180 lines
10 KiB
Text
180 lines
10 KiB
Text
KWin release notes for KDE4.0
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=============================
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= Introduction =
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KWin, the standard KDE window manager, in KDE4.0 ships with the first version
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of built-in support for compositing, making it also a compositing manager.
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This allows KWin to provide advanced graphical effects, like for example with Compiz,
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while also providing all the features from previous KDE releases (such as very good
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intergration with the rest of KDE, advanced configurability, focus stealing prevention,
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well-tested window manager, robust handling of misbehaving applications/toolkits, etc.).
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Unlike Compiz, KWin still functions even when no system support for compositing is
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available, with only compositing features not being available in such case.
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Previous KWin versions in later KDE3.x releases included a standalone compositing
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manager called kompmgr, based on the xcompmgr compositing manager. Kompmgr was only
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loosely tied with KWin, used only XRender for rendering and provided only basic
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features like transparency, shadows and fade in/out animations. Compositing manager
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in KWin in KDE4.0 is integrated with the rest of KWin, can use either OpenGL or XRender
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for rendering and has a framework for compositing effects, all these allowing KWin
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to provide a much wider range of features.
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Note, however, that compositing support in KWin in KDE4.0 is still considered experimental,
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for several reasons. System support for compositing is often being problematic (various bugs
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in X, drivers or other parts of the system), manual configuration of X may be required
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for proper results (see below), some applications may not be prepared and work well
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with compositing, the performance may not be adequate, and other problems.
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Also, while KWin's compositing support is considered usable and reasonably stable, it
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is relatively new code and has been tested only on a limited range of hardware.
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Therefore, compositing support in KWin is disabled by default, and needs to be explicitly
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enabled. If there will be any problems, you can disable it again (see below for troubleshooting)
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and report a bug with all relevant information about the problem.
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= Setting up =
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Compositing support is enabled in KWin's configuration. Press Alt+F3 and select 'Configure Window
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Behavior'. In the configuration module, select page 'Desktop Effects' and enable checkbox
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'Enable desktop effects'. After accepting the changes, a dialog with a timeout will appear,
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asking to confirm enabling of compositing support. If you do not confirm within the timeout,
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compositing support will be disabled again, therefore, if enabling compositing triggers
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any problems, it should be sufficient to wait several seconds before the changes are reverted.
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Note that after enabling or disabling compositing it is recommended to restart your KDE
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session in order to ensure that all applications detect the change.
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If you cannot enable desktop effects, it may be because either your KDE is not built
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with necessary support, or more probably because your system is not capable of providing
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compositing support. See file
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http://websvn.kde.org/*checkout*/trunk/KDE/kdebase/workspace/kwin/COMPOSITE_HOWTO
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for some instructions on setting up your system. Note that there may be other factors
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affecting whether you do or do not have compositing support.
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= Usage =
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A quick overview of features provided by compositing manager in KWin:
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- Ctrl+F9 (and Ctrl+F10 for windows from all desktops) shows an overview of all windows
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and allows activating one of them. The feature can be also activated by moving the mouse
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into the top-left screen corner. A window can be activated by clicking it or by using arrows
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and Enter key. You can also type text to filter the list of windows.
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- Ctrl+F8 shotcut activates a desktop grid - all your virtual desktops will be arranged
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on the screen (as an enlarged pager) - you can select and activate desktops using
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a number, a function key, by clicking on it or by using arrows and Enter key,
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you can move windows by dragging them or by right-clicking on them.
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- The DesktopGrid effect also provides animations when switching between virtual desktops (can
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be turned off).
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- The window switcher (Alt+Tab by default) provides live thumbnails of windows.
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- Windows blocked by modal dialogs are dimmed.
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- Screen can be zoomed in and out using Win+<equals>, Win+<minus> and reset using Win+0 (
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it is currently not possible to use mouse wheel, but this feature is planned). Note that
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because of input transformation not being yet available in X the zoomed screen has to move
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around to keep the mouse pointer at the same place like it would be when not zoomed.
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- Screen can be shown with inverted colors by pressing Ctrl+Win+I (accessibility feature,
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Invert effect is not enabled by default).
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- There are fade animations during login and logout.
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- Windows fade in and out.
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- Minimize animation to/from taskbar.
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- Windows have shadows.
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There are more features that are not enabled by default and need to be explicitly enabled
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in the configuration.
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There are various videos showing various compositing features of KWin. For example,
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search for 'kwin_composite' at youtube.com (please keep in mind that many of those windows
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are old and show testing or demo effects).
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= Using KWin without KDE desktop =
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Just like with older KWin versions it is possible to use KWin also with other desktop
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environments or even as a standalone window manager, as long as required KDE libraries
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are installed. Please note that KWin is a pure window manager and does not provide a panel
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or handle desktop background like some window managers do. KWin's compositing features
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work in the standalone mode, with some functionality missing (because of missing taskbar,
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for example), and, while this has not been tested, it is expected that compositing
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features will work also when running in other desktop environments, possibly with some
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functionality missing again. Reports on using KWin with other desktop environments
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are welcome.
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= Performance =
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Compositing internally works by redirecting window drawing to offscreen memory and composing
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it on the screen in an additional drawing pass. This means that in general composited desktop
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on average has worse performance that non-composited desktop (although in some cases it
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may perform better, be that real improvement or just perceived one due to animations, better
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synchronization or similar factors). For example, binding window pixmaps to OpenGL textures
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(that is, preparing window contents for drawing) can be a relatively costly operation
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with large windows, making things like animations in Plasma desktop window or page scrolling
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in a maximized browser window jerky. Heavy system load can also cause the compositing manager
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not repaint often enough, resulting in lagging or jerky screen redrawing.
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KWin in KDE4.0 is also relatively new code and has not been extensively optimized yet,
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therefore its performance may not be in some areas comparable with performance of other
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compositing managers. In such cases performance should be improved with newer versions.
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Note that current XRender implementations (in X/drivers) often perform rather poorly and
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therefore the OpenGL mode usually should have much better performance. See below for notes
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on XRender mode.
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Tip: Performance/smoothness with nVidia cards: Smoothness of KWin rendering
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can be improved by setting env.variable KWIN_NVIDIA_HACK to 1 (e.g. append
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"export KWIN_NVIDIA_HACK=1" to your ~/.profile file). This sets __GL_YIELD=NOTHING
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for KWin, letting KWin use more CPU time for OpenGL operations, however
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at the expense of affecting performance of other applications. This is
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therefore disabled by default. This setting may be removed in the future
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if the negative impact becomes insignificant. See section "OPENGL YIELD BEHAVIOR"
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in README.txt for nVidia cards.
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= Troubleshooting =
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As already said, compositing support in KWin is considered usable and reasonably stable,
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but due to several reasons it may not work properly for you.
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If there are any problems with compositing support, the simplest option is to disable
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it again. KWin will normally continue functioning, only not providing compositing features.
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If you cannot normally turn off compositing support (for example because the screen
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is corrupted), you can turn it off using one of these ways:
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- run command 'kwriteconfig --file kwinrc --group Compositing --key Enabled false' from
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the command line
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- set environment variable 'KWIN_COMPOSE' to 'N' (append 'export KWIN_COMPOSE=N' at the end
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of your ~/.profile), this affects compositing only temporarily
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You will probably need to switch to text mode or start failsafe session from KDM to be
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able to perform this.
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See file http://websvn.kde.org/*checkout*/trunk/KDE/kdebase/workspace/kwin/COMPOSITE_HOWTO
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for some issues with various graphics cards.
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= XRender mode =
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It is possible to use XRender for compositing instead of the default OpenGL.
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XRender mode in general has less features, however at the moment it is also considered
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unstable - it has not received as much testing as OpenGL mode, some features may be incomplete
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and it is recommended to use the OpenGL mode if possible. Also note that current XRender
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implementations (in X/drivers) often perform rather poorly.
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= Developers =
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KWin provides support for writing compositing effects that may be loaded into KWin as
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plugins. These effects communicate with KWin core using C++ API specially designed for this
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purpose, making effects not directly dependent on KWin core and changes in it.
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At the time of the KDE4.0 release, since compositing support is still under heavy development,
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this API is considered unstable and subject to change. If you write your own effect plugin,
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you may need to recompile it after KWin update. KWin will however detect incompatible
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versions and will not load such plugins (automatic, you do not need to provide any code for it).
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As the compositing support will become more stabilized, this API will be kept backwards and
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binary compatible, just like with other KDE libraries.
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At the time of the KDE4.0 release, API for compositing effects is unfortunately only sparsely
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documented. Developers interested in writing compositing effects for KWin are suggested
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to use source code of effects shipped with KWin (the Howto effect as the starting point)
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and/or ask on the KWin mailing list.
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Links to various KWin-related documents are available at http://techbase.kde.org/Projects/KWin .
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