OpenBoardView

Board-to-schematic cross-probing, finally working on macOS

About

This one isn’t mine — it’s someone else’s project I depend on, and a patch I wrote because I needed it.

OpenBoardView reads .brd board files: tap a part, see its pins, nets, and neighbours. It’s the free replacement for the Test_Link and Landrex tools, and it’s what sits open next to the microscope while I’m tracing a fault. Its best feature is cross-probing — click a designator on the board and the schematic PDF jumps to that part, and vice versa.

That feature did nothing on macOS. Not broken — unimplemented. The #ifdef chain had branches for Linux and Windows and no branch for macOS, so it fell through to a base PDFBridge class whose methods are all empty. Clicking PDF Search called into nothing and returned. Silently.

My patch adds a macOS backend that drives Skim over AppleScript — the same drive-an-existing-viewer model the Linux (Evince) and Windows (SumatraPDF) backends already use. Skim was the right pick for the same reason those two were: open source, maintained, and scriptable out of the box, so there’s nothing to patch upstream of the patch.

Both directions work. Click a part, Skim jumps to the designator and highlights it. Select text in Skim, the matching part lights up on the board.

A couple of things that were more interesting than expected:

  • Reverse search has to poll. Skim has no cross-process signal for “the selection changed,” so a background thread checks. It writes to a mutex-guarded value the render loop only ever compares, so nothing blocks.
  • The poll has to wake the render loop. OpenBoardView stops calling Update() once it’s been idle a while — without an SDL_PushEvent nudge, a selection made in Skim wouldn’t show up until you touched the mouse.
  • The missing entitlement reproduced the original bug exactly. Without NSAppleEventsUsageDescription in the bundle plist, the automation events fail silently and the button does nothing. Same symptom, different cause.

Open upstream since July 2026. Running on my bench in the meantime.