* Write a PostScript backend.

* Add a few new, needed functions:

   cairo_show_page
   cairo_copy_page
   cairo_flush
   cairo_erase
   cairo_mark_dirty

* Add a "real" text API in addition to the current "toy" API.

* Implement text support for the image backend.

* Re-implement pattern support with a more PostScript-like API.

* Verification, profiling, optimization.

* Re-implement the trapezoid rasterization algorithm according to the
new "specification".

A comparison with PostScript
============================

Here's a list of several classes of PostScript operators indicating
which operators have rough equivalents in Cairo and which do not. In
general, the name of a Cairo function corresponding to a PostScript
operator can be obtained by inserting a '_' between each word and
prefixing it with "cairo_". For example, "cairo_move_to" corresponds
to the PostScript "moveto".

In cases where the name of the Cairo function deviates from this
convention, or when the behavior of the Cairo function is
significantly different, the change is noted in parentheses below.

This list is not exhaustive, (there are definitely some minor (major?)
semantic deviations that are not noted below). Also, this list is
almost certainly out of date with respect to the current Cairo
implementation. Caveat lector.

Oerators that are not yet in Cairo, but probably should be: arcto,
strokepath, rectclip?, clipsave/restore?, setstrokeadjust?,
currentdash, grestoreall?, initgraphics?, currentgstate?, setgstate?,
insideness testing?, showpage, copypage?, erasepage?, setsmoothness?

Painting operators
------------------
in Cairo: stroke, fill, eofill (set_fill_rule/fill), image
(show_surface)

not in Cairo: erasepage, rectstroke, rectfill, shfill, colorimage,
imagemask

Path construction operators
---------------------------
in Cairo: arc, arcn (arc_negative), newpath, moveto, rmoveto
(rel_move_to), lineto, rlineto (rel_line_to), curveto, rcurveto
(rel_curve_to), closepath, currentpoint, charpath (text_path)

not in Cairo: arct, arcto, flattenpath, reversepath, strokepath,
clippath, pathbbox, pathforall

Clipping
--------
in Cairo:  clip, eoclip (set_fill_rule/clip)

not in Cairo: initclip, rectclip, clipsave, cliprestore

Graphics state operators
------------------------
in Cairo: setlinewidth, currentlinewidth, setlinecap, currentlinecap,
setlinejoin, currentlinejoin, setmiterlimit, currentmiterlimit,
setdash

not in Cairo: setstrokeadjust, currentstrokeadjust, currentdash

Color specification operators
-----------------------------
in Cairo:  setrgbcolor, currentcolor

not in Cairo: setcolor, setgray, currentgray, currentrgbcolor,
sethsbcolor, currenthsbcolor, setcmykcolor, currentcmykcolor,
setcolorspace, currentcolorspace

Form and pattern operators
--------------------------
in Cairo: setpattern, makepattern (lock_pattern)

not in Cairo: execform

Whole-state manipulation
------------------------
in Cairo:  gsave (save), grestore (restore)

not in Cairo: grestoreall, initgraphics, gstate, currentgstate,
setgstate

Coordinate system and matrix operators
--------------------------------------
in Cairo: identmatrix (identity_matrix), initmatrix (default_matrix),
setmatrix, translate, scale, rotate, concatmatrix, currentmatrix,
transform (transform_point), dtransform (transform_distance)

not in Cairo: matrix, defaultmatrix, concat, itransform, idtransform,
invertmatrix

Insideness testing
------------------
not in Cairo: infill, instroke, inufill, inustroke, ineofill,
inueofill

Device setup
------------
not in Cairo: showpage, copypage, setpagedevice, currentpagedevice,
nulldevice

Glyph and font operators
------------------------
in Cairo: currentfont, definefont (font_create_for_ft_face),
undefine_font (font_destroy), findfont (font_create), makefont
(transform_font), setfont, scalefont, selectfont, show (show_text),
stringwidth (x/y in text_extents), xyshow (glyph_show -- but ignoring
current_point and using absolute positions)

not in Cairo, (and likely not needed): composefont, rootfont, ashow,
widthshow, awidthshow, xshow, xyshow, yshow, glyphshow, cshow, kshow,
FontDirectory, GlobalFontDirectory, StandardEncoding,
ISOLatin1Encoding, findencoding, setcachedevice, setcachedevice2,
setcharwidth

Graphics state operators (device-dependent)
-------------------------------------------
in Cairo:  setflat (set_tolerance), currentflat (current_tolerance)

not in Cairo: sethalftone, currenthalftone, setscreen, currentscreen,
setcolorscreen, currentcolorscreen, settransfer, currenttransfer,
setcolortransfer, currentcolortransfer, setblackgeneration,
currentblackgeneration, setundercolorremoval,
currentundercolorremoval, setcolorrendering, currentcolorrendering,
setoverprint, currentoverprint, setsmoothness, currentsmoothness

PostScript operators never to be in Cairo
-----------------------------------------
Operator Stack Manipulation Operators, Arithmetic and Math Operators,
Array Operators, Packed Array Operators, Dictionary Operators, String
Operators, Rational,Boolean,and Bitwise Operators, Control Operators,
Type,Attribute,and Conversion Operators, File Operators, Resource
Operators, Virtual Memory Operators, Miscellaneous Operators,
Interpreter Parameter Operators, Errors, User Path Operators