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.

In version 1.0.8 to 1.1.0 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 1.1.0 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	class	description
autocrop	158	works	buildin	(feature)	Reduce the board dimensions to just enclose the elements.
autoplace	614	works	buildin	(feature)	Automatically place elements.
autoroute	4343	works	buildin	(feature)	Automatically route selected or all rats. This is the original autorouter.
boardflip	131	WIP (doesn't update rtrees)	disabled	(feature)	All objects on the board are up-down flipped.
dbus	483	WIP (needs to install the xml?)	disabled	(feature)	Remote control PCB using DBUS.
diag	162	works	disabled	(feature)	Actions for pcb-rnd core diagnostics, intended for developers. These are not in core because end users normally don't need these. As a plugin, due to dynamic loading, it can be dropped on an existing pcb-rnd installation with minimal risk of scaring away a reproducible bug.
distalign	428	works	buildin	(feature)	Introducing Align() and Distribute(), which work much like the similarly named functions in Visio. Given that PCB does not have the concept of "first selected object" to draw on, the reference points can be selected by arguments.
distaligntext	466	works	buildin	(feature)	Same as distalign, operates on text objects.
djopt	2320	works	buildin	(feature)	Various board optimization algorithms.
export_bboard	426	WIP	disabled	export	Export breadboard
export_bom	230	works	buildin	export	Export bom (Bill of Materials)
export_dsn	443	Work-in-progress	disable	export	Export specctra .dsn files
export_dxf	3992	WIP	disabled	export	Export dxf
export_gcode	2466	works	buildin	export	Export to gcode
export_gerber	971	works	buildin	export	Export to gerber
export_ipcd356	468	Work-in-progress	disable	export	IPC-D-356 Netlist export.
export_lpr	106	works	buildin	export	Export to lpr (using export_ps to generate postscript)
export_nelma	679	works	buildin	export	Export to nelma (Numerical capacitance calculator)
export_openscad	1394	WIP	disabled	export	Export openscad
export_png	1120	works	buildin	export	Export to png, gif and jpeg
export_ps	1638	works	buildin	export	Export postscript or embedded postscript.
export_test	257	disabled (work in progress)	buildin	export	A thin layer of code to dump exporter calls for testing the HID exporter API.
export_xy	270	works	buildin	export	Export XY centroid element data for pick & place.
fontmode	165	works	buildin	(feature)	Font editing actions.
fp_fs	379	works	buildin	fp	Footprint: file system based implementation. Used to be called Newlib: load footprints from directories. Run external processes for the parametric footprints.
fp_wget	302	works	buildin	fp	Footprint: get static (file) footprints from the web, e.g. from http://gedasymbols.org
gl	590	disabled (pcb-rnd has no support for opengl.)	disabled	(feature)	Common gl functions for hids.
gpmi	3046	works	buildin (if gpmi is installed)	(feature)	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.
hid_batch	333	works	buildin	hid	HID without GUI; read actions from stdin.
hid_gtk	15972	works	buildin	hid	GUI: the GTK HID.
hid_lesstif	6923	works	buildin	hid	GUI: the lesstif HID.
import_dsn	114	Work-in-progress	disable	import	Import specctra .dsn files
import_edif	3621	works	buildin	import	Import plugin for netlists in the EDIF format.
import_netlist	131	works	buildin	import	Import plugin for netlists in the classic pcb netlist format.
import_sch	301	works	buildin	import	Imports element and netlist data from the schematics (or some other source).
io_kicad	998	work-in-progress	disabled	io	Load and save the design and elements in Kicad's s-expression format - this is the new, currently preferred format in Kicad.
io_kicad_legacy	941	work-in-progress	buildin	io	Load and save the design and elements in Kicad's legacy format.
io_lihata	1042	WIP	disabled	io	Load and save the design and elements in the lihata board format.
io_pcb	2174	works	buildin	io	Load and save the design and elements in the original pcb text format.
jostle	446	works	buildin	(feature)	Pushes lines out of the way.
lib_gensexpr	6	works	disabled	(lib)	S-expression parser lib
lib_legacy_func	74	works	buildin	(lib)	Random collection of old/obsolete (legacy) functions. 3rd party plugins may depend on them. This module implements C functions and variables and does not register actions or flags.
loghid	273	WIP	disabled	(feature)	Sits between a HID (or exporter) and the core and logs all core->plugin calls made through the HID structure.
mincut	909	works	buildin	(feature)	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	155	works	disabled	(feature)	Random collection of old/obsolete actions. Bell(): audible feedback; DumpLibrary(): print footprint library on stdout; a set of debug actions useful for writing pcb scripts: Debug(), DebugXY(), Return(). Old plugin actions to toggle or set settings that are now accessible via the unified config system (vendordrill, djopt)
polycombine	208	works	buildin	(feature)	The selected polygons are combined together according to the ordering of their points.
polystitch	185	segfaults	disable	(feature)	The polygon under the cursor (based on closest-corner) is stitched together with the polygon surrounding it on the same layer. Use with pstoedit conversions where there's a "hole" in the shape - select the hole.
propedit	766	works	buildin	(feature)	List and edit properties of a group of objects.
puller	1888	works	buildin	(feature)	Pull traces to minimize their length.
query	1823	WIP	disable	(feature)	pcb-rnd query language: execute expressions on objects and rules for the programmed drc.
renumber	310	works	buildin	(feature)	Renumber elements (renaming them) and generate a text file for back annotation.
report	749	works	buildin	(feature)	Report() and ReportObject() actions - print a report about design objects.
shand_cmd	212	works	buildin	(feature)	vi-like command shorthands (1..3 character long commands)
smartdisperse	173	works	buildin	(feature)	Improve the initial dispersion of elements by choosing an order based on the netlist, rather than the arbitrary element order. This isn't the same as a global autoplace, it's more of a linear autoplace. It might make some useful local groupings. For example, you should not have to chase all over the board to find the resistor that goes with a given LED.
stroke	135	partially works (doesn't work with lesstif; works with the gtk hid, but there's no zoom bindings)	disabled	(feature)	Gesture recognition with libstroke.
teardrops	226	works	buildin	(feature)	Draw teardrops on pins.
toporouter	6162	fails (infinite loop in gts)	disabled	(feature)	Automatically route selected or all rats using a topological algorithm. This is the new autorouter from 2009.
vendordrill	513	works	buildin	(feature)	Vendor drill mapping.

Classes

Each plugin implements a class (rarely a set of classes). Classes are:

name	description
(feature)	random features directly accessible for the user, usually actions
(lib)	support code library for other plugins (core doesn't depend on these); functionality not directly accessible for the user but other plugins may depend on it
hid	Human Interface Device: interactive user interface, usually GUI
import	load alien formats into the design space
export	save (parts of) the design space in alien formats
fp	footprint (element) library implementation
io	native file format (save & load) implementation