XAllocColor(3X11)XAllocColor(3X11)NAME
XAllocColor, XAllocNamedColor, XAllocColorCells, XAllocColorPlanes,
XFreeColors - allocate and free colors
SYNOPSIS
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
Specifies the color name string (for example, red) whose color defini‐
tion structure you want returned. Specifies the colormap. Specifies a
Boolean value that indicates whether the planes must be contiguous.
Specifies the connection to the X server. Returns the exact RGB val‐
ues. Specifies the number of pixel values that are to be returned in
the pixels_return array. Specifies the number of pixels. Specifies
the number of plane masks that are to be returned in the plane masks
array. Specify the number of red, green, and blue planes. The value
you pass must be nonnegative. Specifies an array of pixel values.
Returns an array of pixel values. Returns an array of plane masks.
Specifies the planes you want to free. Return bit masks for the red,
green, and blue planes. Returns the closest RGB values provided by the
hardware. Specifies and returns the values actually used in the col‐
ormap.
DESCRIPTION
The XAllocColor function allocates a read-only colormap entry corre‐
sponding to the closest RGB value supported by the hardware. XAlloc‐
Color 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, XAl‐
locColor returns nonzero if it succeeded or zero if it failed. Multi‐
ple 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. 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.
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 pix‐
els. By ORing together each pixel with zero or more masks, (ncolors *
2**nplanes) 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 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 suc‐
ceeded 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 con‐
tiguous 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 * 2**nreds) independent red entries, (ncolors *
2**ngreens) independent green entries, and (ncolors * 2**nblues) inde‐
pendent blue entries. This is true even for PseudoColor. When the col‐
ormap entry of a pixel value is changed (using XStoreColors, XStore‐
Color, or XStoreNamedColor), the pixel is decomposed according to the
masks, and the corresponding independent entries are updated. XAlloc‐
ColorPlanes 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 unal‐
located or is only allocated by another client) or if the colormap was
created with all entries writable (by passing AllocAll to XCreateCol‐
ormap), 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
A client attempted to free a color map entry that it did not already
allocate. A client attempted to store into a read-only color map
entry. A value for a Colormap argument does not name a defined Col‐
ormap. 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 argu‐
ment defined as a set of alternatives can generate this error.
SEE ALSOXCreateColormap(3X11), XQueryColor(3X11), XStoreColors(3X11)
Xlib -- C Language X Interface
XAllocColor(3X11)
