pcb-rnd modularization

Why bother...

I believe good software should be modular. This is especially important in the context of large software, such as CAD applications. There should be a thin core that can model the world and provide the basic operations defined on it but anything else should go in separate modules.

Fortunately PCB already had a strong infrastructure supporting this idea. It has dynamic loadable plugins and the GUI and exporters are in separate HID modules. While working on pcb-gpmi and later pcb-rnd, I added the gpmi module as a separate plugin.

As of version 1.0.8 a cosiderable chunk of core code has been moved into core plugins. A core plugin is just a plugin that is maintained together with the core, in the same repository, still the code is somewhat detached from the core. More importantly, the user can choose, for each plugin, separately:

to compile it as a buildin (static-link it into the pcb executable)
to compile it as a plugin (dynamic-link it runtime, if the .so is installed in the plugins/ directory)
to disable the plugin, so it is not compiled at all

I believe such modularization has benefits on multiple levels:

it is possible to compiler smaller, potentially faster executables by omitting features the specific user would never use anyway
in a distribution dynamic-link plugins can be distributed as separate packages providing the user with the option to decide what features to install
such plugins have to have some sort of APIs if they want to reference eachother or if the code needs to reference them; such an API may not (and often did not) exist when the code is part of the core

Progress in charts

Before-after

All numbers are in SLOC and are acquired running sloccount on the given directory. While lines of code alone is not a true measure of complexity, it's a good estimation. The slices of pie charts are the major components of the pcb-rnd executable.


Before modularization: pcb-rnd version 1.0.7 Note: gpmi was already a plugin		After modularization: pcb-rnd version 1.0.8 Note: gpmi is part of the "plugins" slice

Zooming on to the plugins

(Red means the plugin doesn't really work).

Progress in numbers

Below is a table with the summary of core plugins.

module	size [sloc]	status	configure default	description
autoplace	608	works	buildin	Automatically place elements.
autoroute	4177	works	buildin	Automatically route selected or all rats. This is the original autorouter.
dbus	438	disabled (TODO: needs scconfig support)	disabled	Remote control PCB using DBUS.
djopt	2315	works	buildin	Various board optimization algorithms.
export_gcode	2450	works	buildin	Export to gcode
export_lpr	96	works	buildin	Export to lpr (using export_ps to generate postscript)
export_nelma	683
export_ps	1608	works	buildin	Export postscript or embedded postscript.
gpmi	2992	works	buildin (if gpmi is installed)	Scriptable plugin system with about 10 scripting languages supported and dynamic load/unload of scripts that can manipulate the GUI, the board, can implement exporters, etc.
import_edif	3578	works	buildin	Import code for netlists in the EDIF format.
import_sch	255	works	buildin	Imports element and netlist data from the schematics (or some other source).
mincut	886	works	buildin	Use the minimal cut algorithm to indicate shorts: instead of highlighting two random pins/pads, try to highlight the least number of objects that connect the two networks.
oldactions	53	works	disabled	Random collection of old/obsolete actions. Bell(): audible feedback; DumpLibrary(): print footprint library on stdout
puller	1878	works	buildin	Pull traces to minimize their length.
renumber	218	works	buildin	Renumber elements (renaming them) and generate a text file for back annotation.
stroke	124	partially works (doesn't work with lesstif; works with the gtk hid, but there's no zoom bindings)	disabled (requires libstroke installed)	Gesture recognition with libstroke.
toporouter	6161	fails (infinite loop in gts)	disabled	Automatically route selected or all rats using a topological algorithm. This is the new autorouter from 2009.
vendordrill	567	works	buildin	Vendor drill mapping.