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<HTML><HEAD><TITLE>Xlib Programming Manual: Properties and Atoms</TITLE></HEAD><BODY><H1 ALIGN=center>4.3 Properties and Atoms</H1>A property is a collection of named, typed data.The window system has a set of predefined properties<!.IN "Atom" "predefined">(for example, the name of a window, size hints, and so on), and users candefine any other arbitrary information and associate it with windows.Each property has a name,which is an ISO Latin-1 string.For each named property,a unique identifier (atom) is associated with it. A property also has a type, for example, string or integer.These types are also indicated using atoms, so arbitrary newtypes can be defined.Data of only one type may be associated with a singleproperty name.Clients can store and retrieve properties associated with windows.For efficiency reasons,an atom is used rather than a character string.<B><A HREF="XInternAtom.html">XInternAtom()</A></B>can be used to obtain the atom for property names.<!.IN "Atom" ><P>A property is also stored in one of several possible formats.The X server can store the information as 8-bit quantities, 16-bitquantities, or 32-bit quantities.This permits the X server to present the data in the byte order that theclient expects.<P ALIGN=center><B>Note</B><BLOCKQUOTE>If you define further properties of complex type, you must encode and decode them yourself.These functions must be carefully written if they are to be portable.For further information about how to write a library extension,see "<A HREF="../appendix/c/">Extensions</A>".</BLOCKQUOTE>The type of a property is defined by an atom, which allows forarbitrary extension in this type scheme.<!.IN "Atom" ><P>Certain property names arepredefined in the server for commonly used functions.The atoms for these properties are defined in <B><CODE>X11/Xatom.h</CODE></B>.To avoid name clashes with user symbols, the <CODE><B>#define</B></CODE>name for each atom has the <CODE>XA_</CODE> prefix.For definitions of these properties,see below.For an explanation of the functions that let you get and setmuch of the information stored in these predefined properties,see "<A HREF="../ICC/">Inter-Client Communication Functions</A>".<P>The core protocol imposes no semantics on these property names,but semantics are specified in other X Consortium standards,such as the <I><A HREF="/gui/x/icccm/">Inter-Client Communication Conventions Manual</A></I>and the <I>X Logical Font Description Conventions</I>.<P>You can use properties to communicate other information betweenapplications.The functions described in this section let you define new properties and get the unique atom IDs in your applications.<P>Although any particular atom can have some client interpretation within each of the name spaces, atoms occur in five distinct name spaces within the protocol: <UL><P><LI><A NAME="#selection">Selections</A><P><LI><A NAME="#property-names">Property names</A><P><LI><A NAME="#property-types">Property types</A><P><LI><A NAME="#font-properties">Font properties</A><P><LI>Type of a <B><A HREF="../events/client-communication/client-message.html">ClientMessage</A></B>event (none are built into the X server)</UL><A NAME="selection"></A><P>The built-in selection property names are:<P><TABLE><TR><TD>PRIMARY<TR><TD>SECONDARY</TABLE><A NAME="property-names"></A><P>The built-in property names are: <TABLE><TR><TD>CUT_BUFFER0 <TD>RESOURCE_MANAGER<TR><TD>CUT_BUFFER1 <TD>WM_CLASS<TR><TD>CUT_BUFFER2 <TD>WM_CLIENT_MACHINE<TR><TD>CUT_BUFFER3 <TD>WM_COLORMAP_WINDOWS<TR><TD>CUT_BUFFER4 <TD>WM_COMMAND<TR><TD>CUT_BUFFER5 <TD>WM_HINTS<TR><TD>CUT_BUFFER6 <TD>WM_ICON_NAME<TR><TD>CUT_BUFFER7 <TD>WM_ICON_SIZE<TR><TD>RGB_BEST_MAP <TD>WM_NAME<TR><TD>RGB_BLUE_MAP <TD>WM_NORMAL_HINTS<TR><TD>RGB_DEFAULT_MAP <TD>WM_PROTOCOLS<TR><TD>RGB_GRAY_MAP <TD>WM_STATE<TR><TD>RGB_GREEN_MAP <TD>WM_TRANSIENT_FOR<TR><TD>RGB_RED_MAP <TD>WM_ZOOM_HINTS</TABLE><A NAME="property-types"></A><P>The built-in property types are: <P><TABLE><TR><TD>ARC <TD>POINT<TR><TD>ATOM <TD>RGB_COLOR_MAP<TR><TD>BITMAP <TD>RECTANGLE<TR><TD>CARDINAL <TD>STRING<TR><TD>COLORMAP <TD>VISUALID<TR><TD>CURSOR <TD>WINDOW<TR><TD>DRAWABLE <TD>WM_HINTS<TR><TD>FONT <TD>WM_SIZE_HINTS<TR><TD>INTEGER <TD><TR><TD>PIXMAP</TABLE><A NAME="font-properties"></A><P>The built-in font property names are: <TABLE><TR><TD>MIN_SPACE <TD>STRIKEOUT_DESCENT<TR><TD>NORM_SPACE <TD>STRIKEOUT_ASCENT<TR><TD>MAX_SPACE <TD>ITALIC_ANGLE<TR><TD>END_SPACE <TD>X_HEIGHT<TR><TD>SUPERSCRIPT_X <TD>QUAD_WIDTH<TR><TD>SUPERSCRIPT_Y <TD>WEIGHT<TR><TD>SUBSCRIPT_X <TD>POINT_SIZE<TR><TD>SUBSCRIPT_Y <TD>RESOLUTION<TR><TD>UNDERLINE_POSITION <TD>COPYRIGHT<TR><TD>UNDERLINE_THICKNESS <TD>NOTICE<TR><TD>FONT_NAME <TD>FAMILY_NAME<TR><TD>FULL_NAME <TD>CAP_HEIGHT</TABLE><P>For further information about font properties,see "<A HREF="../graphics/font-metrics/">Font Metrics</A>".<P>To return an atom for a given name, use <B><A HREF="XInternAtom.html">XInternAtom()</A></B>.To return atoms for an array of names, use <B><A HREF="XInternAtoms.html">XInternAtoms()</A></B>.<P>To return a name for a given atom identifier, use <B><A HREF="XGetAtomName.html">XGetAtomName()</A></B>.<P>To return the names for an array of atom identifiers, use <B><A HREF="XGetAtomNames.html">XGetAtomNames()</A></B>.<H5 ALIGN=right><I>Next: <A HREF="obtain-properties.html">Obtaining and Changing Window Properties</A></I></H5><HR><ADDRESS><A HREF="http://tronche.com/">Christophe Tronche</A>, <A HREF="mailto:ch.tronche@computer.org">ch.tronche@computer.org</A></ADDRESS></BODY></HTML>⌨️ 快捷键说明
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