XAllocColor(3X11) XLIB FUNCTIONS XAllocColor(3X11)NAME
XAllocColor, XAllocNamedColor, XAllocColorCells, XAlloc-
ColorPlanes, 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
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XAllocColor(3X11) XLIB FUNCTIONS XAllocColor(3X11)
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.
The XAllocColorCells function allocates read/write color
cells. The number of colors must be positive and the num-
ber 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
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XAllocColor(3X11) XLIB FUNCTIONS XAllocColor(3X11)
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 pro-
duced. All of these are allocated by the request. How-
ever, 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 the correspond-
ing 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 actu-
ally 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.
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XAllocColor(3X11) XLIB FUNCTIONS XAllocColor(3X11)
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 ALSOXCreateColormap(3X11), XQueryColor(3X11), XStoreCol-
ors(3X11)
Xlib - C Language X Interface
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