Hi, Yesterday I posted in a wrong thread, so I'm opening a new one. I'll copy and paste the previous message and add some notes. Sorry for the mess!
Original post: I am an Italian archaeologist and an enthusiastic QGIS user. I do what I can to spread the knowledge about QGIS and other open source softwares to my university students (I am a contract professor at the Basilicata University and some days ago I've become contract professor at the Specialization School of Archeology of Udin, Venice and Trieste). The main difficulty I have with open source GIS is the advanced editing of vector layers. QGIS doesn't offer too much support for digitizing, the CAD Tools plugin has some useful functions but is far from being complete and the kind of interaction that it proposes is not very productive and time-saving (it's not a critic: CAD Tools saved my life a lot of time, and I want to thank the developers and maintainers). Many times, I had to convert my vector layers to dxf and back in order to perform some complex tasks (with all kind of conversion problems, like the preservation of the attributes values, etc.). I have some experience in programming (about ten years of developement, mainly in C# with the .NET Framework, before I switched to Linux), and I would like to try (only try, without promising anything!!) to implement complete CAD tools and functions (If there isn't and analogous project already active; in that case, nevermind!). I think that developing a CAD plugin from scratch is very hard to me and maybe not the better way to get good results, so I'm oriented to try to augment the interaction between QGIS and an existing CAD software (I'm thinking to LibreCAD). I thought to two possible strategies: 1. Use the LibreCAD library and source code to develop a C++ QGIS plugin; 2. Create a shapefile/spatialite/postgis driver for LibreCAD in order to edit those formats inside LibreCAD. 3. Convert some layers of the QGIS project in a dxf file and back (each QGIS layer in a different layer of the final dxf file). I'm asking your opinion about which of those ways could be the faster or the better to implement, or which one is impossible to undertake according to your knowledge of the QGIS API. My doubts are: Strategy #1: Probably the ideal one, but does the implementation of complex snaps or constraints against the features of other layers (i.e. midpoint, parallels, etc.) require changes to the QGIS API, or all these operations can be contained on a plugin? Is it better to work directly on QGIS vector layers or to create a plugin layer, edit it and then commit the changes to the vector layer? The conversion could help me to manage geometries in the way LibreCAD wants. Is it possible in your opinion to have an interactive shell (i.e. draw the first point, and then inserting the coordinates of the second point)? Strategy #2: Probably the easier, but I should find a way to disable some LibreCAD functions (i.e. the drawing of splines, or the drawing of points on a line layer) without disseminating my changes all over LibreCAD's source files. For this kind of solution I'll ask to the developers of LibreCAD. Strategy #3: The problem is on committing the changes of the dxf file to the original layer: how to specify that a line in the dxf file must replace the geometry of and existing record of the original spatialite layer? Maybe it's impossible, it doesn't seem to me that I can put on a dxf file the necessary metadata to preserve a link to the original features. What do you think? And what do you actually do when you have to draw complex shapes on shapefiles or other vector layers? NEW COMMENTS: - Antonio Locandro is compiling a list of required CAD features. It would be very useful, so please Antonio, get me a link to this list when it's finished. - The more I explore QGIS and LibreCAD source codes, the more I'm convincing that integrating LibreCAD's tools on QGIS is very difficult, and it would be easier to develop those tools from scratch. To get the best results in a short amount of time, I think that I could work to make shapefiles and other vector layers editable in LibreCAD (using GDAL). This solution has the issue that it doesn't allow to snap to other QGIS layers, nevertheless it could be of great help and available in a reasonable amount of time. Then, when I have more practice with QGIS and LibreCAD APIs, I'll try to do something better (i.e. develop a "QGIS driver" for LibreCAD in order to open the whole QGIS project in LibreCAD, organized by layers). I'm waiting for the answers to an analogous thread in LibreCAD's mailing list: http://forum.librecad.org/Using-LibreCAD-s-tools-on-GIS-vector-layers-td5707930.html I think that I'm going to work on this project in a few weeks. Let me know what do you think and if you have suggestions. Diego Gnesi _______________________________________________ Qgis-developer mailing list Qgis-developer@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-developer