XAllocColor(3X11) X Version 11 (Release 6.6) 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
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XAllocColor(3X11) X Version 11 (Release 6.6) XAllocColor(3X11)
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
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XAllocColor(3X11) X Version 11 (Release 6.6) XAllocColor(3X11)
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 * 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.
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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 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.
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XAllocColor(3X11) X Version 11 (Release 6.6) XAllocColor(3X11)
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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