Module org.freedesktop.cairo

Package org.freedesktop.cairo

Class Context

java.lang.Object

io.github.jwharm.cairobindings.Proxy

org.freedesktop.cairo.Context

public final class Context
extends Proxy

The cairo drawing context.

Context is the main object used when drawing with cairo. To draw with cairo, you create a Context, set the target surface, and drawing options for the Context, create shapes with functions like moveTo(double, double) and lineTo(double, double), and then draw shapes with stroke() or fill().

Context's can be pushed to a stack via save(). They may then safely be changed, without losing the current state. Use restore() to restore to the saved state.

The functions with text in their name form cairo's toy text API. The toy API takes UTF-8 encoded text and is limited in its functionality to rendering simple left-to-right text with no advanced features. That means for example that most complex scripts like Hebrew, Arabic, and Indic scripts are out of question. No kerning or correct positioning of diacritical marks either. The font selection is pretty limited too and doesn't handle the case that the selected font does not cover the characters in the text. This set of functions are really that, a toy text API, for testing and demonstration purposes. Any serious application should avoid them.

The functions with glyphs in their name form cairo's low-level text API. The low-level API relies on the user to convert text to a set of glyph indexes and positions. This is a very hard problem and is best handled by external libraries, like the pangocairo that is part of the Pango text layout and rendering library.

The tag functions (tagBegin(String, String) and tagEnd(String)) provide the ability to specify hyperlinks and document logical structure on supported backends. The following tags are supported:

• Link - Create a hyperlink
• Destinations - Create a hyperlink destination
• Document Structure Tags - Create PDF Document Structure

Since:

1.0

Field Summary

Fields

Modifier and Type	Field	Description
static final String	TAG_CONTENT	Create a content tag.
static final String	TAG_CONTENT_REF	Create a content reference tag.
static final String	TAG_DEST	Create a destination for a hyperlink.
static final String	TAG_LINK	Create hyperlink.

Constructor Summary

Constructors

Constructor	Description
Context(MemorySegment address)	Constructor used internally to instantiate a java Context object for a native cairo_t instance

Method Summary

Modifier and Type	Method	Description
Context	appendPath(Path path)	Append the path onto the current path.
Context	arc(double xc, double yc, double radius, double angle1, double angle2)	Adds a circular arc of the given radius to the current path.
Context	arcNegative(double xc, double yc, double radius, double angle1, double angle2)	Adds a circular arc of the given radius to the current path.
Context	clip()	Establishes a new clip region by intersecting the current clip region with the current path as it would be filled by fill() and according to the current fill rule (see setFillRule(FillRule)).
Rect	clipExtents()	Computes a bounding box in user coordinates covering the area inside the current clip.
Context	clipPreserve()	Establishes a new clip region by intersecting the current clip region with the current path as it would be filled by fill() and according to the current fill rule (see setFillRule(FillRule)).
Context	closePath()	Adds a line segment to the path from the current point to the beginning of the current sub-path, (the most recent point passed to moveTo(double, double)), and closes this sub-path.
RectangleList	copyClipRectangleList()	Gets the current clip region as a list of rectangles in user coordinates.
Context	copyPage()	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.
Path	copyPath()	Creates a copy of the current path and returns it to the user as a Path.
Path	copyPathFlat()	Gets a flattened copy of the current path and returns it to the user as a Path.
static Context	create(Surface target)	Creates a new Context with all graphics state parameters set to default values and with target as a target surface.
Context	curveTo(double x1, double y1, double x2, double y2, double x3, double y3)	Adds a cubic Bézier spline to the path from the current point to position (x3, y3) in user-space coordinates, using (x1 , y1) and (x2, y2) as the control points.
void	destroy()	Invokes the cleanup action that is normally invoked during garbage collection.
Point	deviceToUser(Point point)	Transform a coordinate from device space to user space by multiplying the given point by the inverse of the current transformation matrix (CTM).
Point	deviceToUserDistance(Point point)	Transform a distance vector from device space to user space.
Context	fill()	A drawing operator that fills the current path according to the current fill rule, (each sub-path is implicitly closed before being filled).
Rect	fillExtents()	Computes a bounding box in user coordinates covering the area that would be affected, (the "inked" area), by a fill() operation given the current path and fill parameters.
Context	fillPreserve()	A drawing operator that fills the current path according to the current fill rule, (each sub-path is implicitly closed before being filled).
void	fontExtents(FontExtents extents)	Gets the font extents for the currently selected font.
Antialias	getAntialias()	Gets the current shape antialiasing mode, as set by setAntialias(Antialias).
Point	getCurrentPoint()	Gets the current point of the current path, which is conceptually the final point reached by the path so far.
double[]	getDash()	Gets the current dash array.
int	getDashCount()	This function returns the length of the dash array in the context (0 if dashing is not currently in effect).
double	getDashOffset()	Gets the current offset into the dash array.
FillRule	getFillRule()	Gets the current fill rule, as set by setFillRule(FillRule).
FontFace	getFontFace()	Gets the current font face for a Context.
void	getFontMatrix(Matrix matrix)	Stores the current font matrix into matrix.
FontOptions	getFontOptions()	Retrieves font rendering options set via setFontOptions(FontOptions).
Surface	getGroupTarget()	Gets the current destination surface for the context.
boolean	getHairLine()	Returns whether or not hairline mode is set, as set by setHairLine(boolean).
LineCap	getLineCap()	Gets the current line cap style, as set by setLineCap(LineCap).
LineJoin	getLineJoin()	Gets the current line join style, as set by setLineJoin(LineJoin).
double	getLineWidth()	This function returns the current line width value exactly as set by setLineWidth(double).
void	getMatrix(Matrix matrix)	Stores the current transformation matrix (CTM) into matrix.
double	getMiterLimit()	Gets the current miter limit, as set by setMiterLimit(double).
Operator	getOperator()	Gets the current compositing operator for a cairo context.
ScaledFont	getScaledFont()	Gets the current scaled font
SurfacePattern	getSource()	Gets the current source pattern.
Surface	getTarget()	Gets the target surface for the cairo context as passed to create(Surface).
double	getTolerance()	Gets the current tolerance value, as set by setTolerance(double).
static org.gnome.glib.Type	getType()	Get the CairoContext GType
MemorySegment	getUserData(UserDataKey key)	Return user data previously attached to the context using the specified key.
void	glyphExtents(Glyphs glyphs, TextExtents extents)	Gets the extents for an array of glyphs.
Context	glyphPath(Glyphs glyphs)	Adds closed paths for the glyphs to the current path.
boolean	hasCurrentPoint()	Returns whether a current point is defined on the current path.
Context	identityMatrix()	Resets the current transformation matrix (CTM) by setting it equal to the identity matrix.
boolean	inClip(double x, double y)	Tests whether the given point is inside the area that would be visible through the current clip, i.e.
boolean	inFill(double x, double y)	Tests whether the given point is inside the area that would be affected by a fill() operation given the current path and filling parameters.
boolean	inStroke(double x, double y)	Tests whether the given point is inside the area that would be affected by a stroke() operation given the current path and stroking parameters.
Context	lineTo(double x, double y)	Adds a line to the path from the current point to position (x, y) in user-space coordinates.
Context	mask(Pattern pattern)	A drawing operator that paints the current source using the alpha channel of pattern as a mask.
Context	mask(Surface surface, double surfaceX, double surfaceY)	A drawing operator that paints the current source using the alpha channel of surface as a mask.
Context	moveTo(double x, double y)	Begin a new sub-path.
Context	newPath()	Clears the current path.
Context	newSubPath()	Begin a new sub-path.
Context	paint()	A drawing operator that paints the current source everywhere within the current clip region.
Context	paintWithAlpha(double alpha)	A drawing operator that paints the current source everywhere within the current clip region using a mask of constant alpha value alpha.
Rect	pathExtents()	Computes a bounding box in user-space coordinates covering the points on the current path.
SurfacePattern	popGroup()	Terminates the redirection begun by a call to pushGroup() or pushGroupWithContent(Content) and returns a new pattern containing the results of all drawing operations performed to the group.
Context	popGroupToSource()	Terminates the redirection begun by a call to pushGroup() or pushGroupWithContent(Content) and installs the resulting pattern as the source pattern in the given cairo context.
Context	pushGroup()	Temporarily redirects drawing to an intermediate surface known as a group.
Context	pushGroupWithContent(Content content)	Temporarily redirects drawing to an intermediate surface known as a group.
Context	rectangle(double x, double y, double width, double height)	Adds a closed sub-path rectangle of the given size to the current path at position (x, y) in user-space coordinates.
Context	relCurveTo(double dx1, double dy1, double dx2, double dy2, double dx3, double dy3)	Relative-coordinate version of curveTo(double, double, double, double, double, double).
Context	relLineTo(double dx, double dy)	Relative-coordinate version of lineTo(double, double).
Context	relMoveTo(double dx, double dy)	Begin a new sub-path.
Context	resetClip()	Reset the current clip region to its original, unrestricted state.
Context	restore()	Restores the context to the state saved by a preceding call to save() and removes that state from the stack of saved states.
Context	rotate(double angle)	Modifies the current transformation matrix (CTM) by rotating the user-space axes by angle radians.
Context	save()	Makes a copy of the current state of the context and saves it on an internal stack of saved states for the context.
Context	scale(double sx, double sy)	Modifies the current transformation matrix (CTM) by scaling the X and Y user-space axes by sx and sy respectively.
Context	selectFontFace(String family, FontSlant slant, FontWeight weight)	Note: The selectFontFace() method is part of what the cairo designers call the "toy" text API.
Context	setAntialias(Antialias antialias)	Set the antialiasing mode of the rasterizer used for drawing shapes.
Context	setDash(double[] dash, double offset)	Sets the dash pattern to be used by stroke().
Context	setFillRule(FillRule fillRule)	Set the current fill rule within the cairo context.
Context	setFontFace(FontFace fontFace)	Replaces the current FontFace object in the Context with fontFace.
Context	setFontMatrix(Matrix matrix)	Sets the current font matrix to matrix.
Context	setFontOptions(FontOptions options)	Sets a set of custom font rendering options for the Context.
Context	setFontSize(double size)	Sets the current font matrix to a scale by a factor of size, replacing any font matrix previously set with setFontSize() or setFontMatrix(Matrix).
Context	setHairLine(boolean setHairline)	Sets lines within the cairo context to be hairlines.
Context	setLineCap(LineCap lineCap)	Sets the current line cap style within the cairo context.
Context	setLineJoin(LineJoin lineJoin)	Sets the current line join style within the cairo context.
Context	setLineWidth(double width)	Sets the current line width within the cairo context.
Context	setMatrix(Matrix matrix)	Modifies the current transformation matrix (CTM) by setting it equal to matrix.
Context	setMiterLimit(double limit)	Sets the current miter limit within the cairo context.
Context	setOperator(Operator op)	Sets the compositing operator to be used for all drawing operations.
Context	setScaledFont(ScaledFont scaledFont)	Replaces the current font face, font matrix, and font options in the Context with those of the ScaledFont.
Context	setSource(Pattern source)	Sets the source pattern within the context to source.
Context	setSource(Surface surface, double x, double y)	This is a convenience function for creating a pattern from surface and setting it as the source with setSource(Pattern).
Context	setSourceRGB(double red, double green, double blue)	Sets the source pattern within the context to an opaque color.
Context	setSourceRGBA(double red, double green, double blue, double alpha)	Sets the source pattern within the context to a translucent color.
Context	setTolerance(double tolerance)	Sets the tolerance used when converting paths into trapezoids.
UserDataKey	setUserData(UserDataKey key, MemorySegment userData)	Attach user data to the context.
Context	showGlyphs(Glyphs glyphs)	A drawing operator that generates the shape from an array of glyphs, rendered according to the current fontFace, fontSize (fontMatrix), and fontOptions.
Context	showPage()	Emits and clears the current page for backends that support multiple pages.
Context	showText(String string)	A drawing operator that generates the shape from a string of characters, rendered according to the current fontFace, fontSize (fontMatrix), and fontOptions.
Context	showTextGlyphs(String string, Glyphs glyphs)	This operation has rendering effects similar to showGlyphs(org.freedesktop.cairo.Glyphs) but, if the target surface supports it, uses the provided text and cluster mapping to embed the text for the glyphs shown in the output.
Status	status()	Checks whether an error has previously occurred for this context.
Context	stroke()	A drawing operator that strokes the current path according to the current line width, line join, line cap, and dash settings.
Rect	strokeExtents()	Computes a bounding box in user coordinates covering the area that would be affected, (the "inked" area), by a stroke() operation given the current path and stroke parameters.
Context	strokePreserve()	A drawing operator that strokes the current path according to the current line width, line join, line cap, and dash settings.
Context	tagBegin(String tagName, String attributes)	Marks the beginning of the tag_name structure.
Context	tagEnd(String tagName)	Marks the end of the tag_name structure.
void	textExtents(String string, TextExtents extents)	Gets the extents for a string of text.
Context	textPath(String string)	Adds closed paths for text to the current path.
Context	transform(Matrix matrix)	Modifies the current transformation matrix (CTM) by applying matrix as an additional transformation.
Context	translate(double tx, double ty)	Modifies the current transformation matrix (CTM) by translating the user-space origin by (tx, ty).
Point	userToDevice(Point point)	Transform a coordinate from user space to device space by multiplying the given point by the current transformation matrix (CTM).
Point	userToDeviceDistance(Point point)	Transform a distance vector from user space to device space.

Methods inherited from class io.github.jwharm.cairobindings.Proxy

equals, handle, hashCode

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Field Details

TAG_DEST

public static final String TAG_DEST

Create a destination for a hyperlink. Destination tag attributes are detailed at Destinations.

Since:

1.16

See Also:

• tagBegin(String, String)
• Constant Field Values

TAG_LINK

public static final String TAG_LINK

Create hyperlink. Link tag attributes are detailed at Links.

Since:

1.16

See Also:

• tagBegin(String, String)
• Constant Field Values

TAG_CONTENT

public static final String TAG_CONTENT

Create a content tag.

Since:

1.18

See Also:

• tagBegin(String, String)
• Constant Field Values

TAG_CONTENT_REF

public static final String TAG_CONTENT_REF

Create a content reference tag.

Since:

1.18

See Also:

• tagBegin(String, String)
• Constant Field Values

Constructor Details

Context

public Context(MemorySegment address)

Constructor used internally to instantiate a java Context object for a native cairo_t instance

Parameters:

address - the memory address of the native cairo_t instance

Method Details

destroy

public void destroy()

Invokes the cleanup action that is normally invoked during garbage collection. If the instance is "owned" by the user, the destroy() function is run to dispose the native instance.

create

public static Context create(Surface target)
                      throws IOException

Creates a new Context 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 ImageSurface.create(Format, int, int) (or any other backend surface create() variant).

Parameters:

target - target surface for the context

Returns:

a newly allocated Context

Throws:

IOException - attempt to target a surface that does not support writing

Since:

1.0

status

public Status status()

Checks whether an error has previously occurred for this context.

Returns:

the current status of this context, see Status

Since:

1.0

save

public Context save()

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

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

Returns:

the context

Since:

1.0

restore

public Context restore()

Restores the context to the state saved by a preceding call to save() and removes that state from the stack of saved states.

Returns:

the context

Since:

1.0

getTarget

public Surface getTarget()

Gets the target surface for the cairo context as passed to create(Surface).

Returns:

the target surface.

Since:

1.0

pushGroup

public Context pushGroup()

Temporarily redirects drawing to an intermediate surface known as a group. The redirection lasts until the group is completed by a call to popGroup() or popGroupToSource(). 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 pushGroup() /popGroup(). Each call pushes/pops the new target group onto/from a stack.

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

By default the intermediate group will have a content type of Content.COLOR_ALPHA. Other content types can be chosen for the group by using pushGroupWithContent(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:

 cr.pushGroup()
   .setSource(fillPattern)
   .fillPreserve()
   .setSource(strokePattern)
   .stroke()
   .popGroupToSource()
   .paintWithAlpha(alpha);
 

Returns:

the context

Since:

1.2

pushGroupWithContent

public Context pushGroupWithContent(Content content)

Temporarily redirects drawing to an intermediate surface known as a group. The redirection lasts until the group is completed by a call to popGroup() or popGroupToSource(). 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).

The group will have a content type of content . The ability to control this content type is the only distinction between this function and pushGroup() which you should see for a more detailed description of group rendering.

Parameters:

content - a Content indicating the type of group that will be created

Returns:

the context

Since:

1.2

popGroup

public SurfacePattern popGroup()

Terminates the redirection begun by a call to pushGroup() or pushGroupWithContent(Content) and returns a new pattern containing the results of all drawing operations performed to the group.

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

Returns:

a newly created (surface) pattern containing the results of all drawing operations performed to the group.

Since:

1.2

popGroupToSource

public Context popGroupToSource()

Terminates the redirection begun by a call to pushGroup() or pushGroupWithContent(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:

 SurfacePattern group = cr.popGroup();
 cr.setSource(group);
 

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

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

Returns:

the context

Since:

1.2

getGroupTarget

public Surface getGroupTarget()

Gets the current destination surface for the context. This is either the original target surface as passed to create(Surface) or the target surface for the current group as started by the most recent call to pushGroup() or pushGroupWithContent(Content).

Returns:

the target surface

Since:

1.2

setSourceRGB

public Context setSourceRGB(double red,
 double green,
 double blue)

Sets the source pattern within the context 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.

The default source pattern is opaque black, (that is, it is equivalent to setSourceRGB(0.0, 0.0, 0.0)).

Parameters:

red - red component of color

green - green component of color

blue - blue component of color

Returns:

the context

Since:

1.0

setSourceRGBA

public Context setSourceRGBA(double red,
 double green,
 double blue,
 double alpha)

Sets the source pattern within the context 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.

Note that the color and alpha values are not premultiplied.

The default source pattern is opaque black, (that is, it is equivalent to setSourceRGBA(0.0, 0.0, 0.0, 1.0)).

Parameters:

red - red component of color

green - green component of color

blue - blue component of color

alpha - alpha component of color

Returns:

the context

Since:

1.0

setSource

public Context setSource(Pattern source)

Sets the source pattern within the context 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 setSource(). This means that further modifications of the current transformation matrix will not affect the source pattern. See Pattern.setMatrix(Matrix).

The default source pattern is a solid pattern that is opaque black, (that is, it is equivalent to setSourceRGB(0.0, 0.0, 0.0)).

Parameters:

source - a Pattern to be used as the source for subsequent drawing operations.

Returns:

the context

Since:

1.0

setSource

public Context setSource(Surface surface,
 double x,
 double y)

This is a convenience function for creating a pattern from surface and setting it as the source with setSource(Pattern).

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 parameters 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 SurfacePattern.create(Surface). The resulting pattern can be queried with getSource() so that these attributes can be modified if desired, (eg. to create a repeating pattern with Pattern.setExtend(Extend)).

Parameters:

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

Returns:

the context

Since:

1.0

getSource

public SurfacePattern getSource()

Gets the current source pattern.

Returns:

the current source pattern.

Since:

1.0

setAntialias

public Context setAntialias(Antialias antialias)

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 Antialias.SUBPIXEL when drawing shapes.

Note that this option does not affect text rendering, instead see cairo_font_options_set_antialias().

Parameters:

antialias - the new antialiasing mode

Returns:

the context

Since:

1.0

getAntialias

public Antialias getAntialias()

Gets the current shape antialiasing mode, as set by setAntialias(Antialias).

Returns:

the current shape antialiasing mode.

Since:

1.0

setDash

public Context setDash(double[] dash,
 double offset)
                throws IllegalArgumentException

Sets the dash pattern to be used by 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 LineCap.ROUND or LineCap.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 setDash().

If dashes.length is 0 dashing is disabled.

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

Parameters:

dash - an array specifying alternate lengths of on and off stroke portions

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

Returns:

the context

Throws:

IllegalArgumentException - if any value in dashes is negative, or if all values are 0

Since:

1.0

getDashCount

public int getDashCount()

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

See also setDash(double[], double) and getDash().

Returns:

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

Since:

1.4

getDash

public double[] getDash()

Gets the current dash array.

See also getDashOffset().

Returns:

the dash array

Since:

1.4

getDashOffset

public double getDashOffset()

Gets the current offset into the dash array.

See also getDash()

Returns:

the offset

Since:

1.4

setFillRule

public Context setFillRule(FillRule fillRule)

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 fill() and clip(). See FillRule for details on the semantics of each available fill rule.

The default fill rule is FillRule.WINDING.

Parameters:

fillRule - a fill rule, specified as a FillRule

Returns:

the context

Since:

1.0

getFillRule

public FillRule getFillRule()

Gets the current fill rule, as set by setFillRule(FillRule).

Returns:

the current fill rule.

Since:

1.0

setLineCap

public Context setLineCap(LineCap lineCap)

Sets the current line cap style within the cairo context. See LineCap 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 stroke() and strokeExtents(), but does not have any effect during path construction.

The default line cap style is LineCap.BUTT.

Parameters:

lineCap - a line cap style

Returns:

the context

Since:

1.0

getLineCap

public LineCap getLineCap()

Gets the current line cap style, as set by setLineCap(LineCap).

Returns:

the current line cap style.

Since:

1.0

setLineJoin

public Context setLineJoin(LineJoin lineJoin)

Sets the current line join style within the cairo context. See LineJoin 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 stroke() and strokeExtents(), but does not have any effect during path construction.

The default line join style is LineJoin.MITER.

Parameters:

lineJoin - a line join style

Returns:

the context

Since:

1.0

getLineJoin

public LineJoin getLineJoin()

Gets the current line join style, as set by setLineJoin(LineJoin).

Returns:

the current line join style.

Since:

1.0

setLineWidth

public Context setLineWidth(double width)

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 setLineWidth(). The simplest usage makes both of these spaces identical. That is, if there is no change to the CTM between a call to setLineWidth() and the stroking operation, then one can just pass user-space values to setLineWidth() and ignore this note.

As with the other stroke parameters, the current line width is examined by {stroke() and strokeExtents()} but does not have any effect during path construction.

The default line width value is 2.0.

Parameters:

width - a line width

Returns:

the context

Since:

1.0

getLineWidth

public double getLineWidth()

This function returns the current line width value exactly as set by setLineWidth(double). Note that the value is unchanged even if the CTM has changed between the calls to setLineWidth(double) and getLineWidth().

Returns:

the current line width.

Since:

1.0

setMiterLimit

public Context setMiterLimit(double limit)

Sets the current miter limit within the cairo context.

If the current line join style is set to LineJoin.MITER (see setLineJoin(LineJoin)), 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 stroke() and strokeExtents(), but does not have any effect during path construction.

The default miter limit value is 10.0, which will convert joins with interior angles less than 11 degrees to bevels instead of miters. For reference, a miter limit of 2.0 makes the miter cutoff at 60 degrees, and a miter limit of 1.414 makes the cutoff at 90 degrees.

A miter limit for a desired angle can be computed as: miter limit = 1/sin(angle/2)

Parameters:

limit - miter limit to set

Returns:

the context

Since:

1.0

getMiterLimit

public double getMiterLimit()

Gets the current miter limit, as set by setMiterLimit(double).

Returns:

the current miter limit.

Since:

1.0

setOperator

public Context setOperator(Operator op)

Sets the compositing operator to be used for all drawing operations. See Operator for details on the semantics of each available compositing operator.

The default operator is Operator.OVER.

Parameters:

op - a compositing operator, specified as an Operator

Returns:

the context

Since:

1.0

getOperator

public Operator getOperator()

Gets the current compositing operator for a cairo context.

Returns:

the current compositing operator.

Since:

1.0

setTolerance

public Context setTolerance(double tolerance)

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.) The accuracy of paths within Cairo is limited by the precision of its internal arithmetic, and the prescribed tolerance is restricted to the smallest representable internal value.

Parameters:

tolerance - the tolerance, in device units (typically pixels)

Returns:

the context

Since:

1.0

getTolerance

public double getTolerance()

Gets the current tolerance value, as set by setTolerance(double).

Returns:

the current tolerance value.

Since:

1.0

clip

public Context clip()

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

After 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 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 clip() within a save()/restore() pair. The only other means of increasing the size of the clip region is resetClip().

Returns:

the context

Since:

1.0

clipPreserve

public Context clipPreserve()

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

Unlike clip(), clipPreserve() 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 clipPreserve() 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 clipPreserve() within a save()/restore() pair. The only other means of increasing the size of the clip region is resetClip().

Returns:

the context

Since:

1.0

clipExtents

public Rect clipExtents()

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

Returns:

the resulting extents

Since:

1.4

inClip

public boolean inClip(double x,
 double y)

Tests whether the given point is inside the area that would be visible through the current clip, i.e. the area that would be filled by a paint() operation.

Parameters:

x - X coordinate of the point to test

y - Y coordinate of the point to test

Returns:

True if the point is inside, false if outside.

Since:

1.10

See Also:

• clip()
• clipPreserve()

resetClip

public Context resetClip()

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 resetClip() as it will cause results unexpected by higher-level code which clip(). Consider using save() and restore() around clip() as a more robust means of temporarily restricting the clip region.

Returns:

the context

Since:

1.0

copyClipRectangleList

public RectangleList copyClipRectangleList()
                                    throws IllegalStateException

Gets the current clip region as a list of rectangles in user coordinates. Never returns null.

Returns:

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

Throws:

IllegalStateException - if the clip region cannot be represented as a list of user-space rectangles. The exception may also indicate other errors.

Since:

1.4

fill

public Context fill()

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

Returns:

the context

Since:

1.0

fillPreserve

public Context fillPreserve()

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

Returns:

the context

Since:

1.0

See Also:

• setFillRule(FillRule)
• fill()

fillExtents

public Rect fillExtents()

Computes a bounding box in user coordinates covering the area that would be affected, (the "inked" area), by a 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.

Contrast with pathExtents(), which is similar, but returns non-zero extents for some paths with no inked area, (such as a simple line segment).

Note that fillExtents() must necessarily do more work to compute the precise inked areas in light of the fill rule, so pathExtents() may be more desirable for sake of performance if the non-inked path extents are desired.

Returns:

The resulting extents

Since:

1.0

See Also:

• fill()
• setFillRule(FillRule)
• fillPreserve()

inFill

public boolean inFill(double x,
 double y)

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

Parameters:

x - X coordinate of the point to test

y - Y coordinate of the point to test

Returns:

true if the point is inside, or false if outside.

Since:

1.0

See Also:

• fill()
• setFillRule(FillRule)
• fillPreserve()

mask

public Context mask(Pattern pattern)

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.)

Parameters:

pattern - a Pattern

Returns:

the context

Since:

1.0

mask

public Context mask(Surface surface,
 double surfaceX,
 double surfaceY)

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.)

Parameters:

surface - a Surface

surfaceX - X coordinate at which to place the origin of surface

surfaceY - Y coordinate at which to place the origin of surface

Returns:

the context

Since:

1.0

paint

public Context paint()

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

Returns:

the context

Since:

1.0

paintWithAlpha

public Context paintWithAlpha(double alpha)

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 paint(), but the drawing is faded out using the alpha value.

Parameters:

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

Returns:

the context

Since:

1.0

stroke

public Context stroke()

A drawing operator that strokes the current path according to the current line width, line join, line cap, and dash settings. After stroke(), the current path will be cleared from the cairo context.

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 setDash(double[], double). If the cap style is LineCap.ROUND or LineCap.SQUARE then these segments will be drawn as circular dots or squares respectively. In the case of LineCap.SQUARE, the orientation of the squares is determined by the direction of the underlying path.
2. A sub-path created by moveTo(double, double) followed by either a closePath() or one or more calls to lineTo(double, double) to the same coordinate as the moveTo(double, double). If the cap style is LineCap.ROUND then these sub-paths will be drawn as circular dots. Note that in the case of LineCap.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 LineCap.BUTT cause anything to be drawn in the case of either degenerate segments or sub-paths.

Returns:

the context

Since:

1.0

See Also:

• setLineWidth(double)
• setLineJoin(LineJoin)
• setLineCap(LineCap)
• setDash(double[], double)
• strokePreserve()

strokePreserve

public Context strokePreserve()

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

Returns:

the context

Since:

1.0

See Also:

• setLineWidth(double)
• setLineJoin(LineJoin)
• setLineCap(LineCap)
• setDash(double[], double)
• stroke()

strokeExtents

public Rect strokeExtents()

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

Note that if the line width is set to exactly zero, then strokeExtents() will return an empty rectangle. Contrast with pathExtents() which can be used to compute the non-empty bounds as the line width approaches zero.

Note that strokeExtents() must necessarily do more work to compute the precise inked areas in light of the stroke parameters, so pathExtents() may be more desirable for sake of performance if non-inked path extents are desired.

Returns:

The resulting extents

Since:

1.0

See Also:

• stroke()
• setLineWidth(double)
• setLineJoin(LineJoin)
• setLineCap(LineCap)
• setDash(double[], double)

inStroke

public boolean inStroke(double x,
 double y)

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

Parameters:

x - X coordinate of the point to test

y - Y coordinate of the point to test

Returns:

true if the point is inside, or false if outside.

Since:

1.0

See Also:

• stroke()
• setLineWidth(double)
• setLineJoin(LineJoin)
• setLineCap(LineCap)
• setDash(double[], double)
• strokePreserve()

copyPage

public Context copyPage()

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 showPage() if you want to get an empty page after the emission.

This is a convenience function that simply calls Surface.copyPage() on this Context's target.

Returns:

the context

Since:

1.0

showPage

public Context showPage()

Emits and clears the current page for backends that support multiple pages. Use copyPage() if you don't want to clear the page.

This is a convenience function that simply calls Surface.showPage() on this Context's target.

Returns:

the context

Since:

1.0

setHairLine

public Context setHairLine(boolean setHairline)

Sets lines within the cairo context to be hairlines. Hairlines are logically zero-width lines that are drawn at the thinnest renderable width possible in the current context.

On surfaces with native hairline support, the native hairline functionality will be used. Surfaces that support hairlines include:

• pdf/ps: Encoded as 0-width line.
• win32_printing: Rendered with PS_COSMETIC pen.
• svg: Encoded as 1px non-scaling-stroke.
• script: Encoded with set-hairline function.

Cairo will always render hairlines at 1 device unit wide, even if an anisotropic scaling was applied to the stroke width. In the wild, handling of this situation is not well-defined. Some PDF, PS, and SVG renderers match Cairo's output, but some very popular implementations (Acrobat, Chrome, rsvg) will scale the hairline unevenly. As such, best practice is to reset any anisotropic scaling before calling stroke(). See https://cairographics.org/cookbook/ellipses/ for an example.

Parameters:

setHairline - whether or not to set hairline mode

Returns:

the context

Since:

1.18

getHairLine

public boolean getHairLine()

Returns whether or not hairline mode is set, as set by setHairLine(boolean).

Returns:

whether hairline mode is set.

Since:

1.18

copyPath

public Path copyPath()

Creates a copy of the current path and returns it to the user as a Path. See PathData for hints on how to iterate over the returned data structure.

Returns:

the copy of the current path, or null when the Context is in an error state, or there is insufficient memory to copy the path.

Since:

1.0

copyPathFlat

public Path copyPathFlat()

Gets a flattened copy of the current path and returns it to the user as a Path. See PathData for hints on how to iterate over the returned data structure.

This function is like copyPath() except that any curves in the path will be approximated with piecewise-linear approximations, (accurate to within the current tolerance value). That is, the result is guaranteed to not have any elements of type PathDataType.CURVE_TO which will instead be replaced by a series of PathDataType.LINE_TO elements.

Returns:

the copy of the current path, or null when the Context is in an error state, or there is insufficient memory to copy the path.

Since:

1.0

appendPath

public Context appendPath(Path path)

Append the path onto the current path. The path may be either the return value from one of copyPath() or copyPathFlat() or it may be constructed manually. See Path for details on how the path data structure should be initialized, and note that path.status must be initialized to Status.SUCCESS.

Parameters:

path - path to be appended

Returns:

the context

Since:

1.0

hasCurrentPoint

public boolean hasCurrentPoint()

Returns whether a current point is defined on the current path. See getCurrentPoint() for details on the current point.

Returns:

whether a current point is defined.

Since:

1.6

getCurrentPoint

public Point getCurrentPoint()

Gets the current point of the current path, which is conceptually the final point reached by the path so far.

The current point is returned in the user-space coordinate system. If there is no defined current point or if the Context is in an error status, x and y will both be set to 0.0. It is possible to check this in advance with hasCurrentPoint().

Most path construction functions alter the current point. See the following for details on how they affect the current point: newPath(), newSubPath(), appendPath(Path), closePath(), moveTo(double, double), lineTo(double, double), curveTo(double, double, double, double, double, double), relMoveTo(double, double), relLineTo(double, double), relCurveTo(double, double, double, double, double, double), arc(double, double, double, double, double), arcNegative(double, double, double, double, double), rectangle(double, double, double, double), textPath(String), glyphPath(org.freedesktop.cairo.Glyphs).

Some functions use and alter the current point but do not otherwise change current path: cairo_show_text().

Some functions unset the current path and as a result, current point: fill(), stroke().

Returns:

X and Y coordinates of the current point

Since:

1.0

newPath

public Context newPath()

Clears the current path. After this call there will be no path and no current point.

Returns:

the context

Since:

1.0

newSubPath

public Context newSubPath()

Begin a new sub-path. Note that the existing path is not affected. After this call there will be no current point.

In many cases, this call is not needed since new sub-paths are frequently started with moveTo(double, double).

A call to newSubPath() is particularly useful when beginning a new sub-path with one of the arc() calls. This makes things easier as it is no longer necessary to manually compute the arc's initial coordinates for a call to moveTo(double, double).

Returns:

the context

Since:

1.2

closePath

public Context closePath()

Adds a line segment to the path from the current point to the beginning of the current sub-path, (the most recent point passed to moveTo(double, double)), and closes this sub-path. After this call the current point will be at the joined endpoint of the sub-path.

The behavior of closePath() is distinct from simply calling lineTo(double, double) with the equivalent coordinate in the case of stroking. When a closed sub-path is stroked, there are no caps on the ends of the sub-path. Instead, there is a line join connecting the final and initial segments of the sub-path.

If there is no current point before the call to closePath(), this function will have no effect.

Note: As of cairo version 1.2.4 any call to closePath() will place an explicit MOVE_TO element into the path immediately after the CLOSE_PATH element, (which can be seen in copyPath() for example). This can simplify path processing in some cases as it may not be necessary to save the "last move_to point" during processing as the MOVE_TO immediately after the CLOSE_PATH will provide that point.

Returns:

the context

Since:

1.0

arc

public Context arc(double xc,
 double yc,
 double radius,
 double angle1,
 double angle2)

Adds a circular arc of the given radius to the current path. The arc is centered at (xc, yc), begins at angle1 and proceeds in the direction of increasing angles to end at angle2. If angle2 is less than angle1 it will be progressively increased by 2*M_PI until it is greater than angle2.

If there is a current point, an initial line segment will be added to the path to connect the current point to the beginning of the arc. If this initial line is undesired, it can be avoided by calling newSubPath() before calling arc().

Angles are measured in radians. An angle of 0.0 is in the direction of the positive X axis (in user space). An angle of M_PI/2.0 radians (90 degrees) is in the direction of the positive Y axis (in user space). Angles increase in the direction from the positive X axis toward the positive Y axis. So with the default transformation matrix, angles increase in a clockwise direction.

(To convert from degrees to radians, use degrees * (M_PI / 180.).)

This function gives the arc in the direction of increasing angles; see arcNegative(double, double, double, double, double) to get the arc in the direction of decreasing angles.

The arc is circular in user space. To achieve an elliptical arc, you can scale the current transformation matrix by different amounts in the X and Y directions. For example, to draw an ellipse in the box given by x, y, width, height:

 cr.save()
   .translate(x + width / 2., y + height / 2.)
   .scale(width / 2., height / 2.)
         .arc(0., 0., 1., 0., 2 * Math.PI)
   .restore();
 

Parameters:

xc - X position of the center of the arc

yc - Y position of the center of the arc

radius - the radius of the arc

angle1 - the start angle, in radians

angle2 - the end angle, in radians

Returns:

the context

Since:

1.0

arcNegative

public Context arcNegative(double xc,
 double yc,
 double radius,
 double angle1,
 double angle2)

Adds a circular arc of the given radius to the current path. The arc is centered at (xc, yc), begins at angle1 and proceeds in the direction of decreasing angles to end at angle2. If angle2 is greater than angle1 it will be progressively decreased by 2*M_PI until it is less than angle1.

See arc(double, double, double, double, double) for more details. This function differs only in the direction of the arc between the two angles.

Parameters:

xc - X position of the center of the arc

yc - Y position of the center of the arc

radius - the radius of the arc

angle1 - the start angle, in radians

angle2 - the end angle, in radians

Returns:

the context

Since:

1.0

curveTo

public Context curveTo(double x1,
 double y1,
 double x2,
 double y2,
 double x3,
 double y3)

Adds a cubic Bézier spline to the path from the current point to position (x3, y3) in user-space coordinates, using (x1 , y1) and (x2, y2) as the control points. After this call the current point will be (x3, y3).

If there is no current point before the call to curveTo() this function will behave as if preceded by a call to moveTo(x1, y1).

Parameters:

x1 - the X coordinate of the first control point

y1 - the Y coordinate of the first control point

x2 - the X coordinate of the second control point

y2 - the Y coordinate of the second control point

x3 - the X coordinate of the end of the curve

y3 - the Y coordinate of the end of the curve

Returns:

the context

Since:

1.0

lineTo

public Context lineTo(double x,
 double y)

Adds a line to the path from the current point to position (x, y) in user-space coordinates. After this call the current point will be (x, y).

If there is no current point before the call to lineTo() this function will behave as moveTo(x, y).

Parameters:

x - the X coordinate of the end of the new line

y - the Y coordinate of the end of the new line

Returns:

the context

Since:

1.0

moveTo

public Context moveTo(double x,
 double y)

Begin a new sub-path. After this call the current point will be (x, y).

Parameters:

x - the X coordinate of the new position

y - the Y coordinate of the new position

Returns:

the context

Since:

1.0

rectangle

public Context rectangle(double x,
 double y,
 double width,
 double height)

Adds a closed sub-path rectangle of the given size to the current path at position (x, y) in user-space coordinates.

This function is logically equivalent to:

 cr.moveTo(x, y)
   .relLineTo(width, 0)
   .relLineTo(0, height)
   .relLineTo(-width, 0)
   .closePath();
 

Parameters:

x - the X coordinate of the top left corner of the rectangle

y - the Y coordinate of the top left corner of the rectangle

width - the width of the rectangle

height - the height of the rectangle

Returns:

the context

Since:

1.0

glyphPath

public Context glyphPath(Glyphs glyphs)

Adds closed paths for the glyphs to the current path. The generated path if filled, achieves an effect similar to that of showGlyphs(org.freedesktop.cairo.Glyphs).

Parameters:

glyphs - array of glyphs to show

Returns:

the context

Since:

1.0

textPath

public Context textPath(String string)

Adds closed paths for text to the current path. The generated path if filled, achieves an effect similar to that of showText(String).

Text conversion and positioning is done similar to showText(String).

Like showText(String), After this call the current point is moved to the origin of where the next glyph would be placed in this same progression. That is, the current point will be at the origin of the final glyph offset by its advance values. This allows for chaining multiple calls to to textPath() without having to set current point in between.

Note: The textPath() function call is part of what the cairo designers call the "toy" text API. It is convenient for short demos and simple programs, but it is not expected to be adequate for serious text-using applications. See glyphPath(org.freedesktop.cairo.Glyphs) for the "real" text path API in cairo.

Parameters:

string - a string of text

Returns:

the context

Since:

1.0

relCurveTo

public Context relCurveTo(double dx1,
 double dy1,
 double dx2,
 double dy2,
 double dx3,
 double dy3)
                   throws IllegalStateException

Relative-coordinate version of curveTo(double, double, double, double, double, double). All offsets are relative to the current point. Adds a cubic Bézier spline to the path from the current point to a point offset from the current point by (dx3, dy3), using points offset by (dx1, dy1) and (dx2, dy2) as the control points. After this call the current point will be offset by (dx3, dy3).

Given a current point of (x, y), relCurveTo(dx1, dy1, dx2, dy2, dx3, dy3) is logically equivalent to curveTo(x+dx1, y+dy1, x+dx2, y+dy2, x+dx3, y+dy3).

Parameters:

dx1 - the X offset to the first control point

dy1 - the Y offset to the first control point

dx2 - the X offset to the second control point

dy2 - the Y offset to the second control point

dx3 - the X offset to the end of the curve

dy3 - the Y offset to the end of the curve

Returns:

the context

Throws:

IllegalStateException - when called with no current point

Since:

1.0

relLineTo

public Context relLineTo(double dx,
 double dy)
                  throws IllegalStateException

Relative-coordinate version of lineTo(double, double). Adds a line to the path from the current point to a point that is offset from the current point by (dx, dy) in user space. After this call the current point will be offset by (dx, dy).

Given a current point of (x, y), relLineTo(dx, dy) is logically equivalent to lineTo(x + dx, y + dy).

Parameters:

dx - the X offset to the end of the new line

dy - the Y offset to the end of the new line

Returns:

the context

Throws:

IllegalStateException - when called with no current point

Since:

1.0

relMoveTo

public Context relMoveTo(double dx,
 double dy)
                  throws IllegalStateException

Begin a new sub-path. After this call the current point will offset by (x, y).

Given a current point of (x, y), relMoveTo(dx, dy) is logically equivalent to moveTo(x + dx, y + dy).

Parameters:

dx - the X offset

dy - the Y offset

Returns:

the context

Throws:

IllegalStateException - when called with no current point

Since:

1.0

pathExtents

public Rect pathExtents()

Computes a bounding box in user-space coordinates covering the points on the current path. If the current path is empty, returns an empty rectangle ((0,0), (0,0)). Stroke parameters, fill rule, surface dimensions and clipping are not taken into account.

Contrast with fillExtents() and strokeExtents() which return the extents of only the area that would be "inked" by the corresponding drawing operations.

The result of pathExtents() is defined as equivalent to the limit of strokeExtents() with LineCap.ROUND as the line width approaches 0.0, (but never reaching the empty-rectangle returned by strokeExtents() for a line width of 0.0).

Specifically, this means that zero-area sub-paths such as cr.moveTo().lineTo() segments, (even degenerate cases where the coordinates to both calls are identical), will be considered as contributing to the extents. However, a lone moveTo() will not contribute to the results of pathExtents().

Returns:

a Rectangle with the left, top, right and bottom of the resulting extents

Since:

1.6

translate

public Context translate(double tx,
 double ty)

Modifies the current transformation matrix (CTM) by translating the user-space origin by (tx, ty). This offset is interpreted as a user-space coordinate according to the CTM in place before the new call to translate(). In other words, the translation of the user-space origin takes place after any existing transformation.

Parameters:

tx - amount to translate in the X direction

ty - amount to translate in the Y direction

Returns:

the context

Since:

1.0

scale

public Context scale(double sx,
 double sy)

Modifies the current transformation matrix (CTM) by scaling the X and Y user-space axes by sx and sy respectively. The scaling of the axes takes place after any existing transformation of user space.

Parameters:

sx - scale factor for the X dimension

sy - scale factor for the Y dimension

Returns:

the context

Since:

1.0

rotate

public Context rotate(double angle)

Modifies the current transformation matrix (CTM) by rotating the user-space axes by angle radians. The rotation of the axes takes places after any existing transformation of user space. The rotation direction for positive angles is from the positive X axis toward the positive Y axis.

Parameters:

angle - angle (in radians) by which the user-space axes will be rotated

Returns:

the context

Since:

1.0

transform

public Context transform(Matrix matrix)

Modifies the current transformation matrix (CTM) by applying matrix as an additional transformation. The new transformation of user space takes place after any existing transformation.

Parameters:

matrix - a transformation to be applied to the user-space axes

Returns:

the context

Since:

1.0

setMatrix

public Context setMatrix(Matrix matrix)

Modifies the current transformation matrix (CTM) by setting it equal to matrix.

The CTM is a two-dimensional affine transformation that maps all coordinates and other drawing instruments from the user space into the surface's canonical coordinate system, also known as the device space.

Parameters:

matrix - a transformation matrix from user space to device space

Returns:

the context

Since:

1.0

getMatrix

public void getMatrix(Matrix matrix)

Stores the current transformation matrix (CTM) into matrix.

The CTM is a two-dimensional affine transformation that maps all coordinates and other drawing instruments from the user space into the surface's canonical coordinate system, also known as the device space.

Parameters:

matrix - return value for the matrix

Since:

1.0

identityMatrix

public Context identityMatrix()

Resets the current transformation matrix (CTM) by setting it equal to the identity matrix. That is, the user-space and device-space axes will be aligned and one user-space unit will transform to one device-space unit.

Returns:

the context

Since:

1.0

userToDevice

public Point userToDevice(Point point)

Transform a coordinate from user space to device space by multiplying the given point by the current transformation matrix (CTM).

Parameters:

point - X and Y values of coordinates

Returns:

a Point with the transformed X and Y coordinates

Since:

1.0

userToDeviceDistance

public Point userToDeviceDistance(Point point)

Transform a distance vector from user space to device space. This function is similar to userToDevice(Point) except that the translation components of the CTM will be ignored when transforming (dx, dy).

Parameters:

point - X and Y components of a distance vector

Returns:

a Point with the transformed X and Y components

Since:

1.0

deviceToUser

public Point deviceToUser(Point point)

Transform a coordinate from device space to user space by multiplying the given point by the inverse of the current transformation matrix (CTM).

Parameters:

point - X and Y values of coordinate

Returns:

a Point with the transformed X and Y coordinates

Since:

1.0

deviceToUserDistance

public Point deviceToUserDistance(Point point)

Transform a distance vector from device space to user space. This function is similar to deviceToUser(Point) except that the translation components of the inverse CTM will be ignored when transforming (dx, dy).

Parameters:

point - X and Y components of a distance vector

Returns:

a Point with the transformed X and Y components

Since:

1.0

selectFontFace

public Context selectFontFace(String family,
 FontSlant slant,
 FontWeight weight)

Note: The selectFontFace() method is part of what the cairo designers call the "toy" text API. It is convenient for short demos and simple programs, but it is not expected to be adequate for serious text-using applications.

Selects a family and style of font from a simplified description as a family name, slant and weight. Cairo provides no operation to list available family names on the system (this is a "toy", remember), but the standard CSS2 generic family names, ("serif", "sans-serif", "cursive", "fantasy", "monospace"), are likely to work as expected.

If family starts with the string "cairo :", or if no native font backends are compiled in, cairo will use an internal font family. The internal font family recognizes many modifiers in the family string, most notably, it recognizes the string "monospace". That is, the family name "cairo :monospace" will use the monospace version of the internal font family.

For "real" font selection, see the font-backend-specific font_face_create functions for the font backend you are using. (For example, if you are using the freetype-based cairo-ft font backend, see cairo_ft_font_face_create_for_ft_face() or cairo_ft_font_face_create_for_pattern().) The resulting font face could then be used with ScaledFont.create(FontFace, Matrix, Matrix, FontOptions) and setScaledFont(ScaledFont).

Similarly, when using the "real" font support, you can call directly into the underlying font system, (such as fontconfig or freetype), for operations such as listing available fonts, etc.

It is expected that most applications will need to use a more comprehensive font handling and text layout library, (for example, pango), in conjunction with cairo.

If text is drawn without a call to selectFontFace(), (nor setFontFace(FontFace) nor setScaledFont(ScaledFont)), the default family is platform-specific, but is essentially "sans-serif". Default slant is FontSlant.NORMAL , and default weight is FontWeight.NORMAL.

This function is equivalent to a call to ToyFontFace.create() followed by setFontFace(FontFace).

Parameters:

family - a font family name

slant - the slant for the font

weight - the weight for the font

Returns:

the context

Since:

1.0

setFontSize

public Context setFontSize(double size)

Sets the current font matrix to a scale by a factor of size, replacing any font matrix previously set with setFontSize() or setFontMatrix(Matrix). This results in a font size of size user space units. (More precisely, this matrix will result in the font's em-square being a size by size square in user space.)

If text is drawn without a call to setFontSize(), (nor setFontMatrix(Matrix) nor setScaledFont(ScaledFont)), the default font size is 10.0.

Parameters:

size - the new font size, in user space units

Returns:

the context

Since:

1.0

setFontMatrix

public Context setFontMatrix(Matrix matrix)

Sets the current font matrix to matrix. The font matrix gives a transformation from the design space of the font (in this space, the em-square is 1 unit by 1 unit) to user space. Normally, a simple scale is used (see setFontSize(double)), but a more complex font matrix can be used to shear the font or stretch it unequally along the two axes

Parameters:

matrix - a Matrix describing a transform to be applied to the current font.

Returns:

the context

Since:

1.0

getFontMatrix

public void getFontMatrix(Matrix matrix)

Stores the current font matrix into matrix. See setFontMatrix(org.freedesktop.cairo.Matrix)

Parameters:

matrix - return value for the matrix

Since:

1.0

setFontOptions

public Context setFontOptions(FontOptions options)

Sets a set of custom font rendering options for the Context. Rendering options are derived by merging these options with the options derived from underlying surface; if the value in options has a default value (like Antialias.DEFAULT), then the value from the surface is used.

Parameters:

options - font options to use

Returns:

this context

Since:

1.0

getFontOptions

public FontOptions getFontOptions()

Retrieves font rendering options set via setFontOptions(FontOptions). Note that the returned options do not include any options derived from the underlying surface; they are literally the options passed to setFontOptions(FontOptions).

Returns:

the retrieved options

Since:

1.0

setFontFace

public Context setFontFace(FontFace fontFace)

Replaces the current FontFace object in the Context with fontFace. The replaced font face in the Context will be destroyed if there are no other references to it.

Parameters:

fontFace - a FontFace, or null to restore to the default font

Returns:

the context

Since:

1.0

getFontFace

public FontFace getFontFace()

Gets the current font face for a Context.

Returns:

the current font face

Since:

1.0

setScaledFont

public Context setScaledFont(ScaledFont scaledFont)

Replaces the current font face, font matrix, and font options in the Context with those of the ScaledFont. Except for some translation, the current CTM of the Context should be the same as that of the ScaledFont, which can be accessed using ScaledFont.getCTM(org.freedesktop.cairo.Matrix).

Parameters:

scaledFont - a ScaledFont

Returns:

the context

Since:

1.2

getScaledFont

public ScaledFont getScaledFont()

Gets the current scaled font

Returns:

the current scaled font

Since:

1.4

showText

public Context showText(String string)

A drawing operator that generates the shape from a string of characters, rendered according to the current fontFace, fontSize (fontMatrix), and fontOptions.

This function first computes a set of glyphs for the string of text. The first glyph is placed so that its origin is at the current point. The origin of each subsequent glyph is offset from that of the previous glyph by the advance values of the previous glyph.

After this call the current point is moved to the origin of where the next glyph would be placed in this same progression. That is, the current point will be at the origin of the final glyph offset by its advance values. This allows for easy display of a single logical string with multiple calls to showText().

Note: The showText() function call is part of what the cairo designers call the "toy" text API. It is convenient for short demos and simple programs, but it is not expected to be adequate for serious text-using applications. See showGlyphs(org.freedesktop.cairo.Glyphs) for the "real" text display API in cairo.

Parameters:

string - a string of text, or null

Returns:

the context

Since:

1.0

showGlyphs

public Context showGlyphs(Glyphs glyphs)

A drawing operator that generates the shape from an array of glyphs, rendered according to the current fontFace, fontSize (fontMatrix), and fontOptions.

Parameters:

glyphs - array of glyphs to show

Returns:

the context

Since:

1.0

showTextGlyphs

public Context showTextGlyphs(String string,
 Glyphs glyphs)

This operation has rendering effects similar to showGlyphs(org.freedesktop.cairo.Glyphs) but, if the target surface supports it, uses the provided text and cluster mapping to embed the text for the glyphs shown in the output. If the target does not support the extended attributes, this function acts like the basic showGlyphs(org.freedesktop.cairo.Glyphs) as if it had been passed glyphs.

The mapping between the string and glyphs array is provided by an array of clusters. Each cluster covers a number of text bytes and glyphs, and neighboring clusters cover neighboring areas of the text string and the glyphs array. The clusters should collectively cover string and glyphs in entirety.

The first cluster always covers bytes from the beginning of string. If clusterFlags do not have the TextClusterFlags.BACKWARD set, the first cluster also covers the beginning of glyphs, otherwise it covers the end of the glyphs array and following clusters move backward.

See TextCluster for constraints on valid clusters.

Parameters:

string - a string of text

glyphs - array of glyphs to show

Returns:

the context

Since:

1.8

fontExtents

public void fontExtents(FontExtents extents)

Gets the font extents for the currently selected font.

Parameters:

extents - a FontExtents object into which the results will be stored.

Since:

1.0

textExtents

public void textExtents(String string,
 TextExtents extents)

Gets the extents for a string of text. The extents describe a user-space rectangle that encloses the "inked" portion of the text, (as it would be drawn by showText(String)). Additionally, the xAdvance and yAdvance values indicate the amount by which the current point would be advanced by showText(String).

Note that whitespace characters do not directly contribute to the size of the rectangle (extents.width and extents.height). They do contribute indirectly by changing the position of non-whitespace characters. In particular, trailing whitespace characters are likely to not affect the size of the rectangle, though they will affect the xAdvance and yAdvance values.

Parameters:

string - a string of text, or null

extents - a TextExtents object into which the results will be stored

Since:

1.0

glyphExtents

public void glyphExtents(Glyphs glyphs,
 TextExtents extents)

Gets the extents for an array of glyphs. The extents describe a user-space rectangle that encloses the "inked" portion of the glyphs, (as they would be drawn by showGlyphs(org.freedesktop.cairo.Glyphs)). Additionally, the xAdvance and yAdvance values indicate the amount by which the current point would be advanced by showGlyphs(org.freedesktop.cairo.Glyphs).

Note that whitespace glyphs do not contribute to the size of the rectangle (extents.width and extents.height).

Parameters:

glyphs - an array of Glyph objects

extents - a TextExtents object into which the results will be stored

Since:

1.0

tagBegin

public Context tagBegin(String tagName,
 String attributes)
                 throws IllegalArgumentException

Marks the beginning of the tag_name structure. Call tagEnd(String) with the same tagName to mark the end of the structure.

The attributes string is of the form "key1=value2 key2=value2 ...". Values may be boolean (true/false or 1/0), integer, float, string, or an array.

String values are enclosed in single quotes ('). Single quotes and backslashes inside the string should be escaped with a backslash.

Boolean values may be set to true by only specifying the key. eg the attribute string "key" is the equivalent to "key=true".

Arrays are enclosed in '[]'. eg "rect=[1.2 4.3 2.0 3.0]".

If no attributes are required, attributes can be an empty string or null.

See Tags and Links Description for the list of tags and attributes.

Parameters:

tagName - tag name

attributes - tag attributes

Returns:

the context

Throws:

IllegalArgumentException - invalid nesting of tags or invalid attributes, see Status.TAG_ERROR

Since:

1.16

See Also:

• tagEnd(String)

tagEnd

public Context tagEnd(String tagName)
               throws IllegalArgumentException

Marks the end of the tag_name structure.

Parameters:

tagName - tag name

Returns:

the context

Throws:

IllegalArgumentException - Invalid nesting of tags, see Status.TAG_ERROR

Since:

1.16

See Also:

• tagBegin(String, String)

setUserData

public UserDataKey setUserData(UserDataKey key,
 MemorySegment userData)

Attach user data to the context. To remove user data from a context, call this function with the key that was used to set it and null for userData.

Parameters:

key - the key to attach the user data to

userData - the user data to attach to the context

Returns:

the key

Throws:

NullPointerException - if key is null

Since:

1.4

getUserData

public MemorySegment getUserData(UserDataKey key)

Return user data previously attached to the context using the specified key. If no user data has been attached with the given key this function returns null.

The returned memory segment has zero length. It can be resized with MemorySegment.reinterpret(long)^RESTRICTED.

Parameters:

key - the UserDataKey the user data was attached to

Returns:

the user data previously attached or null

Since:

1.4

getType

public static org.gnome.glib.Type getType()

Get the CairoContext GType

Returns:

the GType