xcb_change_gc(3) XCB Requests xcb_change_gc(3)
NAME
xcb_change_gc - change graphics context components
SYNOPSIS
#include <xcb/xproto.h> Request function
xcb_void_cookie_t
xcb_change_gc(xcb_connection_t *
conn,
xcb_gcontext_t
gc, uint32_t
value_mask, const
void *
value_list);
REQUEST ARGUMENTS
conn The XCB connection to X11.
gc The graphics context to change.
value_mask One of the following values:
XCB_GC_FUNCTION TODO: Refer to GX
XCB_GC_PLANE_MASK In graphics operations, given a source and
destination pixel, the result is computed bitwise
on corresponding bits of the pixels; that is, a
Boolean operation is performed in each bit plane.
The plane-mask restricts the operation to a
subset of planes, so the result is:
((src FUNC dst) AND plane-mask) OR (dst
AND (NOT plane-mask))
XCB_GC_FOREGROUND Foreground colorpixel.
XCB_GC_BACKGROUND Background colorpixel.
XCB_GC_LINE_WIDTH The line-width is measured in pixels and can be
greater than or equal to one, a wide line, or the
special value zero, a thin line.
XCB_GC_LINE_STYLE The line-style defines which sections of a line
are drawn: Solid The full path of
the line is drawn. DoubleDash The full
path of the line is drawn, but the even dashes
are filled differently
than the odd dashes (see
fill-style), with Butt cap-style used where even
and
odd dashes meet. OnOffDash
Only the even dashes are drawn, and cap-style
applies to all internal ends of
the individual dashes
(except NotLast is treated as Butt).
XCB_GC_CAP_STYLE The cap-style defines how the endpoints of a path
are drawn: NotLast The result is equivalent to
Butt, except that for a line-width of zero the
final
endpoint is not drawn. Butt The
result is square at the endpoint (perpendicular
to the slope of the line)
with no projection beyond. Round
The result is a circular arc with its diameter
equal to the line-width, centered
on the endpoint; it is equivalent to
Butt for line-width zero. Projecting The result
is square at the end, but the path continues
beyond the endpoint for
a distance equal to half the line-
width; it is equivalent to Butt for line-width
zero.
XCB_GC_JOIN_STYLE The join-style defines how corners are drawn for
wide lines: Miter The outer edges
of the two lines extend to meet at an angle.
However, if the
angle is less than 11
degrees, a Bevel join-style is used instead.
Round The result is a circular arc
with a diameter equal to the line-width, centered
on the joinpoint. Bevel
The result is Butt endpoint styles, and then the
triangular notch is filled.
XCB_GC_FILL_STYLE The fill-style defines the contents of the source
for line, text, and fill requests. For all text
and fill requests (for example, PolyText8,
PolyText16, PolyFillRectangle, FillPoly, and
PolyFillArc) as well as for line requests with
line-style Solid, (for example, PolyLine,
PolySegment, PolyRectangle, PolyArc) and for the
even dashes for line requests with line-style
OnOffDash or DoubleDash: Solid
Foreground Tiled Tile
OpaqueStippled A tile with the same
width and height as stipple but with background
everywhere stipple has
a zero and with foreground everywhere stipple
has a one Stippled
Foreground masked by stipple For the odd dashes
for line requests with line-style DoubleDash:
Solid Background Tiled
Same as for even dashes OpaqueStippled
Same as for even dashes Stippled
Background masked by stipple
XCB_GC_FILL_RULE XCB_GC_TILE The tile/stipple represents an infinite two-
dimensional plane with the tile/stipple
replicated in all dimensions. When that plane is
superimposed on the drawable for use in a
graphics operation, the upper-left corner of some
instance of the tile/stipple is at the
coordinates within the drawable specified by the
tile/stipple origin. The tile/stipple and clip
origins are interpreted relative to the origin of
whatever destination drawable is specified in a
graphics request. The tile pixmap must have the
same root and depth as the gcontext (or a Match
error results). The stipple pixmap must have
depth one and must have the same root as the
gcontext (or a Match error results). For fill-
style Stippled (but not fill-style
OpaqueStippled), the stipple pattern is tiled in
a single plane and acts as an additional clip
mask to be ANDed with the clip-mask. Any size
pixmap can be used for tiling or stippling,
although some sizes may be faster to use than
others.
XCB_GC_STIPPLE The tile/stipple represents an infinite two-
dimensional plane with the tile/stipple
replicated in all dimensions. When that plane is
superimposed on the drawable for use in a
graphics operation, the upper-left corner of some
instance of the tile/stipple is at the
coordinates within the drawable specified by the
tile/stipple origin. The tile/stipple and clip
origins are interpreted relative to the origin of
whatever destination drawable is specified in a
graphics request. The tile pixmap must have the
same root and depth as the gcontext (or a Match
error results). The stipple pixmap must have
depth one and must have the same root as the
gcontext (or a Match error results). For fill-
style Stippled (but not fill-style
OpaqueStippled), the stipple pattern is tiled in
a single plane and acts as an additional clip
mask to be ANDed with the clip-mask. Any size
pixmap can be used for tiling or stippling,
although some sizes may be faster to use than
others.
XCB_GC_TILE_STIPPLE_ORIGIN_X TODO
XCB_GC_TILE_STIPPLE_ORIGIN_Y TODO
XCB_GC_FONT Which font to use for the
ImageText8 and
ImageText16 requests.
XCB_GC_SUBWINDOW_MODE For ClipByChildren, both source and destination
windows are additionally clipped by all viewable
InputOutput children. For IncludeInferiors,
neither source nor destination window is clipped
by inferiors. This will result in including
subwindow contents in the source and drawing
through subwindow boundaries of the destination.
The use of IncludeInferiors with a source or
destination window of one depth with mapped
inferiors of differing depth is not illegal, but
the semantics is undefined by the core protocol.
XCB_GC_GRAPHICS_EXPOSURES Whether ExposureEvents should be generated (1) or
not (0).
The default is 1.
XCB_GC_CLIP_ORIGIN_X TODO
XCB_GC_CLIP_ORIGIN_Y TODO
XCB_GC_CLIP_MASK The clip-mask restricts writes to the destination
drawable. Only pixels where the clip-mask has
bits set to 1 are drawn. Pixels are not drawn
outside the area covered by the clip-mask or
where the clip-mask has bits set to 0. The clip-
mask affects all graphics requests, but it does
not clip sources. The clip-mask origin is
interpreted relative to the origin of whatever
destination drawable is specified in a graphics
request. If a pixmap is specified as the clip-
mask, it must have depth 1 and have the same root
as the gcontext (or a Match error results). If
clip-mask is None, then pixels are always drawn,
regardless of the clip origin. The clip-mask can
also be set with the SetClipRectangles request.
XCB_GC_DASH_OFFSET TODO
XCB_GC_DASH_LIST TODO
XCB_GC_ARC_MODE TODO
value_list Values for each of the components specified in the bitmask
value_mask. The order has to correspond to the order of
possible
value_mask bits. See the example.
DESCRIPTION
Changes the components specified by
value_mask for the specified
graphics context.
RETURN VALUE
Returns an
xcb_void_cookie_t. Errors (if any) have to be handled in
the event loop.
If you want to handle errors directly with
xcb_request_check instead,
use
xcb_change_gc_checked. See
xcb-requests(3) for details.
ERRORS
xcb_alloc_error_t The X server could not allocate the requested resources (no
memory?).
xcb_font_error_t TODO: reasons?
xcb_g_context_error_t TODO: reasons?
xcb_match_error_t TODO: reasons?
xcb_pixmap_error_t TODO: reasons?
xcb_value_error_t TODO: reasons?
EXAMPLE
/*
* Changes the foreground color component of the specified graphics context.
*
*/
void my_example(xcb_connection_t *conn, xcb_gcontext_t gc, uint32_t fg, uint32_t bg) {
/* C99 allows us to use a compact way of changing a single component: */
xcb_change_gc(conn, gc, XCB_GC_FOREGROUND, (uint32_t[]){ fg });
/* The more explicit way. Beware that the order of values is important! */
uint32_t mask = 0;
mask |= XCB_GC_FOREGROUND;
mask |= XCB_GC_BACKGROUND;
uint32_t values[] = {
fg,
bg
};
xcb_change_gc(conn, gc, mask, values);
xcb_flush(conn);
}
SEE ALSO
xcb-requests(3),
xcb-examples(3)AUTHOR
Generated from xproto.xml. Contact xcb@lists.freedesktop.org for
corrections and improvements.
X Version 11 libxcb 1.16.1 xcb_change_gc(3)
