1XAllocStandardColormap(3) XLIB FUNCTIONS XAllocStandardColormap(3)
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6 XAllocStandardColormap, XSetRGBColormaps, XGetRGBColormaps, XStandard‐
7 Colormap - allocate, set, or read a standard colormap structure
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10 XStandardColormap *XAllocStandardColormap(void);
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12 void XSetRGBColormaps(Display *display, Window w, XStandardColormap
13 *std_colormap, int count, Atom property);
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15 Status XGetRGBColormaps(Display *display, Window w, XStandardColormap
16 **std_colormap_return, int *count_return, Atom property);
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19 display Specifies the connection to the X server.
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21 count Specifies the number of colormaps.
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23 count_return
24 Returns the number of colormaps.
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26 property Specifies the property name.
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28 std_colormap
29 Specifies the XStandardColormap structure to be used.
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31 std_colormap_return
32 Returns the XStandardColormap structure.
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35 The XAllocStandardColormap function allocates and returns a pointer to
36 a XStandardColormap structure. Note that all fields in the XStandard‐
37 Colormap structure are initially set to zero. If insufficient memory
38 is available, XAllocStandardColormap returns NULL. To free the memory
39 allocated to this structure, use XFree.
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41 The XSetRGBColormaps function replaces the RGB colormap definition in
42 the specified property on the named window. If the property does not
43 already exist, XSetRGBColormaps sets the RGB colormap definition in the
44 specified property on the named window. The property is stored with a
45 type of RGB_COLOR_MAP and a format of 32. Note that it is the caller's
46 responsibility to honor the ICCCM restriction that only RGB_DEFAULT_MAP
47 contain more than one definition.
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49 The XSetRGBColormaps function usually is only used by window or session
50 managers. To create a standard colormap, follow this procedure:
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52 1. Open a new connection to the same server.
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54 2. Grab the server.
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56 3. See if the property is on the property list of the root window for
57 the screen.
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59 4. If the desired property is not present:
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61 · Create a colormap (unless you are using the default colormap
62 of the screen).
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64 · Determine the color characteristics of the visual.
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66 · Allocate cells in the colormap (or create it with AllocAll).
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68 · Call XStoreColors to store appropriate color values in the
69 colormap.
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71 · Fill in the descriptive members in the XStandardColormap
72 structure.
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74 · Attach the property to the root window.
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76 · Use XSetCloseDownMode to make the resource permanent.
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78 5. Ungrab the server.
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80 XSetRGBColormaps can generate BadAlloc, BadAtom, and BadWindow errors.
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82 The XGetRGBColormaps function returns the RGB colormap definitions
83 stored in the specified property on the named window. If the property
84 exists, is of type RGB_COLOR_MAP, is of format 32, and is long enough
85 to contain a colormap definition, XGetRGBColormaps allocates and fills
86 in space for the returned colormaps and returns a nonzero status. If
87 the visualid is not present, XGetRGBColormaps assumes the default vis‐
88 ual for the screen on which the window is located; if the killid is not
89 present, None is assumed, which indicates that the resources cannot be
90 released. Otherwise, none of the fields are set, and XGetRGBColormaps
91 returns a zero status. Note that it is the caller's responsibility to
92 honor the ICCCM restriction that only RGB_DEFAULT_MAP contain more than
93 one definition.
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95 XGetRGBColormaps can generate BadAtom and BadWindow errors.
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98 The XStandardColormap structure contains:
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100 /* Hints */
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102 #define ReleaseByFreeingCol‐ ( (XID)
103 ormap 1L)
104 /* Values */
105 typedef struct {
106 Colormap colormap;
107 unsigned long red_max;
108 unsigned long red_mult;
109 unsigned long green_max;
110 unsigned long green_mult;
111 unsigned long blue_max;
112 unsigned long blue_mult;
113 unsigned long base_pixel;
114 VisualID visualid;
115 XID killid;
116 } XStandardColormap;
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118 The colormap member is the colormap created by the XCreateColormap
119 function. The red_max, green_max, and blue_max members give the maxi‐
120 mum red, green, and blue values, respectively. Each color coefficient
121 ranges from zero to its max, inclusive. For example, a common colormap
122 allocation is 3/3/2 (3 planes for red, 3 planes for green, and 2 planes
123 for blue). This colormap would have red_max = 7, green_max = 7, and
124 blue_max = 3. An alternate allocation that uses only 216 colors is
125 red_max = 5, green_max = 5, and blue_max = 5.
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127 The red_mult, green_mult, and blue_mult members give the scale factors
128 used to compose a full pixel value. (See the discussion of the
129 base_pixel members for further information.) For a 3/3/2 allocation,
130 red_mult might be 32, green_mult might be 4, and blue_mult might be 1.
131 For a 6-colors-each allocation, red_mult might be 36, green_mult might
132 be 6, and blue_mult might be 1.
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134 The base_pixel member gives the base pixel value used to compose a full
135 pixel value. Usually, the base_pixel is obtained from a call to the
136 XAllocColorPlanes function. Given integer red, green, and blue coeffi‐
137 cients in their appropriate ranges, one then can compute a correspond‐
138 ing pixel value by using the following expression:
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140 (r * red_mult + g * green_mult + b * blue_mult + base_pixel) & 0xFFFFFFFF
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142 For GrayScale colormaps, only the colormap, red_max, red_mult, and
143 base_pixel members are defined. The other members are ignored. To
144 compute a GrayScale pixel value, use the following expression:
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146 (gray * red_mult + base_pixel) & 0xFFFFFFFF
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148 Negative multipliers can be represented by converting the 2's comple‐
149 ment representation of the multiplier into an unsigned long and storing
150 the result in the appropriate _mult field. The step of masking by
151 0xFFFFFFFF effectively converts the resulting positive multiplier into
152 a negative one. The masking step will take place automatically on many
153 machine architectures, depending on the size of the integer type used
154 to do the computation,
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156 The visualid member gives the ID number of the visual from which the
157 colormap was created. The killid member gives a resource ID that indi‐
158 cates whether the cells held by this standard colormap are to be
159 released by freeing the colormap ID or by calling the XKillClient func‐
160 tion on the indicated resource. (Note that this method is necessary
161 for allocating out of an existing colormap.)
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163 The properties containing the XStandardColormap information have the
164 type RGB_COLOR_MAP.
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167 BadAlloc The server failed to allocate the requested resource or
168 server memory.
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170 BadAtom A value for an Atom argument does not name a defined Atom.
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172 BadWindow A value for a Window argument does not name a defined Window.
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175 XAllocColor(3), XCreateColormap(3), XFree(3), XSetCloseDownMode(3)
176 Xlib - C Language X Interface
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180X Version 11 libX11 1.6.4 XAllocStandardColormap(3)