XAllocColor(3X11) X Version 11(Release 5) XAllocColor(3X11)
NAME
XAllocColor, XAllocNamedColor, XAllocColorCells, XAllocColorPlanes,
XFreeColors - allocate and free colors
SYNTAX
Status XAllocColor(display, colormap, screen_in_out)
Display *display;
Colormap colormap;
XColor *screen_in_out;
Status XAllocNamedColor(display, colormap, color_name, screen_def_return,
exact_def_return)
Display *display;
Colormap colormap;
char *color_name;
XColor *screen_def_return, *exact_def_return;
Status XAllocColorCells(display, colormap, contig, plane_masks_return,
nplanes,
pixels_return, npixels)
Display *display;
Colormap colormap;
Bool contig;
unsigned long plane_masks_return[];
unsigned int nplanes;
unsigned long pixels_return[];
unsigned int npixels;
Status XAllocColorPlanes(display, colormap, contig, pixels_return,
ncolors, nreds, ngreens,
nblues, rmask_return, gmask_return,
bmask_return)
Display *display;
Colormap colormap;
Bool contig;
unsigned long pixels_return[];
int ncolors;
int nreds, ngreens, nblues;
unsigned long *rmask_return, *gmask_return, *bmask_return;
XFreeColors(display, colormap, pixels, npixels, planes)
Display *display;
Colormap colormap;
unsigned long pixels[];
int npixels;
unsigned long planes;
ARGUMENTS
color_name
Specifies the color name string (for example, red) whose color
definition structure you want returned.
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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.
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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 deallocates 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. XLookupColor returns nonzero
if a cell is allocated, otherwise it returns zero.
XAllocNamedColor can generate a BadColor error.
The XAllocColorCells function allocates read/write color cells. The
number of colors must be positive 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 *
2nplanes distinct pixels can be produced. All of these are allocated
writable by the request. For GrayScale or PseudoColor, 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 single
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.
The specified ncolors must be positive; and nreds, ngreens, and nblues
must be nonnegative, or a BadValue 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 subfield. By ORing
together subsets of masks with each pixel value, ncolors *
2(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 * 2nreds independent red entries, ncolors * 2ngreens
independent green entries, and ncolors * 2nblues 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
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the corresponding independent entries are updated. XAllocColorPlanes
returns nonzero if it succeeded 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, XAllocNamedColor, XAllocColorCells, and
XAllocColorPlanes). Note that freeing an individual pixel obtained from
XAllocColorPlanes 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 unallocated
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 specific 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), XStoreColors(3X11)
Xlib - C Language X Interface
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