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Added initial draft of internals documentation
git-svn-id: https://svn.o-hand.com/repos/matchbox/trunk/matchbox-documentation@773 b067294f-1dea-0310-9683-c47a78595994
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developers/internals.txt
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developers/internals.txt
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Introduction
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====
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window manager intercepts events.
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3 years of work.
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written in C.
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Aims to be small, light, featureful.
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Coding style
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====
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GNU style coding standards. All functions prefixed with the source file name they live in, for example wm_new() lives in wm.c .
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Overview
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====
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Initialisation , Wm object created. config etc
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The window manager starting point in is main.c . A new toplevel Wm
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'object' is created ( wm_new() ) - this is where various XXX and
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global state data is stored. This function initally loads any user
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configuration data ( via wm_load_config() ) essientially from command
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line paramers and/or XResources. Various Wm enviroment parameters are
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then initialised before the various 'subsystems' - EWMH, key
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shortcuts, various compile time feature etc. Finally a new Wm object
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is returned which of course is then used extensably throughout the
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programs lifecycle.
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Any pre-existing windows are then processed ( wm_init_existing ) and
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the program then enters its main loop ( wm_event_loop() ).
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Like all window managers, Matchbox is event based. Events come mainly
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in the form of redirected ones from clients attempting actions that
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are managed by the window manager. For example an application
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attempting to resize will cause a 'configure request' event to get
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sent to the window manager, which can then decide how this is honored
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or handled.
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When a new client window appears, Matchbox recieves a map notify event
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with the new window ID. Assuming this ID is unknown to matchbox a new
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'Client' object will be created by wm_make_new_client(). This function
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will example various window properties and based on these decide the
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'type' of Client object to be initialised.
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Clients use a C style psudeo object oprientated style where each
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Client object contains pointers to its core methods which are
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dependant on its type. For example a dialog resizing will be handled
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differently to a main application window ( XXX better example ).
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( XXX more on this object stuff - base methods )
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All created client objects are stored in a circular doublely linked
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list, there are various pointers in the toplevel Wm object that
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reference clients in this list.
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Once a client is created various core methods are called in sequence
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to initalise and finall paint it;
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- Properties relevant to the window manager are communicated ( set ) on
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the client. See ewmh_set_allowed_actions() .
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- The configure() method is called to calculate suitable client geometry.
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- The client window is then reparented. It becomes a child window of
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a matchbox frame window. It is the frame window decorations are
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painted on to.
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- The client window is resized and positioned to fit the matchbox management
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style ( from the previously created geometry ).
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- The client show() method is called which will ultimated realize the
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client. Its very likely this method will also cause the window decorations
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to get painted.
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- Finally global root window properties are updated.
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During the lifetime of a client it will generate other events ( such
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as resizing ) which will ultimatly get mapped into the client objects
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methods.
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The other source of events is user interaction. ( XXX more ) keys, buttons.
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A final source of events is X messages.
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File Structure
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====
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structs.h
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All structures ( aka objects ), enums, defines.
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wm.c
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The event loop and event handlers.
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base_client.c - base client 'class'
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dockbar_client.c - panel windows
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main_client.c - application windows
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select_client.c - the application drop down selection menu
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toolbar_client.c - toolbar windows - eg xkbd, input windows
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desktop_client.c - desktop windows
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dialog_client.c - dialog windows
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client_common.c - client shared, utility calls
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ewmh.c - freedesktop.org extended window manager hint protocols
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composite-engine.c - composite engine , can be compiled out.
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keys.c - key shortcuts ( can be compiled out )
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xml.c - simple xml parser used by mbtheme.c
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( can be compiled out for standalone / use expat instead )
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list.c - simple list api ( used by mbtheme )
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misc.c - misc stuff, mainly error reporting.
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mbtheme-standalone.c - 'standalone' simple theme engine.
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mbtheme.c - complicated theme engine, calls libmatchbox
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main.c - main entry, init and startup.
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each .c file has an associated .h header file.
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'Objects'
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====
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structs.h
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base_client -> each kind. ( overview )
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Client*
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base_client_new (Wm *w, Window win);
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void
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base_client_process_name (Client *c);
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/* This will set the window attributes to what _we_ want */
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void
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base_client_configure (Client *c);
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/* sets inital 'object methods' */
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void
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base_client_set_funcs (Client *c);
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/* Frame the window if needed */
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void
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base_client_reparent (Client *c);
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/* redraw the clients frame */
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void
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base_client_redraw (Client *c, Bool use_cache);
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/* button press on frame */
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void
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base_client_button_press (Client *c, XButtonEvent *e);
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/* move and resize the window */
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void
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base_client_move_resize (Client *c);
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/* iconize client */
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void
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base_client_iconize (Client *c);
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/* return the 'area' covered by the window. Including the frame
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Would return 0 for an unmapped window
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*/
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void
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base_client_get_coverage (Client *c, int *x, int *y, int *w, int *h);
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void
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base_client_hide (Client *c);
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void
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base_client_show (Client *c);
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void
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base_client_destroy (Client *c);
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Themeing
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====
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'Themeing' is the name used to describe the painting of window frame
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decorations. Matchbox provides two themeing implementations or
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'engines'; a basic small implementation which uses X drawing
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primitives and no configuration files ( mbtheme-standalone.c ) and an
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advanced implementation which uses libMatchbox pixbufs for painting
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and advanced xml based configuration files. Both engines export a very
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similar api which can be used by the core of the window manager to
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paint created window decorations. I shall explain the operation of the
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advanced engine, but the actual structure also applys to the basic (
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standalone ) implementation.
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The theme engine is initially created with mbtheme_init(), this will
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create and initialise an engine specific theme structure. A suitable
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theme.xml file will then be located and parsed. The parsing ( see
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parse_*_tag )populates more of the mbtheme structure with lists of
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theme resources ( such as fonts, or loaded image data ) and layout
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data for each window type decorations.
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A window that needs its decorations painting will call
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theme_frame_paint(), specifying the frame type to be painted and its
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dimentions relative to the decoration window frame. The frame type is
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basically the window type extended with an actual edge ( eg
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FRAME_MAIN_NORTH for the title area, FRAME_MAIN_EAST for the right
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edge ). The function the builds up the required decoration from the
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lists of layout and resource data before rendering to the clients
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backing pixmap. The function will also create any masks needed for
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window shaping.
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Seperate function is provided for the painting of buttons (
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theme_frame_button_paint() ) and the window select menu (
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theme_frame_menu_paint() ). Both these and theme_frame_paint() share
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various utility calls for painting ( _theme_paint_core(),
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_theme_paint_gradient() etc )
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The theme engine also provides various calls for client to code to get
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specified decoration dimentions ( theme_frame_menu_get_dimentions(),
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theme_frame_defined_width_get(), theme_frame_defined_height_get() )
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When the theme is changed mbtheme_switch() will be called. This
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function will free all current defined theme resources and in effect
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re theme_init() itself with the new theme before repainting window
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decorations.
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Compositing
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====
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Matchbox window manager optionally provides compile time support for
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the new X Composite extension. With this active matchbox manages
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windows *and* the X rednering to the display. Becuause of this
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matchbox also needs to track override redirect windows.
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Optimisations
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====
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Some optimaisations matchbox uses;
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- The theme engine caches a 'base' matchbox pixbuf representation of
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main application window type decoarations. This means a new main
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window needs just text painting rather than its entire decoration
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layers being built up. This cache will be cleared if the
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application window size changes or the theme changes.
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- Decoration painting is done via XSetWindowBackground with a theme
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engine created pixmap, that is immediatly free after the paint.
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Painting to the window background lets the server handle exposes
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and results in simpler smaller code with a 'smoother' appearance.
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