NAME
XCreateColormap, XCopyColormapAndFree, XFreeColormap, XColor - create,
copy, or destroy colormaps and color structure
SYNTAX
Colormap XCreateColormap(Display *display, Window w, Visual *visual,
int alloc);
Colormap XCopyColormapAndFree(Display *display, Colormap colormap);
int XFreeColormap(Display *display, Colormap colormap);
ARGUMENTS
alloc Specifies the colormap entries to be allocated. You can pass
AllocNone or AllocAll.
colormap Specifies the colormap that you want to create, copy, set, or
destroy.
display Specifies the connection to the X server.
visual Specifies a visual type supported on the screen. If the
visual type is not one supported by the screen, a BadMatch
error results.
w Specifies the window on whose screen you want to create a
colormap.
DESCRIPTION
The XCreateColormap function creates a colormap of the specified visual
type for the screen on which the specified window resides and returns
the colormap ID associated with it. Note that the specified window is
only used to determine the screen.
The initial values of the colormap entries are undefined for the visual
classes GrayScale, PseudoColor, and DirectColor. For StaticGray,
StaticColor, and TrueColor, the entries have defined values, but those
values are specific to the visual and are not defined by X. For
StaticGray, StaticColor, and TrueColor, alloc must be AllocNone, or a
BadMatch error results. For the other visual classes, if alloc is
AllocNone, the colormap initially has no allocated entries, and clients
can allocate them. For information about the visual types, see section
3.1.
If alloc is AllocAll, the entire colormap is allocated writable. The
initial values of all allocated entries are undefined. For GrayScale
and PseudoColor, the effect is as if an XAllocColorCells call returned
all pixel values from zero to N - 1, where N is the colormap entries
value in the specified visual. For DirectColor, the effect is as if an
XAllocColorPlanes call returned a pixel value of zero and red_mask,
green_mask, and blue_mask values containing the same bits as the
corresponding masks in the specified visual. However, in all cases,
none of these entries can be freed by using XFreeColors.
XCreateColormap can generate BadAlloc, BadMatch, BadValue, and
BadWindow errors.
The XCopyColormapAndFree function creates a colormap of the same visual
type and for the same screen as the specified colormap and returns the
new colormap ID. It also moves all of the client’s existing allocation
from the specified colormap to the new colormap with their color values
intact and their read-only or writable characteristics intact and frees
those entries in the specified colormap. Color values in other entries
in the new colormap are undefined. If the specified colormap was
created by the client with alloc set to AllocAll, the new colormap is
also created with AllocAll, all color values for all entries are copied
from the specified colormap, and then all entries in the specified
colormap are freed. If the specified colormap was not created by the
client with AllocAll, the allocations to be moved are all those pixels
and planes that have been allocated by the client using XAllocColor,
XAllocNamedColor, XAllocColorCells, or XAllocColorPlanes and that have
not been freed since they were allocated.
XCopyColormapAndFree can generate BadAlloc and BadColor errors.
The XFreeColormap function deletes the association between the colormap
resource ID and the colormap and frees the colormap storage. However,
this function has no effect on the default colormap for a screen. If
the specified colormap is an installed map for a screen, it is
uninstalled (see XUninstallColormap). If the specified colormap is
defined as the colormap for a window (by XCreateWindow,
XSetWindowColormap, or XChangeWindowAttributes), XFreeColormap changes
the colormap associated with the window to None and generates a
ColormapNotify event. X does not define the colors displayed for a
window with a colormap of None.
XFreeColormap can generate a BadColor error.
STRUCTURES
The XColor structure contains:
typedef struct {
unsigned long pixel;/* pixel value */
unsigned short red, green, blue;/* rgb values */
char flags; /* DoRed, DoGreen, DoBlue */
char pad;
} XColor;
The red, green, and blue values are always in the range 0 to 65535
inclusive, independent of the number of bits actually used in the
display hardware. The server scales these values down to the range
used by the hardware. Black is represented by (0,0,0), and white is
represented by (65535,65535,65535). In some functions, the flags
member controls which of the red, green, and blue members is used and
can be the inclusive OR of zero or more of DoRed, DoGreen, and DoBlue.
DIAGNOSTICS
BadAlloc The server failed to allocate the requested resource or
server memory.
BadColor A value for a Colormap argument does not name a defined
Colormap.
BadMatch An InputOnly window is used as a Drawable.
BadMatch Some argument or pair of arguments has the correct type and
range but fails to match in some other way required by the
request.
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.
BadWindow A value for a Window argument does not name a defined Window.
SEE ALSO
XAllocColor(3), XChangeWindowAttributes(3), XCreateWindow(3),
XQueryColor(3), XStoreColors(3)
Xlib - C Language X Interface