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 Look into the polygon winding and rotate_extrude() problem reported by Britton
o CGAL Aff_transformation_3 doesn't support non-affine transformations (non-aff-matrix.scad)
o 2D union of polygons with a touching vertex doesn't work. see testdata/scad/bugs/polygon-touch.scad

STL Import BUGS
---------------

Using STL-imported models is tricky and triggers multiple issues:
(these all fail with the usual "Illegal polygonal object" error)
1) null-faces causes F6 rendering to fail while F5 rendering succeeds.
   (null-faces are exported by OpenSCAD). Example: adns2610_dev_circuit_inv.stl
   by Andrew Plumb
2) Even very simple imported STL models don't render correctly with F5 when taking 
   a difference(), though F6 looks correct. Example: test_cube.stl by Andrew Plumb
   with this scad file:
   difference() {
     import_stl("test_cube.stl");
     translate([2,2,2]) cylinder(h=10);
   }
3) More complex STL models with something simple unioned or subtracted fails rendering 
   using F6 even though F5 works. Example: adns2610_dev_circuit_inv.stl
   by Andrew Plumb with the three null-faces removed by MeshLab with this scad file:
   union() {
     import_stl("adns2610_dev_circuit_inv_4.stl");
     sphere(r=5);
   }
4) More complex STL models cannot be projected (both F5 and F6).
   Example: adns2610_dev_circuit_inv.stl by Andrew Plumb with the three 
   null-faces removed by MeshLab and this scad file:
   projection(cut=true) {
     import_stl("adns2610_dev_circuit_inv.stl");
   }

USER INTERFACE
--------------
o Preferences
  - Beautify color schemes
  - Color schemes read from file
  - Color scheme editor
  - wireframe width
  - pointsize
  - OpenGL params
  - Default language feature settings
  - Make the library search path configurable?
  - Turn on/off caching (advanced)
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
  - Improve mouse rotation/zoom/pan
  - Add modifier key combos to handle pan and zoom on 1 mouse button systems
  - Show grid
  - Measurement ticks on the axes that look like rulers that one can turn off and on.
  - 4 x split view w/orthogonal cameras?
  - Quick highlighting of object under the cursor in the editor
  - View All
  - Allow specifying viewpoint in the scad file
  - overlay indicator displaying current view mode
  - Use OpenGL picking to facilitate ray-tracing like features like measuring
    thicknesses, distances, slot thicknesses etc.
  - Add option to change lights, e.g. add an optional camera light
  - 2D objects are rendered at z = -0.1 - why?
  - Rewrite to use VBOs or smth. - avoid inline calculations
  - Rewrite to a higher-level library (e.g. OSG)?
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
  - Auto-indent on enter and on tab
o Error reporting/debugging
  - Provide better error messages when polygon ordering causes CGAL errors:
    o Supply syntax highlighting of the exact polygon indices which are 
      reported to be wrong
    o Provide some interaction for debug walk-through?
  - Provide visual highlighting of geometry corresponding to code
    -> could aid debugging a lot
o Computation
  - Run CGAL rendering in a background 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)
  - If trying to export STL/DXF but source is newer than the CGAL rendering, ask
    for confirmation.
  - Go through keyboard shortcuts and make them more conformant to platform standards
  - Show design info/stats (sizes, caches etc.)
o Cmd-line
  - Add verbose option (PRINT command from mainwin.cc and progress output)

OpenCSG-related
---------------
o OpenCSG rendering: Coincident surfaces causes z-buffer fighting. Is this somehow
  avoidable tuning the depth tests in OpenCSG? 
o Make the 10.000 element OpenCSG limit configurable (Preferences) ?
o When specifying a transparency with the color() statement,
  the object is not sorted and will be rendered wrongly
o Bug: Using the background operator (%) on the only object in a scene triggers a
  CSG error: No top level object found

ENGINE
------
o Primitives
  - Springs, spirals (requested by Cathal Garvey)
  - (TTF) Text
  - Image-based height field like http://www.thingiverse.com/thing:2078
  - mesh (coordinates and indices)
  - polygon(): Allow omitting the paths parameter to create a single polygon from a list of vertices.
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
  - non-convex minkowski example from chrysn fails with an exception (testdata/scad/bugs/minkowski-assert.scad)
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)
  - 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/Export
  - Use dxflib from RibbonSoft for import/export? -> investigate
  - 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
  - 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?
  - Dependency tracking of libraries (USE'd modules) isn't implemented. See Mail from nophead 20110823.
o Grammar
  - dim->name -> dim->label
  - A random(seed) function
  - linear_extrude()/rotate_extrude(): Cumbersome names? -> (extrude, revolve, lathe, sweep ?) 
o Hollow donut problem
  When extruding a 2D CSG tree (e.g. a polygon with a hole), the hole
  information is lost when performing the extrusion. For linear
  extrusions, this has only a minor visual impact, but for rotate
  extrusion, the resulting CGAL models will lose the hole. The OpenCSG
  rendering keeps the hole, but renders slightly incorrect.
o CGAL issues
  - CGAL doesn't handle almost planar polygons. Consider splitting into triangles ourselves. See WillamAdams/dodec.scad


IDEAS FOR LANGUAGE CHANGES
--------------------------
o More strict checking of module parameters to make e.g. this fail:
  module test(a,b) { a=1; b=2; echo(a,b,c); } test(c=3);

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?
o Consider evaluating all referenced files relative to the document path instead
  of being absolute. This would e.g. make regression testing of dumpcaching easier.
  This would require us to pass a document contect to all traversal methods though.

BUILD SYSTEM
------------
o Fedora is reported to ship with byacc, which doesn't support bison extensions (e.g. %debuig). Look into this, either be yacc-compatible or force the build system to use bison.
o We currently link in -lboost_thread. Should we always use -lboost_thread-mt under Linux or can we pick this up using qmake?

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

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

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 Collect "all" available OpenSCAD scripts from the internets and run the integration
  tests on them all

MISSING TESTS:
--------------
o all functions
o mirror
o scale
o open polyline from dxf using new method
o linear_extrude DXF
o rotate_extrude DXF
o import_stl
o import_off
o import_*
  - open polylines
o include: test subdirs under librarydir (e.g. include <MCAD/gears.scad>)
o use: Basically same tests as include. + use restrictions
o include and use: remember filenames with space
o variants of module transparent() { %child(); }
o define modules
o define functions
o built-in variables and constants (builtin-tests.scad)
o Write a regression test for the hexagonal cylinder orientation issue
o Caching
  - Test that caching is actually performed (speedup + same results)
  - Test the modifier characters correctly influence the cache (also when
    added/removed)
o other tests
  - export
  - cmd-line tests
  - leaf nodes having children, e.g. cube() cylinder();
  - dependency tracking