KDesktop Design Document

Author :
  David Faure, faure@kde.org
  Martin R. Jones, mjones@kde.org (screensaver)
  Geert Jansen, g.t.jansen@stud.tue.nl (background code)

Last modified: 24 Oct 1999

Overall design of KDesktop :
=============================

KDesktop is the program that handles the desktop icons,
the popup menus for the desktop, the mac menubar, and the
screensaver system.

Files :
=======

main.* : main
desktop.* : the icon container for the desktop icons
krootwm.* : right and middle mouse button popup menus, Mac menubar
bg*.*: Background renderer/manager.

icons.* : old code, not used anymore.
  We need to borrow ideas from it for positioning icons after a DnD
 (in kiconcontainer so that it works with konqueror as well)
 - well, only if we want dropped icons to remain where they have been
 dropped :)
  We also need to store the desktop icons position, like was done in kfm.
   and we need to do it for konqy as well.

KDesktopIface* : DCOP interface for kdesktop, used by kfmclient

lock* : screen saver/locker

Libs used by KDesktop
======================
 
kdecore, kdeui, kfile  - usual stuff :)
libkio - I/O stuff, mimetypes, services, registry
libkonq - properties dialog, templates ("new") menu, dir lister, settings

Screensaver
===========

The screensaver now works in a similar way to xscreensaver, i.e. a driver
(kdesktop) provides the timeout, locking, and blanking functionality, but
does no actual drawing.  A separate stand-alone program capable of
drawing on a supplied window is used to do the actual fancy graphics.
xscreensaver's "hacks" will work with the KDE screensaver engine.

This makes adding new screensavers trivial, and means one less process that
must always be running (compared to KDE 1.x).

The screensaver is controlled via DCOP:

KScreensaverIface::configure()  Reloads the screensaver config from desktoprc.
KScreensaverIface::lock()       Locks the screen immediately.
KScreensaverIface::save()       Saves the screen immediately.
KScreensaverIface::isEnabled()  returns true if the screensaver is enabled.
KScreensaverIface::isBlanked()  returns true if the screen is currently blank.

Backgrounds
===========

The new background code is in bgrender.cpp and bgmanager.cpp. Some features:

* Support for xearth like programs.
* Can export a pixmap of the desktop background for pseudo transparency.

Multiple monitors
=================
Two monitors showing different things (not a mirror-setup) can be configured
in X to either use one X screen, or 2 X screens.  Difference is that if I
drag a window from one monitor to the other the application gets asked to
repaint itself on a 2 screen setup and a simple move of the window will be
done in memory (by XFree) if you have a 1 screen setup.

Monitors example:
    +----+ +-----+  2 monitors, with same resolution to keep it simple.
    |    | |     |
    +----+ +-----+

In case of 1 screen (xinerama)
    +------------+
    |            +   desktopGeometry == screenGeometry == 3200 x 1200
    +------------+

In case of 2 screen (multihead)
    +----+ +-----+
    |    | |     |  desktopGeometry = 3200 x 1200
    +----+ +-----+  screenGeometry = 1600 x 1200 (for each monitor)

