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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, char *color_name, XColor
*screen_def_return, XColor *exact_def_return);
Status XAllocColorCells(Display *display, Colormap colormap, Bool contig, unsigned long-plane_masks_return[], longplane_masks_return[],
plane_masks_return[], unsigned int nplanes, unsigned long pixels_return[], unsigned int npix-els); npixels);
els);
Status XAllocColorPlanes(Display *display, Colormap colormap, Bool contig, unsigned long pix-els_return[], pixels_return[],
els_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 readonly
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 posi-tive positive
tive 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 Bad-Value BadValue
Value 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, respec-tively. respectively.
tively. 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 XAl-locColorPlanes XAllocColorPlanes
locColorPlanes 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 pass-ing passing
ing 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
X Version 11 libX11 1.2.1 XAllocColor(3)
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