NAME
xcbchangegc - change graphics context components SYNOPSIS
#include
Request function xcbvoidcookiet xcbchangegc(xcbconnectiont *conn, xcbgcontextt gc, uint32t valuemask, const void *valuelist); REQUEST ARGUMENTS conn The XCB connection to X11. gc The graphics context to change. valuemask One of the following values: XCBGCFUNCTION TODO: Refer to GX XCBGCPLANEMASK 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)) XCBGCFOREGROUND Foreground colorpixel. XCBGCBACKGROUND Background colorpixel. XCBGCLINEWIDTH
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. XCBGCLINESTYLE
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). XCBGCCAPSTYLE
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. XCBGCJOINSTYLE
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. XCBGCFILLSTYLE
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 XCBGCFILLRULE XCBGCTILE
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. XCBGCSTIPPLE
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. XCBGCTILESTIPPLEORIGINX TODO XCBGCTILESTIPPLEORIGINY TODO XCBGCFONT Which font to use for the ImageText8 and Image‐ Text16 requests. XCBGCSUBWINDOWMODE 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. XCBGCGRAPHICSEXPOSURES Whether ExposureEvents should be generated (1) or not (0). The default is 1. XCBGCCLIPORIGINX TODO XCBGCCLIPORIGINY TODO XCBGCCLIPMASK
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. XCBGCDASHOFFSET TODO XCBGCDASHLIST TODO XCBGCARCMODE TODO valuelist Values for each of the components specified in the bitmask valuemask. The order has to correspond to the order of pos‐ sible valuemask bits. See the example. DESCRIPTION Changes the components specified by valuemask for the specified graph‐ ics context. RETURN VALUE Returns an xcbvoidcookiet. Errors (if any) have to be handled in the event loop. If you want to handle errors directly with xcbrequestcheck instead,
use xcbchangegcchecked. See xcb-requests(3) for details. ERRORS xcballocerrort The X server could not allocate the requested resources (no memory?). xcbfonterrort TODO: reasons? xcbgcontexterrort TODO: reasons? xcbmatcherrort TODO: reasons? xcbpixmaperrort TODO: reasons? xcbvalueerrort TODO: reasons? EXAMPLE /* * Changes the foreground color component of the specified graphics context. * */ void myexample(xcbconnectiont *conn, xcbgcontextt gc, uint32t fg, uint32t bg) { /* C99 allows us to use a compact way of changing a single component: */ xcbchangegc(conn, gc, XCBGCFOREGROUND, (uint32t[]){ fg }); /* The more explicit way. Beware that the order of values is important! */ uint32t mask = 0; mask |= XCBGCFOREGROUND; mask |= XCBGCBACKGROUND; uint32t values[] = { fg, bg }; xcbchangegc(conn, gc, mask, values); xcbflush(conn); } SEE ALSO
xcb-requests(3), xcb-examples(3) AUTHOR Generated from xproto.xml. Contact xcb@lists.freedesktop.org for cor‐ rections and improvements. X Version 11 libxcb 1.13 xcbchangegc(3)