BUGS
----
o Some invalid DXF data gets pass the import checks and breaks the tessing code
o Tesselation via GLU sometimes produces strange results
o Export STL: Exports existing CGAL model even though the current model is changed, but not CGAL rendered
o It's now possible to start a new rendering while one is already running.
  -> turn off most (or all) interaction while rendering
o Look into the polygon winding and rotate_extrude() problem reported by Britton

CRASH BUGS
----------
o Broken polyhedron() entities are not correctly detected and cause CGAL segfaults
o linear_extrude(50) square([5,0]);
o union() {
    linear_extrude(height=10, twist=90) circle(5);
    translate([7,-5,0]) linear_extrude(height=10, twist=180) polygon(points = [[0,0], [10,0], [5,10]]);
  }
o non-convex minkowski example from chrysn fails with an exception

USER INTERFACE
--------------
o Preferences
  - Remember settings done in menus between sessions (automatic reload, perspective, show*, hide*)
  - Beautify color schemes
  - Color schemes read from file
  - Color scheme editor
  - wireframe width
  - pointsize
  - OpenGL params
  - Default language feature settings
  - Auto-view CSG/thrown together on load
  - Make the library search path configurable?
o Export etc.: automatically add missing extension as in SaveAs
o MDI
  - Think about how to do MDI the right way
  - Ctrl-W should close the current dialog, not the current main window
    -> implement as for Preferences?
  - Menu bar handling:
    Mac: share menubar among all top-level windows?
  - currentPath is global but is used by each document, e.g. parser
    and handle_dep.
o 3D View
  - OpenGL 2.0 test: What, exactly, is needed from OpenGL 2.0? Can we use 1.x with extensions?
  - Improve mouse rotation
  - Add modifier key combos to handle pan and zoom on 1 mouse button systems
  - Show grid
  - 4 x split view w/orthogonal cameras?
  - Quick highlighting of object under the cursor in the editor
  - View All
  - overlay indicator displaying current view mode
  - OpenCSG rendering: Coincident surfaces causes z-buffer fighting. Is this somehow
    avoidable tuning the depth tests in OpenCSG? 
o Editor wishlist
  - More infrastructure for external editor (allow communication from the outside)
  - Preferences GUI for the features below
  - line numbers
  - tear-off/maximize options?
  - Save somehow uses current dir, even if the file is already saved earlier
  - Code completion/hints for builtin (and user-defined) functions/modules
  - builtin quick function reference/help
  - Drawer/popup with all modules/functions listed which can be inserted into
    the editor by clicking or drag&drop -> icons in toolbar?
    -> This would be moving in the direction of a traditional CAD GUI
       and needs a fair bit of thinking.
  - Display some kind of line wrap indicator
  - Couple the source code to the AST to allow highlighting selected elements
    in the source code in the 3D view
  - Tabbed editor for designs including other files
  - C-c/C-v should work on the focused widget, not always in the editor

o Computation
  - Run CGAL rendering in a backgroud thread
  - Enable viewing/editing while rendering
  - Progress: Call progresswidget more often to avoid app hanging for multiple
    seconds (i.e. make cancel button more responsive)
o Misc
  - Reload and compile: Ask for confirmation if file is locally edited
    (make this configurable in preferences?)
  - Save: Ask for confirmation if file has been externally changed
  - Rename OpenCSG and CGAL to smth. not specific to the underlying libraries
    (e.g Preview, Render)

ENGINE
------
o Primitives
  - Springs, spirals (requested by Cathal Garvey)
  - (TTF) Text
  - Image-based height field like http://www.thingiverse.com/thing:2078
o 2D Subsystem
  - Performance: Is it necessary to union children before extrusion
    when compiling? Can this be postponed to CGAL evaluation time?
  - Add inset() operation
o Built-in modules
  - extrude*: Allow the base 2D primitive to have a Z value
  - rotate_extrude(): Allow for specification of start/stop/sweep angle?
o Advanced Transformations
  - Add statement for refinement via surface subdivision
  - Add statement for intersections in cartesian product of childs
o Function-Module-Interface
  - Pass a module instanciation to a function (e.g. for a volume() function)
  - Pass a function to a module instanciation (e.g. for dynamic extrusion paths)
o Language Frontend
  - Allow local variables and functions everywhere (not only on module level)
  - Add "use" statement to load modules. Like include but read a module only once,
    ignore all top level objects (they are used as module testcase) and search in
    a module search path.
  - allow 0/1 f/t FALSE/TRUE as boolean values
  - allow any expression to be evaluated as boolean (e.g. 1 = true, 0 = false)
  - Rethink for vs. intersection_for vs. group. Should for loops
    generate child lists instead, and make these passable to other
    modules or accessible by child()?
o DXF Import
  - Support for POLYLINE entity
  - Support for SPLINE entity
  - Support for LEADER entity
  - Support for MTEXT entity ?
  - idea: DXF inline - convert from dxf to OpenSCAD syntax -> parametrize dxf content
o Mesh optimization on STL export
  - Remove super small triangles (all sides are short)
  - Replace super thin triangles (one h is short)
o Misc
  - Add symbolic colors to the color() statement
  - When specifying a transparency with the color() statement,
    the object is not sorted and will be rendered wrongly
  - Go through default values of parameters (e.g. cube() has x,y,z=1 while linear_extrude() has height=100)
  - Add support for symbolic names to child() statement 
  - Add 'lines' object type for non-solid 2d drawings
  - Is there a reason why modules like echo, empty if, empty for loop returns an
    empty AbstractNode instead of being ignored?
o Grammar
  - dim->name -> dim->label
  - A random(seed) function
  - import_*() -> *_import() (consistent prefix vs. postfix)
  - linear_extrude()/rotate_extrude(): Cumbersome names? -> (extrude, revolve, lathe, sweep ?) 

CODE
----

o Refactor from MainWindow:
  - Put all application-global data in one place (QApplication subtype?)
  - Fix current_win hack
  - CSG data structure (compiled model)
  - CGAL data structure (compiled model)
o C++-ify
  - Use smart pointers where it makes sense (e.g. instead of homegrown refcount,
    and to get memory ownership under control)
  - Use static_cast/dynamic_cast instead of C-style casts
o dxflinextrude and dxfrotextrude could share code
o Consider decoupling DXF-specific functionality from the 2D subsystem
o Visitation refactoring
  - Make AbstractNode members private/protected?

TESTING
-------
o Caching and MDI looks suspicious when the code relies on external resources
  which might be loaded from difference locations in different documents
  -> we might get a false cache hit
o Are contructs like "child(0)" cached? Could this give false cache hits?
o Write some cmd-line apps that dump an openscad file to misc. formats
  (dump, stl, dxf)
o Write a simple test script that collects verified and current STL renderings
  and displays them side-by-side or smth.
o Write simple driver scripts for comparing output of above command
o Collect "all" available OpenSCAD scripts from the internets and run the integration
  tests on them all

INFRASTRUCTURE
--------------
o Use a logging framework to get debugging/info output more under control?
  (check log4j, google project)

MISC
----
o Streamline the cmd-line interface a bit
  - Implicit output file format
o Mac OS X:
  - 32-bit compatibility
    o Build everything including i386 arch

o Write checklists for typical extension work (add new module, add new function)
  -> make sure new test files are added