Provided by: libxcb-doc_1.17.0-2_all 
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 per‐
formed 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 in‐
stead. Round The result is a circular arc with a diameter equal to the
line-width, centered
on the joinpoint. Bevel The result is Butt end‐
point 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, PolyFillRectan‐
gle, 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 every‐
where 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 des‐
tination 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 re‐
sults). For fill-style Stippled (but not fill-style OpaqueStippled), the stipple pat‐
tern 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 des‐
tination 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 re‐
sults). For fill-style Stippled (but not fill-style OpaqueStippled), the stipple pat‐
tern 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 destina‐
tion 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 inferi‐
ors 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 pix‐
els 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 corre‐
spond 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 1.17.0 xcb_change_gc(3)