XLIB FUNCTIONS XAllocStandardColormap(3x11)
NAME
XAllocStandardColormap, XSetRGBColormaps, XGetRGBColormaps,
XStandardColormap - allocate, set, or read a standard color-
map structure SYNTAXcc [ flag... ] file... -lX11 [ library... ]
XStandardColormap *XAllocStandardColormap(void);void XSetRGBColormaps(Display *display, Window w, XStandard-
Colormap *std_colormap, int count, Atom property);
Status XGetRGBColormaps(Display *display, Window w, XStan-
dardColormap **std_colormap_return, int *count_return,
Atom property); ARGUMENTS display Specifies the connection to the X server. count Specifies the number of colormaps.count_return
Returns the number of colormaps. property Specifies the property name.std_colormap
Specifies the XStandardColormap structure to be used.std_colormap_return
Returns the XStandardColormap structure.DESCRIPTION
The XAllocStandardColormap function allocates and returns a pointer to a XStandardColormap structure. Note that all fields in the XStandardColormap structure are initially setto zero. If insufficient memory is available, XAllocStan-
dardColormap returns NULL. To free the memory allocated to this structure, use XFree. The XSetRGBColormaps function replaces the RGB colormap definition in the specified property on the named window. If the property does not already exist, XSetRGBColormaps sets the RGB colormap definition in the specified property on the named window. The property is stored with a type ofRGB_COLOR_MAP and a format of 32. Note that it is the
caller's responsibility to honor the ICCCM restriction thatonly RGB_DEFAULT_MAP contain more than one definition.
X Version 11 Last change: libX11 1.3.5 1 XLIB FUNCTIONS XAllocStandardColormap(3x11) The XSetRGBColormaps function usually is only used by window or session managers. To create a standard colormap, follow this procedure: 1. Open a new connection to the same server. 2. Grab the server. 3. See if the property is on the property list of the root window for the screen. 4. If the desired property is not present: +o Create a colormap (unless you are using the default colormap of the screen). +o Determine the color characteristics of the visual. +o Allocate cells in the colormap (or create it with AllocAll). +o Call XStoreColors to store appropriate color values in the colormap.+o Fill in the descriptive members in the XStandard-
Colormap structure. +o Attach the property to the root window.+o Use XSetCloseDownMode to make the resource per-
manent. 5. Ungrab the server.XSetRGBColormaps can generate BadAlloc, BadAtom, and BadWin-
dow errors.The XGetRGBColormaps function returns the RGB colormap
definitions stored in the specified property on the namedwindow. If the property exists, is of type RGB_COLOR_MAP,
is of format 32, and is long enough to contain a colormapdefinition, XGetRGBColormaps allocates and fills in space
for the returned colormaps and returns a nonzero status. Ifthe visualid is not present, XGetRGBColormaps assumes the
default visual for the screen on which the window is located; if the killid is not present, None is assumed,which indicates that the resources cannot be released. Oth-
erwise, none of the fields are set, and XGetRGBColormaps
returns a zero status. Note that it is the caller's respon-
sibility to honor the ICCCM restriction that onlyRGB_DEFAULT_MAP contain more than one definition.
X Version 11 Last change: libX11 1.3.5 2 XLIB FUNCTIONS XAllocStandardColormap(3x11)XGetRGBColormaps can generate BadAtom and BadWindow errors.
STRUCTURES The XStandardColormap structure contains: /* Hints */#define Release- ( (XID)
ByFreeingColormap 1L) /* Values */ typedef struct { Colormap colormap;unsigned long red_max;
unsigned long red_mult;
unsigned long green_max;
unsigned long green_mult;
unsigned long blue_max;
unsigned long blue_mult;
unsigned long base_pixel;
VisualID visualid; XID killid; } XStandardColormap; The colormap member is the colormap created by theXCreateColormap function. The red_max, green_max, and
blue_max members give the maximum red, green, and blue
values, respectively. Each color coefficient ranges from zero to its max, inclusive. For example, a common colormap allocation is 3/3/2 (3 planes for red, 3 planes for green,and 2 planes for blue). This colormap would have red_max =
7, green_max = 7, and blue_max = 3. An alternate allocation
that uses only 216 colors is red_max = 5, green_max = 5, and
blue_max = 5.
The red_mult, green_mult, and blue_mult members give the
scale factors used to compose a full pixel value. (See thediscussion of the base_pixel members for further informa-
tion.) For a 3/3/2 allocation, red_mult might be 32,
green_mult might be 4, and blue_mult might be 1. For a 6-
colors-each allocation, red_mult might be 36, green_mult
might be 6, and blue_mult might be 1.
The base_pixel member gives the base pixel value used to
compose a full pixel value. Usually, the base_pixel is
obtained from a call to the XAllocColorPlanes function. Given integer red, green, and blue coefficients in their appropriate ranges, one then can compute a corresponding pixel value by using the following expression:(r * red_mult + g * green_mult + b * blue_mult + base_pixel) & 0xFFFFFFFF
For GrayScale colormaps, only the colormap, red_max,
red_mult, and base_pixel members are defined. The other
X Version 11 Last change: libX11 1.3.5 3 XLIB FUNCTIONS XAllocStandardColormap(3x11) members are ignored. To compute a GrayScale pixel value, use the following expression:(gray * red_mult + base_pixel) & 0xFFFFFFFF
Negative multipliers can be represented by converting the 2's complement representation of the multiplier into an unsigned long and storing the result in the appropriate_mult field. The step of masking by 0xFFFFFFFF effectively
converts the resulting positive multiplier into a negative one. The masking step will take place automatically on many machine architectures, depending on the size of the integer type used to do the computation, The visualid member gives the ID number of the visual from which the colormap was created. The killid member gives a resource ID that indicates whether the cells held by this standard colormap are to be released by freeing the colormap ID or by calling the XKillClient function on the indicatedresource. (Note that this method is necessary for allocat-
ing out of an existing colormap.) The properties containing the XStandardColormap informationhave the type RGB_COLOR_MAP.
DIAGNOSTICS BadAlloc The server failed to allocate the requested resource or server memory. BadAtom A value for an Atom argument does not name a defined Atom. BadWindow A value for a Window argument does not name a defined Window.SEE ALSO
XAllocColor(3x11), XCreateColormap(3x11), XFree(3x11), XSetCloseDownMode(3x11)Xlib - C Language X Interface
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes: X Version 11 Last change: libX11 1.3.5 4 XLIB FUNCTIONS XAllocStandardColormap(3x11)____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | x11/library/libx11 ||_____________________________|_____________________________|
| Interface Stability | Committed ||_____________________________|_____________________________|
| MT-Level | See XInitThreads(3X11) |
|_____________________________|_____________________________|
X Version 11 Last change: libX11 1.3.5 5