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[], 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 *
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 *
distinct pixel values can be produced. All of these are allocated by the
request. However, in the colormap, there are only ncolors *
independent red entries, ncolors *
independent green entries, and ncolors *
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