XAllocColor(3) XLIB FUNCTIONS XAllocColor(3)

NAME

XAllocColor, XAllocNamedColor, XAllocColorCells, XAllocColorPlanes,
XFreeColors - allocate and free colors

SYNTAX

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

Status XAllocNamedColor(Display *display, Colormap colormap, _Xconst
char *color_name, XColor *screen_def_return, XColor
*exact_def_return);

Status XAllocColorCells(Display *display, Colormap colormap, Bool
contig, unsigned long plane_masks_return[], unsigned int
nplanes, unsigned long pixels_return[], unsigned int npixels);

Status XAllocColorPlanes(Display *display, Colormap colormap, 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 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 pixels. 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 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 * 2^nreds
independent red entries, ncolors * 2^ngreens independent green
entries, and ncolors * 2^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 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(3), XQueryColor(3), XStoreColors(3)
Xlib - C Language X Interface

X Version 11 libX11 1.8.10 XAllocColor(3)