the same smallest border width. Metal-only content padding is avoided for Flow and PeppyMeter so their interiors do not read as extra border thickness; their content rects also expand through adjacent joined chrome strips via expandingThroughJoinedEdges(...) in every render style (not just Metal), matching the shared-edge border suppression so no seam shows on a docked edge (issue #364). The helper only bridges small edge-adjacent gaps and must not expand body content across a visible title bar.

Library browser (metal): the window renders as one continuous brushed-metal surface — the top-chrome band fills and the alphabet-index inset are cleared, and the renderer's metal accent strip is suppressed for this window via drawWindowBackground(..., drawMetalAccentStrip:) (other metal windows keep the strip). Compact player bar (CompactPlayerBarView, metal): the upper display row (track-title marquee + inline, vertically-centered time) gets the green LCD fill via drawInsetPanel(displayFill: true), with the seek bar and volume in a separate control row below so they sit off the LCD. The classic compact bar (ClassicCompactPlayerBarView) mirrors the same display-row / control-row layout without the green fill.

Bundled Skins

The following skins ship in Sources/NullPlayer/Resources/Skins/:

Skin	Notes
NeonWave (default)	Cyan/magenta, sprite-based pixel-art title text, perspective grid, seamless docking
Skulls	Cream/amber, skull decorations, amber 7-segment digits, lo-fi receiver aesthetic
ArcticMinimal	Clean minimal arctic color scheme
BananaParty	Bright banana/yellow theme
BloodGlass	Dark glass with blood-red accents
Bubblegum Retro	Pastel retro bubblegum palette
EmeraldForge	Green/forge industrial look
ForgedTitanium	Dark metallic titanium aesthetic
HyperPopPrism	Hyper-saturated prismatic colors
IndustrialSignal	Industrial signal/utility aesthetic
Sakura Minimal	Soft pink sakura minimal theme
SeaGlass	Teal sea-glass translucent look
SmoothGlass	Smooth glass translucent aesthetic

Packaging for Distribution

ZIP your skin directory and rename to .nsz:

cd MySkin/
zip -r ../MySkin.nsz .

Users place .nsz files or folders in:

~/Library/Application Support/NullPlayer/ModernSkins/

Installation

Selecting a Skin

Right-click the player → Skins → Original → choose from the list (or use Load Skin... to import a .nsz bundle).

Skin changes take effect immediately. Switching between the Classic, Original, and Original-Metal displays happens live in-process. Their internal mode identifiers remain classic, modern, and metal for compatibility.

Multi-Window Support

The Original skin system renders multiple windows:

• Main Window -- transport controls, time, marquee, mini spectrum
• Playlist Window -- track list with selection, scrolling
• EQ Window -- 21-band graphic equalizer with integrated PRE control and curve graph
• Spectrum Analyzer Window -- standalone visualization
• ProjectM Window -- MilkDrop visualization with presets
• Library Browser Window -- multi-source browser with columns and an embedded Play History tab

All windows share palette colors, glow, grid, and font settings. Customize individual windows by prefixing element IDs (e.g., spectrum_titlebar vs titlebar).

Key Source Files

File	Purpose
ModernSkin/ModernSkinEngine.swift	Singleton manager, skin loading
ModernSkin/ModernSkinConfig.swift	JSON schema, Codable structs
ModernSkin/ModernSkinLoader.swift	Load skin.json and images
ModernSkin/ModernSkinRenderer.swift	Drawing code for all elements
ModernSkin/ModernSkinElements.swift	Layout constants, element IDs
Windows/ModernMainWindow/	Main window implementation
Windows/ModernSpectrum/	Spectrum window (simplest sub-window)
Windows/ModernPlaylist/	Playlist window
Windows/ModernEQ/	EQ window
Windows/ModernProjectM/	ProjectM window
Windows/ModernLibraryBrowser/	Library browser window

Additional Documentation

For detailed information, see:

• element-reference.md - Complete element catalog with all IDs, positions, states
• advanced-features.md - Title text system, animations, UI Size mode, sub-window creation checklist