path: root/doc/kompmgr/index.docbook

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<book lang="&language;">
<bookinfo>
<title>&kappname; Information</title>

<authorgroup>
<author>
<personname><firstname>Thomas</firstname><surname>Luebking</surname></personname>
<email>thomas.luebking@web.de</email>
</author>

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</authorgroup>

<copyright>
<year>2005</year>
<holder>Thomas Luebking</holder>
</copyright>

<legalnotice>&FDLNotice;</legalnotice>

<date>2005-01-15</date>
<releaseinfo>2.0.1</releaseinfo>

<abstract>
<para>&kappname; is a composite rendering engine to be used by &kwin;.</para>
<para>This document is rather a general explanation of what it does, 
how it works and what the restrictions are than a documentation how to use
it (as it works in the background automatically).</para> 
</abstract>

<keywordset>
<keyword>KDE</keyword>
<keyword>kwin</keyword>
<keyword>render engine</keyword>
</keywordset>
</bookinfo>

<chapter id="introduction">
<title>Introduction</title>

<para>&kappname; is based upon <application>xcompmgr</application>, Keith
Packards reference composing implementation for the use of the new X
features.</para>

<para>A composite manager catches the output of the X windows and renders
them into a single picture that will be displayed on the screen. The advantage
of doing so is that you can do basically anything with the windows contents,
including blending them together (translucency) or attaching shadows. You
could also tint them, add a nasty advertise on any window, squeeze them,
fract them, add scanlines, or anything else you can imagine, limited by
your hardware.</para>

</chapter>

<chapter id="xorg">
<title>Xorg</title>

<para>You necessarily need <emphasis>X.org 6.8 or later</emphasis> to have
&kappname; work. X.org 6.7 or older or XFree86 won't work.</para>

<sect1 id="xsetup">
<title>Setup</title>
<para>You need to explicitly enable the Composite extension. Add a
new Section to your X.org configuration file:</para>

<programlisting>
Section "Extensions"
    Option "Composite" "Enable"
EndSection
</programlisting>

<para>If supported by your <acronym>GPU</acronym> (the complex chip that
powers a modern graphics card), activate the Render acceleration.  This is
best supported by <trademark>NVIDIA</trademark>, and less completely by ATI
cards.</para>

<programlisting>
Section "Device"
....
....
    Option     "RenderAccel" "true"
....
....
EndSection</programlisting>

<para>&kappname; should be available now. For more information, please see
the <link linkend="problems">FAQ</link>.</para>

</sect1>

</chapter>

<chapter id="settings">
<title>Settings</title>

<para>This chapter describes which parameters you can tweak, how they will
result visually and their performance impact.</para>

<sect1 id="translucency">
<title>Translucency</title>

<para>A translucent object is one that allows light to pass through it.  In
terms of windows on your desktop, that means that the contents of windows
can be seen through the one on the top.</para>

<para>Translucency allows you to emphasize special windows, have a 3
dimensional view on your desktop, keep track of covered windows, and just
looks cute. The price is, that blending things together costs some system
capacity.</para>

<para>You can independently configure translucency for the following
items:</para>

<variablelist>
<varlistentry>
<term><guilabel>Active windows</guilabel></term>
<listitem><para>It is suggested you deactivate translucency for the active
window.  The main reason is for perfomance, and secondly because to scan the
content of a translucent window means your brain has to strip the irritating
throughshining information, which is tiring.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><guilabel>Inactive windows</guilabel></term>
<listitem><para>If you set inactive windows translucent, active windows will
appear emphasized and are easier to focus. However, if you choose a lower
value, you may have trouble to find an inactive window. If you choose very
low values (&lt; 20&percnt;) you may not be able to distinguish 
windows in their stack order - so you may accidently click the
<guibutton>OK</guibutton> button of a dialog when you just wanted to
activate a window. Optimal values are between 60&percnt; and
80&percnt;.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><guilabel>Moving windows</guilabel></term>
<listitem><para>Though it's a nice effect to have heavily translucent
(opacity &lt; 20&percnt;) moving windows, there is a heavy price to pay in
performance, especially if you do not deactivate shadows (see below). Just
try out and if you feel your system is too slow, keep moving windows
opaque. This value also applies to windows in resize state.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><guilabel>Dock windows</guilabel></term>
<listitem><para>As docks like kicker are seldom if ever moved and usually of
limited size, this is purely visual and won't detrimentally affect your
system's performance.</para>  
</listitem>
</varlistentry>
<varlistentry>
<term><guilabel>Treat "keep above" windows as active ones</guilabel></term>
<listitem><para>If you set a window to keep above others, you usually want
to keep focus on it, so it can make sense to give it the same
emphasis.</para> 
</listitem>
</varlistentry>
<varlistentry>
<term><guilabel>Disable ARGB windows</guilabel></term>
<listitem><para>XRender supports windows with an alpha mask, &ie;
translucent sections. Currently there are no or only very few applications
that would make use of this feature, as it doesn't make any sense without
using a composite manager. This may change in the future.</para>
<para>On the other side, most gtk 1.x applications (&eg;
<application>xmms</application>) set such an alpha mask, resulting in
almost unusable windows (as long as the sublying windows are not black), so
you can disable the support for ARGB windows here to make use of gtk
applications.  There will hopefully be a patch for gtk in the near future to
fix this.</para>
</listitem>
</varlistentry>
</variablelist>
</sect1>

<sect1 id="shadows">
<title>Shadows</title>
<para>Why should anyone want his windows to throw shadows? Well, maybe just
because it looks cute, or because it allows a better window separation,
or... because it looks cute!</para> 
<variablelist>
<varlistentry>
<term><guilabel>Use shadows</guilabel></term>
<listitem><para>As shadows cost some additional cpu/gpu power, they can be
deactivated, while keeping a general alpha channel capability.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><guilabel>Active window size</guilabel></term>
<term><guilabel>Inactive window size</guilabel></term>
<term><guilabel>Dock window size</guilabel></term>
<listitem><para>You may select different shadow sizes for different window
states/types. The values are not absolute, but will apply to your screen
resolution.</para>
<para>In principle, you can set every value you want (if you edit the config
file with a text editor, far beyond the offered <quote>32</quote>), but
bigger shadows cost more cpu/gpu power.</para> 
</listitem>
</varlistentry>
<varlistentry>
<term><guilabel>Vertical offset</guilabel></term>
<term><guilabel>Horizontal offset</guilabel></term>
<listitem><para>By default, the window would throw a <quote>all around
equal</quote> shadow, implying a frontal light source. Users familiar with
&MacOS; may like a vertical offset, &Windows; users may prefer a
slighter offset to the southeast.  Experiment with the values until you are
happy.</para> 
</listitem>
</varlistentry>
<varlistentry>
<term><guilabel>Shadow color</guilabel></term>
<listitem><para>Usually shadows as the absence of light appear in shades of
grey (so the maximum shadow color is black, or no light at all). But hey,
this is a virtual world, and if you'd like to have even pink shadows, why
not?</para> 
</listitem>
</varlistentry>
<varlistentry>
<term><guilabel>Remove shadows on move</guilabel></term>
<listitem><para>Check this if you need more performance (especially when
using translucent moving windows).</para>
</listitem>
</varlistentry>
<varlistentry>
<term><guilabel>Remove shadows on resize</guilabel></term>
<listitem><para>It's a good idea to check this item whether using
translucent resizing (moving) windows, or not. The windows shadow pixmap has
to be permanently recreated on resizes what has a deep impact on the system
performance.</para>
</listitem>
</varlistentry>
</variablelist>
</sect1>

<sect1 id="effects">
<title>Effects</title>
<variablelist>
<varlistentry>
<term><guilabel>Fade-in windows</guilabel></term>
<term><guilabel>Fade between opacity changes</guilabel></term>
<listitem><para>Instead of just popping up a new window, you might want to
slowly fade it in. While this looks impressive, there is an equally
impressive price to pay in performance speed, and it is difficult to interact
meaningfully with windows that are in the process of fading.
</para>
</listitem>
</varlistentry>

<varlistentry>
<term><guilabel>Fade-in speed</guilabel></term>
<term><guilabel>Fade-out speed</guilabel></term>
<listitem><para>For the usability reasons mentioned under <guilabel>Fade-in
windows</guilabel>, it is most practical to use a fast fade in speed and
(for more eye candy) a slow fade out speed. This will provide you nice
effects and a smooth feeling system as well as low latency before 
information appears.</para> 
</listitem>
</varlistentry>
</variablelist>
</sect1>

</chapter>

<chapter id="problems">
<title>Problems</title>

<para>The whole Composite extension is quite new. It may cause several
problems and even crash X, so <emphasis>it is strongly suggested to not even
enable the Composite extension in Xorg.conf on mission critical production
systems</emphasis>. If you however can risk a slightly more unstable system,
it's certainly nice to have some eye candy around.</para>

<para>
In this case you may notice some glitches.
Here are some common problems - and workarounds:
</para>

<qandaset>
<qandaentry>
<question>
<para>I have X.org 6.8.x, but &kappname; fails to start</para>
</question>
<answer>
<para>You need to explicitly enable the Composite extension, add a new Section to /etc/X11/XorgConfig:</para>
<programlisting>Section "Extensions"
   Option "Composite" "Enable"
EndSection</programlisting>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>Ok, &kappname; works, but it's horribly slow</para>
</question>
<answer>
<para>If supported by your <acronym>GPU</acronym> (mainly
<trademark>NVIDIA</trademark>, and somewhat by ATI cards), first make sure
you activated the Render acceleration</para>
<programlisting>
Section "Device"
....
....
Option     "RenderAccel" "true"
....
....
EndSection
</programlisting>

<para>If it's still slow, you can try to adjust your memory usage.  Either 
decrease you screen depth (&eg; from 24 to 16) or lower your resolution
(&eg; from 1280x1024 to 1024x768).</para> 

<para>Please notice that the currently limiting factor for the Composite
extension seems to be the CPU cache size.</para>

</answer>
</qandaentry>

<qandaentry>
<question>
<para>After enabling the Composite extension, I cannot run any
<acronym>GLX</acronym> applications anymore. I've got an
<trademark>NVIDIA</trademark> card.</para>
</question>
<answer>
<para>To prevent some problems, <trademark>NVIDIA</trademark> deactivated the
GLX support when Coposite is active. Reactivating is possible, but may cause
problems on some kernel/driver/GPU combinations.</para> 
<programlisting>
Section "Device"
....
....
Option  "AllowGLXWithComposite" "true"
....
....
EndSection
</programlisting>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>I wanted to play a game using <acronym>SDL</acronym> (but not
<acronym>GL</acronym>), say <application>scummvm</application>, but when the
compmgr is active, all I can see is a shadow!</para>
</question>
<answer>
<para>This is a problem with the PictType reported by SDL.</para>

<para>Workaround:</para>
<screen>
Instead of calling <command>scummvm</command> directly, call
<command>SDL_VIDEO_X11_VISUALID=0x24 scummvm</command> This will tell SDL to
use a supported format and you can play as ever. </screen>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>    Application XXX refuses to start after enabling the Composite
extension.</para>
<para>Application YYY breaks X after enabling the Composite
extension.</para>
<para>Application ZZZ looks weird after activating the composite
manager.</para>
</question>
<answer>
<para>The Composite extension is still experimental.</para>
<para>Workaround:</para>
<para>Instead of calling <command>appName</command> directly, call <command>XLIB_SKIP_ARGB_VISUALS=1 appName</command></para>
<para>Applications that are known to cause problems:</para>
<itemizedlist>
<listitem><para>All gtk1 applications (&eg; <application>gmplayer</application>,
<application>xmms</application>, <application>gaim</application>) - failing
startup or look unusable weird or crash X</para></listitem>
<listitem><para>&kuickshow; - displays only a black frame</para></listitem>
<listitem><para>&Qt; <application>Designer</application> - crashes
X</para></listitem>
<listitem><para>&kopete; - crashes X</para></listitem>
<listitem><para>&kolf; - crashes X</para></listitem>
</itemizedlist>
</answer>
</qandaentry>

<qandaentry>
<question>
<para>I try to watch a video, but only see artefacts in the Video
Window.</para>
</question>
<answer>
<para>You're using <quote>xv</quote> as video backend. This is the overlay
mode, where the video content is written directly into the video card
memory, bypassing  X. Therefore the window seems to be static (colored
background) and is not  updated by the damage extension.</para>
<para> There will hopefully be a fix for this in the future. Currently I had
the best results using <application>Xine</application> but displaying
translucent videos isn't fast anyway.</para>
</answer>
</qandaentry>

</qandaset>
</chapter>

<chapter id="credits-and-licenses">
<title>Credits and Licenses</title>

<sect1 id="authors">
<title>Authors</title>
<para>Thomas Luebking <email>baghira-style@gmx.net</email> - Editor</para>

&underFDL;
&underGPL;
</sect1>


</chapter>

</book>
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