Control Panel and Settings

What is it?

The Control Panel is where you change system settings: display, date and time, users, installed programs, network and the rest. This roadmap plans a Settings-style window that hosts applets written to the Windows cpl.h interface, nine core applets (system, display, network, sound, date and time, power, mouse, region and taskbar), four more (user accounts, programs, firewall and a date and time alias) and a search box across all settings. Nothing is implemented yet: the Start menu's Settings button and the Control Panel entries do nothing when clicked.

How does it work?

Today. The desktop shows the way in, but there is nothing behind it (desktop.c):

The Start menu footer draws a Settings button with ICON_SETTINGS; clicking it only closes the menu.
The Start menu's right column lists Control Panel, and the desktop shows a Control Panel icon (ICON_CONTROL_PANEL, icon_store.h); neither responds to a click.

Settings are stored in the Registry, read and written with RegGetValue() and RegSetValueEx() (registry.h); there is no separate settings API. The system facts an applet would show are available to kernel code: the CPU brand from cpuid_get(), memory from pmm_get_total_frames(), the CPU count and uptime(). The Settings frame sizes are already design tokens: a 280 pixel navigation pane, 36 pixel navigation items and 64 pixel minimum setting cards (THEME_SIZE_NAV_PANE_WIDTH, THEME_SIZE_NAV_ITEM_HEIGHT, THEME_SIZE_SETTINGS_CARD_MIN_HEIGHT in theme_tokens.h).

Planned design. The frame follows the Settings and Control Panel design.

CPL framework. cpl.h with the Win32 message IDs (CPL_INIT, CPL_GETCOUNT, CPL_NEWINQUIRE, CPL_DBLCLK, CPL_EXIT and the rest) and a compatible NEWCPLINFO.
Host window. A 980 by 640 Settings frame with the navigation pane and Win+I to open it. Applets are compiled in and looked up by .cpl file name; loading .cpl files as separate libraries comes later.
Core applets. System (sysdm.cpl: CPU, memory, uptime, computer name), display (desk.cpl: resolution, scaling, wallpaper, accent colour, light or dark), network (ncpa.cpl), sound (mmsys.cpl), date and time (timedate.cpl, with an analog clock), power (powercfg.cpl), mouse (main.cpl), region (intl.cpl) and taskbar auto-hide.
More applets. User accounts (nusrmgr.cpl), programs (appwiz.cpl, reading HKLM\...\Uninstall), firewall, and a date and time alias.
Search. A case-insensitive substring filter over every setting's name, highlighting matches, with Enter opening the first.

What are its interfaces?

Interface	Status
`RegGetValue()`, `RegSetValueEx()`	Shipped: settings storage
`THEME_SIZE_NAV_PANE_WIDTH` and the other Settings tokens	Shipped design tokens
Settings button and Control Panel icon	Drawn, not wired
`cpl.h`, `CPlApplet`, `control.exe`, applets	Planned

How do I use it?

It cannot be used yet. Settings that exist today are changed in the Registry or in boot.conf.

What is not implemented yet?

CPL Framework
Control Panel Host App
Core Applets, whose wallpaper, scaling and date and time pages depend on Desktop Shell Features and Kernel Time and Taskbar Clock
Additional Applets, with accounts from Security and User Accounts
Settings Search

The toggles, sliders and drop-downs the applets need are owned by Extended Widget Library: Core Controls.

How does it compare with Windows 11 and Linux?

Windows 11 has both the Settings app and the classic Control Panel, with .cpl applets, System Properties, display scaling from 100 to 500 percent, date and time, user accounts, Programs and Features and an indexed Settings search. Linux desktops use GNOME Settings or KDE System Settings, which have no applet ABI, with pages for display, date and time, users and software and a search bar. Impossible OS has no settings window yet. The plan keeps the Win32 applet interface so applets written for Windows could load, inside the Windows 11 Settings layout.