The Scheme Daemon

Documentation / Contents - Color Schemes

• Overview of Colour Schemes
  • Where the Controls Are
  • Fonts Are Separate
  • What Ships
• Choosing a Scheme
  • The Standalone Color Scheme Window
  • What the List Shows
  • The Lock, and Why Names Match
  • If Nothing Changes
• The Roles
  • Ground and Chrome
  • Selection
  • Text and Wells
  • Controls
  • Window Manager
  • Content Accents
  • Metrics
  • The Nine Font Roles
  • What Happens to a Role You Leave Out
• Scheme Files
  • The File
  • Colour Values
  • Where Schemes Are Found
  • Two Names
  • What Ships
  • Writing Your Own
• The Scheme Daemon
  • What It Does
  • Two Kinds of Application
  • The Order of the Resource Block
  • Asking It What It Is Doing
  • Making It Change
  • Signals
  • If Something Wipes the Colours
• Command Line
  • The Daemon
  • The Panel
  • Environment Variables
  • The Background Configuration
• Schemes and the Rest of the Desktop
  • Fonts
  • Wallpaper
  • The Window Manager
  • Bevels

Other cards

• Copyright Information

The Scheme Daemon

cyschemed is the program that serves the colour scheme, and the font scheme, to everything else. It has no window. It runs for the length of your session and is started for you when the session begins.

What It Does

• It owns the scheme selection on the display, so there is exactly one authority per screen.
• It publishes the active scheme's roles as a property, which Blueprint's own applications watch. That is how a scheme change reaches a running program without restarting it.
• It merges a block into the root resource database for older Motif applications, which read their resources once at startup and never again.

Two Kinds of Application

This is the practical distinction.

• Blueprint's own applications follow the property and re-colour themselves while running. Change scheme and they change with you.
• Applications that predate this arrangement read the resource database when they start. They pick up the new scheme the next time they are launched, not before. That is not a bug; there is no way to tell a program something it is not listening for.

The Order of the Resource Block

Three things end up in the resource database and the order matters:

the colour scheme block
the font scheme block
your own resources

The font block sits after the colour block so it outranks the legacy font bindings inside old colour schemes. Your own resources come last, so you outrank both. Nothing Blueprint writes can override a setting you made yourself.

Asking It What It Is Doing

cyschemed --status      the owner, the scheme, and the serial number

It exits non-zero when no daemon is running, which is the quick way to find out whether that is your problem.

cyschemed --list        the installed schemes
cyschemed --dry-run     print the merged resource text without writing it

Making It Change

cyschemed --apply NAME  ask the running daemon to switch

This is what the Background panel's Apply does. It is fire and forget: the request is sent and the exit status does not tell you whether the daemon could actually load the scheme. If a scheme does not take, run --status and see what the daemon thinks is current.

Signals

hang up    reload the current scheme file
terminate  exit cleanly

Reloading is how you pick up an edit you made in a text editor. The daemon does not watch scheme files for changes, so editing the active scheme does nothing until you send it a hang up or use --apply.

If Something Wipes the Colours

Loading a resource file mid-session with xrdb replaces the whole database, including the daemon's block. Nothing notices. Applications started after that get no roles until the daemon is told to reload.

If your desktop suddenly comes up uncoloured after you touched your X resources, that is why. Send the daemon a hang up.

A Startup Race Worth Knowing About

For a short moment after the session begins, the daemon holds the selection but has not yet published the scheme. An application starting in that window can conclude there is no daemon and fall back to reading a scheme file itself. It is brief and it is known.

Next

• Command Line
• Schemes and the Rest of the Desktop