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XAllocStandardColormap(3)       XLIB FUNCTIONS       XAllocStandardColormap(3)



NAME
       XAllocStandardColormap, XSetRGBColormaps, XGetRGBColormaps, XStandard-
       Colormap - allocate, set, or read a standard colormap structure

SYNTAX
       XStandardColormap *XAllocStandardColormap(void);

       void XSetRGBColormaps(Display *display, Window w, XStandardColormap
              *std_colormap, int count, Atom property);

       Status XGetRGBColormaps(Display *display, Window w, XStandardColormap
              **std_colormap_return, int *count_return, Atom property);

ARGUMENTS
       display   Specifies the connection to the X server.

       count     Specifies the number of colormaps.

       count_return
                 Returns the number of colormaps.

       property  Specifies the property name.

       std_colormap
                 Specifies the XStandardColormap structure to be used.

       std_colormap_return
                 Returns the XStandardColormap structure.

DESCRIPTION
       The XAllocStandardColormap function allocates and returns a pointer to
       a XStandardColormap structure.  Note that all fields in the XStandard-
       Colormap structure are initially set to zero.  If insufficient memory
       is available, XAllocStandardColormap returns NULL.  To free the memory
       allocated to this structure, use XFree.

       The XSetRGBColormaps function replaces the RGB colormap definition in
       the specified property on the named window.  If the property does not
       already exist, XSetRGBColormaps sets the RGB colormap definition in the
       specified property on the named window.  The property is stored with a
       type of RGB_COLOR_MAP and a format of 32.  Note that it is the caller's
       responsibility to honor the ICCCM restriction that only RGB_DEFAULT_MAP
       contain more than one definition.

       The XSetRGBColormaps function usually is only used by window or session
       managers.  To create a standard colormap, follow this procedure:

       1.   Open a new connection to the same server.

       2.   Grab the server.

       3.   See if the property is on the property list of the root window for
            the screen.

       4.   If the desired property is not present:

            o    Create a colormap (unless you are using the default colormap
                 of the screen).

            o    Determine the color characteristics of the visual.

            o    Allocate cells in the colormap (or create it with AllocAll).

            o    Call XStoreColors to store appropriate color values in the
                 colormap.

            o    Fill in the descriptive members in the XStandardColormap
                 structure.

            o    Attach the property to the root window.

            o    Use XSetCloseDownMode to make the resource permanent.

       5.   Ungrab the server.

       XSetRGBColormaps can generate BadAlloc, BadAtom, and BadWindow errors.

       The XGetRGBColormaps function returns the RGB colormap definitions
       stored in the specified property on the named window.  If the property
       exists, is of type RGB_COLOR_MAP, is of format 32, and is long enough
       to contain a colormap definition, XGetRGBColormaps allocates and fills
       in space for the returned colormaps and returns a nonzero status.  If
       the visualid is not present, XGetRGBColormaps assumes the default vis-
       ual for the screen on which the window is located; if the killid is not
       present, None is assumed, which indicates that the resources cannot be
       released.  Otherwise, none of the fields are set, and XGetRGBColormaps
       returns a zero status.  Note that it is the caller's responsibility to
       honor the ICCCM restriction that only RGB_DEFAULT_MAP contain more than
       one definition.

       XGetRGBColormaps can generate BadAtom and BadWindow errors.

STRUCTURES
       The XStandardColormap structure contains:

       /* Hints */

       lw(.5i) lw(2i) lw(1i).  T{ #define T}   T{ ReleaseByFreeingColormap
       T}   T{ ( (XID) 1L) T} /* Values */
       typedef struct {
            Colormap colormap;
            unsigned long red_max;
            unsigned long red_mult;
            unsigned long green_max;
            unsigned long green_mult;
            unsigned long blue_max;
            unsigned long blue_mult;
            unsigned long base_pixel;
            VisualID visualid;
            XID killid;
       } XStandardColormap;

       The colormap member is the colormap created by the XCreateColormap
       function.  The red_max, green_max, and blue_max members give the maxi-
       mum red, green, and blue values, respectively.  Each color coefficient
       ranges from zero to its max, inclusive.  For example, a common colormap
       allocation is 3/3/2 (3 planes for red, 3 planes for green, and 2 planes
       for blue).  This colormap would have red_max = 7, green_max = 7, and
       blue_max = 3.  An alternate allocation that uses only 216 colors is
       red_max = 5, green_max = 5, and blue_max = 5.

       The red_mult, green_mult, and blue_mult members give the scale factors
       used to compose a full pixel value.  (See the discussion of the
       base_pixel members for further information.)  For a 3/3/2 allocation,
       red_mult might be 32, green_mult might be 4, and blue_mult might be 1.
       For a 6-colors-each allocation, red_mult might be 36, green_mult might
       be 6, and blue_mult might be 1.

       The base_pixel member gives the base pixel value used to compose a full
       pixel value.  Usually, the base_pixel is obtained from a call to the
       XAllocColorPlanes function.  Given integer red, green, and blue coeffi-
       cients in their appropriate ranges, one then can compute a correspond-
       ing pixel value by using the following expression:

       (r * red_mult + g * green_mult + b * blue_mult + base_pixel) & 0xFFFFFFFF

       For GrayScale colormaps, only the colormap, red_max, red_mult, and
       base_pixel members are defined.  The other members are ignored.  To
       compute a GrayScale pixel value, use the following expression:

       (gray * red_mult + base_pixel) & 0xFFFFFFFF

       Negative multipliers can be represented by converting the 2's comple-
       ment representation of the multiplier into an unsigned long and storing
       the result in the appropriate _mult field.  The step of masking by
       0xFFFFFFFF effectively converts the resulting positive multiplier into
       a negative one.  The masking step will take place automatically on many
       machine architectures, depending on the size of the integer type used
       to do the computation,

       The visualid member gives the ID number of the visual from which the
       colormap was created.  The killid member gives a resource ID that indi-
       cates whether the cells held by this standard colormap are to be
       released by freeing the colormap ID or by calling the XKillClient func-
       tion on the indicated resource.  (Note that this method is necessary
       for allocating out of an existing colormap.)

       The properties containing the XStandardColormap information have the
       type RGB_COLOR_MAP.

DIAGNOSTICS
       BadAlloc  The server failed to allocate the requested resource or
                 server memory.

       BadAtom   A value for an Atom argument does not name a defined Atom.

       BadWindow A value for a Window argument does not name a defined Window.

SEE ALSO
       XAllocColor(3X11), XCreateColormap(3X11), XFree(3X11), XSetCloseDown-
       Mode(3X11)
       Xlib - C Language X Interface



X Version 11                     libX11 1.1.5        XAllocStandardColormap(3)