1XAllocColor(3) XLIB FUNCTIONS XAllocColor(3)
2
6 XAllocColor, XAllocNamedColor, XAllocColorCells, XAllocColorPlanes,
7 XFreeColors - allocate and free colors
8
10 Status XAllocColor(Display *display, Colormap colormap, XColor
11 *screen_in_out);
12 Status XAllocNamedColor(Display *display, Colormap colormap, char
14 *color_name, XColor *screen_def_return, XColor
15 *exact_def_return);
16 Status XAllocColorCells(Display *display, Colormap colormap, Bool con‐
18 tig, unsigned long plane_masks_return[], unsigned int nplanes,
19 unsigned long pixels_return[], unsigned int npixels);
20 Status XAllocColorPlanes(Display *display, Colormap colormap, Bool con‐
22 tig, unsigned long pixels_return[], int ncolors, int nreds, int
23 ngreens, int nblues, unsigned long *rmask_return, unsigned long
24 *gmask_return, unsigned long *bmask_return);
25 int XFreeColors(Display *display, Colormap colormap, unsigned long pix‐
27 els[], int npixels, unsigned long planes);
28 color_name
30 Specifies the color name string (for example, red) whose
31 color definition structure you want returned.
32 colormap Specifies the colormap.
34 contig Specifies a Boolean value that indicates whether the planes
36 must be contiguous.
37 display Specifies the connection to the X server.
39 exact_def_return
41 Returns the exact RGB values.
42 ncolors Specifies the number of pixel values that are to be returned
44 in the pixels_return array.
45 npixels Specifies the number of pixels.
47 nplanes Specifies the number of plane masks that are to be returned
49 in the plane masks array.
50 nreds
52 ngreens
53 nblues
54 Specify the number of red, green, and blue planes. The value
55 you pass must be nonnegative.
56 pixels Specifies an array of pixel values.
58 pixels_return
60 Returns an array of pixel values.
61 plane_mask_return
63 Returns an array of plane masks.
64 planes Specifies the planes you want to free.
66 rmask_return
68 gmask_return
69 bmask_return
70 Return bit masks for the red, green, and blue planes.
71 screen_def_return
73 Returns the closest RGB values provided by the hardware.
74 screen_in_out
76 Specifies and returns the values actually used in the col‐
77 ormap.
78
80 The XAllocColor function allocates a read-only colormap entry corre‐
81 sponding to the closest RGB value supported by the hardware. XAlloc‐
82 Color returns the pixel value of the color closest to the specified RGB
83 elements supported by the hardware and returns the RGB value actually
84 used. The corresponding colormap cell is read-only. In addition, XAl‐
85 locColor returns nonzero if it succeeded or zero if it failed. Multi‐
86 ple clients that request the same effective RGB value can be assigned
87 the same read-only entry, thus allowing entries to be shared. When the
88 last client deallocates a shared cell, it is deallocated. XAllocColor
89 does not use or affect the flags in the XColor structure.
90 XAllocColor can generate a BadColor error.
92 The XAllocNamedColor function looks up the named color with respect to
94 the screen that is associated with the specified colormap. It returns
95 both the exact database definition and the closest color supported by
96 the screen. The allocated color cell is read-only. The pixel value is
97 returned in screen_def_return. If the color name is not in the Host
98 Portable Character Encoding, the result is implementation-dependent.
99 Use of uppercase or lowercase does not matter. If screen_def_return
100 and exact_def_return point to the same structure, the pixel field will
101 be set correctly, but the color values are undefined. XAllocNamedColor
102 returns nonzero if a cell is allocated; otherwise, it returns zero.
103 XAllocNamedColor can generate a BadColor error.
105 The XAllocColorCells function allocates read/write color cells. The
107 number of colors must be positive and the number of planes nonnegative,
108 or a BadValue error results. If ncolors and nplanes are requested,
109 then ncolors pixels and nplane plane masks are returned. No mask will
110 have any bits set to 1 in common with any other mask or with any of the
111 pixels. By ORing together each pixel with zero or more masks, ncolors
112 * 2nplanes distinct pixels can be produced. All of these are allocated
113 writable by the request. For GrayScale or PseudoColor, each mask has
114 exactly one bit set to 1. For DirectColor, each has exactly three bits
115 set to 1. If contig is True and if all masks are ORed together, a sin‐
116 gle contiguous set of bits set to 1 will be formed for GrayScale or
117 PseudoColor and three contiguous sets of bits set to 1 (one within each
118 pixel subfield) for DirectColor. The RGB values of the allocated
119 entries are undefined. XAllocColorCells returns nonzero if it suc‐
120 ceeded or zero if it failed.
121 XAllocColorCells can generate BadColor and BadValue errors.
123 The specified ncolors must be positive; and nreds, ngreens, and nblues
125 must be nonnegative, or a BadValue error results. If ncolors colors,
126 nreds reds, ngreens greens, and nblues blues are requested, ncolors
127 pixels are returned; and the masks have nreds, ngreens, and nblues bits
128 set to 1, respectively. If contig is True, each mask will have a con‐
129 tiguous set of bits set to 1. No mask will have any bits set to 1 in
130 common with any other mask or with any of the pixels. For DirectColor,
131 each mask will lie within the corresponding pixel subfield. By ORing
132 together subsets of masks with each pixel value, ncolors *
133 2(nreds+ngreens+nblues) distinct pixel values can be produced. All of
134 these are allocated by the request. However, in the colormap, there
135 are only ncolors * 2nreds independent red entries, ncolors * 2ngreens
136 independent green entries, and ncolors * 2nblues independent blue
137 entries. This is true even for PseudoColor. When the colormap entry
138 of a pixel value is changed (using XStoreColors, XStoreColor, or
139 XStoreNamedColor), the pixel is decomposed according to the masks, and
140 the corresponding independent entries are updated. XAllocColorPlanes
141 returns nonzero if it succeeded or zero if it failed.
142 XAllocColorPlanes can generate BadColor and BadValue errors.
144 The XFreeColors function frees the cells represented by pixels whose
146 values are in the pixels array. The planes argument should not have
147 any bits set to 1 in common with any of the pixels. The set of all
148 pixels is produced by ORing together subsets of the planes argument
149 with the pixels. The request frees all of these pixels that were allo‐
150 cated by the client (using XAllocColor, XAllocNamedColor, XAllocColor‐
151 Cells, and XAllocColorPlanes). Note that freeing an individual pixel
152 obtained from XAllocColorPlanes may not actually allow it to be reused
153 until all of its related pixels are also freed. Similarly, a read-only
154 entry is not actually freed until it has been freed by all clients, and
155 if a client allocates the same read-only entry multiple times, it must
156 free the entry that many times before the entry is actually freed.
157 All specified pixels that are allocated by the client in the colormap
159 are freed, even if one or more pixels produce an error. If a specified
160 pixel is not a valid index into the colormap, a BadValue error results.
161 If a specified pixel is not allocated by the client (that is, is unal‐
162 located or is only allocated by another client) or if the colormap was
163 created with all entries writable (by passing AllocAll to XCreateCol‐
164 ormap), a BadAccess error results. If more than one pixel is in error,
165 the one that gets reported is arbitrary.
166 XFreeColors can generate BadAccess, BadColor, and BadValue errors.
168
170 BadAccess A client attempted to free a color map entry that it did not
171 already allocate.
172 BadAccess A client attempted to store into a read-only color map entry.
174 BadColor A value for a Colormap argument does not name a defined Col‐
176 ormap.
177 BadValue Some numeric value falls outside the range of values accepted
179 by the request. Unless a specific range is specified for an
180 argument, the full range defined by the argument's type is
181 accepted. Any argument defined as a set of alternatives can
182 generate this error.
183
185 XCreateColormap(3), XQueryColor(3), XStoreColors(3)
186 Xlib - C Language X Interface
187X Version 11 libX11 1.6.4 XAllocColor(3)