.. _constants: ****************************** Module Functions and Constants ****************************** .. currentmodule:: cairo Module Functions ================ .. function:: cairo_version() :returns: the encoded version :rtype: int Returns the version of the underlying C cairo library, encoded in a single integer. .. function:: cairo_version_string() :returns: the encoded version :rtype: str Returns the version of the underlying C cairo library as a human-readable string of the form "X.Y.Z". Module Constants ================ .. data:: version the pycairo version, as a string .. data:: version_info the pycairo version, as a tuple .. _constants_HAS: cairo.HAS --------- .. data:: HAS_ATSUI_FONT HAS_FT_FONT HAS_GLITZ_SURFACE HAS_IMAGE_SURFACE HAS_PDF_SURFACE HAS_PNG_FUNCTIONS HAS_PS_SURFACE HAS_SVG_SURFACE HAS_USER_FONT HAS_QUARTZ_SURFACE HAS_WIN32_FONT HAS_WIN32_SURFACE HAS_XCB_SURFACE HAS_XLIB_SURFACE 1 if the feature is present in the underlying C cairo library, 0 otherwise .. _constants_ANTIALIAS: cairo.ANTIALIAS --------------- ANTIALIAS specifies the type of antialiasing to do when rendering text or shapes. .. data:: ANTIALIAS_DEFAULT Use the default antialiasing for the subsystem and target device .. data:: ANTIALIAS_NONE Use a bilevel alpha mask .. data:: ANTIALIAS_GRAY Perform single-color antialiasing (using shades of gray for black text on a white background, for example). .. data:: ANTIALIAS_SUBPIXEL Perform antialiasing by taking advantage of the order of subpixel elements on devices such as LCD panels. .. _constants_CONTENT: cairo.CONTENT ------------- These constants are used to describe the content that a :class:`Surface` will contain, whether color information, alpha information (translucence vs. opacity), or both. .. data:: CONTENT_COLOR The surface will hold color content only. .. data:: CONTENT_ALPHA The surface will hold alpha content only. .. data:: CONTENT_COLOR_ALPHA The surface will hold color and alpha content. .. _constants_EXTEND: cairo.EXTEND ------------ These constants are used to describe how :class:`Pattern` color/alpha will be determined for areas "outside" the pattern's natural area, (for example, outside the surface bounds or outside the gradient geometry). The default extend mode is *EXTEND_NONE* for :class:`SurfacePattern` and *EXTEND_PAD* for :class:`Gradient` patterns. .. data:: EXTEND_NONE pixels outside of the source pattern are fully transparent .. data:: EXTEND_REPEAT the pattern is tiled by repeating .. data:: EXTEND_REFLECT the pattern is tiled by reflecting at the edges (Implemented for surface patterns since 1.6) .. data:: EXTEND_PAD pixels outside of the pattern copy the closest pixel from the source (Since 1.2; but only implemented for surface patterns since 1.6) New entries may be added in future versions. .. _constants_FILL_RULE: cairo.FILL_RULE --------------- These constants are used to select how paths are filled. For both fill rules, whether or not a point is included in the fill is determined by taking a ray from that point to infinity and looking at intersections with the path. The ray can be in any direction, as long as it doesn't pass through the end point of a segment or have a tricky intersection such as intersecting tangent to the path. (Note that filling is not actually implemented in this way. This is just a description of the rule that is applied.) The default fill rule is *FILL_RULE_WINDING*. .. data:: FILL_RULE_WINDING If the path crosses the ray from left-to-right, counts +1. If the path crosses the ray from right to left, counts -1. (Left and right are determined from the perspective of looking along the ray from the starting point.) If the total count is non-zero, the point will be filled. .. data:: FILL_RULE_EVEN_ODD Counts the total number of intersections, without regard to the orientation of the contour. If the total number of intersections is odd, the point will be filled. New entries may be added in future versions. .. _constants_FILTER: cairo.FILTER ------------ These constants are used to indicate what filtering should be applied when reading pixel values from patterns. See :meth:`SurfacePattern.set_filter` for indicating the desired filter to be used with a particular pattern. .. data:: FILTER_FAST A high-performance filter, with quality similar *FILTER_NEAREST* .. data:: FILTER_GOOD A reasonable-performance filter, with quality similar to *FILTER_BILINEAR* .. data:: FILTER_BEST The highest-quality available, performance may not be suitable for interactive use. .. data:: FILTER_NEAREST Nearest-neighbor filtering .. data:: FILTER_BILINEAR Linear interpolation in two dimensions .. data:: FILTER_GAUSSIAN This filter value is currently unimplemented, and should not be used in current code. .. _constants_FONT_SLANT: cairo.FONT_SLANT ---------------- These constants specify variants of a :class:`FontFace` based on their slant. .. data:: FONT_SLANT_NORMAL Upright font style .. data:: FONT_SLANT_ITALIC Italic font style .. data:: FONT_SLANT_OBLIQUE Oblique font style .. _constants_FONT_WEIGHT: cairo.FONT_WEIGHT ----------------- These constants specify variants of a :class:`FontFace` based on their weight. .. data:: FONT_WEIGHT_NORMAL Normal font weight .. data:: FONT_WEIGHT_BOLD Bold font weight .. _constants_FORMAT: cairo.FORMAT ------------ These constants are used to identify the memory format of :class:`ImageSurface` data. New entries may be added in future versions. .. data:: FORMAT_ARGB32 each pixel is a 32-bit quantity, with alpha in the upper 8 bits, then red, then green, then blue. The 32-bit quantities are stored native-endian. Pre-multiplied alpha is used. (That is, 50% transparent red is 0x80800000, not 0x80ff0000.) .. data:: FORMAT_RGB24 each pixel is a 32-bit quantity, with the upper 8 bits unused. Red, Green, and Blue are stored in the remaining 24 bits in that order. .. data:: FORMAT_A8 each pixel is a 8-bit quantity holding an alpha value. .. data:: FORMAT_A1 each pixel is a 1-bit quantity holding an alpha value. Pixels are packed together into 32-bit quantities. The ordering of the bits matches the endianess of the platform. On a big-endian machine, the first pixel is in the uppermost bit, on a little-endian machine the first pixel is in the least-significant bit. .. data:: FORMAT_RGB16_565 each pixel is a 16-bit quantity with red in the upper 5 bits, then green in the middle 6 bits, and blue in the lower 5 bits. .. _constants_HINT_METRICS: cairo.HINT_METRICS ------------------ These constants specify whether to hint font metrics; hinting font metrics means quantizing them so that they are integer values in device space. Doing this improves the consistency of letter and line spacing, however it also means that text will be laid out differently at different zoom factors. .. data:: HINT_METRICS_DEFAULT Hint metrics in the default manner for the font backend and target device .. data:: HINT_METRICS_OFF Do not hint font metrics .. data:: HINT_METRICS_ON Hint font metrics .. _constants_HINT_STYLE: cairo.HINT_STYLE ---------------- These constants specify the type of hinting to do on font outlines. Hinting is the process of fitting outlines to the pixel grid in order to improve the appearance of the result. Since hinting outlines involves distorting them, it also reduces the faithfulness to the original outline shapes. Not all of the outline hinting styles are supported by all font backends. .. data:: HINT_STYLE_DEFAULT Use the default hint style for font backend and target device .. data:: HINT_STYLE_NONE Do not hint outlines .. data:: HINT_STYLE_SLIGHT Hint outlines slightly to improve contrast while retaining good fidelity to the original shapes. .. data:: HINT_STYLE_MEDIUM Hint outlines with medium strength giving a compromise between fidelity to the original shapes and contrast .. data:: HINT_STYLE_FULL Hint outlines to maximize contrast New entries may be added in future versions. .. _constants_LINE_CAP: cairo.LINE_CAP -------------- These constants specify how to render the endpoints of the path when stroking. The default line cap style is *LINE_CAP_BUTT* .. data:: LINE_CAP_BUTT start(stop) the line exactly at the start(end) point .. data:: LINE_CAP_ROUND use a round ending, the center of the circle is the end point .. data:: LINE_CAP_SQUARE use squared ending, the center of the square is the end point .. _constants_LINE_JOIN: cairo.LINE_JOIN --------------- These constants specify how to render the junction of two lines when stroking. The default line join style is *LINE_JOIN_MITER* .. data:: LINE_JOIN_MITER use a sharp (angled) corner, see :meth:`Context.set_miter_limit` .. data:: LINE_JOIN_ROUND use a rounded join, the center of the circle is the joint point .. data:: LINE_JOIN_BEVEL use a cut-off join, the join is cut off at half the line width from the joint point .. _constants_OPERATOR: cairo.OPERATOR -------------- These constants are used to set the compositing operator for all cairo drawing operations. The default operator is *OPERATOR_OVER*. The operators marked as *unbounded* modify their destination even outside of the mask layer (that is, their effect is not bound by the mask layer). However, their effect can still be limited by way of clipping. To keep things simple, the operator descriptions here document the behavior for when both source and destination are either fully transparent or fully opaque. The actual implementation works for translucent layers too. For a more detailed explanation of the effects of each operator, including the mathematical definitions, see http://cairographics.org/operators. .. data:: OPERATOR_CLEAR clear destination layer (bounded) .. data:: OPERATOR_SOURCE replace destination layer (bounded) .. data:: OPERATOR_OVER draw source layer on top of destination layer (bounded) .. data:: OPERATOR_IN draw source where there was destination content (unbounded) .. data:: OPERATOR_OUT draw source where there was no destination content (unbounded) .. data:: OPERATOR_ATOP draw source on top of destination content and only there .. data:: OPERATOR_DEST ignore the source .. data:: OPERATOR_DEST_OVER draw destination on top of source .. data:: OPERATOR_DEST_IN leave destination only where there was source content (unbounded) .. data:: OPERATOR_DEST_OUT leave destination only where there was no source content .. data:: OPERATOR_DEST_ATOP leave destination on top of source content and only there (unbounded) .. data:: OPERATOR_XOR source and destination are shown where there is only one of them .. data:: OPERATOR_ADD source and destination layers are accumulated .. data:: OPERATOR_SATURATE like over, but assuming source and dest are disjoint geometries .. _constants_PATH: cairo.PATH ---------- These constants are used to describe the type of one portion of a path when represented as a :class:`Path`. .. See #cairo_path_data_t for details. .. data:: PATH_MOVE_TO A move-to operation .. data:: PATH_LINE_TO A line-to operation .. data:: PATH_CURVE_TO A curve-to operation .. data:: PATH_CLOSE_PATH A close-path operation .. _constants_PS_LEVEL: cairo.PS_LEVEL -------------- These constants are used to describe the language level of the PostScript Language Reference that a generated PostScript file will conform to. Note: the constants are only defined when cairo has been compiled with PS support enabled. .. data:: PS_LEVEL_2 The language level 2 of the PostScript specification. .. data:: PS_LEVEL_3 The language level 3 of the PostScript specification. .. _constants_SUBPIXEL_ORDER: cairo.SUBPIXEL_ORDER -------------------- The subpixel order specifies the order of color elements within each pixel on the display device when rendering with an antialiasing mode of :data:`ANTIALIAS_SUBPIXEL`. .. data:: SUBPIXEL_ORDER_DEFAULT Use the default subpixel order for for the target device .. data:: SUBPIXEL_ORDER_RGB Subpixel elements are arranged horizontally with red at the left .. data:: SUBPIXEL_ORDER_BGR Subpixel elements are arranged horizontally with blue at the left .. data:: SUBPIXEL_ORDER_VRGB Subpixel elements are arranged vertically with red at the top .. data:: SUBPIXEL_ORDER_VBGR Subpixel elements are arranged vertically with blue at the top