Avian’s Blog

A couple of weeks ago a post on geda-dev mentioned a new, free (as in freedom) application for designing printed circuit boards - LiquidPCB. At its web site Hugo Elias, LiquidPCB's author, points out some shortcomings of gEDA's PCB and other traditional CAD tools and how he attempts to fix them in his software. He says it's all about a new, modern user interface.

Discussion that followed on gEDA's mailing list didn't actually touch any of the problems pointed out by Hugo. With some help I managed to get LiquidPCB running this weekend on an old laptop with Windows, so here are some of my thoughts about it.

I mostly agree with Hugo regarding user interface problems. gEDA's PCB has an archaic GUI - most core developers still use its Lesstif incarnation (Lesstif is an reimplementation of Motif, a GUI toolkit from 1980). It surely requires quite a lot clicking around that could be avoided in this or other way, not to mention that it looks a bit out of place on a modern desktop. However I think most of these problems could be solved in a way that doesn't depart so radically from what everyone is used to today.

I think problems that LiquidPCB tries to solve can be split into two groups: First there are those that are shared by basically every complex desktop application today. I believe it's wrong to try to solve this kind of problems separately in each application. For example LiquidPCB reimplements a file selector dialog. From the usability standpoint this is a component that should be shared between all applications. So I believe a better way of solving this problem would be for example to submit patches for GTK file chooser dialog.

Another example are problems with the menu and toolbars. I believe this can be solved with better placing of entries in menus (gEDA's PCB for example has a problem with "Select" and "Buffer" menus where I often open the wrong one). I can't say if the hexagon menu system used by LiquidPCB is better than a well done traditional interface. I found it awkward, but that's because I'm used to traditional interfaces. What bothers me the most is the requirement to hold down the right mouse button while traveling through menus. What I'm almost sure of is that it can't replace keyboard shortcuts. The keyboard with its 100 and so buttons still provides a faster way of switching program states (like switching between select mode, via mode, etc.).

The other group of problems is specific to PCB design. In this field the approach of LiquidPCB looks superior to anything PCB has to offer. What you are doing in PCB design is solving a topological problem. You have a graph and you need to place the vertexes and edges on the plane so that their placement follows certain rules. Now the approach LiquidPCB takes is that it makes you solve that exact problem without requiring you to fiddle with side issues like the exact location of elements. You only say "pin A is placed on this side of line B" and LiquidPCB takes care of the rest. It feels like an autorouter that uses a user's brain to do what it does best (solving the topology) and the computer to do what it does best (finding placement for vias and lines). The example of LiquidPCB's web site showing how to insert a via in the middle of four tracks shows just how much work this approach saves you. In PCB this operation would really involve hundreds of steps where you would first move each of the existing lines out of the way (which could also require moving several components) and only then insert that new via.

I see some purely practical problems with LiquidPCB's approach. For example the constant dynamic optimization means that just opening a file also makes modifications in it. And also, at least from half an hour of playing with it today, it seems it is quite easy to make a mess of things if you're not careful. But I'm sure these problems will be easy to fix.

So in conclusion I think LiquidPCB addresses some quite real problems and shows some promising solutions to them. The program itself is in an early stage of development and isn't useful yet for anything more than playing with it. It will be very interesting to follow its development.