Provided by: libxcb-doc_1.15-1_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 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.