Awesome

Drawing Context

Checks whether an error has previously occurred for this context.

Returns: the current status of this context, see Status

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

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

Gets the target surface for the cairo context as passed to Context.new().

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. Context.status() != "success"). A nil surface is indicated by Surface.status() != "success".

Return value: the target surface. This object is owned by cairo. To keep a reference to it, you must call Surface.reference().

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

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

By default the intermediate group will have a content type of "color-alpha". Other content types can be chosen for the group by using Context.pushGroupWithContent() 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);

Temporarily redirects drawing to an intermediate surface known as a group. The redirection lasts until the group is completed by a call to Context.popGroup() or Context.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 Context.pushGroup() which you should see for a more detailed description of group rendering.

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

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

Return value: 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 Pattern.destroy() when finished with it.

Terminates the redirection begun by a call to Context.pushGroup() or Context.pushGroupWithContent() 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 Context.popGroup() function calls Context.restore(), (balancing a call to Context.save() by the push_group function), so that any changes to the graphics state will not be visible outside the group.

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

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. Context.status() != "success"). A nil surface is indicated by Surface.status() != "success".

Return value: the target surface. This object is owned by cairo. To keep a reference to it, you must call Surface.reference().

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

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

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

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

Gets the current source pattern for cr.

Return value: the current source pattern. This object is owned by cairo. To keep a reference to it, you must call Pattern.reference().

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 "subpixel" when drawing shapes.

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

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

Return value: the current shape antialiasing mode.

Sets the dash pattern to be used by Context.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 "round" or "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 Context.setDash().

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 cr will be put into an error state with a status of "invalid-dash".

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

See also Context.setDash() and Context.getDash().

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

Gets the current dash array. If not nil, dashes should be big enough to hold at least the number of values returned by Context.getDashCount().

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

The default fill rule is "winding".

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

Return value: the current fill rule.

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 Context.stroke(), Context.strokeExtents(), and Context.strokeToPath(), but does not have any effect during path construction.

The default line cap style is "butt".

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

Return value: the current line cap style.

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 Context.stroke(), Context.strokeExtents(), and Context.strokeToPath(), but does not have any effect during path construction.

The default line join style is "miter".

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

Return value: the current line join style.

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

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

The default line width value is 2.0.

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

Return value: the current line width.

Sets the current miter limit within the cairo context.

If the current line join style is set to "miter" (see Context.setLineJoin()), 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 Context.stroke(), Context.strokeExtents(), and Context.strokeToPath(), 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)

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

Return value: the current miter limit.

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 "over".

Gets the current compositing operator for a cairo context.

Return value: the current compositing operator.

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.

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

Return value: the current tolerance value.

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

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

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

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

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

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 Context.paint() operation.

See Context.clip(), and Context.clipPreserve().

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

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

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

The status in the list may be "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.

Returns: the current clip region as a list of rectangles in user coordinates, which should be destroyed using Context.rectangleListDestroy().

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

See Context.setFillRule() and Context.fill().

Computes a bounding box in user coordinates covering the area that would be affected, (the "inked" area), by a Context.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 Path.extents(), which is similar, but returns non-zero extents for some paths with no inked area, (such as a simple line segment).

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

See Context.fill(), Context.setFillRule() and Context.fillPreserve().

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

See Context.fill(), Context.setFillRule() and Context.fillPreserve().

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

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.)

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.)

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

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

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

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 Context.setDash(). If the cap style is "round" or "square" then these segments will be drawn as circular dots or squares respectively. In the case of "square", the orientation of the squares is determined by the direction of the underlying path.

2. A sub-path created by Context.moveTo() followed by either a Context.closePath() or one or more calls to Context.lineTo() to the same coordinate as the Context.moveTo(). If the cap style is "round" then these sub-paths will be drawn as circular dots. Note that in the case of "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 "butt" cause anything to be drawn in the case of either degenerate segments or sub-paths.

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

See Context.setLineWidth(), Context.setLineJoin(), Context.setLineCap(), Context.setDash(), and Context.strokePreserve().

Computes a bounding box in user coordinates covering the area that would be affected, (the "inked" area), by a Context.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 Context.strokeExtents() will return an empty rectangle. Contrast with Path.extents() which can be used to compute the non-empty bounds as the line width approaches zero.

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

See Context.stroke(), Context.setLineWidth(), Context.setLineJoin(), Context.setLineCap(), Context.setDash(), and Context.strokePreserve().

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

See Context.stroke(), Context.setLineWidth(), Context.setLineJoin(), Context.setLineCap(), Context.setDash(), and Context.strokePreserve().

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

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

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

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

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

Paths

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

This function will always return a valid pointer, but the result will have no data (data==nil`` and num_data==0), if either of the following conditions hold:

Return value: the copy of the current path. The caller owns the returned object and should call Path.destroy() when finished with it.

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

This function is like Context.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 "path-curve-to" which will instead be replaced by a series of "path-line-to" elements.

This function will always return a valid pointer, but the result will have no data (data==nil`` and num_data==0), if either of the following conditions hold:

Return value: the copy of the current path. The caller owns the returned object and should call Path.destroy() when finished with it.

Append the path onto the current path. The path may be either the return value from one of Context.copyPath() or Context.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 "success".

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

Return value: whether a current point is defined.

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 cr is in an error status, x and y will both be set to 0.0. It is possible to check this in advance with Context.hasCurrentPoint().

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

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

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

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

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 Context.moveTo().

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

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 Context.moveTo()), and closes this sub-path. After this call the current point will be at the joined endpoint of the sub-path.

The behavior of Context.closePath() is distinct from simply calling Context.lineTo() 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 Context.closePath(), this function will have no effect.

Note: As of cairo version 1.2.4 any call to Context.closePath() will place an explicit MOVE_TO element into the path immediately after the CLOSE_PATH element, (which can be seen in Context.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.

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 angle1.

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 Context.newSubPath() before calling Context.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 Context.arcNegative() 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:

cairo_save (cr);
cairo_translate (cr, x + width / 2., y + height / 2.);
cairo_scale (cr, width / 2., height / 2.);
cairo_arc (cr, 0., 0., 1., 0., 2 * M_PI);
cairo_restore (cr);

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

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 Context.curveTo() this function will behave as if preceded by a call to cairo_move_to(cr, x1, y1).

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 Context.lineTo() this function will behave as cairo_move_to(cr, x, y).

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

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:

cairo_move_to (cr, x, y);
cairo_rel_line_to (cr, width, 0);
cairo_rel_line_to (cr, 0, height);
cairo_rel_line_to (cr, -width, 0);
cairo_close_path (cr);

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

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

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

Like Context.showText(), 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 Context.textPath() without having to set current point in between.

Note: The Context.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 Context.glyphPath() for the "real" text path API in cairo.

Relative-coordinate version of Context.curveTo(). 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), cairo_rel_curve_to(cr, dx1, dy1, dx2, dy2, dx3, dy3) is logically equivalent to cairo_curve_to(cr, x+dx1, y+dy1, x+dx2, y+dy2, x+dx3, y+dy3).

It is an error to call this function with no current point. Doing so will cause cr to shutdown with a status of "no-current-point".

Relative-coordinate version of Context.lineTo(). 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), cairo_rel_line_to(cr, dx, dy) is logically equivalent to cairo_line_to(cr, x + dx, y + dy).

It is an error to call this function with no current point. Doing so will cause cr to shutdown with a status of "no-current-point".

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

Given a current point of (x, y), cairo_rel_move_to(cr, dx, dy) is logically equivalent to cairo_move_to(cr, x + dx, y + dy).

It is an error to call this function with no current point. Doing so will cause cr to shutdown with a status of "no-current-point".

Transformations

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 Context.translate(). In other words, the translation of the user-space origin takes place after any existing transformation.

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.

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.

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.

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

Stores the current transformation matrix (CTM) into matrix.

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.

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

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

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

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

Rendering text and glyphs

Note: The Context.selectFontFace() 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.

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 Context.ftFontFaceCreateForFtFace() or Context.ftFontFaceCreateForPattern().) The resulting font face could then be used with ScaledFontFace.new() and Context.setScaledFont().

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 Context.selectFontFace(), (nor Context.setFontFace() nor Context.setScaledFont()), the default family is platform-specific, but is essentially "sans-serif". Default slant is "normal", and default weight is "normal".

This function is equivalent to a call to Context.toyFontFaceCreate() followed by Context.setFontFace().

Sets the current font matrix to a scale by a factor of size, replacing any font matrix previously set with Context.setFontSize() or Context.setFontMatrix(). 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 Context.setFontSize(), (nor Context.setFontMatrix() nor Context.setScaledFont()), the default font size is 10.0.

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 Context.setFontSize()), but a more complex font matrix can be used to shear the font or stretch it unequally along the two axes

Stores the current font matrix into matrix. See Context.setFontMatrix().

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 "default"), then the value from the surface is used.

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

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

Gets the current font face for a Context.

Return value: the current font face. This object is owned by cairo. To keep a reference to it, you must call FontFace.reference().

This function never returns nil. If memory cannot be allocated, a special "nil" FontFace object will be returned on which FontFace.status() returns "no-memory". Using this nil object will cause its error state to propagate to other objects it is passed to, (for example, calling Context.setFontFace() with a nil font will trigger an error that will shutdown the Context object).

Replaces the current font face, font matrix, and font options in the Context with those of the ScaledFontFace. Except for some translation, the current CTM of the Context should be the same as that of the ScaledFontFace, which can be accessed using ScaledFontFace.getCtm().

Gets the current scaled font for a Context.

Return value: the current scaled font. This object is owned by cairo. To keep a reference to it, you must call ScaledFontFace.reference().

This function never returns nil. If memory cannot be allocated, a special "nil" ScaledFontFace object will be returned on which ScaledFontFace.status() returns "no-memory". Using this nil object will cause its error state to propagate to other objects it is passed to, (for example, calling Context.setScaledFont() with a nil font will trigger an error that will shutdown the Context object).

A drawing operator that generates the shape from a string of UTF-8 characters, rendered according to the current font_face, font_size (font_matrix), and font_options.

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 Context.showText().

Note: The Context.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 Context.showGlyphs() for the "real" text display API in cairo.

A drawing operator that generates the shape from an array of glyphs, rendered according to the current font face, font size (font matrix), and font options.

This operation has rendering effects similar to Context.showGlyphs() 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 Context.showGlyphs() as if it had been passed glyphs and num_glyphs.

The mapping between utf8 and glyphs is provided by an array of clusters. Each cluster covers a number of text bytes and glyphs, and neighboring clusters cover neighboring areas of utf8 and glyphs. The clusters should collectively cover utf8 and glyphs in entirety.

The first cluster always covers bytes from the beginning of utf8. If cluster_flags do not have the "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 cairo_text_cluster_t for constraints on valid clusters.

Gets the font extents for the currently selected font.

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 Context.showText()). Additionally, the x_advance and y_advance values indicate the amount by which the current point would be advanced by Context.showText().

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 x_advance and y_advance values.

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 Context.showGlyphs()). Additionally, the x_advance and y_advance values indicate the amount by which the current point would be advanced by Context.showGlyphs().

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