path: root/libX11/man/XAllocStandardColormap.man

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.TH XAllocStandardColormap __libmansuffix__ __xorgversion__ "XLIB FUNCTIONS"
.SH NAME
XAllocStandardColormap, XSetRGBColormaps, XGetRGBColormaps, XStandardColormap \- allocate, set, or read a standard colormap structure
.SH SYNTAX
.HP
XStandardColormap *XAllocStandardColormap\^(void\^);
.HP
void XSetRGBColormaps\^(\^Display *\fIdisplay\fP, Window \fIw\fP,
XStandardColormap *\fIstd_colormap\fP,
int \fIcount\fP, Atom \fIproperty\fP\^);
.HP
Status XGetRGBColormaps\^(\^Display *\fIdisplay\fP, Window \fIw\fP,
XStandardColormap **\fIstd_colormap_return\fP, int *\fIcount_return\fP,
Atom \fIproperty\fP\^);
.SH ARGUMENTS
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.ds Cn colormaps
.IP \fIcount\fP 1i
Specifies the number of \*(Cn.
.ds Cn colormaps
.IP \fIcount_return\fP 1i
Returns the number of \*(Cn.
.IP \fIproperty\fP 1i
Specifies the property name.
.IP \fIstd_colormap\fP 1i
Specifies the
.ZN XStandardColormap
structure to be used.
.IP \fIstd_colormap_return\fP 1i
Returns the
.ZN XStandardColormap
structure.
.SH DESCRIPTION
The
.ZN XAllocStandardColormap
function allocates and returns a pointer to a
.ZN XStandardColormap
structure.
Note that all fields in the
.ZN XStandardColormap
structure are initially set to zero.
If insufficient memory is available, 
.ZN XAllocStandardColormap
returns NULL.
To free the memory allocated to this structure,
use
.ZN XFree .
.LP
The 
.ZN XSetRGBColormaps 
function replaces the RGB colormap definition in the specified property 
on the named window.
If the property does not already exist,
.ZN XSetRGBColormaps
sets the RGB colormap definition in the specified property
on the named window.
The property is stored with a type of RGB_COLOR_MAP and a format of 32.
Note that it is the caller's responsibility to honor the ICCCM
restriction that only RGB_DEFAULT_MAP contain more than one definition.
.LP
The
.ZN XSetRGBColormaps
function usually is only used by window or session managers.
To create a standard colormap, 
follow this procedure:
.IP 1. 5
Open a new connection to the same server.
.IP 2. 5
Grab the server.
.IP 3. 5
See if the property is on the property list of the root window for the screen.
.IP 4. 5
If the desired property is not present:
.RS
.IP \(bu 5
Create a colormap (unless you are using the default colormap of the screen).
.IP \(bu 5
Determine the color characteristics of the visual.
.IP \(bu 5
Allocate cells in the colormap (or create it with
.ZN AllocAll ).
.IP \(bu 5
Call 
.ZN XStoreColors
to store appropriate color values in the colormap.
.IP \(bu 5
Fill in the descriptive members in the 
.ZN XStandardColormap
structure.
.IP \(bu 5
Attach the property to the root window.
.IP \(bu 5
Use
.ZN XSetCloseDownMode
to make the resource permanent.
.RE
.IP 5. 5
Ungrab the server.
.LP
.ZN XSetRGBColormaps
can generate
.ZN BadAlloc ,
.ZN BadAtom ,
and
.ZN BadWindow
errors.
.LP
The 
.ZN XGetRGBColormaps
function returns the RGB colormap definitions stored 
in the specified property on the named window.
If the property exists, is of type RGB_COLOR_MAP, is of format 32, 
and is long enough to contain a colormap definition,
.ZN XGetRGBColormaps
allocates and fills in space for the returned colormaps
and returns a nonzero status.
If the visualid is not present, 
.ZN XGetRGBColormaps 
assumes the default visual for the screen on which the window is located; 
if the killid is not present, 
.ZN None
is assumed, which indicates that the resources cannot be released.
Otherwise, 
none of the fields are set, and 
.ZN XGetRGBColormaps
returns a zero status.
Note that it is the caller's responsibility to honor the ICCCM
restriction that only RGB_DEFAULT_MAP contain more than one definition.
.LP
.ZN XGetRGBColormaps
can generate
.ZN BadAtom
and
.ZN BadWindow
errors.
.SH STRUCTURES
The
.ZN XStandardColormap
structure contains:
.LP
/\&* Hints */
.TS
lw(.5i) lw(2i) lw(1i).
T{
\&#define
T}	T{
.ZN ReleaseByFreeingColormap
T}	T{
( (XID) 1L)
T}
.TE
/\&* Values */
.IN "XStandardColormap" "" "@DEF@"
.Ds 0
.TA .5i 2.5i
.ta .5i 2.5i
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;
.De
.LP
The colormap member is the colormap created by the
.ZN XCreateColormap
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.
.LP
The red_mult, green_mult, and blue_mult members give the
scale factors used to compose a full pixel value. 
(See the discussion of the base_pixel members for further information.)
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.
.LP
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 
.ZN 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:
.LP
.Ds
.TA .5i 1.5i
.ta .5i 1.5i
(r * red_mult + g * green_mult + b * blue_mult + base_pixel) & 0xFFFFFFFF
.De
.LP
For 
.ZN GrayScale
colormaps, 
only the colormap, red_max, red_mult, 
and base_pixel members are defined. 
The other members are ignored.  
To compute a 
.ZN GrayScale 
pixel value, use the following expression:
.LP
.Ds
.TA .5i 1.5i
.ta .5i 1.5i
(gray * red_mult + base_pixel) & 0xFFFFFFFF
.De
.LP
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,
.LP
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
.ZN XKillClient
function on the indicated resource.
(Note that this method is necessary for allocating out of an existing colormap.)
.LP
The properties containing the 
.ZN XStandardColormap 
information have 
the type RGB_COLOR_MAP.
.SH DIAGNOSTICS
.TP 1i
.ZN BadAlloc
The server failed to allocate the requested resource or server memory.
.TP 1i
.ZN BadAtom
A value for an Atom argument does not name a defined Atom.
.TP 1i
.ZN BadWindow
A value for a Window argument does not name a defined Window.
.SH "SEE ALSO"
XAllocColor(__libmansuffix__),
XCreateColormap(__libmansuffix__),
XFree(__libmansuffix__),
XSetCloseDownMode(__libmansuffix__)
.br
\fI\*(xL\fP