gui-themes

name	gui-themes
description	Add, modify, or debug GUI themes in RegiLattice. Use when adding a new colour theme, changing theme colours, fixing theme application on controls, or understanding the ThemeDef record and Theme engine. Triggers on: 'theme', 'colour', 'dark mode', 'ThemeDef', 'Theme.cs', 'catppuccin', 'add theme', 'style'.
argument-hint	Theme to add or modify (e.g. 'add Gruvbox Light theme')

GUI Themes — RegiLattice

Architecture

All theme logic is in src/RegiLattice.GUI/Theme.cs:

// ThemeDef record — immutable colour palette
public record ThemeDef(
    string Name,
    Color Background,    // Window/panel background
    Color Surface,       // Card/control background (slightly lighter/darker)
    Color Foreground,    // Primary text
    Color Accent,        // Highlighted items, buttons
    Color AccentHover,   // Button hover state
    Color AccentText,    // Text rendered ON accent colour
    Color Muted,         // Secondary/disabled text
    Color Border,        // Separators and borders
    Color Success,       // Applied/green state
    Color Warning,       // Warning/yellow state
    Color Error,         // Error/red state
    bool  IsDark         // True for dark themes
);

Current 11 Themes

Name	Style	Key Accent
Catppuccin Mocha	Dark	Lavender #CBA6F7
Catppuccin Latte	Light	Lavender #7287FD
Nord	Dark	Blue #88C0D0
Dracula	Dark	Purple #BD93F9
Tokyo Night	Dark	Blue #7AA2F7
Gruvbox Dark	Dark	Orange #FE8019
Solarized Dark	Dark	Blue #268BD2
One Dark Pro	Dark	Blue #61AFEF
Rosé Pine	Dark	Gold #F6C177
Everforest	Dark	Green #A7C080
Cyberpunk	Dark	Cyan #00F5FF

Adding a New Theme

1. Define the ThemeDef in Theme.cs

Look for the _themes static list and add a new entry:

new ThemeDef(
    Name:        "My New Theme",
    Background:  Color.FromArgb(0xFF, 0x1E, 0x1E, 0x2E),   // deep background
    Surface:     Color.FromArgb(0xFF, 0x28, 0x28, 0x3D),   // card/panel surface
    Foreground:  Color.FromArgb(0xFF, 0xCD, 0xD6, 0xF4),   // primary text
    Accent:      Color.FromArgb(0xFF, 0x89, 0xB4, 0xFA),   // accent/button
    AccentHover: Color.FromArgb(0xFF, 0x74, 0xC7, 0xEC),   // hover
    AccentText:  Color.FromArgb(0xFF, 0x1E, 0x1E, 0x2E),   // text on accent
    Muted:       Color.FromArgb(0xFF, 0x6C, 0x70, 0x86),   // dimmed text
    Border:      Color.FromArgb(0xFF, 0x45, 0x47, 0x5A),   // borders
    Success:     Color.FromArgb(0xFF, 0xA6, 0xE3, 0xA1),   // green/applied
    Warning:     Color.FromArgb(0xFF, 0xF9, 0xE2, 0xAF),   // yellow
    Error:       Color.FromArgb(0xFF, 0xF3, 0x8B, 0xA8),   // red
    IsDark:      true
),

2. Register in the theme list

The _themes list is returned by AvailableThemes(). No extra registration needed — just add to the list.

3. Write a test in tests/RegiLattice.GUI.Tests/ThemeTests.cs

[Fact]
public void Theme_MyNewTheme_HasRequiredProperties()
{
    var theme = Theme.GetTheme("My New Theme");
    Assert.NotNull(theme);
    Assert.True(theme.IsDark);
    Assert.Equal("My New Theme", theme.Name);
    // Verify key colours are not default/empty
    Assert.NotEqual(Color.Empty, theme.Background);
    Assert.NotEqual(theme.Background, theme.Surface);  // surface must differ from bg
}

ApplyTheme — How Themes Are Applied

Theme.ApplyTheme(Control) recursively walks the control tree:

• Sets BackColor / ForeColor on panels, labels, buttons, listviews
• Special handling for RichTextBox (BackColor must be set AFTER ReadOnly to avoid Windows override)
• MainForm re-applies after any dynamic control creation

System Theme Detection

// On startup — follow Windows dark/light preference
Theme.SetTheme(Theme.DetectSystemTheme());

DetectSystemTheme() reads HKCU\Software\Microsoft\Windows\CurrentVersion\Themes\Personalize\AppsUseLightTheme and returns "Catppuccin Mocha" (dark) or "Catppuccin Latte" (light).

Theme Persistence

Selected theme name is saved in AppConfig.Theme → %LOCALAPPDATA%\RegiLattice\config.json.