Description
The cairo drawing contextMethods and Functions
cairoCreate(target)
cairoStatus(cr)
cairoSave(cr)
cairoRestore(cr)
cairoGetTarget(cr)
cairoPushGroup(cr)
cairoPushGroupWithContent(cr, content)
cairoPopGroup(cr)
cairoPopGroupToSource(cr)
cairoGetGroupTarget(cr)
cairoSetSourceRgb(cr, red, green, blue)
cairoSetSourceRgba(cr, red, green, blue, alpha)
cairoSetSource(cr, source)
cairoSetSourceSurface(cr, surface, x, y)
cairoGetSource(cr)
cairoSetAntialias(cr, antialias)
cairoGetAntialias(cr)
cairoSetDash(cr, dashes, offset)
cairoGetDashCount(cr)
cairoGetDash(cr)
cairoSetFillRule(cr, fill.rule)
cairoGetFillRule(cr)
cairoSetLineCap(cr, line.cap)
cairoGetLineCap(cr)
cairoSetLineJoin(cr, line.join)
cairoGetLineJoin(cr)
cairoSetLineWidth(cr, width)
cairoGetLineWidth(cr)
cairoSetMiterLimit(cr, limit)
cairoGetMiterLimit(cr)
cairoSetOperator(cr, op)
cairoGetOperator(cr)
cairoSetTolerance(cr, tolerance)
cairoGetTolerance(cr)
cairoClip(cr)
cairoClipPreserve(cr)
cairoClipExtents(cr)
cairoResetClip(cr)
cairoCopyClipRectangleList(cr)
cairoFill(cr)
cairoFillPreserve(cr)
cairoFillExtents(cr)
cairoInFill(cr, x, y)
cairoMask(cr, pattern)
cairoMaskSurface(cr, surface, surface.x, surface.y)
cairoPaint(cr)
cairoPaintWithAlpha(cr, alpha)
cairoStroke(cr)
cairoStrokePreserve(cr)
cairoStrokeExtents(cr)
cairoInStroke(cr, x, y)
cairoCopyPage(cr)
cairoShowPage(cr)
cairoSetUserData(cr, key, user.data)
cairoGetUserData(cr, key)
cairo(target)Detailed Description
Cairo is the main object used when drawing with cairo. To
draw with cairo, you create a Cairo, set the target surface,
and drawing options for the Cairo, create shapes with
functions like cairoMoveTo and cairoLineTo, and then
draw shapes with cairoStroke or cairoFill.
Cairo's can be pushed to a stack via cairoSave.
They may then safely be changed, without loosing the current state.
Use cairoRestore to restore to the saved state.Structures
Cairo-
A
Cairo contains the current state of the rendering device,
including coordinates of yet to be drawn shapes. Cairo contexts, as Cairo objects are named, are central to
cairo and all drawing with cairo is always done to a Cairo
object. Memory management of Cairo is done with
cairoReference() and cairoDestroy(). CairoRectangle-
A data structure for holding a rectangle.
Since 1.4
CairoRectangle is a transparent-type.
x- [numeric] X coordinate of the left side of the rectangle
y- [numeric] Y coordinate of the the top side of the rectangle
width- [numeric] width of the rectangle
height- [numeric] height of the rectangle
CairoRectangleList-
A data structure for holding a dynamically allocated
array of rectangles.
Since 1.4
CairoRectangleList is a transparent-type.
status- [
CairoStatus] Error status of the rectangle list rectangles- [
CairoRectangle] list containing the rectangles num_rectangles- [integer] Number of rectangles in this list
Convenient Construction
cairo is the equivalent of cairoCreate.Enums and Flags
CairoAntialias-
Specifies the type of antialiasing to do when rendering text or shapes.
default- Use the default antialiasing for
the subsystem and target device
none- Use a bilevel alpha mask
gray- Perform single-color antialiasing (using
shades of gray for black text on a white background, for example).
subpixel- Perform antialiasing by taking
advantage of the order of subpixel elements on devices
such as LCD panels
CairoFillRule-
CairoFillRule is used to select how paths are filled. For both
fill rules, whether or not a point is included in the fill is
determined by taking a ray from that point to infinity and looking
at intersections with the path. The ray can be in any direction,
as long as it doesn't pass through the end point of a segment
or have a tricky intersection such as intersecting tangent to the path.
(Note that filling is not actually implemented in this way. This
is just a description of the rule that is applied.) The default fill rule is CAIRO_FILL_RULE_WINDING. New entries may be added in future versions.
winding- If the path crosses the ray from
left-to-right, counts +1. If the path crosses the ray
from right to left, counts -1. (Left and right are determined
from the perspective of looking along the ray from the starting
point.) If the total count is non-zero, the point will be filled.
even-odd- Counts the total number of
intersections, without regard to the orientation of the contour. If
the total number of intersections is odd, the point will be
filled.
CairoLineCap-
Specifies how to render the endpoints of the path when stroking. The default line cap style is
CAIRO_LINE_CAP_BUTT.
butt- start(stop) the line exactly at the start(end) point
round- use a round ending, the center of the circle is the end point
square- use squared ending, the center of the square is the end point
CairoLineJoin-
Specifies how to render the junction of two lines when stroking. The default line join style is
CAIRO_LINE_JOIN_MITER.
miter- use a sharp (angled) corner, see
cairoSetMiterLimit round- use a rounded join, the center of the circle is the
joint point
bevel- use a cut-off join, the join is cut off at half
the line width from the joint point
CairoOperator-
CairoOperator is used to set the compositing operator for all cairo
drawing operations. The default operator is CAIRO_OPERATOR_OVER. The operators marked as unbounded modify their
destination even outside of the mask layer (that is, their effect is not
bound by the mask layer). However, their effect can still be limited by
way of clipping. To keep things simple, the operator descriptions here
document the behavior for when both source and destination are either fully
transparent or fully opaque. The actual implementation works for
translucent layers too.
For a more detailed explanation of the effects of each operator, including
the mathematical definitions, see
http://cairographics.org/operators/ (http://cairographics.org/operators/).
clear- clear destination layer (bounded)
source- replace destination layer (bounded)
over- draw source layer on top of destination layer
(bounded)
in- draw source where there was destination content
(unbounded)
out- draw source where there was no destination
content (unbounded)
atop- draw source on top of destination content and
only there
dest- ignore the source
dest-over- draw destination on top of source
dest-in- leave destination only where there was
source content (unbounded)
dest-out- leave destination only where there was no
source content
dest-atop- leave destination on top of source content
and only there (unbounded)
xor- source and destination are shown where there is only
one of them
add- source and destination layers are accumulated
saturate- like over, but assuming source and dest are
disjoint geometries