Theme Customization

A bootloader is the first thing your eyes see. Make it beautiful.

ForeB's theme engine scales from 800x600 BIOS VGA to arbitrary-resolution UEFI GOP. Every color, shape, and effect is configurable through forebo.cfg — no recompilation required.

Table of Contents

1. Theme System Overview
2. Color Palette
3. Named Theme Presets
4. Style Presets
5. Selection & Border & Corner Styles
6. Background Images & Icons
7. Font Rendering
8. Widget Styling
9. Visual Effects
10. Audio Feedback
11. Configuration Reference
12. Theme Presets Table
13. Creating Custom Themes
14. Asset Generation Tools

1. Theme System Overview

Three layers of customization, resolved in order:

Level 3: Granular Overrides (forebo.cfg)    color_*, btn_*, win_*, fx_*, menu_*
Level 2: Style Preset (menu_style=)         classic, modern, neon, glass, ...
Level 1: Color Theme (theme=)               forest, midnight, nord, dracula, ...

The renderer (uefi/ui.c) writes 32bpp pixels directly to a GOP linear framebuffer, supporting BGRX and RGBX byte orders. Colors are 0x00RRGGBB matching the BIOS DAC palette for pixel-identical rendering across BIOS and UEFI.

2. Color Palette

14 named slots defined in forebo_theme.h:

Core Palette (Forest Default)

Decorative & Progress

Runtime Overrides

color_bg=0x0E1A12          # background
color_fg=0xDDE7DE          # text
color_accent=0x3FB56B      # highlights / focus
color_sel_bg=0x1F5E3A      # selected row bg
color_sel_fg=0xFFFFFF      # selected row text
color_titlebar=0x1F5E3A    # window title bar
color_window=0x16241B      # window client area
color_cursor=0xFFFFFF      # cursor sprite fill

3. Named Theme Presets

Set theme= to reskin the entire UI in one line:

4. Style Presets

30 layout presets via menu_style=. Each detail can be individually overridden.

5. Selection, Border & Corner Styles

Selection Styles (12)

Border Styles (7)

Corner Styles (3)

6. Background Images & Icons

Backgrounds

BMP (24/32-bit) and TGA (uncompressed), scaled to fill the framebuffer:

background=/forebo/bg.bmp           # global default
img_background=/forebo/skin/bg.bmp  # explicit override
# Per-entry:
menuentry "Forest OS" { background=/forebo/custom-bg.tga }

Custom panel/window/titlebar/button faces:

img_panel=/forebo/skin/panel.tga
img_window=/forebo/skin/window.tga
img_titlebar=/forebo/skin/titlebar.tga
img_button=/forebo/skin/button.tga

Keep images <= 4096px (cursor <= 64px).

Icons

18 shipped 32x32 TGA icons with alpha in /forebo/icons/:

os, text, safe, gear, shield, reboot, ubuntu, debian, arch, fedora, mint, tux, windows, grub, usb, disk, terminal, settings

icon=os                           # short name
icon=/forebo/icons/my-icon.tga    # full path
menu_icon_side=right              # left|right
menu_show_icons=0                 # disable

7. Font Rendering

Crisp 8x16 bitmap font (include/font8x16.h). Auto-scales 2x on 1080p+ panels for legibility. No antialiasing -- pure bitmap precision.

FOREB_GLYPH_W = 8     FOREB_GLYPH_H = 16

8. Widget Styling

Button Styles (6)

btn_style=raised  btn_corner=round  btn_border=1
btn_pad_x=12  btn_pad_y=5
btn_gradient=1  btn_shadow=1  btn_glow=0
btn_fill=0x1C351C  btn_fill_hover=0x246B24  btn_fill_active=0x3FB56B
btn_text=0xFFFFFF  btn_border_color=0x285128  btn_focus_color=0x51CA3D

Window Chrome

window_skin=beveled              # flat|beveled|glass
win_title_h=-1  win_title_fill=0x1F5E3A  win_title_fg=0xFFFFFF
win_border_color=0x3FB56B  win_border_w=1  win_corner=square
win_shadow=1  win_close_color=0xB03030  win_button_style=raised

9. Visual Effects

fx_glass=1          # frosted-glass backdrops (window_skin=glass)
fx_blur=8           # blur radius 0..32 (>16 capped)
fx_opacity=72       # backdrop darken 0..255
fx_vignette=128     # screen-edge darken 0..255
fx_scanlines=64     # CRT scanline dim 0..255
animations=1        # particles / fades / spinner

The blur uses O(w*h) separable box blur via running sums. Vignette darkens radially from center. Scanlines dim every other row for CRT aesthetics.

10. Audio Feedback

PC speaker tones -- no pre-OS audio stack needed:

pcspeaker=1                # master on/off
audio_volume=80            # 0..100
audio_nav_freq=880         # navigation  audio_nav_ms=18
audio_select_freq=1320     # enter       audio_select_ms=40
audio_open_freq=660        # window open audio_open_ms=30
audio_error_freq=220       # rejected    audio_error_ms=90
audio_back_freq=494        # esc/back    audio_back_ms=22

11. Configuration Reference

Complete Key Table

12. Theme Presets Table

Full hex values for all 11 color themes (all slots except tree decorative colors):

13. Creating Custom Themes

Quick Start

1. Pick a base theme
2. Override individual colors
3. Choose a layout preset
4. Fine-tune details
5. Add effects and widgets

Example: Cyberpunk Neon

theme=midnight
menu_style=neon
menu_selection=glow
menu_border=glow
menu_corner=round
color_accent=0xFF00FF
window_skin=glass
fx_glass=1  fx_blur=16  fx_vignette=96
btn_style=glass  btn_corner=round
pcspeaker=1  audio_select_freq=1760  audio_select_ms=25

Example: Retro CRT Terminal

theme=amber
menu_style=terminal
menu_selection=bracket
menu_border=thin
menu_corner=square
menu_gradient=0  menu_shadow=0  menu_accent_strip=0
menu_dividers=1  menu_show_icons=0
fx_scanlines=80  fx_vignette=128
btn_style=flat  btn_corner=square
pcspeaker=1  audio_nav_freq=440  audio_nav_ms=12

14. Asset Generation Tools

forb-config (Python CLI)

Edit, validate, query, and convert forebo.cfg files:

forb-config info forebo.cfg              # summary
forb-config validate forebo.cfg --esp /boot
forb-config themes / forb-config icons   # list assets
forb-config set forebo.cfg theme dracula
forb-config convert grub.cfg --to foreb  # migrate from GRUB

forb-customizer (C++ Qt GUI)

Visual theme editor with live preview, scrollable preset gallery, interactive color picker, diff dialog, and entry inspector. Build:

cd tools/forb-customizer && mkdir build && cd build
cmake .. -DCMAKE_BUILD_TYPE=Release && make -j$(nproc)

Quick Reference

theme=     forest midnight nord dracula gruvbox solarized amber matrix rose ocean mono
style=     classic minimal terminal flat modern card neon outline underline invert brackets
            sidebar-left sidebar-right banner-top dock-bottom fullscreen centered compact
            spacious retro glass hacker ribbon framed dashed spotlight pill boxed ghost elegant
selection= bar doublebar box outline underline arrow bracket invert pill gradient glow none
border=    none thin thick double shadow glow dashed
corner=    square round cut
button=    flat raised pill outline ghost glass