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
uint32_t *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 destina‐
tion pixel, the result is computed bitwise on cor‐
responding 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 ap‐
plies 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 fi‐
nal
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 Opaque‐
Stippled 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-dimen‐
sional 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 draw‐
able specified by the tile/stipple origin. The
tile/stipple and clip origins are interpreted rela‐
tive 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 Opaque‐
Stippled), 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-dimen‐
sional 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 draw‐
able specified by the tile/stipple origin. The
tile/stipple and clip origins are interpreted rela‐
tive 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 Opaque‐
Stippled), 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 Image‐
Text16 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 inferi‐
ors. This will result in including subwindow con‐
tents in the source and drawing through subwindow
boundaries of the destination. The use of Include‐
Inferiors 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 rela‐
tive 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 SetClipRect‐
angles 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 pos‐
sible value_mask bits. See the example.
DESCRIPTION
Changes the components specified by value_mask for the specified graph‐
ics 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_pixmap_error_t
TODO: reasons?
xcb_alloc_error_t
The X server could not allocate the requested resources (no
memory?).
xcb_value_error_t
TODO: reasons?
xcb_gc_error_t
TODO: reasons?
xcb_font_error_t
TODO: reasons?
xcb_match_error_t
TODO: reasons?
EXAMPLE
/*
* Changes the foreground color component of the specified graphics context.
*
*/
void my_example(xcb_connection *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 ALSOxcb-requests(3), xcb-examples(3)AUTHOR
Generated from xproto.xml. Contact xcb@lists.freedesktop.org for cor‐
rections and improvements.
XCB 2012-10-16 xcb_change_gc(3)
