— Function: cairo-create (target <cairo-surface-t>) => (ret <cairo-t>)

Creates a new <cairo-t> with all graphics state parameters set to default values and with target as a target surface. The target surface should be constructed with a backend-specific function such as cairo-image-surface-create (or any other `cairo_<backend>_surface_create' variant).

target

target surface for the context

ret

a newly allocated <cairo-t>.

— Function: cairo-save (cr <cairo-t>)

Makes a copy of the current state of cr and saves it on an internal stack of saved states for cr. When cairo-restore is called, cr will be restored to the saved state. Multiple calls to cairo-save and cairo-restore can be nested; each call to cairo-restore restores the state from the matching paired cairo-save.

It isn't necessary to clear all saved states before a <cairo-t> is freed. If the reference count of a <cairo-t> drops to zero in response to a call to cairo-destroy, any saved states will be freed along with the <cairo-t>.

cr

a <cairo-t>

— Function: cairo-restore (cr <cairo-t>)

Restores cr to the state saved by a preceding call to cairo-save and removes that state from the stack of saved states.

cr

a <cairo-t>

— Function: cairo-get-target (cr <cairo-t>) =>  (ret <cairo-surface-t>)

Gets the target surface for the cairo context as passed to cairo-create.

This function will always return a valid pointer, but the result can be a "nil" surface if cr is already in an error state, (ie. cairo-status`!='`CAIRO_STATUS_SUCCESS'). A nil surface is indicated by cairo-surface-status`!='`CAIRO_STATUS_SUCCESS'.

cr

a cairo context

ret

the target surface. This object is owned by cairo. To keep a reference to it, you must call cairo-surface-reference.

— Function: cairo-push-group (cr <cairo-t>)

Temporarily redirects drawing to an intermediate surface known as a group. The redirection lasts until the group is completed by a call to cairo-pop-group or cairo-pop-group-to-source. These calls provide the result of any drawing to the group as a pattern, (either as an explicit object, or set as the source pattern).

This group functionality can be convenient for performing intermediate compositing. One common use of a group is to render objects as opaque within the group, (so that they occlude each other), and then blend the result with translucence onto the destination.

Groups can be nested arbitrarily deep by making balanced calls to cairo-push-group/cairo-pop-group. Each call pushes/pops the new target group onto/from a stack.

The cairo-push-group function calls cairo-save so that any changes to the graphics state will not be visible outside the group, (the pop_group functions call cairo-restore).

By default the intermediate group will have a content type of CAIRO_CONTENT_COLOR_ALPHA. Other content types can be chosen for the group by using cairo-push-group-with-content instead.

As an example, here is how one might fill and stroke a path with translucence, but without any portion of the fill being visible under the stroke:

          
          cairo_push_group (cr);
          cairo_set_source (cr, fill_pattern);
          cairo_fill_preserve (cr);
          cairo_set_source (cr, stroke_pattern);
          cairo_stroke (cr);
          cairo_pop_group_to_source (cr);
          cairo_paint_with_alpha (cr, alpha);
     

cr

a cairo context

Since 1.2

— Function: cairo-pop-group (cr <cairo-t>) =>  (ret <cairo-pattern-t>)

Terminates the redirection begun by a call to cairo-push-group or cairo-push-group-with-content and returns a new pattern containing the results of all drawing operations performed to the group.

The cairo-pop-group function calls cairo-restore, (balancing a call to cairo-save by the push_group function), so that any changes to the graphics state will not be visible outside the group.

cr

a cairo context

ret

a newly created (surface) pattern containing the results of all drawing operations performed to the group. The caller owns the returned object and should call cairo-pattern-destroy when finished with it.

Since 1.2

— Function: cairo-pop-group-to-source (cr <cairo-t>)

Terminates the redirection begun by a call to cairo-push-group or cairo-push-group-with-content and installs the resulting pattern as the source pattern in the given cairo context.

The behavior of this function is equivalent to the sequence of operations:

          
          cairo_pattern_t *group = cairo_pop_group (cr);
          cairo_set_source (cr, group);
          cairo_pattern_destroy (group);
     

but is more convenient as their is no need for a variable to store the short-lived pointer to the pattern.

The cairo-pop-group function calls cairo-restore, (balancing a call to cairo-save by the push_group function), so that any changes to the graphics state will not be visible outside the group.

cr

a cairo context

Since 1.2

— Function: cairo-get-group-target (cr <cairo-t>) =>  (ret <cairo-surface-t>)

Gets the target surface for the current group as started by the most recent call to cairo-push-group or cairo-push-group-with-content.

This function will return NULL if called "outside" of any group rendering blocks, (that is, after the last balancing call to cairo-pop-group or cairo-pop-group-to-source).

cr

a cairo context

ret

the target group surface, or NULL if none. This object is owned by cairo. To keep a reference to it, you must call cairo-surface-reference.

Since 1.2

— Function: cairo-set-source-rgb (cr <cairo-t>) (red <double>) (green <double>) (blue <double>)

Sets the source pattern within cr to an opaque color. This opaque color will then be used for any subsequent drawing operation until a new source pattern is set.

The color components are floating point numbers in the range 0 to 1. If the values passed in are outside that range, they will be clamped.

cr

a cairo context

red

red component of color

green

green component of color

blue

blue component of color

— Function: cairo-set-source-rgba (cr <cairo-t>) (red <double>) (green <double>) (blue <double>) (alpha <double>)

Sets the source pattern within cr to a translucent color. This color will then be used for any subsequent drawing operation until a new source pattern is set.

The color and alpha components are floating point numbers in the range 0 to 1. If the values passed in are outside that range, they will be clamped.

cr

a cairo context

red

red component of color

green

green component of color

blue

blue component of color

alpha

alpha component of color

— Function: cairo-set-source (cr <cairo-t>) (source <cairo-pattern-t>)

Sets the source pattern within cr to source. This pattern will then be used for any subsequent drawing operation until a new source pattern is set.

Note: The pattern's transformation matrix will be locked to the user space in effect at the time of cairo-set-source. This means that further modifications of the current transformation matrix will not affect the source pattern. See cairo-pattern-set-matrix.

XXX: I'd also like to direct the reader's attention to some (not-yet-written) section on cairo's imaging model. How would I do that if such a section existed? (cworth).

cr

a cairo context

source

a <cairo-pattern-t> to be used as the source for subsequent drawing operations.

— Function: cairo-set-source-surface (cr <cairo-t>) (surface <cairo-surface-t>) (x <double>) (y <double>)

This is a convenience function for creating a pattern from surface and setting it as the source in cr with cairo-set-source.

The x and y parameters give the user-space coordinate at which the surface origin should appear. (The surface origin is its upper-left corner before any transformation has been applied.) The x and y patterns are negated and then set as translation values in the pattern matrix.

Other than the initial translation pattern matrix, as described above, all other pattern attributes, (such as its extend mode), are set to the default values as in cairo-pattern-create-for-surface. The resulting pattern can be queried with cairo-get-source so that these attributes can be modified if desired, (eg. to create a repeating pattern with cairo-pattern-set-extend).

cr

a cairo context

surface

a surface to be used to set the source pattern

x

User-space X coordinate for surface origin

y

User-space Y coordinate for surface origin

— Function: cairo-get-source (cr <cairo-t>) =>  (ret <cairo-pattern-t>)

Gets the current source pattern for cr.

cr

a cairo context

ret

the current source pattern. This object is owned by cairo. To keep a reference to it, you must call cairo-pattern-reference.

— Function: cairo-set-antialias (cr <cairo-t>) (antialias <cairo-antialias-t>)

Set the antialiasing mode of the rasterizer used for drawing shapes. This value is a hint, and a particular backend may or may not support a particular value. At the current time, no backend supports `CAIRO_ANTIALIAS_SUBPIXEL' when drawing shapes.

Note that this option does not affect text rendering, instead see cairo-font-options-set-antialias.

cr

a <cairo-t>

antialias

the new antialiasing mode

— Function: cairo-get-antialias (cr <cairo-t>) =>  (ret <cairo-antialias-t>)

Gets the current shape antialiasing mode, as set by cairo-set-shape-antialias.

cr

a cairo context

ret

the current shape antialiasing mode.

— Function: cairo-set-dash (cr <cairo-t>) =>  (dashes <double>) (num-dashes <int>) (offset <double>)

Sets the dash pattern to be used by cairo-stroke. A dash pattern is specified by dashes, an array of positive values. Each value provides the length of alternate "on" and "off" portions of the stroke. The offset specifies an offset into the pattern at which the stroke begins.

Each "on" segment will have caps applied as if the segment were a separate sub-path. In particular, it is valid to use an "on" length of 0.0 with CAIRO_LINE_CAP_ROUND or CAIRO_LINE_CAP_SQUARE in order to distributed dots or squares along a path.

Note: The length values are in user-space units as evaluated at the time of stroking. This is not necessarily the same as the user space at the time of cairo-set-dash.

If num-dashes is 0 dashing is disabled.

If num-dashes is 1 a symmetric pattern is assumed with alternating on and off portions of the size specified by the single value in dashes.

If any value in dashes is negative, or if all values are 0, then cairo-t will be put into an error state with a status of <cairo-status-invalid-dash>.

cr

a cairo context

dashes

an array specifying alternate lengths of on and off stroke portions

num-dashes

the length of the dashes array

offset

an offset into the dash pattern at which the stroke should start

— Function: cairo-get-dash-count (cr <cairo-t>) =>  (ret <int>)

This function returns the length of the dash array in cr (0 if dashing is not currently in effect).

See also cairo-set-dash and cairo-get-dash.

cr

a <cairo-t>

ret

the length of the dash array, or 0 if no dash array set.

Since 1.4

— Function: cairo-set-fill-rule (cr <cairo-t>) (fill-rule <cairo-fill-rule-t>)

Set the current fill rule within the cairo context. The fill rule is used to determine which regions are inside or outside a complex (potentially self-intersecting) path. The current fill rule affects both cairo_fill and cairo_clip. See <cairo-fill-rule-t> for details on the semantics of each available fill rule.

cr

a <cairo-t>

fill-rule

a fill rule, specified as a <cairo-fill-rule-t>

— Function: cairo-get-fill-rule (cr <cairo-t>) =>  (ret <cairo-fill-rule-t>)

Gets the current fill rule, as set by cairo-set-fill-rule.

cr

a cairo context

ret

the current fill rule.

— Function: cairo-set-line-cap (cr <cairo-t>) (line-cap <cairo-line-cap-t>)

Sets the current line cap style within the cairo context. See <cairo-line-cap-t> for details about how the available line cap styles are drawn.

As with the other stroke parameters, the current line cap style is examined by cairo-stroke, cairo-stroke-extents, and cairo-stroke-to-path, but does not have any effect during path construction.

cr

a cairo context

line-cap

a line cap style

— Function: cairo-get-line-cap (cr <cairo-t>) =>  (ret <cairo-line-cap-t>)

Gets the current line cap style, as set by cairo-set-line-cap.

cr

a cairo context

ret

the current line cap style.

— Function: cairo-set-line-join (cr <cairo-t>) (line-join <cairo-line-join-t>)

Sets the current line join style within the cairo context. See <cairo-line-join-t> for details about how the available line join styles are drawn.

As with the other stroke parameters, the current line join style is examined by cairo-stroke, cairo-stroke-extents, and cairo-stroke-to-path, but does not have any effect during path construction.

cr

a cairo context

line-join

a line joint style

— Function: cairo-get-line-join (cr <cairo-t>) =>  (ret <cairo-line-join-t>)

Gets the current line join style, as set by cairo-set-line-join.

cr

a cairo context

ret

the current line join style.

— Function: cairo-set-line-width (cr <cairo-t>) (width <double>)

Sets the current line width within the cairo context. The line width value specifies the diameter of a pen that is circular in user space, (though device-space pen may be an ellipse in general due to scaling/shear/rotation of the CTM).

Note: When the description above refers to user space and CTM it refers to the user space and CTM in effect at the time of the stroking operation, not the user space and CTM in effect at the time of the call to cairo-set-line-width. The simplest usage makes both of these spaces identical. That is, if there is no change to the CTM between a call to cairo-set-line-with and the stroking operation, then one can just pass user-space values to cairo-set-line-width and ignore this note.

As with the other stroke parameters, the current line width is examined by cairo-stroke, cairo-stroke-extents, and cairo-stroke-to-path, but does not have any effect during path construction.

The default line width value is 2.0.

cr

a <cairo-t>

width

a line width

— Function: cairo-get-line-width (cr <cairo-t>) =>  (ret <double>)

This function returns the current line width value exactly as set by cairo-set-line-width. Note that the value is unchanged even if the CTM has changed between the calls to cairo-set-line-width and cairo-get-line-width.

cr

a cairo context

ret

the current line width.

— Function: cairo-set-miter-limit (cr <cairo-t>) (limit <double>)

Sets the current miter limit within the cairo context.

If the current line join style is set to `CAIRO_LINE_JOIN_MITER' (see cairo-set-line-join), the miter limit is used to determine whether the lines should be joined with a bevel instead of a miter. Cairo divides the length of the miter by the line width. If the result is greater than the miter limit, the style is converted to a bevel.

As with the other stroke parameters, the current line miter limit is examined by cairo-stroke, cairo-stroke-extents, and cairo-stroke-to-path, but does not have any effect during path construction.

cr

a cairo context

limit

miter limit to set

— Function: cairo-get-miter-limit (cr <cairo-t>) =>  (ret <double>)

Gets the current miter limit, as set by cairo-set-miter-limit.

cr

a cairo context

ret

the current miter limit.

— Function: cairo-set-operator (cr <cairo-t>) (op <cairo-operator-t>)

Sets the compositing operator to be used for all drawing operations. See <cairo-operator-t> for details on the semantics of each available compositing operator.

XXX: I'd also like to direct the reader's attention to some (not-yet-written) section on cairo's imaging model. How would I do that if such a section existed? (cworth).

cr

a <cairo-t>

op

a compositing operator, specified as a <cairo-operator-t>

— Function: cairo-get-operator (cr <cairo-t>) =>  (ret <cairo-operator-t>)

Gets the current compositing operator for a cairo context.

cr

a cairo context

ret

the current compositing operator.

— Function: cairo-set-tolerance (cr <cairo-t>) (tolerance <double>)

Sets the tolerance used when converting paths into trapezoids. Curved segments of the path will be subdivided until the maximum deviation between the original path and the polygonal approximation is less than tolerance. The default value is 0.1. A larger value will give better performance, a smaller value, better appearance. (Reducing the value from the default value of 0.1 is unlikely to improve appearance significantly.)

cr

a <cairo-t>

tolerance

the tolerance, in device units (typically pixels)

— Function: cairo-get-tolerance (cr <cairo-t>) =>  (ret <double>)

Gets the current tolerance value, as set by cairo-set-tolerance.

cr

a cairo context

ret

the current tolerance value.

— Function: cairo-clip (cr <cairo-t>)

Establishes a new clip region by intersecting the current clip region with the current path as it would be filled by cairo-fill and according to the current fill rule (see cairo-set-fill-rule).

After cairo_clip, the current path will be cleared from the cairo context.

The current clip region affects all drawing operations by effectively masking out any changes to the surface that are outside the current clip region.

Calling cairo-clip can only make the clip region smaller, never larger. But the current clip is part of the graphics state, so a temporary restriction of the clip region can be achieved by calling cairo-clip within a cairo-save/cairo-restore pair. The only other means of increasing the size of the clip region is cairo-reset-clip.

cr

a cairo context

— Function: cairo-clip-preserve (cr <cairo-t>)

Establishes a new clip region by intersecting the current clip region with the current path as it would be filled by cairo-fill and according to the current fill rule (see cairo-set-fill-rule).

Unlike cairo-clip, cairo_clip_preserve preserves the path within the cairo context.

The current clip region affects all drawing operations by effectively masking out any changes to the surface that are outside the current clip region.

Calling cairo-clip can only make the clip region smaller, never larger. But the current clip is part of the graphics state, so a temporary restriction of the clip region can be achieved by calling cairo-clip within a cairo-save/cairo-restore pair. The only other means of increasing the size of the clip region is cairo-reset-clip.

cr

a cairo context

— Function: cairo-clip-extents (cr <cairo-t>) =>  (x1 <double>) (y1 <double>) (x2 <double>) (y2 <double>)

Computes a bounding box in user coordinates covering the area inside the current clip.

cr

a cairo context

x1

left of the resulting extents

y1

top of the resulting extents

x2

right of the resulting extents

y2

bottom of the resulting extents

Since 1.4

— Function: cairo-reset-clip (cr <cairo-t>)

Reset the current clip region to its original, unrestricted state. That is, set the clip region to an infinitely large shape containing the target surface. Equivalently, if infinity is too hard to grasp, one can imagine the clip region being reset to the exact bounds of the target surface.

Note that code meant to be reusable should not call cairo-reset-clip as it will cause results unexpected by higher-level code which calls cairo-clip. Consider using cairo-save and cairo-restore around cairo-clip as a more robust means of temporarily restricting the clip region.

cr

a cairo context

— Function: cairo-copy-clip-rectangle-list (cr <cairo-t>) =>  (ret <cairo-rectangle-list-t>)

Gets the current clip region as a list of rectangles in user coordinates. Never returns `#f'.

The status in the list may be CAIRO_STATUS_CLIP_NOT_REPRESENTABLE to indicate that the clip region cannot be represented as a list of user-space rectangles. The status may have other values to indicate other errors.

The caller must always call cairo_rectangle_list_destroy on the result of this function.

cr

a cairo context

ret

the current clip region as a list of rectangles in user coordinates.

Since 1.4

— Function: cairo-fill (cr <cairo-t>)

A drawing operator that fills the current path according to the current fill rule, (each sub-path is implicitly closed before being filled). After cairo_fill, the current path will be cleared from the cairo context. See cairo-set-fill-rule and cairo-fill-preserve.

cr

a cairo context

— Function: cairo-fill-preserve (cr <cairo-t>)

A drawing operator that fills the current path according to the current fill rule, (each sub-path is implicitly closed before being filled). Unlike cairo-fill, cairo_fill_preserve preserves the path within the cairo context.

See cairo-set-fill-rule and cairo-fill.

cr

a cairo context

— Function: cairo-fill-extents (cr <cairo-t>) =>  (x1 <double>) (y1 <double>) (x2 <double>) (y2 <double>)

Computes a bounding box in user coordinates covering the area that would be affected by a cairo-fill operation given the current path and fill parameters. If the current path is empty, returns an empty rectangle (0,0, 0,0). Surface dimensions and clipping are not taken into account.

See cairo-fill, cairo-set-fill-rule and cairo-fill-preserve.

cr

a cairo context

x1

left of the resulting extents

y1

top of the resulting extents

x2

right of the resulting extents

y2

bottom of the resulting extents

— Function: cairo-in-fill (cr <cairo-t>) (x <double>) (y <double>) =>  (ret <cairo-bool-t>)

Tests whether the given point is inside the area that would be affected by a cairo-fill operation given the current path and filling parameters. Surface dimensions and clipping are not taken into account.

See cairo-fill, cairo-set-fill-rule and cairo-fill-preserve.

cr

a cairo context

x

X coordinate of the point to test

y

Y coordinate of the point to test

ret

A non-zero value if the point is inside, or zero if outside.

— Function: cairo-mask (cr <cairo-t>) (pattern <cairo-pattern-t>)

A drawing operator that paints the current source using the alpha channel of pattern as a mask. (Opaque areas of pattern are painted with the source, transparent areas are not painted.)

cr

a cairo context

pattern

a <cairo-pattern-t>

— Function: cairo-mask-surface (cr <cairo-t>) (surface <cairo-surface-t>) (surface-x <double>) (surface-y <double>)

A drawing operator that paints the current source using the alpha channel of surface as a mask. (Opaque areas of surface are painted with the source, transparent areas are not painted.)

cr

a cairo context

surface

a <cairo-surface-t>

surface-x

X coordinate at which to place the origin of surface

surface-y

Y coordinate at which to place the origin of surface

— Function: cairo-paint (cr <cairo-t>)

A drawing operator that paints the current source everywhere within the current clip region.

cr

a cairo context

— Function: cairo-paint-with-alpha (cr <cairo-t>) (alpha <double>)

A drawing operator that paints the current source everywhere within the current clip region using a mask of constant alpha value alpha. The effect is similar to cairo-paint, but the drawing is faded out using the alpha value.

cr

a cairo context

alpha

alpha value, between 0 (transparent) and 1 (opaque)

— Function: cairo-stroke (cr <cairo-t>)

A drawing operator that strokes the current path according to the current line width, line join, line cap, and dash settings. After cairo_stroke, the current path will be cleared from the cairo context. See cairo-set-line-width, cairo-set-line-join, cairo-set-line-cap, cairo-set-dash, and cairo-stroke-preserve.

Note: Degenerate segments and sub-paths are treated specially and provide a useful result. These can result in two different situations:

1. Zero-length "on" segments set in cairo-set-dash. If the cap style is CAIRO_LINE_CAP_ROUND or CAIRO_LINE_CAP_SQUARE then these segments will be drawn as circular dots or squares respectively. In the case of CAIRO_LINE_CAP_SQUARE, the orientation of the squares is determined by the direction of the underlying path.

2. A sub-path created by cairo-move-to followed by either a cairo-close-path or one or more calls to cairo-line-to to the same coordinate as the cairo-move-to. If the cap style is CAIRO_LINE_CAP_ROUND then these sub-paths will be drawn as circular dots. Note that in the case of CAIRO_LINE_CAP_SQUARE a degenerate sub-path will not be drawn at all, (since the correct orientation is indeterminate).

In no case will a cap style of CAIRO_LINE_CAP_BUTT cause anything to be drawn in the case of either degenerate segments or sub-paths.

cr

a cairo context

— Function: cairo-stroke-preserve (cr <cairo-t>)

A drawing operator that strokes the current path according to the current line width, line join, line cap, and dash settings. Unlike cairo-stroke, cairo_stroke_preserve preserves the path within the cairo context.

See cairo-set-line-width, cairo-set-line-join, cairo-set-line-cap, cairo-set-dash, and cairo-stroke-preserve.

cr

a cairo context

— Function: cairo-stroke-extents (cr <cairo-t>) =>  (x1 <double>) (y1 <double>) (x2 <double>) (y2 <double>)

Computes a bounding box in user coordinates covering the area that would be affected by a cairo-stroke operation operation given the current path and stroke parameters. If the current path is empty,

cr

a cairo context

x1

left of the resulting extents

y1

top of the resulting extents

x2

right of the resulting extents

y2

bottom of the resulting extents

— Function: cairo-in-stroke (cr <cairo-t>) (x <double>) (y <double>) =>  (ret <cairo-bool-t>)

Tests whether the given point is inside the area that would be affected by a cairo-stroke operation given the current path and stroking parameters. Surface dimensions and clipping are not taken into account.

See cairo-stroke, cairo-set-line-width, cairo-set-line-join, cairo-set-line-cap, cairo-set-dash, and cairo-stroke-preserve.

cr

a cairo context

x

X coordinate of the point to test

y

Y coordinate of the point to test

ret

A non-zero value if the point is inside, or zero if outside.

— Function: cairo-copy-page (cr <cairo-t>)

Emits the current page for backends that support multiple pages, but doesn't clear it, so, the contents of the current page will be retained for the next page too. Use cairo-show-page if you want to get an empty page after the emission.

cr

a cairo context

— Function: cairo-show-page (cr <cairo-t>)

Emits and clears the current page for backends that support multiple pages. Use cairo-copy-page if you don't want to clear the page.

cr

a cairo context