XAllocColor(3)            XLIB FUNCTIONS           XAllocColor(3)



NAME
       XAllocColor, XAllocNamedColor, XAllocColorCells, XAlloc-
       ColorPlanes, XFreeColors - allocate and free colors

SYNTAX
       Status XAllocColor(Display *display, Colormap colormap,
              XColor *screen_in_out);

       Status XAllocNamedColor(Display *display, Colormap col-
              ormap, char *color_name, XColor *screen_def_return,
              XColor *exact_def_return);

       Status XAllocColorCells(Display *display, Colormap col-
              ormap, Bool contig, unsigned long-
              plane_masks_return[], unsigned int nplanes,
              unsigned long pixels_return[], unsigned int npix-
              els);

       Status XAllocColorPlanes(Display *display, Colormap col-
              ormap, Bool contig, unsigned long pixels_return[],
              int ncolors, int nreds, int ngreens, int nblues,
              unsigned long *rmask_return, unsigned long
              *gmask_return, unsigned long *bmask_return);

       int XFreeColors(Display *display, Colormap colormap,
              unsigned long pixels[], int npixels, unsigned long
              planes);

       color_name
                 Specifies the color name string (for example,
                 red) whose color definition structure you want
                 returned.

       colormap  Specifies the colormap.

       contig    Specifies a Boolean value that indicates whether
                 the planes must be contiguous.

       display   Specifies the connection to the X server.

       exact_def_return
                 Returns the exact RGB values.

       ncolors   Specifies the number of pixel values that are to
                 be returned in the pixels_return array.

       npixels   Specifies the number of pixels.

       nplanes   Specifies the number of plane masks that are to
                 be returned in the plane masks array.

       nreds
       ngreens
       nblues
                 Specify the number of red, green, and blue
                 planes.  The value you pass must be nonnegative.

       pixels    Specifies an array of pixel values.

       pixels_return
                 Returns an array of pixel values.

       plane_mask_return
                 Returns an array of plane masks.

       planes    Specifies the planes you want to free.

       rmask_return
       gmask_return
       bmask_return
                 Return bit masks for the red, green, and blue
                 planes.

       screen_def_return
                 Returns the closest RGB values provided by the
                 hardware.

       screen_in_out
                 Specifies and returns the values actually used
                 in the colormap.

DESCRIPTION
       The XAllocColor function allocates a read-only colormap
       entry corresponding to the closest RGB value supported by
       the hardware.  XAllocColor returns the pixel value of the
       color closest to the specified RGB elements supported by
       the hardware and returns the RGB value actually used.  The
       corresponding colormap cell is read-only.  In addition,
       XAllocColor returns nonzero if it succeeded or zero if it
       failed.  Multiple clients that request the same effective
       RGB value can be assigned the same read-only entry, thus
       allowing entries to be shared.  When the last client deal-
       locates a shared cell, it is deallocated.  XAllocColor
       does not use or affect the flags in the XColor structure.

       XAllocColor can generate a BadColor error.

       The XAllocNamedColor function looks up the named color
       with respect to the screen that is associated with the
       specified colormap.  It returns both the exact database
       definition and the closest color supported by the screen.
       The allocated color cell is read-only.  The pixel value is
       returned in screen_def_return.  If the color name is not
       in the Host Portable Character Encoding, the result is
       implementation-dependent.  Use of uppercase or lowercase
       does not matter.  If screen_def_return and
       exact_def_return point to the same structure, the pixel
       field will be set correctly, but the color values are
       undefined.  XAllocNamedColor returns nonzero if a cell is
       allocated; otherwise, it returns zero.

       XAllocNamedColor can generate a BadColor error.

       delim %% The XAllocColorCells function allocates
       read/write color cells.  The number of colors must be pos-
       itive and the number of planes nonnegative, or a BadValue
       error results.  If ncolors and nplanes are requested, then
       ncolors pixels and nplane plane masks are returned.  No
       mask will have any bits set to 1 in common with any other
       mask or with any of the pixels.  By ORing together each
       pixel with zero or more masks, ncolors * %2 sup nplanes%
       distinct pixels can be produced.  All of these are allo-
       cated writable by the request.  For GrayScale or Pseudo-
       Color, each mask has exactly one bit set to 1.  For
       DirectColor, each has exactly three bits set to 1.  If
       contig is True and if all masks are ORed together, a sin-
       gle contiguous set of bits set to 1 will be formed for
       GrayScale or PseudoColor and three contiguous sets of bits
       set to 1 (one within each pixel subfield) for DirectColor.
       The RGB values of the allocated entries are undefined.
       XAllocColorCells returns nonzero if it succeeded or zero
       if it failed.

       XAllocColorCells can generate BadColor and BadValue
       errors.

       delim %% The specified ncolors must be positive; and
       nreds, ngreens, and nblues must be nonnegative, or a Bad-
       Value error results.  If ncolors colors, nreds reds,
       ngreens greens, and nblues blues are requested, ncolors
       pixels are returned; and the masks have nreds, ngreens,
       and nblues bits set to 1, respectively.  If contig is
       True, each mask will have a contiguous set of bits set to
       1.  No mask will have any bits set to 1 in common with any
       other mask or with any of the pixels.  For DirectColor,
       each mask will lie within the corresponding pixel sub-
       field.  By ORing together subsets of masks with each pixel
       value, ncolors * %2 sup (nreds+ngreens+nblues)% distinct
       pixel values can be produced.  All of these are allocated
       by the request.  However, in the colormap, there are only
       ncolors * %2 sup nreds% independent red entries, ncolors *
       %2 sup ngreens% independent green entries, and ncolors *
       %2 sup nblues% independent blue entries.  This is true
       even for PseudoColor.  When the colormap entry of a pixel
       value is changed (using XStoreColors, XStoreColor, or
       XStoreNamedColor), the pixel is decomposed according to
       the masks, and the corresponding independent entries are
       updated.  XAllocColorPlanes returns nonzero if it suc-
       ceeded or zero if it failed.

       XAllocColorPlanes can generate BadColor and BadValue
       errors.

       The XFreeColors function frees the cells represented by
       pixels whose values are in the pixels array.  The planes
       argument should not have any bits set to 1 in common with
       any of the pixels.  The set of all pixels is produced by
       ORing together subsets of the planes argument with the
       pixels.  The request frees all of these pixels that were
       allocated by the client (using XAllocColor, XAllocNamed-
       Color, XAllocColorCells, and XAllocColorPlanes).  Note
       that freeing an individual pixel obtained from XAllocCol-
       orPlanes may not actually allow it to be reused until all
       of its related pixels are also freed.  Similarly, a read-
       only entry is not actually freed until it has been freed
       by all clients, and if a client allocates the same read-
       only entry multiple times, it must free the entry that
       many times before the entry is actually freed.

       All specified pixels that are allocated by the client in
       the colormap are freed, even if one or more pixels produce
       an error.  If a specified pixel is not a valid index into
       the colormap, a BadValue error results.  If a specified
       pixel is not allocated by the client (that is, is unallo-
       cated or is only allocated by another client) or if the
       colormap was created with all entries writable (by passing
       AllocAll to XCreateColormap), a BadAccess error results.
       If more than one pixel is in error, the one that gets
       reported is arbitrary.

       XFreeColors can generate BadAccess, BadColor, and BadValue
       errors.

DIAGNOSTICS
       BadAccess A client attempted to free a color map entry
                 that it did not already allocate.

       BadAccess A client attempted to store into a read-only
                 color map entry.

       BadColor  A value for a Colormap argument does not name a
                 defined Colormap.

       BadValue  Some numeric value falls outside the range of
                 values accepted by the request.  Unless a spe-
                 cific range is specified for an argument, the
                 full range defined by the argument's type is
                 accepted.  Any argument defined as a set of
                 alternatives can generate this error.

SEE ALSO
       XCreateColormap(3X11), XQueryColor(3X11), XStoreCol-
       ors(3X11)
       Xlib - C Language X Interface



X Version 11               libX11 1.1.5            XAllocColor(3)